Investigation of relationship between some physiological and biochemical characteristics with yield and its components in grain sorghum genotypes under water stress conditions

The yield of each crop is determined by several factors, which affect the growth and development of the plant. These factors include environmental, managerial, and plant factors. Environmental stresses are one of the most important environmental factors, including the most important stresses of drought stress. The aim of this study was to investigate the effects of drought in the vegetative and reproductive growth stages on Yield, its Components and Biochemical traits in grain Sorghum genotypes. In order to evaluate the effect of water stress on grain yield and its components and Biochemical traits in grain Sorghum genotypes (Sorghum bicolor L.), a field experiment as a split plot design was carried out with 3 replications in 2014 at the research farm of the southern khorassan Agriculture and natural resources research and education center. Water stress treatments including normal irrigation (control), irrigation cut off in vegetative growth stage(emergence of terminal leaf as rolled) and irrigation cut off in generative growth stage(50% of plants in start of flowering) as the main plot and 10 genotypes of sorghum including KGS29, MGS2, Sepideh, KGF27, MGS5, KGF5, KGF17, KGF13 and KGF30 were considered as sub plots. Each plot consists of 4 lines with a length of 6 m and line spacing of 60 cm, between plants on row 10 cm was considered. In addition, between each plot and the adjacent plot a line was considered. To determine the yield components of each plot, half a meter in length was harvested and number of plants, number of panicle, grain yield, 1000 seeds weight and number of seeds per panicle were determined. To determine the yield , after the removal of 2 margin lines and a half meter of beginning and end of each plot, plants were harvested from the surface of 3 square meters. Biochemical parameters including chlorophyll a, chlorophyll b, carotenoids, proline and carbohydrates were measured on the flag leaf after flowering stage in each plot. chlorophyll a content, chlorophyll b, and carotenoid content was done according to Arnon method. Simple correlation coefficients between the characteristics studied under normal conditions and drought stress conditions were calculated using SPSS software version 13. Results showed that water stress had significantly effect on grain yield, 1000 seed weight, seed number per panicle and caused to decrement of them. Genotypes were significantly different for all traits, indicating high variability among them. The interaction between water stress and genotype did not show a significant difference about 1000 seed weight, other traits which mentioned above showed a significant difference in this aspect. The results of correlations between the studied traits showed that in normal conditions (without stress), plant height, number of seeds per panicle, Brix of stem sugar, free leaf proline content, biological yield and harvest index could be used to improve seed yield. In terms of drought stress, stem sugar, plant height, canopy temperature, free leaf proline content had the highest correlation with yield and its components. In general, physiological traits due to their low cost could be used as good indicators in water stress investigations and provide more comprehensive information as compared with morphological traits. Keywords: Free prolin, Generative growth, Irrigation cut off, Sorghum, yield