Saini, RajParmar, Shweta2020-09-212020-09-212020-07-30https://krishikosh.egranth.ac.in/handle/1/5810151645The present investigation entitled “Isolation, characterization and evaluation of phosphate solubilizing bacteria (PSB) in rhizosphere soil of cauliflower” was carried out during 2018-2019 with the aim to explore native phosphate solubilizing bacterial isolates from the rhizosphere of cauliflower crop grown at different locations (Nadaun, Hamirpur and Bhoranj) in district Hamirpur of Himachal Pradesh. The culturable population of bacteria in cauliflower rhizosphere ranged from 82.76 to 232.91×104 cfu/g on nutrient agar medium. Only 23.27% of the total 275 bacterial isolates screened on Pikovskaya’s agar medium were found to solubilize tricalcium phosphate (TCP). Most of them were Gram negative rods and varied in their biochemical characteristics. Among the 61 PSB isolates screened for plant growth promoting traits, all showed growth on nitrogen free Jensen’s medium, 6.55% were HCN producers, 50.81% isolates showed siderophore production and 68.85% were ammonia producers. PSB isolates also exhibited amylase (27.87%) and gelatinase (47.54%) activity. Their phosphate solubilization index (PSI) widely varied from 1.13 to 6.0. Twenty six isolates having PSI more than 3.5 solubilized phosphate (P) in the range of 68.30 to 454.55 μg ml-1 in liquid medium with TCP. Out of them, twenty best PSB isolates produced IAA (3.63 to 37.70 μg ml-1) in tryptophan supplemented medium and highest was recorded for isolate MUN-2. The isolates NAD3-11 from Nadaun, NER-32 and BAL1-11 from Hamirpur and MUN-6 from Bhoranj that accumulated maximum P (395.38, 417.05, 392.88 and 454.55 μg ml-1 respectively) in liquid medium and exhibited multifarious plant growth promoting activities were selected for molecular identification. On the basis of results obtained from the 16S rRNA gene analysis, the four PSB isolates NAD3-11, BAL1-11, NER-32, and MUN-6 were identified as Pseudomonas sp. strain NAD11, Pseudomonas sp. strain BAL11, Pseudomonas sp. strain NER32 and Pseudomonas sp. strain MUN6 respectively. Ten isolates that showed maximum P solubilization were screened for in vitro cauliflower seed germination and growth studies in filter paper assay. The maximum percent increase in root length, shoot length, root and shoot dry weight, and vigour index was recorded for NAD3-11, BAL1-11, NER-32 and MUN-2. The present study concludes that these PSB isolates could be tested as bioinoculants to achieve more sustainable and environment friendly crop production.EnglishThesis