Resistance of Argentine maize germplasm to Gibberella and Fusarium ear rots

Abstract

Fusarium graminearum (Schwabe) and F. verticillioides (Saccardo) Nirenberg infect maize (Zea mays L.) causing Gibberella and Fusarium ear rots, respectively. This study was conducted to evaluate maize germplasm from Argentina as sources of resistance to Gibberella and Fusarium ear rots. Forty-one landraces, six improved populations and six commercial hybrids from Argentina were compared to two local check hybrids in inoculated field experiments conducted in Ottawa, Ontario, Canada. Inoculation involved injection of conidial suspensions of F. graminearum or F. verticillioides into the silk channel or into developing kernels. A cluster analysis was performed for grouping the accessions according to the ratings of disease severity obtained after inoculation. Several Argentinian accessions exhibited disease resistance, with a higher frequency of resistance to Fusarium rather than Gibberella ear rot consistent with the fact that F. verticillioides is more prevalent than F. graminearum in Argentina. The 55 genotypes were grouped into two major clusters, with one of the clusters consisting of thirty-one of the most resistant exotic genotypes and the resistant check hybrid (Syngenta G4106). All accessions from certain races, such as Cristalino Colorado, and all the improved populations were grouped in this cluster and appear to be promising sources of resistance to these ear rots. The probability of finding sources of resistance to Fusarium and Gibberella ear rots from Argentinian native maize germplasm seems to differ according to the race and the region from which the accessions were collected. Positive correlations between disease severity obtained after silk and kernel inoculation and after inoculation with both pathogens indicated that general resistance mechanisms may exist.