Sex: Male
Education:
- Doctor of Philosophy in Agricultural Science (Plant Pathology), University of Tasmania, Australia
Field of Specialization
Plant pathology
Crop protection
Disease resistance
Plant disease management
Host plant resistance
Food safety
Food security
Researches:
Article title: Commelina benghalensis harbors Corynespora cassiicola, the tomato target spot pathogen
Authors: Deborah Dimayacyac and Mark A. Balendres
Publication title: International Journal of Pest Management, September 2021
Abstract:
This study elucidates the causative agent of a leaf spot in Commelina benghalensis, grown nearby a tomato field, through a polyphasic approach. Pathogenicity of the causative agent to C. benghalensis and cross infectivity to tomato was performed. Morphological, cultural, and molecular characterization identified the fungal isolate as Corynespora cassiicola. C. cassiicola CB005 produced leaf spot symptoms to C. benghalensis and tomato in all three independent trials. The same fungus was reisolated from the inoculated leaves and thus, confirming Koch’s postulate. Together, C. cassiicola was identified as the causative agent of a leaf spot in C. benghalensis, which is the first record from the Philippines, and was pathogenic to tomato. The fungus’ survival in C. benghalensis, an invasive weed, poses a problem to nearby crops on the next cropping season. Hence, the removal of this weed is important in reducing the source of inoculum in the field. It would be worthwhile to further study other potential plant hosts of C. benghalensis in the Philippines and select for resistance to target leaf spot in tomato cultivars and breeding lines.
Full text available upon request to the author
Article title: Contributions to Agriculture, Forestry and Fisheries (AFF) Research of Non-AFF Undergraduate Researches: The Case of Bicol University Biology Department
Authors: Jonathan Jaime G. Guerrero1, Mark Angelo O. Balendres, Luis O. Amano, Charmaine A. Malonzo, and Amelia A. Dorosan
Publication title: Bicol University R&d D Journal 24(1):1-8 July 2021
Abstract:
Agriculture, forestry and fisheries (AFF) researches' contribution to the economy is far-reaching. While there are a number of institutional researches produced, many AFF researches are lodged at the undergraduate level, many of which remain underutilized. The role of non-AFF undergraduate programs as a means to further research in AFF fields are highlighted in this study using the case of the BS Biology Program of Bicol University which may be reflective of other HEIs in the country. A total of 271 of the 865 undergraduate theses conducted in the Department of Biology from 1986 to 2019 were under AFF. Majority of the studies were on post-harvest and plant pathology of locally important commodities such as rice, coconut and pili. However, there were no records of publication. AFF - allied undergraduate programs like biology can be a source of valuable and valid research data to augment AFF researches in the region and in the country. Mechanisms to encourage publication of student outputs are also imperative for proper and wide dissemination of results. Inclusive undergraduate research agenda, co-mentoring and cohesive institutional academic policies are among the strategies to further strengthen the AFF contributions of allied undergraduate programs.
Full text link https://tinyurl.com/3jukbbj6
Article title: Reduction of Selenicereus stem cuttings weight by fungal plant pathogens during storage
Authors: John Darby Willy Taguiam, Edzel Evallo, Mark A. Balendres
Publication title: Journal of Phytopathology 169(1), June 2021
Abstract:
Dragon fruit (Selenicereus spp.) is a high-value crop in the Philippines. It is commonly propagated using stem cuttings, which quality is essential for fruit production. Several pathogens have been reported to cause various diseases on dragon fruit worldwide. These diseases affect stem and fruit quality in the field, but the consequences during storage are unknown. This study aims to determine the effect of three pathogens (Neoscytalidium dimidiatum, Epicoccum sorghinum, and Nigrospora sphaerica) on Selenicereus stem cuttings in controlled storage conditions. Three weeks after inoculation, only N. dimidiatum significantly reduced Selenicereus stem weight in both cooler (air-conditioned storage area/19-25C) and warmer (room temperature/28-30C) temperatures. Nonetheless, all pathogens induced symptoms on stems, which caused a loss in product quality. Neoscytalidium dimidiatum caused significantly more severe symptoms under control conditions. In general, symptoms were more severe on the stems kept in the air-conditioned storage area. This study highlights the importance of disease-free planting materials and adequate temperature in the storage area in the preparation and dissemination of high-quality dragon fruit stem cuttings.
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Article title: First report of Lasiodiplodia theobromae causing jackfruit (Artocarpus heterophyllus) brown rot in the Philippines
Authors: April Dawn Taylaran, Irish Bagsic- Posada, Fe M. Dela Cueva, Mark A. Balendres
Publication title: Indian Phytopathology, June 2021
Abstract:
Jackfruit (Artocarpus heterophyllus) brown rot has been observed in Los Baños, Laguna, Philippines. The disease was characterized by dark brown to black discoloration in the center of the lesion, advancing radially with a yellow to brown margin. The lesion center has grayish mycelial mass and is relatively more tender than the margin and unaffected areas. Only one fungus was isolated and identified as Lasiodioplodia theobromae based on combined morphological and molecular characterization assays. The fungus was pathogenic to jackfruit and showed brown rot six days post-inoculation. The same fungus was reisolated from the inoculated sites, thus establishing Koch’s postulate. To our knowledge, this is the first confirmed report of jackfruit brown rot caused by Lasiodiplodia theobromae in the Philippines.
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Article title: Identification of Epicoccum sorghinum and Its Effect on Stalk Sugar Yield
Authors: Niño Redondo Laurel, Rachele L. De Torres, Jayvee Mendoza, Mark A. Balendres, et al.
Publication title: Sugar Tech, May 2021
Abstract:
Ring spot disease of sugarcane is associated with several fungal pathogens worldwide. In the Philippines, the disease is considered a minor one with limited knowledge of its pathosystem. Thus, this present study was conducted (1) to identify the fungal pathogen associated with ringspot of sugarcane through combined morphological and molecular characterization, (2) to determine the pathogenicity of the isolated fungus in detached leaf and planta trials, and (3) to evaluate its effects on the stalk sugar yield. Morphological characters and gene sequences of internal transcribed spacer (ITS-rDNA), beta-tubulin (TUB2) and actin (ACT) regions of fungal isolates VNOC62a and VNR26 showed high similarity with Epicoccum sorghinum. Both isolates were pathogenic in detached leaf, and planta trials and the same fungi were reisolated from the symptomatic leaves, thereby fulfilling Koch’s postulate. Further, E. sorghinum VNOC62a significantly reduced the stalk sugar level (Brix) at seven days post-inoculation (dpi) while E. sorghinum VNR26 reduced sugar level at 14 dpi. This study successfully identified Epicoccum sorghinum as the cause of ringspot of sugarcane and revealed to significantly reduce stalk sugar yield, in vitro.
