Genotypic variation for traits associated with dry matter remobilization in grain sorghum (Sorghum bicolor L. Moench) genotypes under drought stress conditions

This study was conducted to evaluate traits that have an effect on yield, and genetic variation for these traits, including dry matter accumulation, remobilization, and traits associated with them, in 10 grain sorghum genotypes obtained from the National Plant Gene Bank of Iran under moisture stress conditions. Field trials were carried out in the 2008 cropping season using split-plot arrangements in a randomized complete block design with three replications at Torogh Agricultural Research Station of the Agricultural and Natural Resource Research Center of Khorasan Razavi Province, Mashhad, Iran. Trials were conducted separately under three water regimes: normal conditions and two water deficit levels at the vegetative and reproductive stages. Genotypes were assigned to main plots and two levels of photosynthetic status, normal and disturbed current photosynthesis, by applying potassium iodide after anthesis, in sub-plots. Results revealed significant genetic variation for traits related to dry matter remobilization (amounts of remobilized dry matter [ARDM], remobilization efficiency [REE] and remobilization percentage [REP]) among sorghum genotypes under moisture stress and well-watered conditions. Cluster analysis using the Ward method grouped sorghum genotypes differently under different irrigation conditions. There were no differences between grouping of genotypes treated with potassium iodide (disturbed current photosynthesis) and grouping under normal current photosynthesis as well as in the drought stress environment at the vegetative stage. Results also showed that genotype 04-12 had the highest REE and REP under the three irrigation regimes. Therefore, these traits could be used to improve grain yield and yield stability in sorghum breeding programs