Qualitative traits in sunflower breeding: UGA-SAM1 phenotyping case study

Authors: TERZIC, SRETEN - Institute Of Field And Vegetable Crops; ZORIC, MIROSLAV - Institute Of Field And Vegetable Crops; Seiler, Gerald

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2019
Publication Date: 2/18/2020
Citation: Terzic, S., Zoric, M., Seiler, G.J. 2020. Qualitative traits in sunflower breeding: UGA-SAM1 phenotyping case study. Crop Science. 60:303-319. https://doi.org/10.1002/csc2.20059.
DOI: https://doi.org/10.1002/csc2.20059

Interpretive Summary: The vulnerability of sunflower to many biotic and abiotic stresses is generally attributed to the crops narrow range of genetic diversity. To increase the genetic diversity of sunflower, one needs to look outside of this narrow genetic pool. A sunflower association mapping population (UGA-SAM1) composed of 288 accessions from around the world provided the first permanent, and publicly available source to access new and improved traits. The objective of this study was to evaluate the observable diversity (also referred to as phenotype) in the UGA-SAM1 population, which was accomplished by evaluating the usefulness of qualitative traits such as flowering time, leaf size and shape, seed color and shape, and plant height and branching. Phenotypic diversity was moderately high for the studied traits confirming their potential importance for sunflower improvement. Adequate selection of these traits for germplasm evaluation should improve the efficiency of breeding programs and reduce loss of diversity that occurs by focusing only on yield and oil quality. This research suggests that loss of genetic diversity in sunflower could be lowered by focusing on additional traits associated with leaf and seed morphology, plant height, and certain flower traits, instead of only focusing on yield and oil quality.

Technical Abstract: Germplasm collections often serve as a source for discovering traits and genotyping, while phenotyping is predominantly used for early line development to compare hybrid performance. The production of the first permanent, publicly available sunflower association mapping population (UGA-SAM1) provided material to test the usability of morphological descriptors for discriminating germplasm accessions. The objective of this study was to evaluate the phenotypic diversity in UGA-SAM1 population and evaluate the usefulness of qualitative traits for the discrimination of sunflower genotypes. The SAM1 population consists of 285 accessions characterized for 20 morphological traits. The Shannon-Weaver diversity index (H') was used to determine phenotypic diversity, while HOMALS (homogeneity analysis) and association statistics were used to determine discriminative power of the descriptors. Phenotypic diversity was moderately high for the traits (0.74). The highest diversity was found in the less developed genotypes followed by non-oil genotypes, while the lowest diversity was in the oil restorer genotypes. Association of genotype groups and category traits was generally negatively correlated with an increased diversity index. The moderately high phenotypic diversity for the studied traits confirmed the UGA-SAM1 as a valuable resource for sunflower breeding. The association test proved to be a useful addition to HOMALS analysis for determining the trait discriminative power. Adequate selection of traits used in germplasm evaluation can improve the efficiency of breeding programs, while the loss of variability could be lowered if diversity focused traits were used including leaf, seed, and certain flower traits, instead of only focusing on yield and quality.