Department of Plant Breeding, CCS Haryana Agricultural University, Hisar 125 004.
1Present address: National Research Centre for Citrus, Post Bag No. 464, Shankar Nagar P.O., Nagpur 440010.
Citrus rootstocks viz. Rough lemon (Citrus jambhiri Lush.), Rangpur lime (C. Iimonia Osbeck) and trifoliate orange (Poncirus trifoliata Raf.) were screened for salt tolerance using callus cultures established from internodal stem segments of in vitro grown 14–18 days old nucellar seedlings. Salt concentration varied from control to 0.20M NaCl in MS medium supplemented with 2 mg/l NAA, 2 mg/l 2–4, 0 and 0.5 mg/l Kinetin. Salt stress, imposed for 6 weeks, decreased fresh and dry callus weight in all the rootstocks, but highest reduction occurred in trifoliate orange and lowest in Rangpur lime. Na+, cl− and Na: K ratio increased with increase in salt level in all the rootstocks, but they were maintained at a lower level in Rangpur lime. Rangpur lime also maintained Mg++ content at moderate salt levels (up to 0.10 M). Callus browning was highest in trifoliate orange and lowest in Rangpur lime. Rangpur lime was determined as tolerant, Rough lemon moderately tolerant and trifoliate orange as susceptible to salinity. Maintenance of low Na: K ratio, high Mg++, and low Cl− in callus were observed as reliable markers for screening citrus rootstocks for salt tolerance and the use of in vitro techniques is suggested for screening of large citrus germplasm for salt tolerance.
Citrus rootstocks, salt tolerance, Rough lemon, Rangpur lime, trifoliate orange, callus cultures
