Studies on Type of Gene Action in Some Crosses of Rice (Oryza Saliva L.) in Egypt

الملخص

A field study was performed at the Faculty of Agriculture Experimental Farm, Alexandria University, Egypt, during 1972-1975 to determine the type of gene action through partitioning the genetic variance in two crosses of rice; namely, Nahda x I.R.8 (cross I) and Taichung (N.)l x Nahda (cross II). Heritability estimates and the expected gain from selection were also determined.
The characters that showed significant additive genetic variance were plant height and number of total tillers per plant in cross I and II, respectively. However, the additive effect was not significant for the other characters in the two crosses. On the other hand, significant dominance genetic variance was obtained for the number of total and earbearing tillers per plant in cross I and for plant height, number of total and ear-bearing tillers per plant, and panicle length in cross 11.
Heritability values in broad sense, based on F2 data, were found to be of moderate magnitude with respect to plant height and mean of panicle length in cross I. High estimates of heritability were obtained for the number of total and ear-bearing tillers per plant in cross I and for all characters studied in cross II. Low estimates of heritability percentages were obtained for the characters in the narrow sense in the two crosses. When F3 data were used, however, all the characters showed moderate heritability magnitude in broad and narrow senses in cross I, but high values were found in cross IL The expected gain from selection was different for each character in the two crosses.
Significantly phenotypic correlation coefficients were obtained among the characters except for the correlation between plant height and panicle length and between number of ear-bearing tillers per plant and panicle length in cross I, and between number of earbearing tillers per plant and panicle length in cross II. Different estimates of genotypic and environmental correlation coefficients were obtained among traits studied in the two crosses.