Genetic diversity and evacuation of advanced lines for resistance to downy mildew (Psuedopernospora cubensis) diseases in cucumber [Cucumis sativus]

Abstract

An investigation was under taken to assess the genetic diversity, heritability, genetic advance, morphological and molecular characterization and screening for downy mildew disease resistance in advanced lines was conducted at IIHR, Bangalore, during 2010- 2011. To assess the genetic variability and diversity of 38 genotypes of diverse origin were tested for 17 quantitative morphological traits. Genotypic and phenotypic variation was high for node at first female and male flower appear and yield per plant. High heritability coupled with genetic advance over mean was recorded for node at first female flower appears and yields per plant. Fruit yield had positive and highly significant association phenotypically and genotypically with 100 seed weight, vine length, number of fruits per plant and flesh thickness. Vine length, number of fruits per plant and flesh thickness had positive and direct genotypic and phenotypic effects on fruit yield per plant. The cucumber lines were analysed by using 13 RAPD primers those produced 103 DNA markers bands. A total of 67 polymorphic bands were obtained with a mean of 5.15 bands per primer. The cluster drawn out of the distance matrix grouped various genotypes in to two major cluster as A and B, than again major cluster A is sub divided in to A1 to A9. The highest dissimilarity percentage was between genotypes IIHR-409-2 and 595920. The genotypes Swarna Ageti, Sangeeta, Nandini, Barsati, Ajax, VR-101, VR-06-07, IIHR-405, Karur Local IIHR-407-1, and IIHR-409-2 were found to be moderately resistant and Cucumis hardiwickii showed highly resistant to the downy mildew disease.