JWSS - Journal of Water and Soil Science

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In order to study the genetic and environmental variability of morphological and phenological characteristics and also to gain a better understanding of the morphological basis of yield variation in soybean, an experiment was conducted at Research Farm, College of Agric., Isfahan University of Technology, in 1996. The experiment was arranged in three augmented designs with 285 lines and 5 control varieties. There were highly significant differences among genotypes for all the characteristics studied. The phenotypic coefficients of variability were greater than the genotypic ones for all the traits although the differences for most of them were small. The highest phenotypic and genotypic coefficients of variation, in order of magnitude, were obtained for number of pods per plant, days to flowering, plant height, height of the lowest pod, and number of lateral branches. Heritability estimates and the percent of genetic improvement for these traits and seed weight were high but for seed yield per plant were low. The lowest coefficients of variability were related to number of seeds per pod and days to germination. The results of stepwise regression analysis indicated that the maximum variation in seed yield could be attributed to the number of pods per plant, number of seeds per pod, and 100-seed weight. Factor analysis in addition to emphasizing the importance of yield components, resulted in four factors which determined 97.34% of yield variation. These factors which were indicators of physiological sink and source, with respect to the traits contained, were named as photosynthetic sink, plant architecture, fixed capital, and weight, respectively. In general, it was concluded that in order to improve soybean cultivars, selection should be in favor of plants with stronger structure, higher number of leaves, nods and pods per plant, and higher seed weights.

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In order to map the genomic regions affecting barley forage quantity and quality, two experiments were conducted with 72 doubled haploid lines and their two parents (‘Steptoe’ and ‘Morex’), at the Research Farms of the Faculty of Crop and Animal Sciences, University College of Agriculture and Natural Resources, University of Tehran and Agriculture and Natural Resources Research Station of Sistan, in 2007. The experiments were arranged in a randomized complete block design with two replications. Each plot consisted of six rows that were 3m in length and spaced 25cm apart. QTL analysis was conducted by Composite interval mapping (CIM) method separately for each trait in each location. The main effect of genotype was high significant for all the studied traits. Transgressive segregation in both directions (positive and negative) was observed for all the studied traits. There was a negative relationship between forage qualityrelated with quantity-related traits. Thirty-three QTLs controlling different studied traits were identified. Phenotypic variance explained by these QTLs varies from 7.07 to 39.04%. Highest LOD scores were obtained for the leaf to stem ratio on chromosome 2H. QTLs of forage quality (total digestible nutrient, dry organic matter digestibility, leaf to stem ratio, seed to forage ratio and number of tiller per plant) and quantity (plant height, forage wet and dry matter) indexes were found on chromosomes 1H, 2H, 3H, 4H, 5H, 6H and 7H. Most of mapped QTLs appear to be fairly stable between locations and can become candidates for marker-assisted selection.