Genetics of root characteristics in sunflower (Helianthus annuus L.) under contrasting water regimes

Root characteristics are important while breeding for drought tolerance. Therefore, an experiment was carried out in the large size pots to study the root characteristics under contrasting water regimes. Results indicated repressing effect of drought on root weight and shoot length while root length and root-to-shoot ratio showed higher values under drought stress. Increase in root-to-shoot ratio was observed in almost all genotypes regardless of their drought tolerance while drought tolerant inbred lines only showed increase in root length. Correlation analysis indicated significant positive relationship with root-to-shoot ratio and absence of relationship between root length, shoot length and root weight. There were two types of genetical responses in drought stress regime. The traits, i.e. root length and root to shoot ratio showed higher contribution of additive gene action under drought stress when compared with non-stress regime while traits like shoot length and root weight showed decreased contribution of additive genes under drought. This showed that drought environment was more feasible for the selection of genotypes for traits, i.e. root length and root-to-shoot since it was promoting the expression of additive genes. Breeding procedure such recurrent selection may be used for the improvement of the traits. (AMES-10103 x CM-631) a good specific combiner may be used for the development of molecular markers for root length and root-to-shoot ratio.