MODGIL, MANJUVIKRANT2019-08-022019-08-022019-05http://krishikosh.egranth.ac.in/handle/1/5810118722ABSTRACT To facilitate the use of marker assisted selection in apple breeding programme, six PCR based specific sequence characterized amplified region (SCAR) markers were developed from crab apple. Seven biotypes of indigenous crab apple biotypes maintained at two field gene banks of Himachal Pradesh state of India were used to identify RAPD markers for resistance to apple scab and woolly aphis. RAPD molecular analysis was evaluated among seven biotypes using 119 primers. Among these, 94 primers generated polymorphism. Four primers OPB-12, OPB-14, OPD-06 and OPA-18 amplified five unique bands of 500bp, 1kbp, 1kbp, 1kbp and 1kbp in M. baccata Shillong, M. baccata Khrot, M. baccata Kinnaur (Dhack), M. baccata Kashmir and M. baccata J&K respectively. These markers were gel purified and cloned into easy cloning TA vectors. Plasmid of the confirmed positive clones after restriction digestion and colony PCR was subjected to sequencing and homology search. Sequences showing homology with the apple scab and woolly aphid resistant genes were used to design pairs of six SCAR primers, which specifically amplified these RAPD fragments in crab apple biotypes as well as M. floribunda and apple rootstock MM106 of known resistance. No amplification was observed in commercially grown varieties of apple, therefore, it is verified that all six SCAR markers were able to distinguish between the resistant and susceptible apple genotypes. Molecular marker assessment with already developed nine SCAR markers in fourteen individual plants of crab apple verified their presence/absence and in accordance with the bioassay results.ennullThesis