March 19-22, 2011 - San Juan, Puerto Rico
(Joint with the Southeastern Branch of the Entomological Society of America)
Sorghum as a barrier and intercrop option against non-persistently transmitted viruses
V. Acevedo-Torres (1), C. Estévez de Jensen (1), L. Wessel-Beaver (1), J. C. Rodrigues (1)
(1) Crops and Environmental Sciences, University of Puerto Rico, Mayagüez
Watermelon, an important cucurbit crop in Puerto Rico, is susceptible to viral infections. Aphids and whiteflies vector different diseases in watermelon. To study the influence of Sorghum bicolor (L.) Moench as a border and intercrop in watermelon plots two experiments were planted in November 2009 and May 2010. Plots were sown in a randomized complete block design replicated four times. Populations of whitefly (Bemisia tabaci) were greater in 2009 when compared with 2010, and the treatment with sorghum intercrop resulted in the lowest number of adults of whitefly. During the third week of the crop cycle in 2010 significant differences in the whitefly populations were detected with a greater whitefly population in the control. The aphid (Aphis gossypii) population was not influenced by sorghum as a border or an intercrop. Presence of watermelon vine decline associated with a Potyvirus, Papaya ringspot virus and Zuchinni yellow mosaic virus were assessed using DAS-ELISA tests during five weeks of the growth cycle. Results indicate these viruses were less frequent in 2010 than 2009. In the 2009 and 2010 experiments the border treatment yielded 26,580 kg/ha and 27,188 kg/ha, respectively. Sorghum intercrop and the control had an average of 56,943 kg/ha and 57,766 kg/ha in 2009, respectively, while in 2010 yields were 63,033 kg/ha with intercrop sorghum and 119,281 kg/ha in the control, respectively. These experiments demonstrated that used of sorghum did not contribute to the management of these viral diseases in watermelon. However use of sorghum as a barrier affected insect populations.
Characterization of endophytic bacteria isolated from healthy and diseased coffee trees showing witches broom and other symptoms under field conditions in Puerto Rico
C. Bolaños-C (1), M. Zapata (1)
(1) Department of Crops and Agroenvironmental Sciences, University of Puerto Rico, Mayagüez campus, Mayagüez, Puerto Rico
Coffee (Coffea arabica L.) an economic and socially important crop, generates revenues of $35 million for Puerto Rico in 2009. Main production problems are of biotic origin. Among bacterial diseases affecting this crop, coffee leaf scorch (CLS), caused by the bacterium Xylella fastidiosa (Xf) Wells et al., is significantly important in many countries due to economic losses. In this study, we tried to characterize the bacterial species related to the vascular system of symptomatic and symptomless plants from coffee farms of the municipalities: Las Marías (18°13’14’’; W66°01’38’’), Adjuntas (18°09’30’’W66°45’27’’), Yauco (N18°09’57’’; W66°49’36’’) and Jayuya (N18°09’35’’; W66°38’45’’). In February, August, November and December of 2010, samples were collected from coffee trees showing marginal and apical leaf scorch, yellowing of new leaves, reduction of internode length, and abnormal production of new flushes (witches broom). Isolations on PW (periwinkle) medium were made from branches and leaf veins, to identify endophytic bacteria associated with the symptoms. Strains were differentiated by colony morphology, Gram stain, biochemical tests (oxidase, catalase), growth in TSA (tryptic soy agar), incubation period and in vitro pathogenicity tests. DAS-ELISA for Xf (AGDIA, Elkhart, IN) was performed for all gram negative bacteria. Cluster analysis using the nearest neighbor method indicated that twice as many Gram negative bacteria of fastidious growth (PW+, TSA–) were found in diseased versus healthy trees.
