|Koga, Lucimara - University Of Illinois|
|Bowen, Charles - Roger|
|Godoy, Claudia - Embrapa|
|De Oliveira, Maria - Embrapa|
Submitted to: Brazilian Journal of Agricultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2014
Publication Date: 7/1/2014
Publication URL: http://handle.nal.usda.gov/10113/60178
Citation: Koga, L., Bowen, C.R., Godoy, C., De Oliveira, M., Hartman, G.L. 2014. Mycelial compatibility and aggressiveness comparison of Sclerotinia sclerotiorum isolates from Brazil and the United States. Brazilian Journal of Agricultural Research. 49:265-272.
Interpretive Summary: Brazil and the USA are the top two soybean producing countries in the world. Sclerotina stem rot, a disease caused by a fungus, is considered an important disease in both countries. Pathogenic diversity and variation in isolate aggressiveness may influence the success of screening soybeans for resistance to the fungus. The objectives of this study were to identify genetic diversity among isolates from Brazil and the USA, and assess the variability of aggressiveness among these isolates. No common genetic diversity groups were observed among isolates from Brazil and the USA. When soybean cultivars were inoculated using a cut-stem method of inoculation, differences in aggressiveness among isolates were observed, but there was no inteaction between soybean genotpyes and fungal isolates. This study indicated that independent of the genetic diversity, aggressiveness differences, and region or country of origin of the isolate, soybean cultivars rank remained the same after inoculation with a number of different isolates. This study is important to plant pathologists, biologists, and others intersted in fungal diverstiy and host plant resistance.
Technical Abstract: Variability of Sclerotinia sclerotiorum isolates collected in Brazil and the USA were determined by mycelial compatibility grouping (MCG) and 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 field in Brazil and nine from the Midwest region of the USA. The second set included 16 isolates from several regions in 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 in a single MCG. No common MCGs were observed among isolates from Brazil and the USA. When soybean cultivars were inoculated with cut-stem method, differences in aggressiveness among isolates were observed in the first set, but not in the second set of isolates. Although aggressiveness differed among isolates in the first set, no significant interaction was detected between soybean cultivars and isolates. Independent of the genetic diversity, aggressiveness difference, and region or country of origin of the isolate, soybean cultivars rank remained the same. This study showed that the evaluation of soybean cultivars using the cut-stem method would be similar regardless of the origin (Brazil or USA) of the S. sclerotiorum isolate.