Comportamento de genótipos RB de cana-de-açúcar a nematoide das galhas e avaliação dos mecanismos de resistência envolvidos

Abstract

One of the most economic importance crops in Brazil, the sugarcane (Saccharum spp.) cultivation is severely affected by several biotic and abiotic factors. Within the biotic one the damage caused by Meloidogyne species points out due to lesions in parasite roots resulting in decreases of productivity. The non-availability of root-knot nematode resistant varieties becomes more serious after reduction in nematicides use, increasing efforts in turn resistant varieties a possible alternative. Therefore, the objectives of the present work was screening promising sugarcane genotypes for M. incognita and M. javanica resistance (Study 1) and determine the resistance mechanisms involved through evaluation of penetration, development and reproduction of the nematodes in the selected material (Study 2), under greenhouse. In Study 1, evaluations were carried out 120 days after inoculation with 9000 eggs per plant and based on host development and nematode reproduction. There was significant difference (P≤0.05) within genotypes for all plant development and nematode reproduction variables. Although all genotypes were susceptible (FR≥1.0) to M. incognita and M. javanica, in some of them the reproductive factor (FR) was lower than the control. In Study 2, five genotypes were inoculated with 20000 eggs per plant and evaluations carried out at 5, 10, 15, 20, 40 and 60 days after inoculation. There was difference in nematode penetration among genotypes, and despite juveniles of both nematode species penetrated all genotypes at five days after inoculation, nematode development significantly differed among clones. At 60, but 45, days after inoculation eggs were evident in the genotypes. Reduced penetration and development rates were demonstrate by the genotypes RB041594 e RB071095.