Identification of powdery mildew in ornamentals and herbs in Puerto Rico
L. L. BONILLA AVILÉS (1), C. Estévez de Jensen (1), L. I. Rivera Vargas (1), B. Román Avilés (2)
(1) Department of Crops and Agroenvironmental Sciences, Mayagüez Campus, Mayagüez, Puerto Rico; (2) Department of Biology, University of Puerto Rico, Cayey
Powdery mildew (Erysiphales) can cause economic losses on a wide range of ornamental plants. A survey was conducted in 2010/2011 in Puerto Rico. Symptomatic plants were collected and symptoms included spots of white to grayish mycelia on the leaves. The identification was carried out using light and scanning electron microscopy (SEM) and morphological characteristics such as conidial germination, germ tube morphology, fibrosin bodies, appressorial shape and the patterns on the outside of the conidia wall. To confirm fungal identity the internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and sequenced. In Poinsettia (Euphorbia pulcherrima) Erysiphe australiana was identified based on the lobulate appresorial type, the terminal germination tube and using SEM where the end wall patterns are fibrillar and the turgid conidia surface is fluted. Neoerysiphe sp. was found in Crape myrtle (Lagerstroemia indica) using SEM where a lineal pattern of the conidia surface and smooth of the lateral sides were observed. Results indicated that E. pisi infected Eryngium foetidium and Euphorbia heterophylla and sequenced-based identification showed a 93% and 97% identity respectively with reference ITS sequences of GenBank. In Oxalis barrelieri a 97% of identity was found with E. pisi. In Lablab purpureus, E. polygoni was identify and sequencing analyses indicated a 93% of identity. In Gerbera jamesonii, Podosphaera fusca with a 99% of identity after sequence analyses. The weeds E. heterophylla and O. barrelieri were not the source of inoculum of the powdery mildew found in Poinsettia and Crape myrtle respectively.
Weeds and insects with potential as hosts and vectors of disease agents prevalent on shaded coffee plantations in two localities of Puerto Rico
A. G. Cruz-Gonzalez (1), M. Zapata (1), B. V. Brodbeck (2)
(1) Department of Crops and Agroenvironmental Sciences, University of Puerto Rico, Mayagüez campus, Mayagüez, Puerto Rico; (2) NFREC, Quincy, University of Florida
Coffee (Coffea arabica L.) is the agricultural crop of mayor social and ecological importance of the mountainous area of Puerto Rico. Coffee production is concentrated in the central west of the island of P.R., which is composed of 21 municipalities. Weeds and their interaction with insects are potential problems in coffee plantations. Weeds can limit production and crop yield if not controlled. Insects represent another problem by direct damage or as vectors of diseases. In this study, a survey of weeds and insects found in coffee plantations under shade and sun was conducted to quantify and identify the species. Surveys were carried out during October and November 2010 in Adjuntas and Yauco, P.R. In Adjuntas, there were a total of 3,126 weeds counted under shade within the trees of Carbonero (Pithecellobium carbonarum), and Guaba (Inga vera) and under sun (control). In Yauco a total of 1,893 weeds under shade with Guaba (Inga vera) and under sun. The most abundant weeds of 5,019 counted were: Brachiaaria purpurascens, Fimbristylis miliaceae, Commelina diffusa, Impatiens walleriana, Dieffenbachia seguine and Spathodea campanulata. Over two hundreds insects were found associated with the weeds such as Commelina diffusa, Impatiens walleriana, Brachiaria purpurascens, Paspalum fimbriatum, Dieffenbachia seguine, Eleusine indica L. and Echinochloa colona. Among the insects of mayor importance in coffee are the Hemiptera, family Cicadellidae. The most abundant insects found in the weeds were Hortensia similis, Caribovia coffeacola, both are xylem feeders and potencial vectors of Xylella fastidiosa and Bothriocera undata and Petrusa marginata both phloem feeders.
Disease incidence in Phaseolus vulgaris in the regions of Chianga, Cuanza Sul and Malange, Angola
C. Estévez de Jensen (1), T. Porch (2), J. Beaver (1), A. Chicapa Dovala (3), L. Baptista (3)
(1) University of Puerto Rico, Crops and Environmental Sciences, Mayagüez, PR; (2) USDA-ARS Tropical Agriculture Research Station, Mayagüez, PR; (3) Instituto de Investigacão Agronómica, Angola
In Angola, 70% of the common beans (Phaseolus vulgaris L.) are grown in the Northern and Central Provinces of Bie, Huambo, Huila, Kwanza Sul, Malange, and Uige. Approximately 240,000 ha of common beans are cultivated by subsistence farmers with average yields of 220 kg/ha (NEPAD-CAADP, 2005). A survey of diseases in nurseries, planted as part of a Pulse CRSP (USAID) project, was conducted during two visits to Huambo, Cela and Malange on the temperate Central Plateau and Northern Provinces, respectively, during 2009 and 2010. Disease identification was conducted at the Instituto de Investigacão Agronómica (IIA), Plant Pathology laboratory in Huambo. Symptom recognition, humid chamber, serology and tissue isolations on media were conducted. Angular leaf spot (ALS) caused by Phaeoisariopsis griseola was prevalent on the local cultivar Olho de Perdiz and incidence was moderate in the nurseries. Anthracnose (Colletotrichum lidemuthianum), rust (Uromyces appendiculatus) and Ascochyta leaf spot (Phoma exigua) were identified with low incidence in the nurseries and in growers’ fields. Root rot, caused by Rhizoctonia solani, was predominant in Malange in part due to excessive soil moisture. Pythium myriotylum, producing damping-off, was identified through DNA sequence analysis, and is the first report of this pathogen in common bean in Angola. There was also high incidence of common bacterial leaf blight (Xanthomonas axonopodis pv. phaseoli) in a seed multiplication field. Bean Common Mosaic Necrotic Virus symptoms were observed as vein and stem necrosis in the Huambo nursery. Developing germplasm with resistance to these major diseases affecting beans in Angola is in process.
