The present investigation was carried out at the Lysimeter of the Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt during 2009, 2010 and 2011 summer seasons. The aim of this investigation estimate heterosis, heterobeltiosis, heritability in broad and narrow senses, expected genetic advance, inbreeding depression, phenotypic and genotypic coefficient of variability and nature of gene action for grain dimensions, yield and its related traits in rice using six populations technique, viz., P1, P2, F1, BC1, BC2 and F2 generation of (Nabatat Asmar x Sakha 105) rice cross under both saline soil irrigated with 10.6 dSm-1 of sodium chloride (NaCL2) and calcium chloride (CaCL2) at the ratio of 1: 2, respectively, and normal soil conditions irrigated with tap water (EC, 0.77 dSm-1). The main finds could be summarized as follows: The results indicated that highly significant and positive heterosis and heterobeltiosis were obtained for all the studied traits under saline soil conditions, except 100-grain weight, grain width and grain shape traits, which, showed highly significant and negative estimates of heterosis when it were measured as a deviation from better-parent under normal soil conditions for the first two traits. Highly significant and negative estimates of heterosis when it was measured as a deviation from midparent for the third trait. Phenotypic coefficient of variability (P.C.V) was higher than genotypic coefficient of variability (G.C.V) for all the studied traits, indicating that they all affected by environment conditions. High estimates of broad sense heritability coupled with high genetic advance was observed for days to 50 heading, plant height, 100-grain weight, panicle weight, grain length, grain width and grain shape under two conditions. Therefore, direct selection for these characters is recommended in early generations. In addition, incomplete dominance to over-dominance was operative for most the studied traits under two conditions. The estimates of nature of gene action showed that mid-parent values were positively and highly significant for all the studied traits under two conditions except days to 50 % heading, plant height and sterility % under two conditions. Additive gene action was important for all the studied traits except plant height, grain length and grain shape under saline soil conditions. Whereas, dominance gene action was played an important role in the inheritance of 100-grain weight and grain yield/ plant. Moreover, additive x additive type of gene interaction were important for plant height, 100-grain weight and sterility % under normal conditions. On the other hand, grain yield/ plant followed by number of filled grains/ panicle, panicle length, grain length and panicle weight were affected by dominance x dominance gene interaction. The results in general, revealed that days to 50 % heading, plant height, panicle length, grain length, grain width, and grain shape were controlled by almost one pairs of effective genes suggesting that these traits were inheri...
