Evaluation of broad spectrum sources of resistance to Fusarium verticillioides and advanced breeding lines

Fusarium verticillioides is the fungus commonly associated with maize production in temperate regions of the world, producing ear rot and contamination of grain by fumonisins. Genetic resistance is the best preventive action against fumonisins contamination, although no commercial maize hybrids are completely resistant at present. Several studies of the relationship between Fusarium and other species producing ear rot suggest that these fungal species interact in similar ways with the host plant. Consequently, host plant resistance to one pathogen could be associated with resistance to another. The aim of this study was to introduce sources of resistance to Fusarium spp. into maize inbred lines and to evaluate ear rot severity and fumonisin B1 contamination in advanced breeding lines and hybrids after artificial and natural infection with F. verticillioides. Two inbred lines (Co430 and Mp420) with resistance to kernel infection by F. graminearum and A. flavus, respectively, were crossed and backcrossed to susceptible inbred 1203. The BC1S1 progenies were evaluated for plant morphology and silk date and the selected S1 plants were self-pollinated. The S2 families were evaluated under artificial and natural infection with F. verticillioides. Selected S2 progenies were grown ear-to-row until S5-derived inbreds were developed. The S5 lines were evaluated under artificial and natural infection and used as males to produce single crosses. In both crosses, the mean ear rot of the S5 lines with the lowest ear rot was not significantly different from the resistant parent means. Significant progress was observed in the hybrids regarding ear rot performance: on average, ear rot severity decreased significantly from 23% in check hybrids to 5.3% in Co430-derived hybrids. Our results suggest that inbred lines bred for resistance to A. flavus and F. graminearum ear rot could be used to select advanced breeding lines with increased resistances to F. verticillioides ear rot.