Fungi associated with roots and crowns of diseased wheat samples in Texas
R. D. FRENCH-MONAR (1), L. M. Serrato-Diaz (1), L. I. Rivera-Vargas (2)
(1) Texas AgriLife Extension Service-Texas A&M System, Amarillo, TX; (2) University of Puerto Rico-Mayaguez Campus, Mayaguez, Puerto Rico
In 2010, 84 diseased samples of wheat that were brought in for diagnosis to the plant diagnostic laboratory in Amarillo tested negative for viruses, showed no foliar leaf spots, or stem lesions. None were moribund or dead. Plants were diseased with symptoms such as chlorosis, root discoloration, and some crown discoloration. Roots and crowns were plated onto Potato Dextrose Agar amended with ampicillin and rifampicin for isolation of general fungi and plated onto Cornmeal Agar amended with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene for isolation of Pythium spp. A total of 69 samples had Fusarium spp. isolated from crown or root tissue, 28 had Pythium spp., 18 had Rhizopus spp., 13 had Bipolaris spp., 10 had Alternaria spp., seven had Mucor spp., three had Nigrospora spp. or Phoma spp., two had Epicoccum spp. or Septoria spp., and one sample had Colletotrichum sp., Leptosphaerulina sp., Pythomyces sp., or Sordaria sp. Thirteen fungal isolates have yet to be identified. Fungi in the genera Alternaria, Bipolaris, Fusarium, Nigrospora, and Rhizopus, have the potential to cause black point, a disease that affects wheat seeds or kernels. Fungi in the genera Alternaria and Epicoccum have the potential to cause sooty molds; Fusarium spp. have the potential to cause several diseases such as foot rot, crown rot, head blight, seedling blight, and seed scab; Pythium spp. can cause root rot and seedling blight; and Bipolaris sp. could cause seedling blight, common root rot, leaf spots or spot blotch. The potential exists for several of these fungi, alone or in combination, to be undermining growth and health of wheat plants without causing severe symptoms or death. A better understanding of the interactions of these fungi with wheat under low soilborne disease pressure systems will allow for better plant disease management strategies in Texas.
First demonstration of infectivity in Nicotiana benthamiana using infectious clones of two monopartite begomoviruses, Sweet potato golden vein and Sweet potato leaf curl, and the bipartite Merremia mosaic virus, isolated from Merremia species in Puerto Rico
Z. He (1), J. K. Brown (2)
(1) Plant Protection Research Institute, Guangdong Academy of Agricultural Sciences, Guangzhou, Guangdong, China; (2) School of Plant Sciences, The University of Arizona, Tucson, AZ, U.S.A.
The New World monopartite begomoviruses, Sweet potato golden vein (SPGVV) and Sweet potato leaf (SPLCV-PR) were discovered in Puerto Rico infecting two Merremia species, endemic to the Caribbean Basin. Also infecting these species was the bipartite Merremia mosaic virus. Infectious clones were constructed for the three viral genomes and delivered separately or together to Nicotiana benthaminana plants by agro-infiltration. Symptoms varied in severity depending on the genome combinations. Results demonstrate the first infectivity for these viral genomes and show that no associated satellite is required for infection of N. benthamina. The range of symptom severity for the different genome combinations was suggestive of synergism, providing a unique system to study monopartite-bipartite begomovirus interactions.
