Foliar application of chitosan and plant probiotic bacteria influencing the growth, productivity and bulb storage life of onion

Abstract

Onion having several health promoting phytochemical contents is an important spices in most of the countries of the world as well as vegetables in particular and chitosan and plant probiotic bacteria are few proven natural growth enhancing agents. Here, three bio-stimulants namely Chitosan (100 and 200 ppm), Paraburkholderia BRRh-4 bacteria (1.5 × 109 CFU mL-1) and Clybio (0. 1%) in singly as well as combining one another were applied at twelve different treatment combinations including control with the aim of investigating the below and above ground vegetative growth, bulb productivity and post-harvest storage performance of onion cv. “Taherpuri”. The experiment was set up in Randomized Complete Block Design (RCBD) maintaining three replicates and conducted during November 2019 to June 2020 where the bio-stimulant formulations were sprayed in the foliage at 20, 40 and 60 days after transplanting (DAT). Reproductive behaviors of the onion cultivar differed significantly among the treatments and those were the resultants of statistically varied vegetative performances recorded at 30, 60 and 90 DAT. Chitosan @ 100 ppm + Clybio (0.1%) + Paraburkholderia BRRh-4 (1.5 × 109 CFU mL-1) combination exhibited statistical superiority over the other treatments in terms of plant height (53.230 cm), number of leaves (10.13/plant), leaf length (41.20 cm) and diameter (10.33 mm), number of roots (32.53/plant), root length (12.23 cm), neck and bulb diameter (11.20 mm and 4.83 cm, respectively) and bulbing ratio (0.23) at 90 DAT. While, shoot and root growth didn’t vary significantly at earlier stages (at 30 DAT). Again, the highest yield (3.36 kg/plot and 10.45 t/ha) was also obtained from Chitosan @ 100 ppm + Clybio (0.1%) + Paraburkholderia BRRh-4 (1.5 × 109 CFU ml-1) treatment. The combination of chitosan and probiotic bacteria had significant influence on post-harvest storage qualities of onion where the longest shelf life/marketable life (8.17 months) with the lowest physiological weight loss and bulb rotting at 90 days after harvest was administered in Chitosan @ 100 ppm + Clybio (0.1%) + Paraburkholderia BRRh-4 (1.5 × 109 CFU mL-1) treatment. Besides the best treatment, Chitosan @ 100 ppm + Clybio (0.1%) and Chitosan @ 100 ppm + Paraburkholderia BRRh-4 (1.5 × 109 CFU mL-1) produced statistically superior results over control for onion growth and development. Therefore, chitosan and plant probiotic bacteria can be judiciously used for quality onion production in the warm and humid areas of the world