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Article title: First report of Colletotrichum fructicola, causing anthracnose of Hylocereus plants, in the Philippines
Authors: Edzel Evallo, John Darby Willy Taguiam, Jennelyn C. Bengoa, Rodel Maghirang, et al.
Publication title: Czech Mycology 73(1): 79–90 , April 2021
Abstract:
Cultivation of dragon fruit plants (Hylocereus spp.) in the Philippines has increased over the past years, and its diseases remain one of the major production challenges. In this study, a fungal pathogen, so far unknown in the country, was isolated from H. undatus from anthracnose-like lesion. Isolate MBDF0037C-1 was identified as Colletotrichum fructicola, based on combined morphological and molecular characterisation. This is the first record of C. fructicola causing anthracnose of dragon fruit plants in the Philippines. The isolate caused anthracnose to H. undatus and H. monacanthus, but not to H. megalanthus, in repeated in-vitro and in-vivo pathogenicity tests. Therefore, this study also highlights H. megalanthus as a potential source of resistance to anthracnose in dragon fruit breeding programmes.
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Article title: Dragon fruit calli development and fungal contamination as influenced by activated charcoal
Authors: Angela Cruz and Mark A. Balendres
Publication title: Journal of the Professional Association for Cactus Development 23:58-73, March 2021
Abstract:
Activated charcoal is often used in plant tissue culture systems to reduce phenolic oxidation and improve cell growth and development. This study investigated activated charcoal's effectonthesomatic embryogenesis of dragon fruit (Hylocereus species). Nine-month-old seed-derived dragon fruit stems wereplacedin basal Murashige and Skoog (MS) plates supplemented with 2,4-D (1.5 mg/L) and activated charcoal (1g/L).Cultures were incubated in 14h continuous light or under dark condition. MS medium without activated charcoal served as the control. Percent fungal contamination, degree of tissue browning, and callus growth(length, width, and total area) were assessed. A significant decrease in contamination was observed fourdays after inoculation (dai) in a medium containing activated charcoal regardless of the light condition used (p<0.05, T-test analysis). In contrast, no significant difference in fungal contamination between the two treatments was found eightdays after incubation (dai). Fungal contaminants’ identities were done using a combined morphocultural and molecular analyses. The fungal isolates showed thick and white to grayish mycelia without spore production seven dai in potato dextrose agar medium. DNA sequence analysis showed a high percent similarity(99-100%)of the isolates to two Diaporthespecies.Activated charcoal did not affect the length, width, and total area of the calli produced. However, asignificant decrease in tissue browning was recorded (p<0.05). Overall results demonstrated the applicability of activated charcoal in dragon fruit tissue culture to reduce in-vitrobrowning. Additionally, examining further the possible role of fungal contaminantsindragon fruitswould be valuable. A hedonic scale that can be used to assess tissue browning in dragon fruit is also described.
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Article title: A brief review of plant diseases caused by Cactus virus X
Authors: Edzel Evallo, ohn Darby Willy Taguiam, Mark A. Balendres
Publication title: Crop Protection 143(2):105566, February 2021
Abstract:
Plant pathogens, including viruses, have a known negative impact on plant growth and development. Here, plant diseases caused by cactus virus X (CVX) are reviewed. CVX infects a range of plant species within the Cactaceae family. When expressed, symptoms include chlorosis, necrosis, and morphological alterations, such as the twisting of arms, but at times plants can be asymptomatic. CVX may be transmitted through contaminated grafting or cutting tools and can also occur as mixed infections with other viruses, including zygocactus virus X and pitaya virus X. CVX may also play a role in altering the plant’s physiology. The virus can be detected by molecular assays, including polymerase chain reaction (PCR), and transmitted to indicator plants. Sanitation in both nurseries and fields is critical in controlling the spread of CVX. This paper highlights CVX as a potential production threat to some Cactaceae family members, particularly the now popular Hylocereus species or dragon fruits.
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Article title: Epicoccum species: ubiquitous plant pathogens and effective biological control agents
Authors: John Darby Willy Taguiam, Edzel Evallo, Mark A. Balendres
Publication title: European Journal of Plant Pathology 159(1):1-13, January 2021
Abstract:
Epicoccum species are ubiquitous ascomycetes. Several species are known to cause plant diseases and some species act as biological control agents against a range of plant pathogens. Accurate identification of Epicoccum species is paramount to a successful disease management program and successful development of biological control products. There are 18 Epicoccum species that are associated with diseases of 46 plant species. The diseases occur in 20 countries with leaf spot as the most commonly reported disease symptom. There are a further five Epicoccum species (E. nigrum, E. layuense, E. dendrobii, E, mezzettii and E. minitans) that have biological control activity against various plant pathogens. Of the five species, Epicoccum nigrum is the most promising and has been shown to reduce incidence and severity of a wide range of plant diseases. The use of bioactive metabolites (e.g. flavipin and epicolactone) from Epicoccum spp. may offer growers a cheap and safe alternative to conventional pesticides which are widely used to manage plant diseases. We review the current knowledge of Epicoccum species, both those species that are plant pathogens, and those species that are biological control agents for plant disease.
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Article title: Detection of Nigrospora sphaerica in the Philippines and the susceptibility of three Hylocereus species to reddish-brown spot disease
Authors: John Darby Willy Taguiam, Jennelyn C. Bengoa, Rodel Maghirang, Edzel Evallo, et al.
Publication title: Journal of the Professional Association for Cactus Development 22:49-61, October 2020
Abstract:
Diseases are among the major problems that negatively affect dragon fruit profitability worldwide. Diseases of dragon fruit in the Philippines are yet to be identified and reported. This study elucidates the causal agent of a disease infecting stems of dragon fruit grown in Los Baños, Laguna, Philippines. The fungus was isolated and identified as Nigrospora sp. based on morphological and cultural characteristics in potato dextrose agar medium. Using the DNA sequence of the internal transcribed spacer (ITS) gene region, isolate MBDF0016b was identified as Nigrospora sphaerica. The Philippines strain was closely related to the Malaysian strain, which also causes reddish-brown spot in dragon fruit (H. polyrhizus), and to other N. sphaerica isolates from other host-plant species. Nigrospora sphaerica MBDF0016b was pathogenic to H. megalanthus, H. undatus, and H. polyrhizus in detached stem and glasshouse assays. The same fungus was re-isolated from the inoculated stems and thus, establishing Koch’s postulate. This paper is the first confirmed scientific record of a dragon fruit disease in the Philippines and the first report of N. sphaerica as a dragon fruit pathogen causing reddish-brown spot disease in H. megalanthus.
