IN VITRO SELECTION OF SOMACLONES OF SUGARCANE UNDER DROUGHT STRESS CONDITION AND THEIR EVALUATION IN FIELD CONDITION

Abstract

In vitro selection was conducted to select for drought tolerant somaclones derived from sugarcane variety Isd 28. Unexpanded spindle leaf sheath was used as explants. MS medium supplemented with 2,4-D (3 mg l-1 ) and coconut water (10 %) or BAP (2 mg l-1 ) with Kn (1 mg l-1 ), or NAA (5 mg l-1 ) was used for callus induction, shoot regeneration and root formation, respectively. To screen for drought tolerant sugarcane somaclones, in vitro medium was stressed with different concentrations of PEG at 5, 7.5 and 10 % along with control (without PEG). Callus growth was vigorous at control as well as at lower concentration of PEG. However, the frequency of callus induction decreased with the increase of PEG concentration. The same for shoot and root production. Most calli became reddish black and died within 40-45 d on medium supplemented with 10 % PEG. Shoot and root formation was observed on medium supplemented with 5 % PEG. Twenty somaclones were studied for drought tolerance. In correlation to drought tolerance in somaclones and parents, biochemical parameters such as total chlorophyll, chlorophyll a, chlorophyll b, ratio of chlorophyll a:b and CSI showed positive correlation but morphological parameters such as leaf number and leaf area showed negative correlation to drought tolerance in somaclones and parents. Tolerance level was measured based on leaf greenness and the biochemical and morphological data. A close association between biochemical and morphological parameters was observed for drought tolerant reaction. Less variation on Brix (%) was observed among somaclones and their parents. Somaclones Isd 28Sc-3, Isd 28Sc8,Isd 28Sc-11, Isd 28Sc-17 and Isd 28Sc-18 were observed as highly tolerant somaclones to drought.