Anthracnose, caused by Colletotrichum lindemuthianum (Sacc. and Magnus) Briosi and Cavara is a fungal disease that affects common bean worldwide. Seed yield loses sometimes reach 100% when the seed is infected and environmental conditions favor the disease. Climbing beans in Guatemala represent the main source of protein for the habitants of this region (9.4 kg/person/year). Unfortunately, anthracnose threatens climbing bean production in the region. Six races were found among samples collected in Guatemala Highlands using the standard common bean differential lines. Also, a germplasm collection from ICTA Guatemala was evaluated for resistance to C. lindemuthianum race 73, which is the predominant race in the U.S. Approximately 10% of 369 climbing bean accessions showed no symptoms (score of 1). GWAS results using 78754 SNP markers indicated that genomic regions for resistance to C. lindemuthianum exist in Pv04 and Pv07. / USAID-Legume Innovation Lab / ICTA (Guatemala)

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Anthracnose (caused by Colletotrichum capsici or C. gloeosporioides) of bell peppers (Capsicum annum) has become a serious problem in recent years on the Eastern Shore of Virginia. The purpose of this research was to characterize isolates of the fungus from the Eastern United States, to compare them with the type species from the American Type Culture Collection, and to evaluate fungicides for disease management. Two cultivars of pepper were inoculated with a conidial suspension, and held in a dew chamber. Lesions were counted and measured every 48 hours. The type species was either not pathogenic or only mildly virulent; most of the virulent isolates originated in areas of intensive pepper production. In addition to pathogenicity experiments and traditional morphology, the Biolog® system was used to compare the ability of fungi to utilize different carbohydrate combinations in 96-well plates. Plates were read at 96 and 168 hours. Analysis of data, by Ward's statistical method, could reliably distinguish field isolates if based on 15 or more replications, but species-level identification was inconsistent. Standard fungicides and new compounds were compared in a field test with four replications of treatments in a randomized complete block design. Fruits were harvested three times, weighed for yield, and the number of marketable and diseased fruit recorded. Aggressive isolates from green pepper were controlled by applications of maneb, or alternation of maneb and strobilurin fungicides. / Master of Science