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Article title: Premature defoliation in Zinnia sp. and mycoparasitism of Ampelomyces quisqualis against the powdery mildew pathogen Golovinomyces cichoracearum from the Philippines
Authors: Mark A. Balendres, John Darby Willy Taguiam, Maria Luz Josue Sison, Edzel Evallo
Publication title: Indian Phytopathology 74(1), September 2020
Abstract:
This paper reports for the first time a premature defoliation of the ornamental plant Zinnia sp. caused by Golovinomyces cichoracearum and the presence of Ampelomyces quisqualis in the Philippines.
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Article title: Resistance of roselle to bacterial wilt caused by Ralstonia pseudosolanacearum and R. solanacearum
Authors: Mark A. Balendres, Claudette Oraye, Rodel Maghirang, Fe M. Dela Cueva
Publication title: International Journal of Vegetable Science in press(2), May 2020
Abstract:
Roselle (Hibiscus sabdariffa L.), a tropical plant used as a vegetable, is detrimentally affected by bacterial wilt (BW). Limited information is available on resistance of roselle to BW. Roselle collections were sourced in the Philippines and assessed for reaction to BW caused by Ralstonia pseudosolanacerum and R. solanacearum in glasshouse and field experiments. No plants exhibited symptoms of wilting in glasshouse and field trials. High incidence and severe wilting were observed only on susceptible check tomato plants. Weather conditions conducive for BW development had no effect on lack of disease incidence. These roselle genotypes could be possibly used as an alternate to vegetable crops in BW-infested fields.
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Article title: Susceptibility of the three dragon fruit species to stem canker and growth inhibition of Neoscytalidium dimidiatum by chemicals
Authors: John Darby Willy Taguiam, Jennelyn C. Bengoa, Rodel Maghirang, Edzel Evallo, et al.
Publication title: Journal of Plant Pathology 102(2), April 2020
Abstract:
In the Philippines and other Southeast Asian countries, dragon fruits (Hylocereus species) have the potential to be a major “cash crop”. However, among the major problems currently faced by growers are yield- and quality-limiting diseases. In the Philippines, little is known of the dragon fruit diseases and measures that may be used in disease management. In this study, Neoscytalidium dimidiatum has been identified, by a combined morphological and molecular identification approach, as the cause of dragon fruit stem canker. The three dragon fruit species, H. monacanthus, H. undatus, and H. megalanthus, were susceptible to stem canker in both detached stems (3 laboratory trials) and rooted-stem cuttings (2 glasshouse trials) assays. The symptom was more severe in inoculated rooted-stem cuttings than in detached stems. Growth of N. dimidiatum was suppressed in potato dextrose agar (PDA) medium amended with B. subtilis (2 ml/400 mL, 100% fungal growth inhibition, fgi), mancozeb (2 g/400 mL, 100% fgi) and pyraclostrobin (1 mL/400 mL, 100% fgi) (chemical control). Citronella oil (1.25 uL/mL, up to 85.42% fgi) and isoprothiolane (2.25 mL/400 mL, up to 100% fgi) also showed promising results. However, the growth of N. dimidiatum was not inhibited in PDA medium amended with propamocarb (1.60 mL/400 mL). This is the first scientific report of N. dimidiatum as a pathogen of dragon fruit in the Philippines, the susceptibility of H. megalanthus to stem canker, and the growth inhibitory effect of B. subtilis and other chemicals that can be used alternatively or in rotation with synthetic chemicals.
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Article title: Pathogenicity of Epicoccum sorghinum towards dragon fruits (Hylocereus species) and in vitro evaluation of chemicals with antifungal activity
Authors: John Darby Willy Taguiam, Jennelyn C. Bengoa, Rodel Maghirang, Edzel Evallo, et al.
Publication title: Journal of Phytopathology 168(12), March 2020
Abstract:
Recent reports of plant diseases that result in yield reduction and increasing demand for dragon fruits raise concerns of fruit-supply shortage. Emerging plant diseases may play an important role in increasing yield losses and reducing the availability of stem-cuttings (source of planting materials). Understanding the etiology of current and new diseases of dragon fruit is important to address production issues and to formulate effective disease control measures. This study reports Epicoccum sorghinum as a potential emerging pathogen of dragon fruit. Epicoccum sorghinum MBDF0024a was isolated from dragon fruit stems (Hylocereus monacanthus) showing brown spot symptoms. DNA sequence of the internal transcribed spacer (ITS-rDNA), beta-tubulin, and actin gene regions of fungal isolate MBDF0024a had high similarities to E. sorghinum stains. Epicoccum sorghinum MBDF0024a was pathogenic to three cultivated dragon fruit species (Hylocereus undatus, H. monacanthus, and H. megalanthus) in repeated laboratory and glasshouse trials. Large brown lesions developed on 3-week old inoculated rooted stem cuttings three days post-inoculation (dpi). Yellowing of the lesion (advance part) started at five dpi, and at seven dpi, yellowing was observed in the stem. As there are no reported control measures for diseases caused by E. sorghinum, this study screened chemicals with antifungal properties. A biopesticide containing B. subtilis (2 ml/400 mL), and chemicals isoprothiolane (2.25 mL/400 mL), mancozeb (2 g/400 mL) and pyraclostrobin (1 mL/400 mL) (chemical control) completely inhibited the in vitro growth of E. sorghinum MBDF0024a. The results establish E. sorghinum as a new and emerging pathogen of dragon fruit that could be a major yield-limiting disease if left uncontrolled. The biopesticide can be considered a fairly safe option for disease management, but glasshouse and field studies are needed for validation.
