Protected cultivation of vegetables is often hampered by declining nutrient availability in soil due to year-around farming, which in turn, leads to poor quality and yields, causing serious concern. Our study aimed towards evaluating the potential of novel biofilm formulations-Anabaena or Trichoderma as matrices with Azotobacter sp. as Anabaena-Azotobacter (An-Az) and Trichoderma-Azotobacter (Tr-Az) or together as Anabaena-Trichoderma (An-Tr), on the growth, physiological activities, yield, and changes in the profiles of soil microbial communities in two cultivars (cv. DAPC-6 and cv. Kian) of cucumber (Cucumis sativus). Photosynthetic pigments, evaluated as an index of growth showed two-threefold increase, while elicited activity of defense and antioxidant enzymes was stimulated; this facilitated significant improvement in the plants belonging to the inoculated treatments. Microbial biomass carbon and polysaccharides in soil enhanced by two-threefolds in treatments receiving microbial formulations. Available N in soil increased by 50-90% in An-Az and An-Tr biofilm inoculated treatments, while the availability of P and organic C content of soil improved by 40-60%, over control. PCR-DGGE profiles generated revealed signification modulation of cyanobacterial communities and cultivar-specific differences. Significant enhancement in leaf chlorophyll pigments, soil microbiological parameters and nutrient bio-availabilities along with positive correlation among the analysed parameters, and distinct profiles generated by PCR-DGGE analyses illustrated the promise of these novel inoculants for cucumber.
Keywords: Antioxidant enzymes: biofilm; Cyanobacteria; Nutrients; Protected cultivation; Trichoderma.