Método do rolo de papel toalha modificado para a detecção de Sclerotinia sclerotiorum em sementes de feijão

Abstract

White mold, caused by the fungus Sclerotinia sclerotiorum (Lib.) is one of the most damaging diseases of beans. Dissemination of the pathogen by infected seeds is important because it can infest new planting areas and the disease may establish in the beginning of the crop cycle. The present work describes an adaptation of the seed health test using the germination paper towel method, originally developed for the detection of Colletotrichum lindemuthianum, for assessing the presence of S. sclerotiorum in bean seeds. The test consisted of placing bean seeds in germination paper towels, which were rolled and placed in a germination chamber and kept at 100% relative humidity and 20 o C for seven days. After this period, the infected seedlings and the dead seeds surrounded by a white cottony growth were collected and placed in a gerbox over two wet filter papers. The sclerotia characteristic of the pathogen appeared around the seeds after tree to four days of incubation. This method is relatively rapid, inexpensive, and has the additional advantage of detecting simultaneously other important plant pathogens in bean seeds, such as Colletotrichum lindemuthianum, Macrophomina phaseolina and Rhizoctonia solani.Additional keywords: Phaseolus vulgaris L., Colletotrichum lindemuthianum, Macrophomina phaseolina, Rhizoctonia solani, white mold. RESUMOO mofo branco do feijoeiro, causado pelo fungo Sclerotinia sclerotiorum (Lib.) de Bary, é uma das principais doenças da cultura. O patógeno pode ser disseminado por sementes infectadas, que têm um importante papel na infestação de novas áreas de plantio e no estabelecimento da doença no início do ciclo da cultura. Este trabalho apresenta uma adaptação do método do rolo de papel toalha, originalmente desenvolvido para a detecção de Colletotrichum lindemuthianum, com o objetivo de detectar a presença de S. sclerotiorum em sementes de feijão. Neste método, as sementes foram incubadas por 7 dias a 20 o C em rolos de papel toalha para germinação, sendo mantidas sob condições de 100% de umidade relativa. Após esse período, as plântulas infeccionadas e as sementes mortas, circundadas por micélio característico de S. sclerotiorum, foram transportadas para caixas tipo gerbox, sobre duas folhas de papel de filtro umedecido. Após 3 a 4 dias de incubação a 20 o C e sob regime de 12 horas de luz por 12 horas de escuro, os escleródios foram observados nas sementes e plântulas. O método foi relativamente rápido, simples e barato, além de apresentar a vantagem de possibilitar a detecção simultânea de S. sclerotiorum e de outros importantes patógenos transmitidos por sementes de feijão, como C. lindemuthianum, Macrophomina phaseolina e Rhizoctonia solani. 1118O mofo branco do feijoeiro, causado pelo fungo Sclerotinia sclerotiorum (Lib.) de Bary, é uma das principais doenças da cultura, acarretando danos severos nos plantios de inverno em áreas irrigadas (2, 6). A disseminação do fungo pode ocorrer pelos ascósporos, que são liberados das ascas e ejetados no ar, pelos escleródios transport...

Biocontrol of seed pathogens and growth promotion of common bean seedlings by Trichoderma harzianum

“…After this procedure, 50 seeds were evenly distributed on two layers of germitest paper, moistened with distilled water, covered with a third moistened germitest paper sheet and then rolled (Regras para Análise de Sementes, 2009). Rolls were kept in a growth chamber at 20ºC and 98% relative humidity for seven days (Parisi et al, 2006). Then, the rolls were moistened with distilled water and incubated in a refrigerator at 8ºC for 10 days, without light incidence.…”

Detection of Sclerotinia sclerotiorum on soybean and common bean seeds by modified neon-s test

“…All methods compared in our study can overestimate the incidence of the fungus if it spreads from infected seeds to neighboring ones by contact (PARISI; PATRÍCIO;OLIVIERA, 2006), resulting in percentages of infection higher than 2% -proportion generally found for common bean and soybean samples (PERES, 1996). The determination of a minimum distance between seeds could help alleviate this concern, though no research has focused on it.…”

Performance of common bean seeds infected by the fungus Sclerotinia sclerotiorum

“…One of the most effective ways to control the causal agent of white mold disease is the use of seeds with high physiological and health qualities, i.e., free of the resistance structures of pathogen (sclerotia) mixed with the seeds and/or the fungus mycelia sheltered within tegument as well as in the embryonic tissues; thus avoiding its dissemination or its introduction in non-infected areas. Within this context Parisi et al (2006) point out that the use of seeds with good physiological and health qualities, and that are within the standards of the tolerance established for major crops and diseases, are among the most effective modes to reduce the spread of pathogens; besides contributing on reduction in the use of seeds noncertified that in the case of common beans is quite large in the country. In the last years, the tolerance standards proposed in Brazil for fungus S. sclerotiorum establish a zero (0) value to the different classes for common bean seed certification, i. e., by not allowing the presence of the pathogen together with seeds, either in form of contamination through sclerotia and/or the concomitant infection by the fungal mycelia within those seeds (Oliveira, 2005).…”