Características patogênicas de isolados do complexo Fusarium graminearum e de Fusarium verticillioides em sementes e plântulas de milho

Abstract

In Brazil, several Fusarium species are pathogenic to corn affecting seeds, seedlings, stalks and grains. This research aimed to compare isolates from F. verticillioides and from two species of the F. graminearum complex (F. graminearum sensu stricto and F. meridionale) prevalent on corn seeds in relation to mycelial growth rate, ability to colonize and reduce seed germination, reduction in seedling emergence and infect ion and colonization of corn stalk. Permutational test and contrast analysis was performed to discriminate the isolates and species. Principal component analysis was used to identify the variables leading to greatest variance among the isolates. With the exception of seed germination, F. verticillioides isolates showed lower values for mycelial growth rate, infection efficiency, reduction in seedling emergence and lesion size than F. graminearum complex isolates that were all similar. Seedling emergence and seed germination showed greater influ ence on the characterization of isolates, suggesting that seeds infected with F. graminearum isolates of any of the species tested represent a greater threat to crop stand than F. verticillioides isolates.