Physio-biochemical traits in improved 'KDML105' jasmine rice lines containing drought and salt tolerance gene under drought and salt stress

Drought and salinity are important abiotic stress factors negatively affecting productivity of the world-renowned jasmine rice (Oryza sativa L. subsp. indica Kato) 'KDML105' in the northeast Thailand. Two chromosome segment substitution lines (CSSLs) of 'KDML105' which were introgressed with drought tolerance quantitative trait loci (DT-QTLs), designated CSSL94 and CSSL103, and two improved 'KDML105' lines, designated RGD1 and RGD4, carrying the salt tolerant gene (SKC1) were used for evaluation of growth, physiological and biochemical traits in response to drought and salt stress conditions in comparison with 'KDML105' (sensitive parental cultivar) and DH103 (DT-QTL donor). Seedlings were grown for 21 d in hydroponic solutions and then subjected to drought stress (20% polyethylene glycol 6000) or salt stress (150 mM NaCl) for 10 d. Under both stresses, all four improved rice lines showed lower percent reduction in growth compared with 'KDML105'. Under drought stress, CSSL94 and CSSL103 had significantly higher relative water content (88% and 89%) compared with that of 'KDML105' (82%). These lines accumulated 42% and 45% lower hydrogen peroxide, resulting in 25% and 32% lower malondialdehyde, and less membrane damage (24% lower electrolyte leakage). On the other hand, better growth of RGD1 and RGD4 under salt stress, compared with 'KDML105', was associated with an efficient maintenance of ion homeostasis (57% and 69% lower Na+/K+), 34% and 43% lower hydrogen peroxide, and 54% lower electrolyte leakage. The introgression of DT-QTL conferred not only drought but also salt tolerance to the recipient genotype. Likewise, introgression of SKC1 conferred both salt and drought tolerance.