Evaluation of Musa spp. hybrids for resistance to black Sigatoka, caused by Mycosphaerella fijiensis Morelet
B. M. IRISH (1), J. Chavarria-Carvajal (2), R. Ploetz (3), R. Goenaga (1)
(1) USDA-ARS Tropical Agriculture Research Station, Mayaguez, Puerto Rico; (2) University of Puerto Rico, Department of Crop Protection, Mayaguez, Puerto Rico; (3) University of Florida, IFAS, Tropical Research and Education Center, Homestead, FL
In Puerto Rico, bananas and plantains are important agricultural commodities; their combined production totaled 133,500 tons in 2008. Black and yellow Sigatoka leaf spot diseases, caused by Mycosphaerella fijiensis and M. musicola respectively, are responsible for significant losses of these crops in Puerto Rico, due to the high susceptibility of the most important cultivars. Consequently, new clones were introduced from Bioversity’s Musa International Transit Center in Leuven, Belgium. Clones were evaluated in the field over two crop cycles (2007–2010) for their responses to these diseases, as well as their agronomic and organoleptic traits. Clear differences in resistance were found among the clones. On a 0–6 scale (0 = no disease; 6 = >50% leaf area with lesions), mean disease severities at harvest ranged from 5.8 for the susceptible control ‘Grand Naine’ to 1.2 for FHIA-18. Wide ranges were also observed in mean bunch weights (7.57 to 45.1 kg), numbers of hands (6.5 to 14.8), and numbers of fruit (57.0 to 263.7). Several clones, mainly from the Fundación Hondureña de Investigación Agrícola (FHIA), possessed excellent resistance and agronomic traits (e.g. short pseudostems, large bunches and satisfactory organoleptic profiles) and could potentially replace susceptible cultivars in commercial production or play roles in a nascent organic market.
Identification of anamorphic powdery mildews on fruits and vegetables in Puerto Rico
E. I. LATONI-BRAILOWSKY (1), L. I. Rivera-Vargas (1), C. Estévez de Jensen (1), M. J. Cafaro (2)
(1) Department of Crops and Agroenvironmental Sciences, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico; (2) Department of Biology, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico
Powdery mildews (Ascomycetes: Erysiphales) are considered among the major plant diseases of economic importance in the world. In Puerto Rico the limited knowledge of the specific species of Erysiphales that affect our crops and their ecology worsen the plant-pathogen problems. In 2010 and 2011 we conducted surveys to examine powdery mildew diversity. Tissue samples from Abelmoschus esculentus, Carica papaya, Cucumis melo var. reticulatus, Cucurbita moschata, Cucurbita pepo, Lagenaria siceraria, Mangifera indica and Solanum lycopersicum, and the weeds: Euphorbia heterophylla, E. hirta and Sonchus oleraceus were collected in orchards and greenhouses throughout the island. Podosphaera sp., Oidium mangiferae, O. caricae, O. neolycopersici, Cystotheca lanestris and Erysiphe pisi were morphologically identified using light and scanning electron microscopy. Conidia germination, appressoria shape, fibrosin bodies and patterns found on the outside wall of the conidia were the morphological criteria used for preliminary identification. Molecular identification was performed using PCR amplification of the ITS1-5.8S-ITS2 region of the rDNA. So far, Oidium neolycopersici was identified affecting tomato using both techniques. This pathogen is closely related to North American O. neolycopersici and differs from O. lycopersici which is restricted to Australia. Correct identification of powdery mildews in Puerto Rico is of economic importance to prevent the introduction of new genera and species that could affect our crops and their ecology.
Six decades with Julio Bird
K. Maramorosch (1)
(1) Entomology Department, Rutgers-The State University of New Jersey, New Brunswick, NJ
In 1957 Dr. Julio Bird, returning home from Prof. Stakrnan’s plant pathology department in St. Pau1, MN, visited me at Rockefeller University in New York City. I learned about his work with the rugaceous (whitefly transmitted) viruses in Puerto Rico. His description of tropical plant virus diseases stimulated my own interest in this subject. In 1963 1 got my first opportunity to come to Puerto Rico during a worldwide survey of tropical plant diseases, carried out for the Food and Agriculture Organization of the United Nations. This started a series of scientific visits to Julio at Rio Piedras and Mayaguez, where we shared our interest in insect vector interactions with tropical plants. Julio edited with me “Tropical Diseases of Legumes” (Academic Press, 1974) and we published several joint scientific papers. I accompanied Julio to make comprehensive observations of plant diseases, collect samples for electron microscopic examination and record by color photography the disease symptoms. Photography was our joint hobby. The originality of Julio’s ideas made his work with whiteflies outstanding, accounting for the extraordinarily wide scope of his achievements. But very few people knew that in addition to his research and teaching, Julio excelled as a sculptor and as an archeologist. His keen observing powers permitted him to discover places where the prehistoric occupants of Puerto Rico gathered and where the remnants of their meals resulted in permanent changes of the flora. Traveling with Julio to different areas of the island, we found ornamented vessels, stone jewelry, and once an ancient burial place of the pre-Columbian inhabitants, only a few steps from the Munoz airport. Where huge trees were uprooted to clear the land for new construction, Julio collected pieces of wood to transform them into exquisite sculptures. He donated several to me and I am treasuring them as a permanent reminder of my dear friend and admired scholar.
