PRODUCTIVITY OF SUNFLOWER HYBRIDS GROWN UNDER EXTREME DROUGHT IN TWO DIFFERENT ECOLOGICAL REGIONS

The experiment was set up using a block method in 4 replications after a wheat predecessor in the fields of two different ecological regions -Thrace (Plovdiv region) and Dobrudja (Dobrich region), Bulgaria.Six sunflower hybrids were studied -P64LP170, breeded in Corteva, USA as a standart, and Bulgarian hybrids Dalena, Deveda, Enigma, Krasela and Sunny, breeded at the Dobruja Agricultural Institute -General Toshevo.Seed yield (SY), kg/da was determined by indirect method from a harvested plot.Both harvest years were characterized by extremely low rainfall during the critical periods of sunflower vegetation, accompanied by higher average monthly temperatures than the climatic norm.This is typical for both agro-ecological regions -Thrace and Dobrudzha and had an extremely negative impact on the productivity of all tested sunflower hybrids.In the first year of the study, the seed yield of all studied hybrids was higher in the Dobrich region.In both regions, the highest yields were recorded for the control hybrid P64LP170 and the lowest seed yield was recorded for the Krasela.In the second year of the study, the seed yield of all studied hybrids in both agro-ecological regions was lower than in the first.Comparing the two regions, the yield in the Plovdiv region was higher than that in Dobruja.In the Plovdiv region, the highest yields were recorded for the Dalena CLP hybrid, and in the Dobrich region for the control hybrid P64LP170.The lowest seed yield was recorded for the Krasela hybrid in Plovdiv, and in Dobrich for the Dalena CLP hybrid, which makes the interaction between the two factors non significant in the second year.