Effect of drought stress at different growth stages on dry matter remobilization in grain sorghum genotypes

In order to evaluate the effect of water stress on grain yield and its components and parameters of dry matter remobilization in sorghum genotypes (Sorghum bicolor L.), a field experiment as a split plot design was carried out with three replications in 2014 at the research farm of the southern Khorasan Agriculture and natural resources research and education center. Main factors 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) and genotypes including KGS29, MGS2, Sepideh, KGFS27, MGS5, KGFS5, KGFS17, KGFS13 and KGFS30 were as sub factors. Results showed that water stress had significantly effect on grain yield, biological yield, harvest index, 1000 seed weight, seed number per panicle and caused to decrement of them. The grain yield reduction was about 42% at the highest level of water stress (irrigation cut off in vegetative growth stage) in comparison with the control. The genotype KGFS13 had the highest grain yield, biological yield and harvest index. The effect of water stress was significant on ARDM (Amount of Remobilized Dry Matter) and %REP (Remobilization Percentage) at %5 probability level and this effect was not significant on %REE but each of those parameters were highly increased with water stress inducing and stress severity increasing. Generally, remobilization process can be considered as one of the optimal and selective mechanisms in sorghum cultivars and genotypes, especially in terms of drought stress condition.