Generation and DNA Characterization of High-lysine Mutants by Biochemical Selection from Callus Culture of Hwayeongbyeo

Lysine is the first essential amino acid for optimal nutrient quality in rice grain. For the narrow genetic diversities of lysine contents in rice, somaclonal variation was the source of mutation in our breeding program. Biochemical selection was conducted using 1 mM S-(2-aminoethyl) cysteine followed by two passages of 5 mM lysine plus threonine in the callus subculture medium. The lysine contents in endosperm of all progenies recovered from the biochemical selection were higher than those of their donor cultivar Hwayeongbyeo . These elevated lysine levels of mutants were successfully transmitted to M₄ generation. The lysine contents in endosperm varied 3.85 to 4.80% compare to their donor cultivar Hwayeongbyeo was 3.85%. Three of high-lysine germplasms, Lys-l, Lys-2 and Lys-7 were selected by biochemical selection and rapid screening methods. DNA analysis showed that a new insertion of Tos 17 which mapped to rice chromosome 11 on the high-lysine mutant, Lys-2.