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Agrárias, Programa de Pós-Graduação em Recursos Genéticos Vegetais, Florianópolis, 2014 / Made available in DSpace on 2015-02-05T21:04:35Z (GMT). No. of bitstreams: 1 328845.pdf: 3297142 bytes, checksum: 27a2f1115c660c9e8bfe3202b21ce437 (MD5) Previous issue date: 2014 / A Podridão Amarga (PA) e a Mancha Foliar de Glomerella (MFG) estão entre as doenças de maior importância na cultura da macieira, pelo rápido progresso dos sintomas e elevada susceptibilidade da cultivar "Gala", uma das mais consumidas no mundo. O presente trabalho objetivou determinar os grupos de compatibilidade vegetativa (GCVs) de isolados brasileiros e uruguaios de Colletotrichum spp. de PA e MFG e monitorar a formação de tubos de anastomose conidial (TACs) in vitro e in vivo. OsGCVs foram determinados pelo pareamento em Meio Mínimo (MM) de mutantes defectivos na via de assimilação de nitrogênio. Os mutantes foram gerados em meio BDA+KClO3 e mantidos em MM. Os isolados foram classificados em mesmo GCV quando seu pareamento resultou na formação de heterocárion. Isolados de complexos ou espécies diferentes nunca perteceram ao mesmo GCV. Somente um isolado brasileiro de MFG foi incluido em mesmo GCV que isolados uruguaios de fruto Quatro e nove grupos foram encontrados dentre os isolados uruguaios e brasileiros, respectivamente. Em três GCVs, foram incluidos tanto isolados de PA quanto de MFG. Para monitorar o desenvolvimento de TACs e estruturas pré-infectivas, distribuiram-se gotas de 10 e de 20µL de supensão conidial (1x106 conídios/mL) sobre lâminas de poliestireno e superfície de folhas destacadas de macieira. O desenvolvimento foi examinado microscopicamente a cada duas horas de incubação a 25°C,entre 14 e 24h e após 48h, sobre poliestireno e folhas destacadas, respectivamente. O percentual e tempo de máxima germinação, formação e melanização de apressórios foram avaliados. Os TACs foram quantificados e categorizados conforme a conexão em três tipos: tubo-tubo(t-t), tubo-conídio (t-c) e conídio-conídio (c-c). Isolados de Colletotrichum gloeosporioides apresentaram elevada germinação e formação mais precoce de apressórios melanizados. As conexões do tipot-t foram encontradas em menor frequência, para todos os isolados testados. As conexões do tipo c-c foram as mais frequentes em isolados de Colletotrichum acutatum. Dentres todos os isolados analisados, os que apresentaram maior percentual de conexões t-t, também formaram mais t-c. Isolados de Colletotrichum fragariae e C. gloeosporioides de folha nunca desenvolveram TACs sobre poliestireno ou folhas destacadas. Aqueles que formaram TACs sobre poliestireno também o fizeram sobre a superfície do hospedeiro. Foram observados vários núcleos através dos TACs e alguns conídios com nenhum e mais de um núcleo. Em geral, populações de Colletotrichum spp. do Brasil e do Uruguai foram aparentemente distintas, sugerindo que estas mantiveram-se separadas. Os processos de formação de TACs e apressórios parecem ser antagônicos. O desenvolvimento de TACs é um processo comum para C. gloeosporioides de frutos e C. acutatum. A possível contribuição dos TACs para aumento da variabilidade de Colletotrichum spp. é discutida.<br> / Abstract: Bitter Rot (BR) and Glomerella leaf spot (GLS) are amongst the major apple diseases, due to the fast progress of symptoms and high susceptibility of the cultivar "Gala", one of most worldwide consumed. The present study aimed to determinate the vegetative compatibility groups of brazilian and uruguayan strains of Colletotrichum spp causing BR and GLS as well as to monitor the development of conidial anastomosis tubes (CATs) in vivo and in vitro. VCGs were determined by pairing mutants defective in nitrogen assimilation pathway on Minimal Medium (MM). Mutants were generated on PDA+ KClO3 medium and kept on MM. Strains were classified in same VCG when pairing led to heterokaryon formation. Strains of different complexes or species never belonged to the same VCG. Only one GLS-brazilian strain was includedin the VCG of fruit uruguayan strains. Four and nine groups were found among uruguayan and brazilian strains, respectively. In three VCGs, both PA and MFG strains were included. In order to monitor the development of CATs and pre-infective structures, drops of 10 and 20 µL of conidial suspension (1x106 conídios/mL) were distributed on polystyrene slides and detached apple leaves surfaces. The development was microscopically examined at every two hours of incubation at 25°C, from 14 to 24h and at 48h, on polystyrene and detached leaves, respectively. Percentage and time of maximum germination, apressoria development and melanization were evaluated. CATs were quantified and categorized into three types, according to the kind of connections: tube-tube (t-t),tube-conidium (t-c) and conidium-conidium (c-c). Strains of Colletotrichum gloeosporioides showed a high percentage of germination and early formation of melanized appressoria. The t-t connections were less frequent for all strains. The c-c connections were the most frequent type for Colletotrichum acutatum strains. Among all tested strains, those showing a higher percentage of t-t- connections, also formed more t-c. Strains of Colletotrichum fragariae and C. gloeosporiodes from leaves never developed CATs, neither on polystyrene nor on detached leaves.Those that formed CATs on polystyrene also did it on host surface. Many nuclei were observed through CATs, such as many conidia with none and more than one nucleus. Generally, populations of Colletotrichum spp. from Brazil and Uruguay were apparently distinct, suggesting that they were kept isolated. Appressoria melanization and CATs development seem to be antagonist processes. Formation of CATs is a common processin C. gloeosporioides from fruits and C. acutatum. The possible contribution of CATS and its consequence for increasing variability in Colletotrichum ssp. is discussed.

Ripe rot of grape is caused by two fungal species complexes: <i>Colletotrichum gloeosporioides</i> and <i>C. acutatum</i>, both of which cause disease on a variety of crops, such as strawberry and apple. To investigate effect of cultivar and cluster developmental stage on the development of ripe rot, controlled environment and field studies were conducted during 2013-2014. We have identified that a certain level of infection could can take place on most cultivars tested from bloom to the near harvest. In most of the cases, significant cultivar and cluster developmental stage interaction effects were observed (<i>P</i> < 0.05) for the development of disease symptoms in both studies. In general, susceptible cultivar (Cabernet Franc, Cabernet sauvignon, and Chardonnay) demonstrated fluctuations of disease susceptibility among cluster development stages, while resistant cultivars (Merlot) showed consistently low level of the disease throughout the season. To investigate the effect of eleven ten modes of action for control of <i>C. gloeosporioides</i> and <i>C. acutatum</i>, two methods, alamarBlue® assay and inoculation on fungicide-treated detached fruits, were used. Protective fungicides (mancozeb, captan, and copper) as well as some of newer formulations such as azoxystrobin and tetraconazole were identified as excellent products against ripe rot of grape. Four additional materials were identified as good potential candidates to investigate further. The information gained from these studies will help growers to determine the critical period for ripe rot management and chemicals to be applied for management. With better control of cluster rot pathogens, Virginia growers can experience an increase in yield and wine quality. / Master of Science in Life Sciences