Morphological and biochemical basis of resistance in okra to whitefly, Bemisia tabaci andokra yellow vein mosaic virus (OYVMV)

Field screening studies were conducted with 25 okra germplasm accessions during the summer season of 2015 and 2016 at the National Bureau of Plant Genetic Resources (NBPGR) Regional Station, Rajendranagar, Hyderabad. The morphological and biochemical parameters analyzed in the selected okra germplasm lines indicated that among the morphological parameters the germplasm lines possessing high trichome density, less leaf area and dark green leaf colour and biochemical parameters like low nitrogen, protein, less total and reducing sugars and high phenol content offered resistance mechanism against the vector as well as the virus. The three immune okra accessions viz., RJR-124, PSRJ-12952 and IC344598 possessing the above characters were completely free from OYVMV, while the highly susceptible accessions PSRJ-13040 and RJR-193 and the susceptible check Pusa Sawani possessing less trichome density, more leaf area, high sugars, nitrogen content and low phenol content were highly preferred by the vector and were highly susceptible to OYVMV. Total sugars, reducing sugars, nitrogen and protein content had a positive correlation with the whitefly population and OYVMV incidence. The multiple linear regression analysis revealed that the morphological and biochemical parameters together explained the variation in whitefly population and subsequent OYVMV incidence to an extent of 99.00 per cent.