Margarida Fumiko Ito

Two new Ceratocystis species associated with mango disease in Brazil

The National Research Foundation (NRF), members of the Tree Protection Co-operative Programme (TPCP), the THRIP initiative of the Department of Trade and Industry, and the Department of Science and Technology (DST)/NRF Centre of Excellence in Tree Health Biotechnology (CTHB).

Resistência genética em genótipos de feijoeiro a Curtobacterium flaccumfaciens pv. flaccumfaciens

ABSTRACT Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), thecausal agent of the bacterial wilt of common bean ( Phaseolusvulgaris ), is a vascular pathogen of difficult control. The disease wasfirst detected in Brazil 1995, in Sao Paulo State. Due to the difficultyin controlling this disease, genetic resistance has been the betteroption. The aim of this study was to evaluate the reaction of commonbean genotypes to the bacterial wilt, in 333 accesses of the beanplant germplasm database of the Instituto Agronomico de Campinas(IAC). Highly resistant and susceptible bean genotypes were selectedfor the observation of Cff colonization in the xylem vessel by scanningelectron microscopy. The results of the screening for genetic resistancein 333 genotypes indicated variability in relation to a Cff Feij 2634 Souza, V.L.; Maringoni, A.C.; Carbonell, S.A.M.; Ito, M.F. Genetic resistance to Curtobacterium flaccumfaciens pv. flaccumfaciens in beangenotypes. Summa Phytopathologica , v.32, n.4, p.339-344, 2006.

Tratamento térmico solar da água para controle de fitopatógenos

Some phytopathogenic microorganisms may be transmitted by water representing an efficient means way of inoculum dissemination. The objective of the work was to quantify the efficiency of thermal treatment by solar heating in the control of pathogens in contaminated water. The equipment developed for this purpose was composed of flat collectors and used both natural and forced convection to transfer heat to the circulating water. Thermostats, placed in different locataions, automatically equalized the temperature of the system. The equipment was verified to peform well at 60 oC, in terms of water processed as well as in the eradication of economically important pathogens such as Botrytis cinerea, Colletotrichum spp., Fusarium spp., Pythium spp., Verticillium dahliae and Rhizoctonia solani. Except for F. oxysporum f. sp. phaseoli, the other pathogens were inactivated at temperatures above 55 oC. The technique is a promising option to disinfest the water to be used in nurseries, greenhouses and in small or midsize agricultural exploitations.

Co-evolução entre raças fisiológicas de colletotrichum lindemuthianum e feijoeiro

The causal agent of anthracnose (Colletotrichum lindemuthianum) of common bean and its host, are classified as Andean and Mesoamerican. Response to infection depends on the genetic origin of both plant and fungus. The objective this study was to evaluate 220 accessions from Common Bean Germplasm Collection of Instituto Agronomico, IAC, us to infection by three physiological races of the pathogen (31, 65 and 89), and to investigate a possible co-evolution between the origin of the accessions and the pathogen. One hundred and twenty accessions of Mesoamerican origin, 57 Andean and 43 genetically improved cultivars were used in the study. Besides infection data, 23 morpho-agronomic descriptors were evaluated to characterize the plants. Statistical analyses were based on principal components as a way of showing in graphics the variability related to origin of pathogen and accessions. Fifty percent of the Mesoamerican accessions were susceptible to the three races, while only 33% of the Andean were susceptible. Also, of the genetically improved cultivars 79% were resistant to at least one physiological race, probably due to previous selections for resistance to C. lindemuthianum. Diagrams of the analysis of the principal components, showed that most of the resistant accessions clustered in the dispersion region of the Andean accessions. The results allowed the association between the origin of Phaseolus vulgaris and the anthracnose pathogen, increasing the biological understanding of the reaction defense to C. lindemuthianum infection, and orienting the choice of parents to be used in crossings aiming at resistance to C. lindemuthianum.

Classification of physiological races of Fusarium oxysporum f. sp. phaseoli in common bean

Fusarium wilt, caused by Fusarium oxysporum Schlecht. f. phaseoli Kendrick and Snyder (FOP), is a major disease of common bean, causing large economic losses. Genetic resistance is one of the main mechanisms of pathogen control, and knowledge of the physiological variability is fundamental in breeding for resistant cultivars. Thus, a method of pathogen classification that describes the variability and is useful in plant breeding of isolates from different sources was evaluated by different methodologies. Common bean plants of different sets of differentiating cultivars were inoculated with 25 FOP isolates and 3 controls, totaling 28 isolates evaluated 30 days after inoculation. The variability in the isolates found in this study differs from the results of other authors, who reported a small number of physiological races of the pathogen and disagrees with their evaluation of the races and the evaluation methodology. The proposed approach for binary classification based on a group of 12 differentiating cultivars demonstrated that the variability in pathogenicity of FOP is greater than reported so far. By this methodology, 27 different physiological races of the pathogen were obtained. The methods led to contrasting results, with double race classification in the same isolate. The physiological variability found indicates that the physiological races of the pathogen are not limited to 7 as previously mentioned.

