Mycelial compatibility and aggressiveness of Sclerotinia sclerotiorum isolates from Brazil and the United States

Abstract

-The objective of this work was to evaluate the genetic diversity among Sclerotinia sclerotiorum isolates from Brazil and the USA, assess their aggressiveness variability, and verify the existence of an isolate-cultivar interaction. Isolate variability was determined by mycelial compatibility grouping (MCG), and isolate aggressiveness by cut-stem inoculations of soybean cultivars. Two experiments for MCGs and two for aggressiveness were conducted with two sets of isolates. The first set included nine isolates from the same soybean field in Brazil and nine from the Midwest region of the USA. The second set included 16 isolates from several regions of Brazil and one from the USA. In the first set, 18 isolates formed 12 different MCGs. In the second set, 81% of the isolates from Brazil grouped into a single MCG. No common MCGs were observed among isolates from Brazil and the USA. The isolates showed aggressiveness differences in the first set, but not in the second. Although aggressiveness differed in the first set, soybean cultivars and isolates did not interact significantly. Cultivar rank remained the same, regardless of the genetic diversity, aggressiveness difference, and region or country of origin of the isolate. Results from screening of soybean cultivars, performed by the cut-stem method in the USA, can be used as reference for researchers in Brazil.Index terms: Glycine max, Sclerotinia stem rot, disease resistance, screening of cultivars, white mold. Termos para indexação: Glycine max, podridão-de-esclerotinia, resistência a doenças, seleção de cultivares, mofo-branco. Compatibilidade micelial e agressividade de isolados de Sclerotinia sclerotiorum do Brasil e dos Estados Unidos

Partial resistance of soybean lines to asian rust and white mold

“…The temperature detected between the inoculation and experiment evaluation periods varied from 17 to 28ºC. According to Link, Johnson (2015), the optimal temperature for mycelial development of S. sclerotiorum must be between 12 and 24ºC. This fact may explain in part the occurrence of smaller lesions in plants, as in a study conducted in field by Juliatti et al (2014), in which the lesions ranged from six to 11 cm.…”

“…When the plants were at the V2-V3 stage, i.e., second and third trifoliate (32 days), the main stem was cut horizontally. The inoculation with a 200microliter pipette tip containing fungal mycelium was performed, which was prepared on the cut stem (CHAWLA et al, 2013;KOGA et al, 2014).…”

Reaction of common bean lines derived from recurrent selection for white mold resistance and aggressiveness of Sclerotinia sclerotirum isolates

“…Some of them identified in Brazil (CARNEIRO et al, 2011;KOGA et al, 2014;SILVA et al, 2014). Similar aggressiveness among isolates from different cultivated areas of Southeast Brazil, have been identified by Lehner et al (2016a), although the authors have used only two common bean genotypes; however, small variation among isolates was observed in the more resistant A195 genotype, which probably induced the expression of different aggressiveness of the isolates.…”

“…It is worth mentioning the great variability to the aggressiveness of different isolates of S. sclerotiorum, identified by Carneiro et al (2011), Koga et al, (2014), Otto-Hanson et al (2011), Pascual et al (2010, and Silva et al (2014). Some of them identified in Brazil (CARNEIRO et al, 2011;KOGA et al, 2014;SILVA et al, 2014).…”

Resistência de genótipos de soja a isolados de Sclerotinia sclerotiorum em casa de vegetação e câmara de crescimento

“…Neste sentido, o teste estatístico dividiu os genótipos de soja avaliados no presente trabalho em 5 grupos ao serem inoculados com os dois isolados. O sucesso da avaliação fenotípica da resistência a este fungo é influenciada pela diversidade patogênica e a variação da agressividade de isolados (KOGA et al, 2014).…”