Use of semi-seletive media for detection of Sclerotinia sclerotiorum on bean and soybean seeds

Abstract

This work was aimed at evaluating the possibility of using bromophenol blue as an indicator for detecting the presence of Sclerotinia sclerotiorum in the seeds of dry-beans (Phaseolus vulgaris) and soybean (Glycine max), through incubation of the seeds on an agar medium and "blotter" substrates. The seeds were artificially inoculated with four S. sclerotiorum isolates, plated on the agar medium, named Neon, and on modified Neon agar media all incubated at 14 and 20 ºC for seven days in the dark. Half of the seeds inoculated were surface desinfested prior to plating on the medium. The seeds showing change of colour in the medium, from blue to light yellow, as well as formation of typical mycelium and sclerotia in some cases, were considered to be infected or contaminated by S. sclerotiorum. The two incubation temperatures compared did not show significant (P<0.05) differences in detection level for most of the isolates tested on the different media. According to results obtained in this study, the Neon agar medium with incubation at 14 or 20 ºC has proved to be a reliable and quick method for the detection of S. sclerotiorum mycelium in naturally infected seeds of bean and soybean.

Incidência de Sclerotinia sclerotiorum em sementes de soja e sensibilidade dos testes de detecção

“…Além disso, à medida que se aumentou a incidência da amostra, verificou-se acréscimo no número de sementes detectadas com S. sclerotiorum. Esses resultados estão de acordo com os obtidos na literatura, em que a inoculação artificial da semente foi utilizada para avaliar a sensibilidade do método em detectar o fungo (Peres et al, 2002;Napoleão et al, 2006). Ao se analisar a repetibilidade (variação observada em quatro replicatas) dos resultados (Tabela 1), observou-se que os métodos foram eficientes na detecção do fungo S. sclerotiorum em sementes contaminadas artificialmente.…”

“…de Bary é um patógeno de importância mundial, por ocorrer tanto em regiões temperadas quanto subtropicais e tropicais, além de ser um fungo polífago, que infecta 408 espécies e 278 gêneros de plantas hospedeiras (Bolton et al, 2006). Epidemias causadas pelo patógeno, na cultura da soja, têm sido responsáveis pela diminuição da produção em vários países, com perdas que chegam a 100%, em condições favoráveis (Saharan & Mehta, 2007;Silva et al, 2008).…”

“…Há diferentes métodos para a detecção do patógeno na semente de soja, entre os quais se destaca a incubação em substrato de papel ou método do papel de filtro ("blotter test"); em rolo de papel; e em meio agar-bromofenol Neon (Nasser et al, 1999;Machado, 2002;Peres et al, 2002;Taylor et al, 2006 …”

Potential of antimicrobial volatile organic compounds to control Sclerotinia sclerotiorum in bean seeds

“…For the artificial inoculation, bean seeds (Phaseolus vulgaris L.) from the cultivar Carioca, free of S. sclerotiorum, were used. Seeds were submitted to surface sterilization with sodium hypochlorite (1%) for 2 min, washed in sterile distilled water and dried at room temperature for 24 h. For inoculation, seeds were placed in Petri dishes with PDA medium, colonized with a five days old S. sclerotiorum culture (Peres et al, 2002). The incubation was performed at 21ºC, in the dark, for 48 h. Seeds were dried at room temperature for 72 h, mixed with healthy seeds in the proportion 1:2 (w/w), and homogenized.…”

Relationship between mycelial inoculum of Sclerotinia sclerotiorum and performance of sunflower seeds under controlled condition

“…The seed health test consisted in incubation of seeds on a semi seletive-bromophenol agar substrate (NEON), as widely described in literature (NASSER et al, 1999;PERES et al, 2002;NAPOLEÃO et al, 2006), using a total of 200 seeds of control and inoculated seeds for each inoculum potential. The plates were distributed in incubation chamber at 20ºC.…”