Screening and characterization of nutrient solubilizing phytobeneficial rhizobacteria from healthy coconut palms in root (wilt) diseased tract of Kerala, India

Abstract

Aim: Isolation, screening and characterization of beneficial rhizosphere bacteria associated with healthy (field-resistant) coconut palms in root (wilt) disease endemic hotspot areas of Kerala. Methodology: One hundred and ten rhizobacterial isolates associated with healthy coconut palms of root (wilt) diseased tract of Kerala were isolated and screened in-vitro for IAA production and solubilization of fixed forms of mineral nutrients. Seven isolates showing multiple phytobeneficial properties were characterized and the selected isolate was tested for its biopriming effect on maize. Results: Of the total isolates screened, 54 isolates produced IAA. Among the nutrient solubilizers, silicate solubilizers (57%) and phosphate solubilizers (48%) dominated. Of the seven isolates with multiple phytobeneficial properties, five rhizobacterial isolates belonged to Enterobacteriaceae family including three Enterobacter spp. The isolate T4HFB9 belonged to Acinetobacter sp. The green fluorescent Pseudomonas isolate K3HPSB2, showed 99% sequence similarity with Pseudomonas migulae. Seed biopriming of maize with Pseudomonas sp. strain K3HPSB2 recorded significant increase in germination percentage and seedling vigour index over untreated control. Interpretation: Disease-resistant coconut palms in RWD endemic tracts host a good proportion of phytobeneficial rhizosphere bacteria,with demonstrable multiple plant growth promoting traits. Multi-nutrient solubilizing Pseudomonas sp. with bioinoculant prospects has been selected for further studies on bio-priming for palm health management in RWD endemic tracts.