Characters of sunflower genotypes ( Helianthus annuus) suited to irrigated production

Abstract

During two seasons six genotypes of sunflower ( Helianthus annuus L.) were grown under irrigation in two or three population densities. The aim was to relate seed yields to developmental characters and to determine whether genotypes with more days between sowing and maturity would give higher yields than quicker-maturing genotypes. Seed number per plant was related to the size of the integrated generative area producing floret initials on the floral meristem. Floret numbers were not related to the size of the shoot at the time of floret initiation nor to the number of days between sowing and the start of floret initiation. Single seed weight was greatest in genotypes having a relatively high capitular growth rate at the end of anthesis and was also positively related to leaf weight at anthesis. Between genotypes there was a negative relationship between large single-seed weights and seed number per plant. Under irrigated cropping only small differences in the number of days from sowing to maturity were found between short-stature, supposedly early-maturing, and giant, late-maturing genotypes. For a giant variety the days from sowing to maturity were related to the daylength at the 2-leaf stage so that the shortest development cycle was in plants emerging at the summer solstice. The results suggest that for irrigated production of sunflower, where water supply is not limiting, genotypes that exhibit a good capitular growth rate through anthesis will produce large seeds and will give more weight of seed and oil per plant than genotypes with large numbers of small seeds.