Changes in seed quality of dill (Anethum graveolens) ecotypes in response to water limitation and harvest time

A split plot experiment based on randomized complete block design with three replications was carried out in 2015 to determine the best stage for harvest of three dill (Anethum graveolens) ecotypes (Varamin, Isfahan, Malayer) under different irrigation conditions (irrigation after 70, 100, 130 and 160 mm evaporation from class A pan), in order to produce high quality seeds. Results clearly showed that seed quality of all ecotypes under different irrigation intervals was increased with improving seed development on the mother plants. Maximum seed quality on the basis of electrical conductivity of seed leachates, germination percentage and rate and seedling dry weight was obtained at about 2-12 days after mass maturity, depending on ecotypes and irrigation intervals. Earlier harvests due to immaturity and later harvests because of aging reduced seed germination and vigor. Seed vigor of all dill ecotypes gradually diminished with declining water availability to the mother plants. It was, therefore, concluded that irrigation of dill plants particularly during seed filling could improve the quality of seeds. Nevertheless, the best seed moisture content for harvesting dill plants and producing high-quality seeds was about 15-20%. The most vigorous seeds on the basis of germination rate and seedling dry weight were produced by Varamin, followed by Malayer ecotypes.