Plant growth promoting effects of Pseudomonas sp. on coinoculation with Mesorhizobium sp. Cicer strain under sterile and “wilt sick” soil conditions

Abstract

Fluorescent Pseudomonas spp. were studied to determine their effects on seedling growth, nodulation and plant growth in chickpea ( Cicer arietinum L.). Seed inoculation with the rhizobacteria caused stunting of root growth of chickpea seedlings at 5 days in comparison to the control, whereas the same rhizobacteria caused stimulation of shoot growth of both green gram ( Vigna radiata L.) and chickpea seedlings at 9 days of plant growth under aseptic conditions. Coinoculation of the rhizobacteria with an effective Mesorhizobium strain from chickpea (Ca181) resulted in a significant increase in nodule weight and shoot biomass, when grown in sterilized chillum jar conditions. The shoot dry weight gains at different stages of plant growth varied from 1.05 to 1.57 times that in Mesorhizobium-inoculated treatments and 2.28–3.38 times that in uninoculated controls at 75 days of plant growth. Three Pseudomonas strains (MRS13, CRS55b and CRS68) caused maximum gains in plant dry weight ratios, i.e. 1.92, 1.84 and 1.98 times those of Mesorhizobium-inoculated and 4.08, 3.92 and 4.20 times those of uninoculated control plants, respectively, at 90 days of plant growth. Under pot culture conditions, seed inoculation with rhizobacteria, singly or in coinoculation, significantly increased root and shoot biomass, even in wilt sick soil amended with fungal pathogens. The plant growth-promoting effects of Pseudomonas strain MRS13 from the rhizosphere of green gram on coinoculation with Mesorhizobium sp. Cicer strain Ca181 in legumes particularly chickpea indicated the usefulness of introduced rhizobacteria in improving the plant growth of subsequent crop.