Drought and salt tolerance screening of papaya (Carica papaya l.) Cultivars using in vitro techniques

Studies on drought and salt tolerance screening of four papaya cultivars namely ?Ranchi Dwarf?, ?Honey Dew?, ?Farm Selection? and ?Local? were conducted at the tissue culture lab of CCS Haryana Agricultural University, Hisar, India. The callus of above stated four cultivars was induced and transferred in the MS media containing 0.5, 1.0 and 1.5 per cent NaCl. After 20 days these calli were transferred back on normal MS medium and it was found that the callus of cultivar ?Local? (earlier kept at 0.5 per cent NaCI)expressed 90 per cent recovery followed by 64 per cent in ?Honey Dew?. These two cultivars exhibited almost the same pattern at 1.0 and 1.5 per cent NaCl concentrations. The recovery percentage decreased with the increase in the NaCl concentration (1.5 percent). The ranking of these cultivars for their in vitro screening revealed ?Ranchi Dwarf? and ?Farm Selection? as susceptible/sensitive, ?Honey Dew? as moderately tolerant and ?Local? comparatively tolerant to salt (NaCI). For studying the comparative drought tolerance, the induced calli of all the above stated cultivars were transferred on MS medium supplemented with 10, 15 and 20 per cent PEG 6000. After 25 days these calli were transferred back on normal MS media and it was observed that 83-97 per cent calli of Local cultivar recovered followed by 60-75 per cent recovery in ?Farm Selection? depending upon the concentration of PEG 6000 treatment. The recovery percentage in all the four papaya cultivars decreased with increase in PEG 6000 concentration. On the basis of the ranking made depending upon browning and recovery of callus, the cultivars Ranchi Dwarf and Honey Dew were found susceptible/sensitive, ?Farm Selection? as moderately tolerant and ?Local? as comparatively tolerant.