Evaluation of genetic diversity among sunflower (Helianthus annuus L.) genotypes from different origins through agro-morphological traits for use in future breeding

The cultivated sunflower (Helianthus annuus L.) is one of the important oilseed crops, cultivated throughout the world for its edible oil and seeds. Low seed yield due to the cultivation of local traditional populations presents a constraint for sunflower production in Tunisia. Therefore, it is necessary to assess the available genetic resources to develop high and stable-yielding varieties. The current study focuses on the evaluation of genetic diversity in a collection of introduced sunflower genotypes for various agro-morphological traits in respect to their diverse geographical origins. The results revealed a significant variation among the tested genotypes for all measured traits, indicating a broad genetic base. The principal component analysis (PCA) showed that the first two principal components explained 64.39% of the total variability on the basis of all agro-morphological traits and accounted with values of 47.54% and 16.85%, respectively. Cluster analysis based on PCA grouped all sunflower genotypes into six major clusters. These genotypes were grouped independently from their geographic provenance. Significant correlations were found between most of the examined traits. The correlation studies revealed that the number of seeds/head depends on the weight of seeds/head, the head diameter and the number of lines/head. Based on all studied traits, the hierarchical cluster analysis divided the 80 sunflower genotypes from different countries into four distinct groups. The highest cluster mean values for most traits were found in group G4, followed by group G1. These results can be used in future studies for sunflower breeding programs.