Genetic variations associated with salt tolerance detected in mutants of KDML105 (Oryza sativa L. spp. indica) rice

Genetic variations in associate with salt tolerance were investigated in Khao Dawk Mali105 (KDML105), a well-known Thai rice that has high cooking quality and aroma. Forty-treatment combinations of gamma irradiation and ethyl methanesulfonate (EMS) were applied to M-0 seeds of KDML105 and micropropagated M-1 lines in vitro prior to cultivate in field for M-2 seeds. The M-2 seedlings were screened for salt tolerance in Hoagland solutions contained 171 mM NaCl or 342 mM NaCl. Salt tolerance (ST) lines could withstand for 15 days under salt stress up to 342 mM NaCl, whereas those of sensitive (SS) lines are drastically susceptible to condition of 171 mM NaCl after 5 days of screening. Identification of genetic variations among SS and ST populations was performed by Amplified Fragment Length Polymorphism (AFLP) using 56 primer combinations. A total of 889 polymorphic bands were detected and scored to investigate the degree of genetic change among 46 ST and 57 SS mutants. The polymorphism percentage was 92.2 and heterozygosity was 0.159 within mutant populations. The genetic distance between ST and SS populations was 0.0141, the mutants were then classified into 3 clusters as cluster I for 35 ST lines, cluster II for 37 SS lines and cluster III containing 12 ST and 11 SS lines. The 4 primers generated 5 novel fragments were obtained which gave more than 80% reliability in identifying 25.68 % of ST mutants gained form this study.