The present investigation was conducted at the Experimental Farm of Faculty of Agriculture, Kafrelsheikh University during 2008 and 2009 seasons. The main objectives of this investigation were to study the association between some quantitative characters in rice, using path coefficient analysis to determine the relative importance of such characters to grain yield variation and estimation of some genetic parameters of twenty five rice genotypes under water stress environments (irrigation every 6, 9 or 12 days).
Grain yield was positively correlated with each of number of panicles/plant (under the two severely stressed environments), number of grains/panicle (under the first and the third water intervals) and with panicle length under all environments. Panicle length was positively correlated with number of grains/panicles under all treatments.
Fertility percentage was negatively correlated with number of panicles/plant under all environments and positively correlated with 1000-grain weight under the first and the third treatments. Meanwhile, number of panicles/plant was negatively correlated with 1000-grain weight, this may be due to their compensatory relationship.
Path coefficient analysis revealed that under the most stressed environments, number of panicles/plant had the largest direct effect on grain yield, while under slight stress (irrigation every 6 days), number of grains/panicle appeared to be the most important yield component followed by number of panicles/plant and panicle length.
Phenotypic coefficient of variability (PCV) was, in general, higher than genotypic (GCV) coefficient of variability for different traits, indicating less environmental influence in the expression of different traits.
Heritability estimates in broad sense were either relatively moderate or high for all studied traits. Such estimates ranged from 55 to 94% for grain yield and 1000-grain weight, respectively. Relatively higher genetic advance coupled with high heritability estimates was detected for 1000-grain weight and plant height.