Evaluation of sunflower hybrids for yield variability at very high air temperatures

Abstract

Purpose and objective. The purpose of the study was to develop methodological approaches to quantification of the yield variability of sunflower hybrids at very high air temperatures (heat).

Materials and methods. The field investigations were conducted in the moderately arid zone and the insufficiently humidified zone of Ukraine, in five geographical locations. Ninety nine simple and three-line hybrid combinations were tested. The response of the hybrids to the growing conditions was evaluated by general and specific adaptability measures.

Results and discussion. The possibility of differentiation of hybrids according to the specific combining ability effects was proved. The effect values in environments with very high temperatures during the susceptible stages of sunflower development were taken as the heat resistance indices of genotypes (I_h). At very high temperatures in July, hybrid combinations with significantly high I_h were detected. Five hybrid combinations (7.2% of the studied ones) combined a high general adaptability with a high I_h. At very high temperatures during the first 10 days of August, two hybrid combinations (5.9% of the studied ones) with a high general adaptability and a high I_h were singled out.

Conclusions. The heat resistance index is suitable for detecting accessions that, in a certain group of genotypes, at very high air temperatures, are able to maintain stable yields, or reduce them less than other genotypes.