Response of Phaseolus vulgaris lines to angular leaf spot
M. Mbui Martins (1), C. Estévez de Jensen (1), T. G. Porch (2), J. Beaver (1)
(1) Crop and Environmental Sciences, University of Puerto Rico, Mayaguez, PR; (2) Tropical Agriculture Research Station, USDA, TARS, Mayaguez, PR
Common bean (Phaseolus vulgaris L.) production is affected by angular leaf spot (ALS) caused by Phaeoisariopsis griseola (Sacc.) Ferr. The objective of this study was to identify sources of resistance to ALS in cultivars from Angola. Inoculation of P. griseola on common bean genotypes was carried out with one isolate from Isabela, Puerto Rico in two separate experiments. Phaeoisariopsis griseola 1 × 105 conidia/ml was inoculated with an atomizer and evaluated using the CIAT scale (1–9), where: 1 to 3 = resistant, 4 to 6 moderate resistant and 7 to 9 = susceptible. The isolate of P. griseola from Isabela infected bean lines of both Mesoamerican and Andean origen materials. In the first experiment, genotypes G05685 (Andean) and Flor de Mayo (Mesoamerican) were resistant to ALS. Montcalm, Amendoin and Canario, and Angolan cultivars Ermelinda, Amarelo, Cebo and Manteiga presented the highest disease severity. Cultivars Catarina and Calembe were moderately resistant. In the second experiment, ALS disease severity scores did not increase compared to the first experiment. However, initial symptoms of ALS was observed between 10–12 days after inoculation, and cultivar Ermelinda showed a disease severity of 6 nineteen days after the inoculation, indicating moderate susceptibility to the P. griseola isolate from Isabela. Cultivars Amarelo, Carioca, Catiolo, Fernando, Chumbo, Quilumba, Olho de Perdiz, Pedro and Manteiga were also moderately resistant. Cultivar Canario had a low disease severity compared to the first experiment. The level of disease severity in the second experiment indicated that environmental conditions were not favorable for the disease.
Phytopathogenic fungi as an alternative for the biological control of the invasive weed, Hyparrhenia rufa
V. Rivera (1), L. I. Rivera (1), A. Rodríguez (2)
(1) Dept. of Crops and Agroenvironmental Sciences, University of Puerto Rico – Mayagüez Campus, Mayagüez, PR; (2) Dept. of Animal Industry, University of Puerto Rico – Mayagüez Campus, Mayagüez, PR
Hyparrhenia rufa commonly known as Jaragua grass or thatching grass, is an aggressive weed that has invaded croplands in Puerto Rico. Several strategies have been proposed for its control such as the use of phytopathogenic fungi and small ruminants. During 2009, plots invaded by H. rufa were examined for disease symptoms. Plants were collected and fungi was isolated from leaf tissues. Curvularia sp. Fusarium sp., Sphaeropsis sp. and Phoma sp. were identified from leaf lesions. Pathogenicity tests conducted at greenhouse conditions demonstrated that all fungi identified were pathogenic to H. rufa, being Phoma sp. the most virulent. Future experiments will be expanded to test fungal pathogenicity to plant stems and panicles under greenhouse conditions and further evaluation of the potential biological control agents at field conditions.