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Article title: First report on the detection of fumonisin biosynthetic (FUM1) gene in Fusarium verticillioides and F. proliferatum associated with sugarcane diseases
Authors: Rachele De Torres, Fe M. Dela Cueva, Mark A. Balendres
Publication title: Indian Phytopathology Indian Phytopathology(3), March 2020
Abstract:
Several Fusarium verticillioides and F. proliferatum strains produce fumonisin, a mycotoxin that negatively affects animals and humans. These two Fusarium species also cause Pokkah boeng and are associated with red rot-like disease, two important sugarcane diseases. In this study, we determined the presence of FUM1, a gene that is required for fumonisin biosynthesis, in 21 isolates of plant pathogenic Fusarium species associated with sugarcane Pokkah boeng and the red rot-like disease. Out of the 21 Fusarium isolates, four F. proliferatum and one F. verticillioides isolates conferred the FUM1 gene as detected by repeated polymerase chain reaction assay. The result indicates that pathogenicity and fumonisin biosynthesis are likely two separate events as other isolates, which did not confer the FUM1 gene, still induced Pokkah boeng and red rot. This study reports, for the first time, the occurrence of fumonisin-producing F. verticillioides and F. proliferatum that cause Pokkah boeng and red rot-like disease in sugarcane.
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Article title: Confirmed record of Spongospora subterranea subsp. subterranea in potato cv. Igorota in Northern Philippines and the susceptibility of tomato cv. Yellow plum to Spongospora root infection
Authors: Mark A. Balendres and Teresita Masangcay
Publication title: Archives of Phytopathology and Plant Protection 53(1/2):37-47, January 2020
Abstract:
This study confirms the presence of Spongospora subterranea subsp. subterranea in the Northern Philippines, provides information on the morphology of the Philippine strain (PHLSs0003) of S. subterranea, and reports for the first time the susceptibility of potato cv. Igorota to powdery scab and tomato cv. Yellow plum to Spongospora root infection. Spongospora subterranea PHLSs0003 was recovered from scab-infected potato tubers cv. Igorota grown in Bauko, Mountain Province, Philippines. The sporosori characteristics of PHLSs0003 were similar to other sporosori collections worldwide and sporosori and resting spore sizes were within the range reported elsewhere. Plant bait assay revealed zoosporangia infection by S. subterranea in Tomato cv. Yellow plum seedlings. The findings from this study will help establish the relative importance of powdery scab and Spongospora root infection in potato and tomato production, respectively, in the country. The information presented here could also improve research on Spongospora disease monitoring and management in the country.
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Article title: Diseases of dragon fruit (Hylocereus species): Etiology and current management options
January 2020
Authors: Mark A. Balendres and Jennelyn C. Bengoa
Publication title: Crop Protection in press(No. 1), August 2019
Abstract:
More than seven billion people compete for food to survive. Agriculture has increased the production of staple crops, through plant breeding and biotechnology, in arable areas that are now becoming limited due to industrialization. With staple crops becoming a common diet and with people getting the same nutrients from these foods, wild, exotic and underutilized edible plants are being explored as supplements or alternatives. One potential plant is dragon fruit or pitahaya. This vine cactus plant is water-efficient, rich in betalains and antioxidants, has medicinal benefits and is a source of income to growers. However, dragon fruit production faces significant challenges. Among these, losses due to diseases play a significant role in fruit-yield reduction and profitability. This paper provides a comprehensive review of dragon fruit diseases, their associated pathogens, distribution, and their current management options. We conclude that anthracnose, fruit and stem rot, stem canker and the cactus viral disease are among the most frequently reported diseases of dragon fruit and actions are needed to address the growing problems associated with these diseases as effective, sustainable and practical management strategies are yet to be identified.
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Article title: Mycotoxigenic Fungi and Mycotoxins in Agricultural Crop Commodities in the Philippines: A Review
Authors: Mark A. Balendres, Petr Karlovsky, Christian Joseph Cumagun
Publication title: Foods 8(7):249, July 2019
Abstract:
The tropical, warm, and humid conditions that are favorable to the growth and development of mycotoxigenic fungi put the Philippines at a high risk of mycotoxin contamination. To date, seven mycotoxigenic Aspergillus species, four Fusarium species, and one Penicillium species have been isolated from various agricultural crop commodities in the country. There are five mycotoxin groups (aflatoxin, fumonisin, ochratoxin, nivalenol, and zearalenone) that have been detected in both the raw form and the by-products of major crops grown in the country. Since the first scientific report of aflatoxin contamination in the Philippines in 1972, new information has been generated on mycotoxins and mycotoxigenic fungi, but little has been known of other mycotoxins until the last two decades. Further, despite the increase in the understanding of mycotoxigenic fungi and mycotoxins in the country, very limited knowledge exists on practices and measures that control both the fungi and the toxins. This paper reviews the current literature on mycotoxigenic fungi and mycotoxins in the Philippines with emphasis on the last two decades and on other mycotoxins.
Full text link https://tinyurl.com/2hyb9bnk
Article title: Culture storage age and fungal re-isolation from host-tissue influence Colletotrichum spp. virulence to pepper fruits
Authors: Mark A. Balendres, Fe M. Dela Cueva, Rachele De Torres
Publication title: Journal of Phytopathology 167:510-515, June 2019
Abstract:
Using resistant cultivars is the most sustainable and practical approach to plant diseases. Plant germplasm and breeding lines are selected and assayed against, usually, the most aggressive or virulent strains of a pathogen (e.g. fungus) that causes the disease. However, prolonged storage of the pathogen in culture media could affect virulence that, consequently, also influence the outcome of the resistance assay. This study demonstrates that long-term storage (at least a year) of Colletotrichum truncatum and C. scovillei, causal agents of pepper anthracnose, in potato dextrose agar (PDA) medium decreased the aggressiveness and virulence of the fungus in host-pepper fruits. However, re-introduction of the pathogen to the host and isolation of the pathogen as the new inoculum, prior to inoculation assays, increased the virulence of the fungi. These findings suggest that re-inoculation and re-isolation of Colletotichum truncatum and C. scovillei that have been stored for at least 1 year in PDA medium are necessary when using fungal cultures in pathogenicity and plant resistance assays to achieve desirable, comparable and reliable results.
