PERFORMANCE AND YIELD OF SUNFLOWER (HELIANTHUS-ANNUUS) CULTIVARS UNDER RAIN-FED AND IRRIGATED CONDITIONS IN SUDAN

A trial of open-pollinated (OP) cultivars and hybrids of different origins was conducted in 1986-88 at two sites in the central clay plains of Sudan, rainfed at one site and under supplementary irrigation at the other. Throughout this study, the patterns of growth of the OP cultivars differed greatly from those of the hybrids, despite differences amongst cultivars within each group. Differences in seed yield between OP cultivars and hybrids under irrigation were not significant; but, under rainfed conditions, the hybrids gave higher yields than the OP cultivars. Partitioning efficiency (PE; reproductive mass: total biomass) increased more rapidly during flowering and seed filling in the hybrids than in the OP cultivars; differences in PE between the two groups were significant. The higher leaf area index, leaf area duration and crop growth rate of the OP cultivars were compensated to some extent by the higher PE and leaf efficiency values of the hybrids, resulting in similar seed yields of all cultivars under irrigation. Overall, irrigation increased seed yield by 0.6-1.9 t/ha and increased oil content by 8-15%.