Biocontrol of Pratylenchus zeae and sugarcane growth promotion by rhizobacteriaABSTRACT
The root lesion nematode (Pratylenchus zeae) is one of the main phytosanitary problems of sugarcane, and the biological control is an important tool in the integrated nematode management. Thus, the objective of this study was to evaluate the potential of rhizobacteria in the biocontrol of P. zeae and their plant growth promotion (PGPR) in sugarcane. Seedlings of sugarcane ‘RB008347’ were microbiolized with individual suspensions of nine bacterial isolates in a greenhouse. After 15 days, the plants were transplanted to pots containing sterilized soil, and then were inoculated or not with 1000 specimens of P. zeae/plant under greenhouse conditions. Non-microbiolized seedlings inoculated or not with the nematode were used as controls. Ninety days after inoculation, each plant was evaluated for its development, number of nematodes/root system, nematode/g of roots and nematode reproduction factor. In an in vitro bioassay, the nematicidal activity of these bacteria on specimens of P. zeae was evaluated. Additionally, the bacterial isolates were characterized biochemically regarding production of compounds related to nematode biocontrol and PGPR. The majority of isolates promoted significant increases in the number of tillers, shoot fresh and root fresh mass, and suppressed P. zeae reproduction (48-74%) compared to the control. In the in vitro bioassays, the isolates XT23, XT26, XT51, XT56, XT37 and P17 showed nematicidal activity and produced at least one compound related to the biological control of phytonematodes and PGPR. In this way, the microbiolization of sugarcane seedlings with rhizobacteria demonstrates its effectiveness as a bionematicide and growth promoter for sugarcane crops.
Keywords:
Biological control; PGPR; Root-lesion nematode; Saccharum spp.