Streptomyces consortium improved quality attributes of bell pepper fruits, induced plant defense priming, and changed microbial communities of rhizosphere under commercial greenhouse conditions

Abstract

Although many studies have shown the positive effect of PGPRs on the yield and quality characteristics of crops, only a few are successful in commercial greenhouses. This study aimed to evaluate the efficiency of PGP-Streptomyces in commercial greenhouse conditions. Greenhouse trials were done with four treatments including strains SS12, Y17, an effective combination of strains SS14 and IT20, and a commercially available bio-fertilizer (Barvar NPK®) on two cultivars of bell pepper. Treatment with strain SS12 improved the yield of green (26%) and orange (5%) bell pepper compared to the control while SS14 + IT20 increased only the yield of green pepper (23%). The score value of overall acceptance obtained from the sensory evaluation of orange bell peppers treated with SS14+ IT20 was the highest, following the higher score values of quality properties including appearance, flavor, smell, and juiciness. Treatments of Barvar and SS14+ IT20 reduced the nitrate content of both cultivars by about 32–41% and based on the analysis of variances, SS14+ IT20 was more effective than Barvar. Lower concentrations of fruit sugar without affecting its acceptance and higher levels of micronutrients Ca, Zn, and Fe indicate the higher nutritional value of SS14+ IT20 -treated peppers. Increased expression of defense genes ERF and PR1 and higher activity of antioxidant enzymes in SS14+ IT20 and Barvar showed that treated plants are ready to deal with possible pathogens that cause damage in commercial greenhouses. The results of this study showed for the first time that PGP-Streptomyces can be effective in commercial bell pepper greenhouses.