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Article title: Phylotypes of the potato bacterial wilt pathogen in the Philippines and their relationship to pathogen aggressiveness
Authors: Fe M. Dela Cueva, Mark A. Balendres, Valeriana P. Justo, Nandita Pathania
Publication title: Journal of Plant Pathology 101(1):23-29, February 2019
Abstract:
Three hundred seventy-two Ralstonia solanacearum isolates were collected from potato fields, in the Philippines, and characterized based on phylotypes, distribution and aggressiveness to host plants. Two major genetic group were identified: Phylotype I (Asiaticum), which were predominant in the southern region (Bukidnon), and Phylotype II (Americanum), found mainly in the northern region (Benguet). Phylotypes I and II were both pathogenic to tomato and potato host plants, but Phylotype I induced significantly earlier wilting symptoms to tomato and potato than Phylotype II (P = 0.03 – <0.01). No correlation was found between elevation and phylotype distribution (coefficient = 0.03–0.22). Based on the current taxonomic classification of R. solanacearum species complex, R. pseudosolanacearum and R. solanacearum cause potato bacterial wilt in the Philippines. Implications for quarantine regulations and breeding programs are discussed.
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Article title: Susceptibility of sugarcane to red rot caused by two Fusarium species and its impact on stalk sugar level
Authors: Fe M. Dela Cueva, Rachele De Torres, Alyssa de Castro, Jayvee Mendoza, et al.
Publication title: Journal of Plant Pathology, January 2019
Abstract:
Red rot of sugarcane is caused by Colletotrichum falcatum. A recent survey, however, indicates that other fungal species may be associated with red rot-infected sugarcane leaves. This study (i) investigates the cause of the red rot-like symptoms using a polyphasic approach, (ii) determines the pathogenicity of the fungi in sugarcane leaves and infection potential in leaves and stalks in detached-plant assays, and (iii) assesses their effect on the stalk sugar level. Based on combined morpho-cultural and molecular characterization, the associated fungi were identified as Fusarium sacchari and F. proliferatum. The two Fusarium species induced red rot in leaves and stalk, as did the C. falcatum control isolate. Stalks infected with the two Fusarium species had reduced sugar level after 14 days, compared to the healthy stalk checks. To our knowledge, this is the first record of Fusarium species associated with red rot in sugarcane. These results suggest that the causal agent of red rot in the field is likely to be considered when developing or implementing disease control measures. Further, sugarcane breeding programs for red rot resistance would be likely aimed at all known causal pathogens.
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Article title: Efficacy of Citronella Essential Oil for the Management of Chilli Anthracnose
Authors: Fe M. Dela Cueva and Mark A. Balendres
Publication title: European Journal of Plant Pathology 152(2):461-468, October 2018
Abstract:
The potential of citronella essential oil for the management of chilli anthracnose caused by Colletotrichum acutatum was investigated. In in vitro tests citronella essential oil inhibited mycelial growth at 0.25, 1.25 and 2.5 µL citronella/mL water, reduced conidial germination and inhibited germ tube elongation at 1.25 µL/mL. Citronella essential oil applied as a protective or curative treatment to chilli cv. Django fruits reduced anthracnose infection. Efficacy of citronella essential oil was substantially effective to chemical fungicides and relatively superior to a biofungicide in both protective and curative tests. However, citronella essential oil at 2.5 µL/mL was phytotoxic to chilli fruits. Therefore, the most effective rate of citronella essential oil was at 1.5 µL/mL, inhibition of pathogen growth, reduction of anthracnose symptoms and no observable phytotoxic response on chilli fruits. Citronella essential oil may be a viable alternative to chemical fungicides for the management of chilli anthracnose.
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Article title: A new Colletotrichum species causing anthracnose of chilli in the Philippines and its pathogenicity to chilli cultivar Django
Authors: Mark A. Balendres, Jayvee Mendoza, Fe M. Dela Cueva
Publication title: Crop Protection 112:264-268, June 2018
Abstract:
Chilli fruits with symptoms of anthracnose were collected from Batangas, Philippines, to determine the etiology of the disease. The fungus was initially identified as Colletotrichum acutatum sensu lato based on its morpho-cultural characteristics and molecular identity by using primer sets CaInt2/ITS4. Further analyses of three important gene regions, namely internal transcribed spacer (ITS), partial β-tubulin (BTUB), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH), used in discerning species within the C. acutatum species complex, revealed that the gene sequence of Philippine isolate 0013 had high similarity to known authentic gene sequence of C. scovillei. The fungus induced the anthracnose symptoms on chilli cv. Django fruits in both wounded and unwounded conditions. This is the first record of C. scovillei as chilli anthracnose pathogen in the Philippines and of the chilli cultivar “Django” as highly susceptible host of C. scovillei 0013.
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Article title: Zoosporangial root infection of tomato by Spongospora subterranea in hydroponic and glasshouse culture results in diminished plant growth
Authors: Mark A. Balendres, Jonathan Amponsah, Robert S. Tegg, Calum Wilson
Publication title: Journal of Phytopathology 166(6):412-419, June 2018
Abstract:
Tomato plants are highly susceptible to root infection by Spongospora subterranea and are commonly used as bioassay hosts. The impact of root infection with S. subterranea on plant productivity and yield has been debated. Recent experiments with potato, themajor economic host of S. subterranea, have indicated significantly reduced plant growth and potato yield following heavy infection. However there have been very few similar studies that have examined the possible impacts of S. subterranea infection on tomato plant growth. Three tomato cultivars, ‘Grape’, ‘Roma’ and ‘Truss’, were challenged with S. subterranea inoculum in hydroponic culture. Moderate to severe zoosporangial infections were observed with minor but statistical significant differences in susceptibility among the three tomato cultivars. Zoosporangial root infection in absence of root gall formation resulted in significantly diminished shoot lengths and plant fresh weights in pathogen challenge tests conducted both in hydroponic culture and glasshouse grown plants in potting mix. Root lengths were reduced but the differences were statistically significant in a single trial only. The findings from this study demonstrate that, as with potato, root infection by S. subterranea can result in reduced tomato plant growth and that root gall production associated with root infection was not necessary for this retardation of growth response. This further suggests that possible yield impacts in other crop species that are hosts for S. subterranea root infection is worthy of examination.
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Article title: Germinate to Exterminate: Chemical stimulation of Spongospora subterranea resting spore germination and its potential to diminish soil inoculum
Authors: Mark A. Balendres, Robert S. Tegg, Calum Wilson, T. J. Clark
Publication title: Plant Pathology 67(4):902-908, May 2018
Abstract:
Hoagland's solution (HS), a defined nutrient supplement for plants, has been previously reported to stimulate zoospore release from resting spores of the potato pathogen Spongospora subterranea f. sp. subterranea. This study obtained direct empirical evidence for an increase in zoospore release with HS treatment, and identified Fe-EDTA as the stimulant component of HS. Stimulation of resting spores by HS and Fe-EDTA resulted in greater and earlier zoospore release compared to a distilled water control, and in the presence of a susceptible tomato host plant resulted in enhanced root infection. Given the labile nature of S. subterranea zoospores, it was postulated that stimulation of premature release of zoospores from the dormant resting spores in absence of susceptible hosts could reduce soil inoculum levels. In two glasshouse trials in absence of host plants, both Fe-EDTA and HS soil treatments reduced S. subterranea soil inoculum levels, providing proof of concept for the ‘germinate to exterminate’ approach to inoculum management. This article is protected by copyright.
