AGGRESSIVENESS OF DIFFERENT ISOLATES MACROPHOMINA PHASEOLINA AND THEIR INTERACTION WITH SOYBEAN CULTIVARS AGGRESSIVENESS OF MACROPHOMINA PHASEOLINA ISOLATES ON SOYBEAN

Abstract

The objective of this research was to evaluate the aggressiveness of ten Macrophomina. phaseolina isolates on two soybean cultivars. This fungus is the etiologic agent of charcoal rot and occurs on most of the crop areas in Brazil, causing losses in quality, productivity and rentability. The isolates, originating from different Brazilian states, were inoculated on soybean cultivars, Brasmax Bônus IPRO and Brasmax Desafio RR, through immersion of seeds on a mix of fungus spores, mineral oil and sugar solution. The research was conducted on a greenhouse with controlled temperature and irrigation system, where the evaluated variables were seedling emergence percentage, radicle and necrosis length (mm). An interaction between the factors of cultivar and isolates was observed for the seedling emergence percentage, but not for the radicle and necrosis length. All tested isolates were pathogenic to soybean, having differing levels of aggressiveness depending on the cultivar and isolate. The isolates MACRO – UFU 5 and MACRO – UFU 2 resulted in the death of 90 to 100% of Brasmax Bônus IPRO and Brasmax Desafio RR seeds, being considered the most aggressive. Although the resistance to M. phaseoline is quantitative, with a variable defense system depending on cultivar and isolate, the selection of a highly aggressive isolate can help with the analysis of resistant cultivars.