Genetic diversity assessment and gene expression analysis of prolonged shelf-life genes in Mangalore melon (Cucumis melo ssp. agrestis var. acidulus)

Mangalore melon (Cucumis melo ssp. agrestis var. acidulus) is a non-dessert melon, extensively grown in the coastal districts of South India, but hardly known to the rest of the World. Immature or mature fruits of Mangalore melon are used in preparation of delicious dishes such as vegetable stew, chutneys and curries. They are appreciated for nutritional values, long shelf life and biotic stress resistance. Seventy-nine accessions of Mangalore melon were collected from five states of South India and their genetic diversity was assessed using inter simple sequence repeat (ISSR) markers. Putative candidate genes of extended shelf life in Mangalore melon were studied by quantitative reverse transcription polymerase chain reaction in comparison with cantaloupe (Cucumis melo L.). Shelf life varied from 65 to 300 days at room temperature. Six ISSR primers amplified 142 fragments ranging from 80 to 2380 bp with an average of 23.66 bands per marker on a high-resolution capillary electrophoresis system. Neighbor joining phylogenetic tree construction from the ISSR allele similarity based genetic distance revealed two major clusters with 46 and 33 accessions in each cluster. Expression of fruit ripening related genes of ethylene biosynthesis (1-aminocyclopropane-1-carboxylate synthase, 1-aminocyclopropane-1-carboxylate oxidase) and cell wall metabolism (polygalacturonase, xyloglucan endotransglucosylase/hydrolase and expansin) in Mangalore melons was significantly lower than the cantaloupe melon at 180 days after harvest. Mangalore melon is a promising genetic resource for enhancing the shelf life of melons. The putative candidate genes identified here are useful in enhancing shelf life of cantaloupe.