Biological Control and Plant Growth-Promotion Traits of Streptomyces Species Under Greenhouse and Field Conditions in Chickpea

Thirty-five isolates of actinomycetes were characterized for their antagonistic potential against phyto-pathogens of chickpea by dual-culture and metabolite production assays. The seven most promising isolates of Streptomyces were evaluated for their physiological and plant growth-promoting traits under in vitro and in vivo conditions. All the seven isolates exhibited good growth at temperatures between 20 and 40 °C, pH between 7 and 11 and saline concentrations up to 4%; all the isolates were highly tolerant to fungicide Bavistin, three isolates were moderately tolerant to Captan and all the isolates were susceptible to Thiram, Benlate and Ridomil. All the seven isolates of Streptomyces produced siderophore, chitinase (except isolate CAI-133), cellulase, lipase, protease (except isolates BCA-689 and CAI-133), hydrocyanic acid (except isolate CAI-133), indole acetic acid and β-1,3-glucanase. The greenhouse studies revealed that the isolates of Streptomyces enhanced the plant growth by promoting root length and weight, nodule numbers, shoot weight, pod numbers and pod weight over the un-inoculated control. Under field conditions, the Streptomyces treated plots increased the nodule numbers, root weight, stover yield and grain yield over the un-inoculated control plots. In the rhizosphere, the Streptomyces were also found to enhance the total nitrogen, available phosphorus and organic carbon compared to un-inoculated control. The colonizing capability of the Streptomyces on the roots of chickpea was confirmed by scanning electron microscopic analysis. All the isolates were identified as Streptomyces species by 16S rDNA analysis; five of the seven isolates clustered in one clade, whereas the other two belonged to two different clades in phylogenetic analysis