Detection of citrus greening with hi-fidelity PCR
G. Romero (1), C. Estévez de Jensen (1), A. Palmateer (2)
(1) Crops and Environmental Sciences, University of Puerto Rico, Mayaguez 00680; (2) Tropical Research & Education Center, University of Florida, Homestead, FL
In 2009, citrus greening caused by Candidatus liberibacter asiaticus (CLA) was identified in Puerto Rico. A survey on prevalence of CLA in citrus orchards on the island was conducted. After DNA extraction (DNeasy, Plant Mini Kit - QIAGEN) from symptomatic and asymptomatic leaves, Hi-Fidelity Polymerase Chain Reaction (Hi-Fi PCR) was compared with standard PCR for CLA detection in leaf midribs. Amplification of DNA with PCR often resulted in false negatives (2.5 µl primers OI1 and OI2c; 12.5 µl of Go Green Tag; 2.5 µl molecular water). The Hi-Fi PCR consisted of Buffer Mix: 1.75 µl; dNTP, 8 µl OI1 and OI2c, 12 µl molecular water; Enzyme Mix: 1 µl Taq, 0.2 µl Accuzyme.; Template Mix: 5 µl PCR buffer (Acuzyme), 1 µl Enzime Mix 12.25 µl molecular water, for a final reaction of 50 µl of 29.75 µl Buffer Mix, 18.25 µl Template Mix and 2 µl DNA. The Hi-Fi PCR was more sensitive for detection of CLA in contrast with the traditional PCR. From a total of 138 citrus samples, 11 samples amplified a 1160 bp band of the 16S rDNA with Hi-Fi PCR and no DNA amplified with traditional PCR. Accurate diagnosis is indispensable for the establishment of disease-free nurseries and orchards to implement control measures to prevent the spread of the disease.
The search for resistance to a disease of common bean caused by a soilborne necrotrophic fungus
J. R. STEADMAN (1), S. McCoy (1), R. Higgins (1)
(1) University of Nebraska
Bean cultivars with intermediate resistance and/or avoidance to white mold (WM) would reduce disease losses and require no input costs for growers. Thus, one goal was to identify sources of resistance in adapted and nonadapted common bean lines utilizing standardized greenhouse screening methods and field nurseries across major bean production regions. Multi-site testing facilitates identifying highly variable disease reactions encountered with this pathogen. A second project goal was to assess variation in common bean isolates of the necrotroph pathogen Sclerotinia sclerotiorum. We devised a unique study on pathogen variation across bean-production areas that tests the hypothesis that pathogen variation within and between test sites influences identification of WM resistance. Mycelial compatibility groupings (MCGs), aggressiveness, and microsatellites are used to identify genotype and phenotype differences in the isolates that can influence stability of identified WM resistance over time and location. Collecting isolates from specific bean host lines replicated at each resistance screening site permitted us to assess within and between location variations. High variation in aggressiveness and genetic variability (measured by MCGs and microsatellites) of pathogen isolates within and between field screening nursery locations and greenhouse test isolates has been found. Another hypothesis we are testing is that isolates collected from screening nursery sites and greenhouse tests show similar phenotype and genotype variability as isolates collected from growers’ fields in the same region. When isolates from screening nurseries in each of 3 states were compared with grower field isolates in the same state, there were significant differences in aggressiveness. Our database of characterized isolates now facilitates new isolate characterization. The expected outcome is a set of characterized isolates for breeders and pathologists searching for unique and common clones with more or less aggressiveness to use in screening for resistance.
Evaluation of biocontrols, coffee compost and Arachis glabrata on Phytophthora root rot in avocado
J. TORRES (2), C. Estevez de Jensen (1), D. Sotomayor (2)
(1) University of Puerto Rico; (2) University of Puerto Rico, Mayaguez, Puerto Rico
The effects of Arachis glabrata, coffee compost amendment, and biocontrol agents (Bacillus subtilis, and Trichoderma harzianum) on Phytophthora root-rot incidence in avocado were evaluated. The treatments were compared with an uninoculated control and a Fosetyl-Al treatment arranged in a randomized complete design with four replications using commercial organic growth media (Promix®) and pasteurized field soil (Cumulic Haplustolls) as substrates. The coffee compost amendment reduced root-rot symptoms of plants growing in pasteurized soil presenting the lowest percentage of avocado root rot (15%), and higher dry root weight (2.08g) in comparison with the other treatments. The chemical treatment Fosetyl-Al showed the lowest percentage of avocado root rot (2.94%) grown in Promix and the lowest infection percentage in the mature avocado grove (0%). The two biocontrols agents were not effective in reducing root-rot symptoms or increasing these beneficial microorganisms’ populations significantly when applied, even when in vitro experiments demonstrated that T. harzianum was efficient to control P. cinnamomi mycelial growth. Soil respiration which was used as an indicator of suppressive conditions in growth media and pasteurized soil did not differ among treatments. The beneficial effects of coffee compost suppression of Phytophthora under field conditions should be explored further.