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Article title: Resting Spore Dormancy and Infectivity Characteristics of the Potato Powdery Scab Pathogen Spongospora subterranea
Authors: Mark A. Balendres, Calum Wilson, Robert S. Tegg
Publication title: Journal of Phytopathology 165(5):323–330, May 2017
Abstract:
The soil-borne potato pathogen Spongospora subterranea persists in soil as sporosori, which are aggregates of resting spores. Resting spores may germinate in the presence of plant or environmental stimuli, but direct evidence for resting spore dormancy is limited. A soilless tomato bait plant bioassay and microscopic examination were used to examine features of S. subterranea resting spore dormancy and infectivity. Dried sporosori inocula prepared from tuber lesions and root galls were infective after both short- and long-term storage (1 week to 5 years for tuber lesions and 1 week to 1 year for root galls) with both young and mature root galls inocula showing infectivity. This demonstrated that a proportion of all S. subterranea resting spores regardless of maturity exhibit characteristics of stimuli-responsive dormancy, germinating under the stimulatory conditions of the bait host plant bioassay. However, evidence for constitutive dormancy within the resting spore population was also provided as incubation of sporosorus inoculum in a germination-stimulating environment did not fully exhaust germination potential even after 2.4 years. We conclude that S. subterranea sporosori contain both exogenous (stimuli-responsive) and constitutively dormant resting spores, which enables successful host infection by germination in response to plant stimuli and long-term persistence in the soil.
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Article title: Potato Root Exudation and Release of Spongospora subterranea Resting Spore Germination Stimulants are Affected by Plant and Environmental Conditions
Authors: Mark A. Balendres, David Scott Nichols, Robert S. Tegg, Calum Wilson
Publication title: Journal of Phytopathology 165(1):64-72, January 2017
Abstract:
Variation in plant and environmental conditions were studied to determine the effect thereof on the exudation of low-molecular-weight organic compounds by potato roots. The results of the phytochemical analyses showed that among the conditions investigated, root vigour, potato cultivar, nutrients in incubation solution and temperature influenced the number and the type of primary metabolites released. Moreover, these conditions influenced our detection of compounds known to stimulate germination of resting spores of the pathogen Spongospora subterranea, causal agent of powdery scab and root diseases of potato. We conclude that changes in plant and environmental conditions can affect the release of specific compounds that stimulate germination of S. subterranea resting spores. The impact of the factors affecting potato root exudation on subsequent disease development is discussed.
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Article title: Grading Seed Potato Lots to Remove Tubers with Powdery Scab Damage may not Eliminate the Pathogen Threat
Authors: Robert S. Tegg, Tamilarasan Thangavel, Mark A. Balendres, Calum Wilson
Publication title: American Journal of Potato Research 93(3), February 2016
Abstract:
Grading seed tubers is a common practice to remove visually diseased tubers and meet certification standards. This study sought to quantify Spongospora subterranea inocula, the causal agent of powdery scab in eight commercial seedlots prior to and following grading. Pathogen levels generally decreased although the extent of reduction was dependant on the mean disease level within each seedlot, prior to grading. Where mean seedlot disease incidence was high (20 to 40 %) grading was not effective, reducing pathogen levels by only 2-fold (P > 0.05) on the visually disease-free seed following grading which remained a high risk for disease in progeny plants. However, where mean seedlot disease incidence was low (5 to 7 %) grading substantially reduced S. subterranea inoculum (12–23-fold, P < 0.05) on the visually disease-free seed to low risk levels. In further pot and field trials, planting visually disease-free tubers graded from contaminated lines gave variable disease levels in progeny plants, although under conducive conditions resulted in root and tuber disease no different to planting diseased seed.
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Article title: Key events in pathogenesis of spongospora diseases in potato: a review
Authors: Mark A. Balendres, Robert S. Tegg, Calum Wilson
Publication title: Australasian Plant Pathology 45(3), February 2016
Abstract:
Spongospora subterranea (Wallr.) Lagerh. is the causative agent of powdery scab and root diseases of potato. Diseases induced by S. subterranea causes substantial economic losses to the global potato industry. The process of disease development in the S. subterranea-potato pathosystem have long been studied, but critical events prior to infection and disease development remain poorly understood because the subject have received relatively little attention. Nonetheless, new knowledge of host-pathogen-environment interactions have been gained in recent years. This paper provides the current knowledge of the key events which leads to the development of potato diseases caused by S. subterranea and highlights future research to address identified knowledge gaps. This will further our understanding of the interactions between S. subterranea and its potato host and contribute to improved disease control measures.
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Papers Presented:
Article title: Microscopic examination of Ralstonia pseudosolanacearum and R. solanacearum colonies and the response of tomato breeding lines to bacterial wilt caused by the two species
Authors: Mark A. Balendres, Villamor Ladia Jr., Fe M. Dela Cueva
Conference title: Australasian Plant pathology Society Conference, November 2019
Article title: Current research on bacterial wilt in the Philippines: pathogen biology and host-plant resistance screening
Authors: Mark A. Balendres, Fe M. Dela Cueva, Rodel Maghirang, Claudette Oraye
Conference title: 51st PMCP Anniversary and Annual Scientific Conference, July 2019
Abstract:
Bacterial wilt is one of the world’s most destructive bacterial diseases. In the Philippines, bacterial wilt of vegetables is caused by Ralstonia pseudosolanacaerum and R. solanacearum. However, little is known of the characteristics of the former. This paper presents current research on the bacterial wilt pathogens R. pseudosolanacaerum and R. solanacearum with emphasis on their morphology and pathogenicity in tomato, roselle and eggplant. Morphology of representative isolates from two genomic species were distinct between species. Nevertheless, variations in colony morphology did not influence their pathogenicity to tomato cv. Yellow Plum. In replicated glasshouse trials, several tomato breeding lines were found to tolerate the presence of the bacteria and were comparable to the response of the relatively resistant tomato line Hawaii 7996. The same result was observed in eggplant breeding lines. Interestingly, no roselle plants wilted during in two trials. The susceptible check plants (tomato cv. Yelllow) plum wilted in both R. pseudosolanacaerum and R. solanacearum inoculated pots. The non-inoculated tomato, eggplant and roselle plants also did not wilt.
