Assessment of nematicidal properties of fluorescent pseudomonads using peanut root-knot nematode, Meloidogyne arenaria

Abstract

The primary objective of this study was to identify natural isolates of fluorescent pseudomonads with superior antagonistic activity towards plant parasitic nematodes. Nematicidal potential of eighteen isolates of fluorescent pseudomonads were compared against peanut root-knot nematode, Meloidogyne arenaria. Cell-free culture filtrate of DAPG-producing isolates of Pseudomonas putida caused significantly higher mortality of M. arenaria (J2) with highest in isolate DAPG3 (87.36%), followed by DAPG1 (84.16%) compared to other isolates of fluorescent pseudomonads, i.e., P. gessardii BHU1 and P. aeruginosa BM6 after exposure period of 72h at 100% concentration. The selected DAPG-producing isolates of P. putida caused significant inhibition in egg hatching. The lowest cumulative per cent hatch of M. arenaria was observed in the isolate DAPG3 (17.84%) followed by DAPG1 (18.10%). The isolates DAPG1 and DAPG3 also inhibited the nematode invasion in the roots of peanut by 41.30% and 36.34%, respectively. Significant reduction in number of galls/plant in peanut roots was recorded. The maximum reduction (51.30%) in root galling was recorded with combination of seed treatment and soil application of P. putida DAPG1 followed by 41.73% in combined treatment of seed treatment and soil application of P. putida DAPG3. The levels of Peroxidase (POD), Catalase (CAT) and Polyphenol Oxidase (PPO) were non-significant in the leaves of peanut in the treatment that received P. putida DAPG1 and DAPG3, either as seed treatment and/or soil application, compared to inoculated and un-inoculated control. However, significantly enhanced phenol content was recorded in the leaves of peanut in the treatment that received combination of seed treatment and soil application of P. putida DAPG1 and seed treatment alone.