Pathak, D.V.Sharma, Nidhi2022-03-172022-03-172020https://krishikosh.egranth.ac.in/handle/1/5810183638The studies on chitinase activity of bacterial isolates against thrips on Kinnow were carried out at citrus orchard with the objective Impact of chitinase producing bacteria on thrips infestation in citrus plantation. Plant growth promoting rhizobacteria (PGPR) are root associated bacteria and benefit plants by providing growth promotion through a variety of mechanism. The public concern over the harmful effects of chemical pesticides on the environment and human health has enhanced the search for safer, environmentally friendly control alternatives. Due to the importance of chitinolytic enzymes in insect, nematode, and fungal growth and development, they are receiving attention in regard to their use as biopesticides and microbial biocontrol agents. Therefore, the present study was aimed to isolate and characterize the chitinolytic bacterial isolates and also evaluate their efficacy. A total of eighty morphologically distinct bacterial isolates were retrieved from soil samples of different microbiomes on King‘s B media and these bacterial isolates were screened for chitinase production out of these twenty isolates was showed zone of clearance on the collodial chitin agar plates where zone of clearance and enzyme activity index were used for initial screening of chitinolytic bacteria. Twenty out of eighty bacterial isolates were selected as chitinase producers on the basis of zone size ranging from 12.40 mm to 38.50 mm and were further screened for quantitative chitinase production. Quantitatively it was screened for chitinase enzyme activity on the basis of release of N-acetylglucosamine units (U) by action of chitinase, maximum enzyme activity was recorded for isolate B1 (3.905) followed by B5 (3.52) and D2 (1.35). A total of twenty bacterial isolates, were studied on the basis of their morphological and microscopic characterstics which showed a variation in margins, elevation, shape, pigmentation, Gram‘s reaction and cell shape. These bacterial isolates was biochemically characterized, isolate B5 was found positive for various biochemical tests such as citrate utilization test, Voges Proskauer (VP) test and negative for methyl red test. All the twenty isolates was screened for multifarious plant growth promoting traits viz. IAA production and HCN production. Three bacterial isolates which exhibited maximum chitinase activity were further evaluated for their biocontrol potential against thrips of citrus under field conditions. Kinnow were sprayed with three different bacterial isolates B1, B5, D2 (106 cfu/ml), dimethoate phosphamide spray and nimbicide at different concentrations (1.5ml/L, 2ml/L respectively). One isolate B1 showed maximum biocontrol efficacy in reduction of thrips population -79.66 percent against thrips in kinnow in comparison to control where -37.70 percent of reduction of thrips population was recorded. The percent infestation recorded for B1 isolate was 20 percent as compared to control where infestation was 36 percent. The mean population density recorded for B1 was 0.4 as compared to control where density of thrips was 0.96. The identification of B1 was tentatively confirmed by biochemical characterization and it was identified as strain belonging to Bacillus sp.EnglishThesis