Relationships between Burkholderia populations and plant parasitic nematodes in sugarcane

It is suggested that the bacterium Burkholderia tropica might be used to reduce nematode damage in sugarcane by promoting certain nematode species to create a less pathogenic nematode community. This suggestion arises from an investigation of the plant parasitic nematodes and their relationship with Burkholderia species along a sugarcane row. During the course of this analysis sugarcane root and soil samples were taken atintervals (15,45,55, 75, 80, 85, 120, 150, 185, 190, 195 in) along a 200 in cane row across a cane field for nematode and bacterial analyses at various times after planting. Soil physical and chemical characteristics were similar at all sampling points. The numbers of culturable bacteria and Burkholderia were significantly greater during the early part of the crop cycle when plants were younger. The diversity of the Burkholderia communities was characterized by groups using Amplified Ribosomal 16S rDNA Restriction Analysis. Six groups were present. Burkholderia species in each group were identified using 16S rDNA sequencing. It was observed that B. ambifaria and B. cenocepacia, were dominant at all sampling dates, although less so as the crop aged. The common nematode species were Pratylenchus zeae, Paratrichodorous minor, Xiphinema elongatum and Helicotylenchus dihystera. A spatial association of nematodes and Burkholderia species along the cane row was identified using Principle Component Analysis (ADE-4 software). The more pathogenic X. elongatum, was associated with B. graminis, B. silvatiantica, B. gladioli, B.fungorum and was dominant at the beginning of the cane row where planting started. In contrast the less pathogenic species H. dihystera and P. zeae, were associated with B. tropica and were more common towards the end of the cane row where planting ended. Coinertia analysis revealed that B. tropica was positively correlated with H. dihystera and P. zeae, but negatively correlated with X. elongatum