Influence of biochemical constituents on thrips incidence in selected mulberry (Morus spp.) accessions

Abstract

A study was conducted during 2024-25 at the Department of Sericulture, UAS, GKVK, Bengaluru, to evaluate the seasonal incidence of thrips and to identify resistant mulberry accessions from one hundred mulberry accession. Thrips counts were taken at 15, 30, 45 and 60 days after pruning during rabi, summer and kharif seasons, and accessions were classified into resistance groups based on mean thrips population. From these groups, eleven accessions viz., ME-86, ME-01, ME-52, M-66, ME-18, ME-84, MI-79, MI-524, MI-517, MI-32 and MR-2 were selected for biochemical analysis under healthy and thrips-infested conditions. Thrips infestation significantly reduced total chlorophyll (7-13%), chlorophyll-a (7-15%), and chlorophyll-b (4-12%) across all accessions. Nutrients such as nitrogen (6-13%), potassium (7-13%), protein (6-13%), moisture (8-16%) and carbohydrates (6-12%) also declined, with the highest losses observed in highly susceptible accessions viz., MI-79, MI-517, MI-524, MI-32 and MR-2. Moderately resistant accessions like ME-86, ME-01, ME-52 and M-66 showed only small reductions in nitrogen (6-8%), potassium (6-7%) and protein (6-8%), indicating stronger physiological tolerance to thrips feeding. In contrast, secondary metabolites increased in resistant accessions viz., ME-86, ME-01 and ME-52 showed higher phenol (3.66-3.85 mg/g) and tannin levels (0.96-1.01 mg/g), while susceptible accessions such as MR-2, MI-79 and MI-524 showed slight decreases. Accessions with higher nutrient content viz., ME-84, ME-18 and the highly susceptible group viz., MI-79, MI-24, MI-517, MI-32 and MR-2 supported more thrips, whereas those with higher defensive compounds restricted pest buildup effectively. These findings help identify stable, thrips-tolerant accessions viz., ME-86, ME-01, ME-52 and M-66 for improving mulberry cultivation and sustainable sericulture.