Fusarium graminearum species complex occurrence on soybean and F. graminearum sensu stricto inoculum maintenance on residues in soybean‐wheat rotation under field conditions

Abstract

Aims: The aims of this study were to determine the occurrence of Fusarium graminearum species complex (FGSC) on soybean pods, seeds and roots, including rhizoplane, during the soybean crop in rotation with wheat and to evaluate the FGSC dynamics on wheat and soybean residues during two soybean growing season in rotation with wheat, particularly of F. graminearum sensu stricto (FGss). Methods and Results: Soybean roots, pods and seeds were analyzed during 2012/13 and 2013/14 season. The morphological identification of FGSC and mycotoxin analysis were done. Crop residues were taken in both soybean season in wheat rotation and FGss was quantificated by real‐time PCR. The results showed that Fusarium species, mainly FGSC, survive in a soybean crop in rotation with wheat. Isolation frequency of these species was higher on soybean pods than on seeds at R6 stage. Deoxynivalenol contamination on soybean seeds was higher in 2013/14 season in comparison with 2012/13 season. Low isolation levels of Fusarium species and no species belonging to FGSC were observed in soybean root whereas in rhizoplane a higher level was observed. Fusarium species inoculum on residues remained stable during crop succession and the FGSC were recovered from both wheat and soybean residues. Real time PCR data showed a higher DNA concentration of FGss in wheat residues in the first development stages of soybean plants, being the levels more significant during 2012/13 season. As regard soybean residues collected during the wheat growing stages, an increase in DNA from anthesis until wheat harvest was observed. Conclusions: In a notill production system the populations of FGSC can colonize wheat and soybean residues to become an inoculum source. Significance and Impact of the Study: This study provides new data on the occurrence of FGSC populations in soybean plant and FGss on residues in soybean‐wheat rotation, a cultural practice commonly used in in Argentina.