Genome-wide association mapping of post-harvest dormancy in cultivated sunflower

MONTENEGRO, IVÁN; HERNÁNDEZ, FERNANDO; PRESOTTO, ALEJANDRO

Congreso; RAFV CONFERENCE 2021- XXXIII Argentinian meeting of Plant Physiology; 2021

In sunflower, fruits often display post-harvest dormancy (PHD), which negatively affect the quality of hybrid seed. Marker-assisted selection (MAS) is a useful tool to increase selection efficiency, especially for traits which need extensive phenotyping efforts, as PHD. However, the lack of markers associated with target traits is a major bottleneck in MAS. To find marker-trait associations (MTA), we performed genome-wide association mapping of PHD. PHD was evaluated in 76 sunflower lines (37 maintainer and 39 restorer lines), genotyped at ~14 K SNP markers. Fruits were produced in two environments (field and greenhouse), and germination evaluated under three conditions: two weeks after harvest at 20 / 10 °C (T1) or constant 25 °C (T2), and six weeks after harvest at constant 10 °C (T3), totaling five treatments (2 environments x 3 conditions except seeds from the greenhouse in T2). Two traits, the proportion of germinated fruits at five (G5) and 16 (G16) days were measured. We found 13 MTA (-log10 > 4), eight for G5 and five for G16. No SNPs were associated with more than one trait/treatment, evidencing the complex genetic architecture of PHD in sunflower. In the associated loci, dormant alleles were found at high frequency (mean = 0.36; 0.07 - 0.9). In lines, the cumulative number dormant alleles varied from 1 to 8 (of 13) and it significantly explained PHD variation in 5 / 10 trait-treatment combinations (r2 = 0.08 - 0.32). Validating these markers in biparental populations and/or unrelated genotypic collections is necessary for their application in MAS.