Phytotoxic effects of different antibiotics on leaf explants and their potential as Agrobacterium counter selection agents during gene transfer in apple

Different antibiotics were evaluated for their effects on in vitro callusing of leaf explants and suppressing the growth of Agrobacterium tumefaciens strain LBA 4404 in suspension cultures as well as during co-cultivation in apple rootstock MM 111. Maximum callusing on leaf explant (85–93%) was observed in 300 mg/l carbenicillin, 200 mg/l augmentin and 100–200 mg/l timentin. Low conc. of timentin (100–200 mg/l) effectively inhibited the bacterial growth in suspensions and completely controlled the bacterial overgrowth during co-cultivation after 1^st and 2^nd blot without leaving any deleterious effect on the leaf explants of MM 111.