JWSS - Journal of Water and Soil Science

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Identification of easily measured physiological traits contributing to yield under specified environmental conditions would benefit genotypic selection for grain sorghum. A field experiment was conducted to determine broad-sense heritability and expected genetic advance, and to examine the relationships of grain yield with 11 physiological traits related to developmental periods, vegetative growth, growth rate, grain filling rate, and partitioning to the grain.

Sorghum genotypes exhibited significant differences for all traits, except for grain yield. Broad-sense heritability estimates ranged from a low of 49.6 (for grain filling rate per unit area) to a high of 99.4 (for days to maturity). Expected genetic advance ranged between 9.2% (for days to transition of vegetative to reproductive phase, days to maturity and number of leaves) and 39.8% (for grain filling rate per grain unit). Generally, grain yield gave a significant negative correlation with physiological traits related to development and vegetative growth. But, this correlation was positive and significant for growth rate, grain filling rate, and harvest index. Grain yield was low in its coefficient of genetic variation and expected genetic advance. It is, therefore, concluded that indirect selection for grain yield via growth rate, grain filling rate per unit area and harvest index is efficient. Results suggest that use of easily measured physiological traits in sorghum breeding is possible.

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To study relationship between grain yield and important agronomic traits of rapeseed in paddy fields as second culture, fourteen varieties of spring rapeseed were grown in a randomized complete block design of experiment with three replications at Rice Research Institute of Iran, Rasht, during 2005-2006. Analysis of variance showed that there were significant differences between varieties for most of traits. Broad sense heritability ranged from 0.29 for pod length to 0.99 for days to maturity. Phenotypic and genotypic coefficients of variation for days to maturity and the number of pods in secondary branches were the lowest and highest, respectively. Moreover, genetic advance with 5% of selection intensity varied from 3.68% (0.25 cm) for pod length in main branch to 31.48% (915.58 Kg.ha^-1) for grain yield. Results from genotypic correlation coefficients demonstrated that there were positive significant correlations between grain yield and the number of secondary branches, the number of pod in main and secondary branches, pod length in secondary branches, pod diameter in main and secondary branches, 1000-grain weight and oil percentage, and negative significant correlations between grain yield and days to 90% of flowering and days to maturity. Path analysis on genotypic correlations for grain yield as a dependent variable and the other traits as independent variables showed that the 1000-grain weight and the number of pods in secondary branches had the highest direct effects and days to 90% of flowering had low and negative direct effect on grain yield. Therefore, indirect selection for increasing 1000-grain weight and the number of pods in secondary branches are recommended for improving grain yield in rapeseed as second culture in paddy fields.