This study was aimed to study the heterosis, degree of dominance and minimum number of effective factors for yield components (Panicle length, Panicle weight and Grain yield/plant) and some grain quality traits in rice (Hulling percentage, Milling percentage and Head rice percentage) under normal conditions. The materials for this study consisted of six rice genotypes namely; Sakha101, Sakha102, Egyptian Yasmin, GZ1368s-5-4, IET1444 and IR78875-176-B2-B, These genotypes have a wide range of variation due to their different genetic background. The six rice parents were crossed to produce F1 hybrid seeds of three crosses, namely, Sakha101 x GZ1368s-5-4(I), Sakha102 x IET1444(II) and Egyptian Yasmin x IR78875-176-B2B(III). The six populations, P1, P2, F1, F2, BC1 and BC2 for each cross were utilized to determine the genetic parameters of the studied characters.
The results revealed that heterosis better parent values were highly significant in positive direction for all traits in all crosses in agronomy characters except for the cross III in panicle length character were negative direction. The mid parent values were highly significant in positive direction for all traits in all crosses in agronomy characters except for the cross I for panicle weight and cross III for panicle length character. Degree of dominance values were less than unity in the positive direction for the crosses I, II and III, for all agronomic traits except for cross II intraits panicle weight andgrain yield\ plant and the cross III in Grain yield\ plantrait were negative direction, indicating the importance of partial dominance in the inheritance of this trait in these crosses, Moreover, the Castle-Wright formula revealed that the estimated values of minimum number of gene inPanicle lengthtrait in the crosses I and II is simple trait governed by one or two pairs of genes while the cross III governed by large number of genes (-12.63). Panicle weight trait was controlled by less than two pairs of genes suggested that trait is qualitative character in the crosses I and III while the crosses II governed by large number of pair of genes more than 9 pair of genes. Meanwhile, theGrain yield\ plant trait governed by large number of genes in the three crosses suggested that trait is quantitative character.
On the other hand, the heterosis of quality traits revealed the hulling trait in mid parents and better parent were no significant except the cross II in mid parent while milling and head rice traits were highly significant in negative direction except the cross III in better parent to two traits. Obviously. degree of dominance values were less than unity in the negative direction for all crosses of hulling and milling traits for each crosses except the cross III were positive direction to two traits while the head rice trait was less than unity in all crosses in the positive direction except the cross I was negative.
These results indicating the importance of partial dominance in the inheritance of this trait in these crosses. The Castle-Wright formula revealed that the estimated values of minimum number of gene inhulling%trait in the crosses I and III is simple trait governed by one or two pairs of genes while cross II governed by large number of genes (7.180),milling% trait was controlled by (2.160, 4.100 and0.890) pairs of genes in the three studied crosses respectively. The head rice% was governed by(2.470, -21.26 and 2.30) suggested that trait governed by large number of genes in crosses II.