To determine the optimum sowing date for some sunflower hybrids i.e. A11 x Rf7, A11 x Rf9, A12 x Rf9, A8 x Rf10, A11 x Rf10, A8 xRf12, A9 x Rf12, A15 x Rf12, A2 x Rf20 and the check variety Sakha 53, along with to assess their genetic variability and to determine selection criteria for improving their yield. These materials were sown at four adjacent field represent four sowing dates i.e. 20th of April, 20th of May, 20th of June and 20th of July using randomized complete block design with three replications at the experimental Farm of El Mattana Agricultural Research Station, (latitude of 25.17o N and longitude of 32.33o E), Luxor Governorate, during the two successive summer seasons 2018 and 2019. Results revealed that early sown plants on 20th of April had high yield potential compared to other sowing dates. The promising sunflower hybrid for seed yield feddan-1 and more yield attributes was A12 x Rf9 when sown on 20th of April and across sowing dates, whereas A15 x Rf12 when it sown on 20th of July and across sowing dates was the best for seed oil content. Considerable genetic variability was detected among sunflower genotypes, and hence the selection would be effective to genetic improvement of seed weight plant-1 for these materials, which can be achieved through selecting genotypes having the largest head diameter and the heaviest weight of 100-seed.
