Sensibilidade a fungicidas e adaptabilidade de Lasiodiplodia theobromae patogênico ao mamão

Abstract

Application of fungicide is the main measure of management to stem-end rot and there is no information on the sensitivity and on the fitness costs arising from the reduction in sensitivity of its causal agent, Lasiodiplodia theobromae. One hundred and twenty monosporic isolates collected in producing areas of the Northeast region of Brazil, were divided into six populations. We evaluated the in vitro sensitivity (inhibition of mycelial growth) of the isolates to class the fungicides belonging to two groups: benzimidazoles and sterol demethylation inhibitors (DMIs). We also evaluated the fitness of isolates with different levels of sensitivity the fungicides both in vitro and in vivo (mycelial growth and aggressiveness). The average EC50 for DMIs ranged from 0,141 to 4,054, 0,045 to 0,691 and from 0,001 to 1,529 for tebuconazole, prochloraz and imazalil, respectively. The level of sensitivity to DMIs did not differ among populations. For the benzimidazoles EC50 of 91.6% of the isolates ranged from 0,002 to 0,14 and 0,36 in 1,272 (benomyl and thiabendazole,respectively).The 8.4% isolates, classified as not sensitive (NS) were not inhibited at the highest concentration evaluated (100μg ml of a.i-1). All NS isolates were from the same population. The aggressiveness of NS isolated was lower.