Isolation and Screening of Fluorescent Pseudomonads and am Fungi Against Sclerotium rolfsii Sacc in Brinjal Solanum melongena L

Abstract

The present investigation was carried out for assessing the biocontrol efficacy of native AM fungi and fluorescent pseudomonads against Sclerotium rolfsii Sacc. in brinjal. As many as 125 fluorescent pseudomonads and 40 native AM fungi were isolated from different rhizosphere soils of brinjal growing areas. Out of 125 fluorescent pseudomonad isolates screened, only seven isolates inhibited the mycelial growth of the S. rolfsii Sacc. to an extent of 51.08 per cent. Among the forty native AMF isolates screened, the brinjal plants inoculated with ASAMF24, ASAMF10 and ASAMF18 exhibited higher peroxidase activity, higher per cent of root colonization and lower per cent disease incidence compared to others. Based on the preliminary screening, three each promising isolates of fluorescent pseudomonads and AMF were selected for further studies. The three efficient AMF isolates viz., ASAMF10, ASAMF18 and ASAMF24 were tentatively identified based on morphology of the chlamydospores as Glomus fasciculatum, G. leptotichum and G. macrocarpum, respectively. The biochemical characterization of fluorescent pseudomonads revealed that all them were positive for indole, catalase activity, oxidase activity, citrate utilization, denitrification, gelatin liquefication as well as lipase tests. Whereas, negative for starch hydrolysis, methyl-red, Voges-Proskauer and gas production tests. The functional diversity of the isolates with respect to beneficial traits revealed that all the isolates were positive for P, K and Zn solubilization; production of plant growth promoting substances like IAA, GA3 and ammonia. Two isolates were able to produce HCN. Based on the 16S rDNA sequencing, the isolate APF91 was identified as Pseudomonas fluorescens; APF110 as Pseudomonas sp and APF121 as P. aeruginosa. Pot culture experiment was conducted in the greenhouse conditions to investigate the effect of inoculation of these native fluorescent pseudomonad and AMF isolates (APF110, APF121, APF91, ASAMF 24 ASAMF10 and ASAMF18) on the growth and yield of br