DEVELOPMENT OF DIPLOID POLLINATOR LINES FOR DROUGHT TOLERANCE IN SUGAR BEET

Drought stress is the most important and common abiotic factor that limits sugar beet production in the world. In arid and semiarid regions that crop production depends on continuous irrigation over the growth season, any water limitation in terms of duration or intensity causes losses n sugar beet production. Drought tolerance contributes to yield stability. Characteristics related to drought tolerance can help breeders to developed drought varieties. For studying the variation of the characteristics related to drought tolerance in an improved sugar beet population, BP Mashhad, S1 pollinator lines and their testcrosses with a male sterile single cross (Ms 7112*261) were produced .All testcrosses along with five checks were evaluated in 2007 field trials. In 2008, 23 superior drought tolerant testcrosses along with two checks (drought tolerant hybrids) were retested in field trials. Two adjacent field trials with the same treatments (stress and non-stress) and S2 lines were also carried out. The duration of water stress in 2007 and 2008 was 6 and 5 times of irrigation, respectively. An unbalanced lattice design was carried in the both years: in 2007 with 81 genotypes and three replications and in 2008 with 25 genotypes with 4 replications. Sixty eight traits were measured on morphological, physiological, and yield traits as well as stress indices. Analysis of variance for 81 genotypes in 2007and 2008 in stress and non-stress conditions indicated that there were significant differences for most of the traits. Water regimes had significant effects on all traits. The genotypes did not differ for sugar content (SC) and white sugar content (WSC) which was evident from the common origin of the hybrids. Heritability estimates for sugar yield (SY) were the same in stress and non-stress conditions (0.31 and 0.34, respectively) but for root yield it was higher in stress than non-stress condition (0.46). There were differences for root yield (RY), SY, white sugar yield (WSY), mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI). It can be concluded that GMP and STI are useful indices for improving the early season drought tolerance of sugar beet. M113, M116, M142, M143, M158 and M175 were selected as drought tolerant Pollinator lines for breeding program.