In vitro screening of citrus rootstocks for salt tolerance

摘要

Citrus rootstocks viz. Rough lemon (Citrus jambhiri Lush.), Rangpur lime (C. limonia Osbeck) and trifoliate orange (Poncirus trifoliata Raf.) were screened for salt tolerance using callus cultures established from internodal stem segments of in vitrogrown 14-18 days old nucellar seedlings. Salt concentration varied from control to 0.20M NaCI in MS medium supplemented with 2 mg/l NAA, 2 mg/l 2-4, O 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 limealso maintained Mg~(++) content at moderate salt levels (up to 0.10M). 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.