Antagonistic potential of rhizobacterial liquid formulations against Meloidogyne incognita infecting okra under field conditions

Abstract

Okra (Abelmoschus esculentus L. Moench) is one among the commercially exploited vegetable crops. Okra fruits are low in calories and have high dietary fibre content and also rich source vitamins and minerals. However, this crop highly prone to root-knot nematodes. Largely, chemical nematicides have been opted for combating this nematode pest, nevertheless threats associated with chemical nematicides on human being and the environment led towards developing biocontrol agents as alternative approach. The biocontrol agents significantly adhere to biosafety regulations and being highly effective. In recent years, use of rhizobacteria such as Pseudomonas spp. and Bacillus spp. has shown greater biocontrol potential against root knot nematodes. In this endeavor, bio-efficacy of liquid formulation such as Bacillus pumilus (1% A.S) and Pseudomonas putida (1% A.S) were evaluated against Meloidogyne incognita infecting okra (cv. Kashi Pragati) under field conditions for three consecutive years (2015, 2016 and 2017). Both formulations were applied in two methods of application such as seed treatment and soil application of enriched farm yard manure. The results revealed that, seed treatment with P. putida (1% A.S. @ 10 ml/ kg seed) + application of 20 tonnes of FYM enriched with 5 L of P. putida/ ha was found most effective against M. incognita by consistently reducing production of egg mass per root system (73.3%, 84.6% and 76.3%), nematode final population in soil (66.6%, 61.5% and 78.3%)with lesser root gall index (1.0, 1.0 and 1.86) during 2015, 2016 and 2017 respectively, compared to control. The results were comparable with chemical treatments. The application of P. putida formulation (1% A.S) in combination of seed treatment and soil application of enriched FYM significantly protect okra crop from M. incognita incidence and it can be considered as a component under integrated management of M. incognita in okra under field conditions.