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Article title: Pepper anthracnose research in the Philippines: status and prospects
Authors: Mark A. Balendres
Conference title: 51st PMCP Anniversary and Annual Scientific Conference, July 2019
Abstract:
Anthracnose is a destructive fungal disease of pepper and is caused by several Colletotrichum species. This paper presents findings from the Philippine pepper research program. Three Colletotrichum species complex, C. gloeosporioides sensu lato, C. truncatum sensu lato and C. acutatum sensu lato, were identified by morphology and PCR analysis using complex-species-specific markers/primers. These isolates were collected from the three main island regions (Luzon, Visayas, and Mindanao). In another study, long-term storage of Colletotrichum spp. cultures in potato dextrose agar (PDA) medium decreases aggressiveness and virulence of the fungus in host-pepper fruits. However, re-inoculation to and re-isolation from the host of the pathogen increases the virulence of the fungus. An actinomycete isolate was also found to suppress mycelial growth of the Colletotrichum species to up to 75% in dual culture test. Sequences of the 16S rDNA of the actinomycete indicate that the isolate belongs to Streptomyces sp. This actinomycete was not pathogenic to pepper fruits and thus, has potential as a biological control agent against pepper anthracnose. However, further efficacy tests would be needed. The three Colletotrichum species complex also responded variably to elevated and fluctuated temperature regimes, to synthetic and bio-fungicides, and to different essential oils. The research findings presented in this paper provide new and improved knowledge of the pepper-Colletotrichum pathosystem in the country that is important when developing a sustainable integrated management program for pepper anthracnose.
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Article title: Current state of pepper anthracnose in the Philippines
Authors: Mark A. Balendres, Jayvee Mendoza, Catherine Hazel Macorol Aguilar, Catherine Hazel Macorol Aguilar
Conference title: 1st State of the World's Fungi Symposium, September 2018
Abstract:
Anthracnose is one of the most devastating diseases of horticultural crops. It is also a major problem of pepper growers that contributes to yield loss. The disease is caused by several species of Colletotrichum, of which some can be morphologically similar but phylogenetically different, broadly grouped into species complex. Different species may vary in pathogenic lifestyle and they react variably to chemical control. In the Philippines, severe infection of anthracnose in pepper fields have been reported. Studies on the etiology of chilli anthracnose diseases in the country are limited. Understanding of the causal pathogen of pepper anthracnose is needed to develop and utilize appropriate disease management strategies. We collected pepper fruits in the field in select regions. We then performed a polyphasic approach employing a combination of morpho-cultural, pathogenicity and molecular characterization techniques to identify the pathogens associated with pepper anthracnose. We also determined the response of these species to various chemicals which have varying mode of actions against certain fungi. Finally, we assessed pepper accessions and breeding lines against the anthracnose pathogens. Here, we identified Colletotrichum species associated with pepper anthracnose in the Philippines, provided baseline information on the chemical sensitivity of the Philippine isolates to various chemicals, and identified potential sources of resistance to pepper anthracnose. The information provided a better understanding of the pepper-Colletotrichum pathosystem in the country.
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Article title: Volunteer and cover crops as a reservoir for building soilborne pathogen levels
Authors: Robert S. Tegg, Calum Wilson, Mark A. Balendres
Conference title: 10th Australasian Soilborne Disease Symposium, September 2018
Abstract:
Many soilborne pathogens persist as recalcitrant structures that can survive in a dormant, resting form within the soil for time periods greater than 10 years. Part of managing soilborne diseases is the usage of rotation to negate pathogen survival. However, the presence of both weeds, cover crops and crop volunteers within subsequent crops that can host and multiply some of these key pathogens, can often result in pathogen and disease levels increasing. In the case of the soil-borne plasmodiophorid pathogen, Spongospora subterranea, which causes root disease and powdery scab of potato, it is often able to survive in potato volunteers and nightshade weeds that frequently follow a potato crop. Likewise, the related pathogen, Plasmodiophora brassicae, which causes clubroot of brassica is able to survive in a wide range of weed and crop species. In this paper, we present field results confirming the role of volunteer and cover crops in increasing pathogen levels. We discuss the importance of weed and volunteer crop removal as an important component in managing disease.
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Article title: Understanding the role of root exudation for pathogen germination and attraction, and their application for disease control
Authors: Calum Wilson, Mark A. Balendres, Jonathan Amponsah, David Scott Nichols, et al.
Conference title: ICPP Boston 2018, July 2018
Abstract:
Plant roots release a substantial quantity of primary metabolites (root exudates) into the rhizosphere, the majority of which are low molecular weight organic compounds. These exudates play important roles in interactions between the plant, and other soil biota including soil-borne plant pathogens. Exudate compounds may benefit pathogens, promoting their germination, growth, survival, pathogenesis and reproduction, or may be detrimental inhibiting growth or disrupting motility. With a combined in vitro bioassay, light microscopy and targeted metabolomics approach using HILIC UPLC-MS analysis, we demonstrate the importance of potato root exudates for stimulating germination of resting spores of the pathogen Spongospora subterranea f. sp. subterranea. Furthermore, we show these compounds provide a chemotactic signal to attract released zoospores to the host roots enabling efficient infection. We also demonstrate application of this knowledge for novel management of soil inoculum through a ‘germinate to exterminate’ approach, and propose novel disease management approaches through disruption of pathogen chemical signalling.
