Title : Biological management of bacterial blight of pomegranate using Bacillus subtilis based bioformulations
Abstract:
Pomegranate is an important commercial fruit crop of tropical and sub-tropical parts of the world, known for its rich medicinal and nutraceutical values. Productivity of pomegranate is compromised by a bacterial blight disease caused by Xanthonomas axonopodis pv. punicae (Xap), account for 60-80 % of yield loss. Use of biological management of this disease is prospective option, as antibiotics and synthetics have negative impact on non-targeted beneficial microflora and have consumer repercussions on health. In this context, a potential Xap antagonistic bio-agent Bacillus subtilis UHSBs11 (KX950669) was isolated from the rhizosphere of bacterial blight infected pomegranate. Using this bio-agent as an active ingredient, a liquid based formulation was developed by impregnating plant extracts, chitosan (a sea weed extract), and other substrate molecules that are required for improved bio-efficacy and long viability of candidate bio-agent. Application of this formulation as foliar spray (5 mL/L) recorded 88 % of disease protection under green house condition and 79 % under field when evaluated for two seasons. Foliar application of the formulation also imparts resistance against disease by inducing various defense responsive genes such as phenylalanine ammonia lyase, chitinase, callose synathse and pathogenesis related proteins at different time points of post pathogen inoculation. Prophylactic foliar application resulted in reduced disease compared to generally used chemicals such as streptomycin sulphate, copper oxychloride and Bronopol (2-bromo-2-nitropropane-1,3-diol) simultaneously decreasing cost of cultivation. Further, Bio-formulation improved the reproductive parameters such as total yield and average productivity when compared to control and regularly used synthetic antibiotic.
