Inoculum sources and chemotype characterization of Fusarium graminearum species complex isolated from soybean fields in Argentina

CHIOTTA M. L; TANO, M. J; BARROS G.G.; CHULZE , S.N

Durban

Congreso; World Soybean Research Conference; 2013

International Soybean Society

Inoculum sources and chemotype characterization of Fusarium graminearum species complex isolated from soybean fields in Argentina. María L. CHIOTTA, María J. TANO, Germán G. BARROS, Sofía N. CHULZE Departamento de Microbiología e Inmunología. Universidad Nacional de Río Cuarto. Ruta Nacional 36 Km 601, Río Cuarto, Córdoba, Argentina. E-mail schulze@exa.unrc.edu.ar Soybean (Glycine max L.) is the most important crop in Argentina. Most of the studies within the Fusarium graminearum species complex (FGSC) have focused on populations isolated from wheat, barley and maize, and there is little information about the epidemiology of members belonging to this complex in soybean crop. The aim of the present study was to: (i) evaluate the inoculum sources of FGSC in two soybean fields (ii) characterize the chemotype and genotype diversity among the FGSC isolated from soybean. Samples were collected during the 2011/12 growing season in experimental plots conducted at the Universidad Nacional de Río Cuarto, Córdoba, Argentina. The cultivar used is genetically modified for tolerance to glyphosate (maturity group IV) under no-till cultivation system. The samples were taken in two diagonal transects extending from opposing corners. A total of twenty samples (ten from each transect) of either debris, pods and seeds were taken sequentially at two soybean reproductive stages: R6 (full seed) and R8 (full maturity). Viable airborne spores were collected on Petri plates contained Nash-Snyder medium follow the methodology proposed by Schmale et al. (2006). For trichothecene chemotype, toxin analysis was done by using a modified version of that originally reported by Cooney et al. (2001). For determination of genotype, multiplex PCR experiments were conducted according to Quarta et al. 2005, 2006. Among the Fusarium species identified, F. equiseti was the most frequently recovered from pods seeds and air, while F. solani was the dominant species isolated from debris. Members of FGSC were isolated from the four substrates evaluated showing higher isolation frequencies in pods and debris at plant growth stages R6 and R8at two soybean fields. The F. graminearum species complex isolated from soybean consisted mostly of the 15-ADON based on PCR genotype and chemical determination.