Variability in the Sensitivity of Rhizoctonia solani Anastomosis Groups to Fungicides

Abstract

Tolclofos-methyl, iprodione and cyproconazole, among the eleven fungicides tested in vitro, gave consistently strong inhibition against all ten anastomosis groups (AGs) of Rhizoctonia solani. Carboxin, furmecyclox, thiabendazole, fenpropimorph and vinclozolin also inhibited all AGs but with wide variations in toxicity levels (EC90 values). Pencycuron showed strong activity against four AGs but was ineffective against the other six AGs. Generally, R. solani AGs were insensitive to fenarimol and imazalil. Tolclofos-methyl strongly inhibited 23 AG2-1 and 20 AG4 rapeseed/canola R. solani isolates from different locations in Saskatchewan, Alberta and Manitoba. The same isolates were also sensitive to iprodione, cyproconazole and carboxin. All AG4 canola isolates were insensitive to pencycuron (EC90 > 500 mg/1) while AG2-1 isolates showed highly variable levels of sensitivity with EC90s ranging from 0.5 to 220 mg/1. Tolclofos-methyl, applied to Brassica napus (canola) cv. Westar seed at 1 g a.i./kg, provided 75-100 % control of seedling damping-off in pots infested with AG2-1 or AG4 isolates. In parallel experiments, pencycuron (1 g a.i./kg seed) failed to control damping-off by AG4 canola isolates and gave variable disease control against AG2-1 isolates.

Controle químico da queima de folhas e da mela de estacas de eucalipto, causadas por Rhizoctonia spp.

“…Isolados pertencentes a dez grupos de anastomose de R. solani (AG1 a AG10), bem como pertencentes a Rhizoctonia spp. binucleadas, foram igualmente sensíveis a baixas concentrações de methyl-tolclophos, com valores de EC 90 inferiores a 3 ppm (Kataria et al, 1991a(Kataria et al, , 1991b. Todavia, para R. solani AG1, os autores observaram ampla variação nos valores de EC 90 a pencycuron (1 a 500 ppm), alto valor de EC 90 para benomyl (38 ppm) e baixo valor de EC 90 para iprodione (1,8 ppm).…”

“…A sensibilidade variável de Rhizoctonia spp. a pencycuron e a benomyl, pode ser explicada pelo fato de esses fungicidas terem modo de ação sítio-específica (Kataria et al, 1991a;1991b). A sensibilidade de R. solani e Rhizoctonia spp.…”

“…são sensíveis a vários grupos de fungicidas, dentre os quais incluem-se os hidrocarbonetos aromáticos (PCNB, chloroneb e o fosforado methyl-tolclophos), benzimidazóis (benomyl, carbendazim, tiofanato-metílico e thiabendazol), carboximidas (carboxin), dicarboximidas (iprodione, vinclozolin e diclozolin), triazóis e triciclazóis (triadimenol, propiconazole, cyproconazole), morfolinas (fenpropimorph) e fenil-uréia (pencycuron). Todavia, existe variação quanto à sensibilidade aos fungicidas, avalidada pela inibição do crescimento micelial in vitro, entre várias espécies de Rhizoctonia (Kataria et al, 1991a) e entre diferentes grupos de anastomose de R. solani (Kataria et al, 1991b …”

Effect of Pencycuron on Fluidity of Lipid Membranes of <i>Rhizoctonia solani</i>

“…12 Kataria et al reported that the sensitivities of R. solani to such fungicides as carboxin, fenarimol, fenpropimorph, imazalil and pencycuron were different in accordance with anastomosis groups. 13 However, as shown in Table 2, even the isolates in the same AG4 were separated into two groups in terms of the sensitivity to pencycuron. Further, the sensitivity of R. solani to pencycuron was found to be in negative correlation with the mycelial growth retardation at high temperature (30C), though an exceptional isolate HI 521-21 existed.…”

Host Range Studies of Rice Sheath Blight Fungus Rhizoctonia solani (Kuhn)

“…has been classified according to 14 anastomosis groups (AGs, AG-1 to AG13 and AG-BI) (Carling et al, 2002). AG is a genetic feature that results in exchange of nuclei and the combining of different genotypes (Kataria et al, 1991 andMartin, 1992).…”