Caracterização morfológica e agressividade de populações de Pratylenchus spp. provenientes de cana-de-açúcar e manejo de fitonematoides na cultura pelo emprego de rizobactérias

Abstract

Sugarcane is among the crops most affected by the presence of phytonematoids, with large losses in productivity observed each year. In view of this problem, the objective of this work was to characterize the nematode populations of the Pratylenchus spp. and evaluate the aggressiveness of Pratylenchus populations in two sugarcane genotypes and to evaluate in vitro and in vivo the potential of bacteria in the biocontrol of the nematodes Meloidogyne javanica and Pratylenchus zeae and promotion of the Growth of this culture In the survey 16 Pratylenchus spp. Populations were obtained, which were characterized by morphological and morphometric characters, with Pratylenchus zeae being found in 100% of the evaluated samples and P. brachyurus associated to P. zeae in only one sample Collected in the municipality of Caxias do Sul. The aggressiveness of four Pratylenchus populations was evaluated in the greenhouse, with three populations of P.zeae, from Crissiumal, Pelotas and Caxias do Sul, and a population of P. brachyurus from Porto Xavier, which were inoculated in two susceptible cane genotypes, P. zeae, being RB9 35581 and RB966928. All populations reproduced in both sugarcane cultivars, presenting RF> 1, showing distinct levels of aggressiveness, which negatively influenced the development of some parameters of plant development, being the most affected, the diameter of the stem And fresh root dough. In order to evaluate the potential of rhizobacteria as growth promoters and phytonuthoid suppression agents, an in vitro selection was carried out in which 48 isolates of bacteria from the fig tree rhizosphere and pyrobetum shales were tested and evaluated for their production capacity Compounds related to biocontrol and / or growth promotion and the intensity of root colonization of sugarcane. Preselected rhizobacteria were then evaluated in vitro on hatching and mortality of second stage (J2) juveniles of M. javanica and in vivo on their nematicidal potential and as growth promoters of M. javanica-infected seedlings and P. zeae. Most of the bacteria selected in vitro and in vivo demonstrated potential as microbiolization agents of sugarcane seedlings, presenting different levels of root colonization intensity. The rhizobacteria XT39 (Micrococcus luteus) and XT23 (Micrococcus luteus), isolated from pyrobetumine shales, showed a promising potential in the biocontrol of Meloidogyne javanica and in the promotion of growth of sugarcane plants.