MODGIL, MANJUPATIDAR, SHIRISH2019-07-232019-07-232019-05http://krishikosh.egranth.ac.in/handle/1/5810116341DEVELOPMENT OF COLLAR ROT RESISTANT SOMACLONAL VARIANTS IN APPLE ABSTRACT Apple rootstock MM106 is a commercially productive and semi dwarf tree which is resistant to woolly apple aphid but highly susceptible to collar/crown rot. In the present investigation, an attempt has been made to develop collar rot resistant somaclones using in vitro shoot selection technique. Leaf raised regenerants of MM106 recently selected in vitro on 70-74% fungal culture filtrate (FCF) supplemented MS medium, were exposed to similar concentration of FCF for third continuous selection cycle. It was observed that approx 8187% tolerant regenerants survived on 72% and 70%, while 74% concentration was found inhibitory to all the regenerants. 100% survival was obtained in discontinuous cycle. Multiplication ability was reduced initially but in successive subcultures, FCF tolerant regenerants showed similar multiplication rates as found in axillary bud raised control shoots. Rooting frequency and root system in tolerant regenerants were found better than control shoots. Maximum hardening success of 42.37% was observed in tolerant regenerants. Sixteen FCF tolerant regenerants were screened for resistance in the pathogen inoculated soil. Symptoms like lesion, girdling of stem below the soil level, colour change in roots to reddish brown appeared on control plants, while no such type of symptoms in somaclones. RAPD analysis clearly distinguished the control plants and somaclones. Two unique bands generated by one primer was sequenced which showed leaf rust resistant gene. In conclusion, collar rot resistant plants of apple rootstock MM106 have been developed using in vitro selection of somaclonal variants which may be recommended as cost effective, non- transgenic and promising approach.ennullThesis