Aplicação de marcadores SCARs para seleção de linhagens resistentes à antracnose em feijoeiro

Low yield of common bean, in Brazil, occurs mainly due to diseases such as anthracnose caused by Colletotrichum lindemuthianum Sacc & Magnus. Fifty physiological strains of this fungus have already been described races 31, 65 and 89 being the most important in the State of Sao Paulo. In the present work, six SCAR (Sequence-Characterized Amplified Regions) markers were evaluated in 42 parental lines and in 76 lines of the bean breeding program of Instituto Agronomico (IAC) aiming at to identify genotypes carrying resistance genes to C. lindemuthianum and the probable most frequent genes. Based on the SCAR markers, three parents and nine derived lines were identified as carrying four resistance genes, demonstrating the effectiveness of the markers for the on going breeding program. Co-6 was the most frequent resistance gene followed by Co-42, Co-33, Co-5, and Co-4.

Efeito de Colletotrichum dematium var. truncata e Cercospora kikuchii na germinação de sementes de soja

Anthracnose, caused by Colletotrichum dematium var. truncata, is the main soybean disease that affects soybean yields. Cercospora kikuchii is the fungus that causes the purple stain disease in soybean seeds that causes severe reductions in the yield and quality of the seeds. The objective of this study was to determine the optimum period of contact of the soybean seeds with C. dematium var. truncata and C. kikuchii, for subsequent evaluation of the damage caused by the fungus on seed germination. The fungus was cultivated in PDA medium. The soybean seeds cv. MSOY 6101 were placed on Petri dishes with culture media colonized by C. dematium var. truncata for 0 (control), 4, 16, 24, 32 and 40h. The seeds of the cv. CD 208 were inoculated with C. kikuchii for the same mentioned periods, with the addition of 48 and 56h. After the respective periods of contact, they were submitted to the Blotter test, with and without superficial asepsis (sodium hipoclorite 1%, 3 minutes). After determining the optimum incubation period, other seeds were infected with the pathogen and, later, germination tests were accomplished in paper and in sand with a mixture of healthy seeds (placed on PDA medium) and inoculated seeds, resulting in lots with 0, 20, 40, 60, 80 and 100% infected seeds. The incubation time of C. dematium var truncata and C. Kikuchii, was 40 and 56 hours, respectively, and was sufficient to obtain completely infected seeds. C. Kikuchii not reduce seed germination.

Reação de genótipos de algodoeiro à mancha-de-alternária

In three field experiments, carried out at Cambara-PR and Londrina-PR in the crop year 2011/12 and at Piracicaba-SP in 2012/13, and under natural incidence of the pathogen, 12 cotton genotypes were evaluated for their reaction to the incidence of Alternaria leaf spot (Alternaria macrospora). Highly significant differences among genotypes were observed at all three localities, allowing the establishment of three, four and six groups of reaction to the disease, according to the considered environment. At the extreme positions, and without great changes in their performance, the group of most resistant genotypes included IAC 08-2031, FMT 709 and BRS 336, and the group of most susceptible genotypes, FMT 705, IMA CD 08-12427 and DP 555 BG RR. Considering the intermediate groups, some inconsistencies were observed for certain genotypes, which explains the significant interaction genotypes x localities. However, as the less satisfactory performance occurred at the locality where the disease occurred at higher intensity, such interaction may translate only the phenotypic instability of the resistance to the pathogen for the involved genotypes.

A new set of microsatellite markers for the genetic characterization of Ceratocystis fimbriata, an economically important plant pathogen

Ceratocystis fimbriata is a fungal pathogen which attacks several economically important plants, but occurs in host-associated, morphologically indistinguishable forms. In Brazil, this fungus seriously attacks mango trees (Mangifera indica), causing severe loss of yield. This work aimed to develop and characterize a novel set of microsatellite markers for this important pathogen, providing researchers with new molecular tools for the characterization of isolates. Twenty polymorphic primer pairs were designed from a microsatellite-enriched library. We tested the usefulness of these markers through genotyping thirteen isolates of the fungus. On average, 6.65 alleles per locus were detected, revealing the ability of this set of markers to characterize C. fimbriata isolates associated to mango and to other plant species.

Sistema automatizado de aquecimento solar para controle de fitopatógenos da água de irrigação

O sistema automatizado de aquecimento solar, baseou-se em um processo misto de aquecimento da agua em circuito fechado, atraves de coletores planos e dois principios integrados de transmissao de calor, um por conveccao natural e o outro por conveccao forcada. A automatizacao foi realizada por monitores termostaticos diferenciais. Os testes normativos abrangeram as temperaturas programadas de 50, 55 e 60 oC, que contemplam a faixa de temperatura letal para a maioria dos fitopatogenos. Os resultados indicaram rendimentos termicos da ordem de 63, 55 e 52%, superiores, quando comparados aos rendimentos medios de 50, 47 e 45% dos sistemas convencionais. Os resultados experimentais mostraram que o sistema e eficiente para a eliminacao de patogenos da agua de irrigacao, sendo promissor como uma opcao de baixo custo para ser usado em viveiros, casas-de-vegetacao e pequenas ou medias propriedades agricolas.