INHERITANCE OF HOMOZYGOUS SOMACLONAL VARIATION IN RICE

Homozygous mutations are common phenomena in rice (Oryza sativa L.) so maclones. Previous reports indicated that inheritance of the variants from these mutations were stable only in the homozygous condition resu lting from selfing. To better understand the inheritance of homozygous somaclonal variation in rice, five variants, two from the U.S. long-g rain cultivar Labelle (short and light tawny apiculus) and three from the U.S. long-grain cultivar Lemont (tall, purple apiculi, and dwarf), were used in this study. Reciprocal crosses between the original cult ivars and the somaclones with mutations were made in 1987 and the F-1 plants were grown in the greenhouse to produce seeds. The F-2 populati ons and F-3 families were grown in the field at the Louisianna State U niversity Rice Research Station in Crowley, LA, during 1988 to 1990 an d evaluated for segregation of the variants. The light tawny apiculus character was controlled by a single recessive gene. The purple apicul us character was controlled by a dominant gene. The tall character was controlled by two complementary dominant genes. No disappearance of t hese three characteristics in the segregating generation was observed. The dwarf character was controlled by one or two recessive genes, whi ch were not stable in the heterozygous condition due to gene conversio n. The short character was controlled by quantitative genes, but the s ingle mode distributions observed in the F-2 populations may be anothe r case of aberrant segregation. Stability of useful homozygous somaclo nal variation in rice should be determined prior to its use in breedin g programs.