Study on drought tolerance and interrelationships among some agronomic and morphophysiological traits in sugar beet lines

ABSTRACT: Drought stress is an important factor limiting crop productivity in arid and semi-arid regions like Iran. The use of drought-tolerant cultivars is one of the sustainable methods for coping with water deficiency in such regions. Prior to breeding and introduction of a cultivar, it is necessary to determine the relative drought tolerance of potential parental genotypes. The present study was carried out in research field of Sugar Beet Seed Institute (SBSI) in Karaj, Iran. Half-sib families derived from two sugar beet populations, namely 111 and 110, were evaluated under moisture stress and non-stress conditions in three separate experiments on the basis of a Randomized Complete Block Design with four replications. Irrigation timing was determined by cumulative evaporation from the Class-A evaporation pan. Irrigation was conducted after 90 and 200 mm evaporation under non-stress and stress conditions, respectively. The traits measured during the growth period included leaf chlorophyll content and leaf specific weight and the traits measured at harvest included root yield, sugar content, sugar yield, Na, K, amino-N and drought tolerance indices. It was found that the studied genotypes were significantly different in terms of the most studied traits. The study of the relations amongthe traits revealed that sugar content, root yield, extractable sugar percentage and sugar extraction coefficient had a positive, significant correlation with white sugar yield. But, the correlation of chlorophyll content and specific leaf weight with yield traits was found to be insignificant suggesting that the selection for these two traits cannot lead to an increase in sugar beet yield. Out of the studied genotypes, 111-HSF.42 had the highest values of stress tolerance index, arithmetic mean productivity (MP) and geometric mean productivity (GMP) suggesting that it can be used as a potential pollination parent in the subsequent selection cycle for improving drought tolerance of sugar beet.