Survival of Bacillus thuringiensis and Bacillus pumilus, antagonistic bacteria to the coffee berry borer, in coffee trees under field conditions in Puerto Rico
D. A. Vázquez (1), M. Zapata (1)
(1) Department of Crops and Agroenvironmental Sciences, University of Puerto Rico, Mayagüez campus, Mayagüez, Puerto Rico
Coffee (Coffea arabica L.) is one of the most important crops in Puerto Rico (PR). Currently, the main problem in coffee is the coffee borer caused by the insect Hypothenemus hampei. The pest feeds and reproduces inside of the coffee berry, reducing its weight and quality, causing losses up to 50% of the harvest. The Bacillus group is one of the potential natural enemies that has been evaluated for the control of the coffee berry borer because it contains species with insecticidal properties. Bioassays were performed using the female insect with Bacillus thuringiensis (Bt) and Bacillus pumilus (Bp) treatments to determine their potential to control the mortality and movement. One strain of each species was selected based on insect mortality at 96h after inoculation. In year 2010, the selected bacterial strains were inoculated on coffee trees at flowering stage in Adjuntas, PR to determine their survival under field conditions. Four evaluations for colonizing bacteria were performed using stem and fruits samples from inoculated coffee trees. A RCB design and LDS were used to contrast the differences between total bacteria and Bacillus. Four bacterial collections were established containing strains with different pigmentation, gram positive bacteria and spore-forming Bacillus. A significant reduction of the total bacterial population from fruits was detected when treated with B. thuringiensis of 24 hours growth. Survival of both species was positive six months after inoculation although total bacterial populations including Bacillus showed a reduction six months after inoculation apparently caused by the high precipitation observed during September.
Endophytic bacteria from the vascular tissue of coffee (Coffea arabica L.) and citrus (Citrus sinensis L.) leaves found during the attempt to isolate the pathogen, Xylella fastidiosa in Puerto Rico
M. Zapata (1), J. Hartung (2), B. Brodbeck (3), P. Andersen (3)
(1) Department of Crops and Agroenvironmental Sciences, Univ. of Puerto Rico, Mayagüez Puerto Rico; (2) USDA-ARS, Molecular Plant Pathology Laboratory, Beltsville Agricultural Research Center-West, Beltsville, MD; (3) North Florida Research and Education Center-Quincy, Univ. of Florida, Quincy, FL
Xylella fastidiosa (Xf) is the causal agent of coffee leaf scorch coffee and citrus variegated chlorosis. Xf is xylem limited and difficult to grow in artificial media. Periwrinkle agar is semiselective for Xf, as other endophytes can grow on it. Bacteria with potential to interact with Xf can impact expression of disease and may represent biological control agents. Interactions of Xf with other endophytes have been reported including Methylobacterium extorquens (synergistic) and Methylobacterium mesophylicum and Curtobacterium flaccumfaciens (both antagonistic). Xylella fastidiosa and a list of the culturable endophytes identified while attempting to isolate Xf in the vascular tissue of coffee and citrus are reported for the first time. Five hundred and sixty five isolates were obtained during over three years. Xf was detected using DAS-ELISA with a 75% in coffee and 6% in citrus. Fatty acid analysis, BIOLOG® and PCR were used for identification. Two species of Methylobacterium were found: M. mesophylicum with high frequency in both crops and M. extorquens found only in coffee. Curtobacterium flacumfaciens, antagonistic to Xf, was found in low frequency and only in coffee. Frequent bacteria in coffee were: Bacillus cereus, B. coagulans, B. pumilus, Citrubacter farmeri, Curtobacterium pusilum, Erwinia stewartii ss. stewartii, Kokuria kristinae, K. varians, Methylobacterium mesophylicum, Microbacterium chocolatum, Micromonas paracarbonacea, Pantoea dispersa, P. agglomerans (Erwinia herbicola), Pseudomonas amyloderamosa, Psycrobacter immobilis, Staphylococcus aureus S. epidermidis, Staphylococcus simulans, Stenotrophomonas maltophilia, and Xanthomonas axonopodis pv. vasculorum. Frequent bacteria in citrus were: B. cereus, B. coagulans, M. mesophylicum, P. putida, Staphylococcus warneri, Stenotrophomonas maltophilia, and X. axonopodis pv. vasculorum.