Selection Index of Ideal Genotype (SIIG) in Order to Evaluate Drought Stress Tolerance in Some Sunflower Cultivars

Sunflower (Helianthus annuus L.) is one of the most important oil crops and due to its high content of unsaturated fatty acids and lack of cholesterol, the oil benefits from a desirable quality. Drought is the most important crop production limiting factor in the changing climate scenario and its intensity is predicted to increase in future. In this research, drought tolerance of some sunflower cultivars under non-stress and drought stress conditions was studied and SIIG method was used for integrating studied traits in order to select the best drought stress tolerant cultivars.

In order to evaluate the drought and susceptible cultivars using tolerance index (Ti) for studied traits and selection index of ideal genotype (SIIG), an experiment was conducted in 2022 cropping season based on randomized complete block design with three replication under non-stress and drought stress conditions separately on 10 sunflower cultivars including Azargol, All-star, Master, Hysun33, Golsa, Ghasem, Farrokh, Shams, Golshid and Barzegar in field in Abarkouh city. Grain yield, plant height, number of days to maturity, number of seeds per head and 1000 seed weight were measured in this research.

The results of combined analysis of variance revealed that drought stress and cultivar had significant effect on all studied traits. Cultivar effect was significant in all studied traits. Stress × cultivar interaction was significant only in grain yield. Drought stress led to a significant decrease in all studied traits. Mean comparisons showed that Farrokh, Barzegar and Shams cultivars had the highest value in the most traits and so these cultivars were suggested for cultivation under both conditions. Ghasem, Farrokh and Shams had the highest value of Ti index for grain yield, 1000 seed weight and number of seeds per head. Ghasem, Barzegar, Farrokh, Shams and Golsa had the highest value and All-star, Golshid and Hysun33 had the lowest value of SIIG, respectively. Cluster analysis, based on ward method and by using Eucilidian distance, classified studied cultivars using Ti index of traits into two groups. Azargol, Barzegar, Golsa, Shams, Master, Ghasem and Farrokh cultivars were placed in first group and these cultivars in terms of Ti index values for grain yield, 1000 seed weight and number of seeds per head were higher than second group and whole mean.

The results of cluster analysis using Ti index of traits are similar to the results of cultivar ranking based on SIIG and it can be said that Farrokh, Ghasem, Shams, Barzegar, Azargol, Golsa and Master cultivars were drought tolerant and All-star, Hysun33 and Golshid were susceptible cultivars according to cluster analysis and SIIG values.