Somaclonal genetics of rice, Oryza sativa L.

The inheritance and variations of some traits of more than 2,000 somatic cell derived plants of rice (Oryza sativa L.) were investigated in the second and third generations (T2 and T3) of regenerated plants (somaclones). The percentages of multiploids occurring in somaclones ranged from 0–13.3 in nine varieties (or hybrids) of ‘Hsien’ (indica) group, but no multiploid was found in nine varieties (or hybrid) of ‘Keng’ (japonica) group. A dwarf mutant with the height of only 20 cm was isolated in the T2 of ‘Tai-Zhong-Yu 39’. Genetic analysis indicated that it was controlled by a single recessive gene. The frequencies of chlorophyll mutations probably controlled by cytoplasmic genes decreased gradually with the advance of generations. The variations of five quantitative traits — plant height, grain weight, etc. — in 950 T2 pedigree lines of four varieties were also studied. Only 24.4% of the lines were normal in all the traits studied. Variation frequencies of different traits were from 11.5% to 39.5%. And there was an obvious tendency for the plant height to become shorter, number of productive tillers to increase and 1,000 grain weight to be lighter, whatever the variety studied. Traits were uniform within each of more than 90% of all T2 lines studied. What is more interesting, variations phenotyped in T2 proved to breed true. Causes of somaclonal variations are discussed, as well as their potentials in breeding.