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Article title: Root attachment of Spongospora subterranea in susceptible and resistant potato genotypes
Authors: Mark A. Balendres, Robert S. Tegg, Annabel J. Wilson, Calum Wilson
Conference title: 50th PMCP Anniversary and Annual Scientific Conference, May 2018
Abstract:
Powdery scab, root galling and root zoosporangial infection are important potato diseases caused by Spongospora subterranea. Disease develops when S. subterranea zoospores successfully penetrate the host below ground tissues and is exacerbated by the polycyclic nature of infection. Using resistant potato cultivars is the best approach to control Spongospora diseases. No potato cultivar is immune to Spongospora infection, but there is substantial variation in cultivar susceptibility to disease. However, the mechanisms of resistance to Spongospora diseases have not been elucidated. Here, we hypothesize that inhibition or reduction of zoospore root attachment, critical for initiating and maintaining disease epidemics, is associated with the resistance to Spongospora root and tuber diseases. In controlled in vitro bio-assays, we quantified the population of zoospores that encysted on roots of potato cultivars that differ in resistance to powdery scab and root diseases. Correlation analyses were then used to determine if a relationship between zoospore attachment and tuber, and root, disease resistance ranking existed. The number of zoospores that encysted on potato roots significantly decreased as resistance ranking of the cultivar to powdery scab, root zoosporangia and root galling increased (rs = 0.552 to 0.782, P<0.05). The results strongly suggest that zoospore attachment is associated with potato cultivars resistance to Spongospora diseases. Our study also highlights the critical nature of zoospore attachment on roots in developing epidemic and final expression of disease. Furthermore, the method used in this study could be useful in determining cultivar resistance to Spongospora diseases without the need for pot or field challenge assays to assess symptom severity, thus expediting the selection process and avoiding the variable influence of soil environment.
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Article title: Potato root exudates contain stimulants of resting spore germination of Spongospora subterranea
Authors: Mark A. Balendres, David Scott Nichols, Robert S. Tegg, Calum Wilson
Conference title: 9th Australasian Soilborne Diseases Symposium, November 2016
Abstract:
Root exudates play important roles in the soil chemical ecology influencing rhizosphere microbiota. It was suspected that root exudates from host and non-host plants could stimulate resting spore germination of Spongospora subterranea, the powdery scab pathogen of potato. Empirical evidence for stimulation has not been available, and the identity of specific stimulatory compounds was unknown. This study showed that potato root exudates stimulate S. subterranea resting spore germination. Treating pathogen sporosori with exudates and specific individual constituent components (certain amino acids, sugars, organic acids and other low molecular weight organic compounds) resulted in release or greater numbers of zoospores at an earlier time than water experimental controls. Given that several identified stimulatory compounds are commonly found in exudates of diverse plant species, we indirectly support observations of non-host stimulation of resting spore germination. This study has provided new knowledge of S. subterranea resting spore biology and chemical ecology that may be useful in formulating new disease management strategies.
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Article title: Potato root exudates stimulate zoospore release of Spongspora subterannea
Authors: Mark A. Balendres, David Scott Nichols, Robert S. Tegg, Calum Wilson
Conference title: 8th Australasian Soilborne Diseases Symposium, November 2014
Article title: Somaclonal selection for enhanced resistance to Spongospora subterranea tuber and root infection in potato and studies on zoospore dormancy, release and chemotaxis
Authors: Mark A. Balendres, Robert S. Tegg, Calum Wilson
Conference title: 2nd International Powdery Scab Workshop, July 2014
Article title: Endogenous Banana streak virus species in the Philippines
Authors: Fe M. Dela Cueva, Eric Dinglasan, Mark A. Balendres
Conference title: 19th Australasian Plant Pathology Conference, January 2013
Article title: Mechanism of Resistance to Banana Bunchy Top Virus
Authors: Fe M. Dela Cueva, Eric Dinglasan, Mark A. Balendres, Cecilia Pascual
Conference title: International Banana Symposium, November 2012
Abstract:
One of the practical yet effective measures against banana bunchy top disease (BBTD) is the use of varieties that confer resistance against the Banana bunchy top virus (BBTV). Some banana cultivars with resistance to the virus have been identified in previous studies. The mechanism of resistance against the virus needs to be elucidated, hence this study. This paper reports the mechanism of resistance of four (4) banana cultivars representing different genomes (AAB, BBB and AA) based on host preference of a viruliferous aphid vector (Pentalonia negronervosa) as well as virus replication, transport and distribution. Among the four, Pisang Lingi (unknown genome) is the most preferred cultivar followed by Latundan (AAB) and Lakatan (AA) with mean aphid populations of 120, 148.9, and 81.2, respectively. The least preferred cultivar is Cardaba (BBB) with 54.7 mean aphid population. An increase in aphid colony count was noted from 2 to 3 weeks after inoculation (WAI) and decreases at 4 WAI. Typical symptoms of marginal chlorosis and rosetting were observed at 4 to 7 WAI and progresses into bunchy top until 3 months after inoculation. Highest incidence was observed on Lakatan (70%) and the lowest was noted on Pisang Lingi (10%)Results showed that aphid preference varied depending on banana cultivar. Cardaba (BBB) gave the lowest aphid population (54.7) and lower BBTV incidence (30%) indicating that it was not preferred by the aphid as host and resistance to the virus can be attributed to non-preference of aphid for colonization. In contrast, Pisang Lingi had the highest number of aphids and the lowest BBTV incidence. Although most preferred by aphids, there could be host derived mechanism that limits virus multiplication in this cultivar. The virus transport and distribution are being assessed using PCR-based method.
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Article title: Species of Banana Streak Virus (BSV) in the Philippines and Its Activation by Tissue Culture Processes and Gamma Irradiation
Authors: Fe M. Dela Cueva, Mark A. Balendres, Olivia Damasco, Jyko Consignado
Conference title: International Banana Symposium, November 2012
Abstract:
Banana streak virus (BSV) causes banana streak disease (BSD) in many tropical and subtropical banana-producing countries. Interests to study BSV have increased in the past year because of the virus’ behaviour as an integrant (endogenous and non-pathogenic) in the Musa genome that when activated becomes pathogenic (episomal). The activation was attributed to many host and environmental stress factors including, but not limited to, the association of A and B genome groupings, tissue culture processes and gamma irradiation. In this study, national and germplasm collections of Musa spp. were indexed using standard and Immunocapture PCR to detect BSV, identify species and determine its relationship with various genome groups. Tissue culture (TC) processes and gamma irradiation (GR) studies were also initiated to determine their effects on the frequency and distribution of both endogenous and episomal BSVs. Results showed the existence of three known BSV species in the collection namely, Mysore, Goldfinger and Imove that appear as integrant but were not detected as episomal BSVs. These species were strongly associated to cultivars with B and AB genomes. Although endogenous sequences were detected, no episomal BSVs were detected in tissue cultured and gamma irradiated materials. These suggest that the first proliferation stage of tissue culture and different gamma ray dosages (as low as 5 and as high as 50 Gy) bear no effect on the activation of the virus to its pathogenic state.
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