Genetic and phenotypic analyses indicate that resistance to flooding stress is uncoupled from performance in cultivated sunflower

Abstract

Summary Given the rising risk of extreme weather caused by climate change, enhancement of abiotic stress resistance in crops is increasingly urgent. But will the development of stress‐resistant cultivars come at the cost of yield under ideal conditions? We hypothesize that this need not be inevitable, because resistance alleles with minimal pleiotropic costs may evade artificial selection and be retained in crop germplasm. Genome‐wide association (GWA) analyses for variation in plant performance and flooding response were conducted in cultivated sunflower, a globally important oilseed. We observed broad variation in flooding responses among genotypes. Flooding resistance was not strongly correlated with performance in control conditions, suggesting no inherent trade‐offs. Consistent with this finding, we identified a subset of loci conferring flooding resistance, but lacking antagonistic effects on growth. Genetic diversity loss at candidate genes underlying these loci was significantly less than for other resistance genes during cultivated sunflower evolution. Despite bottlenecks associated with domestication and improvement, low‐cost resistance alleles remain within the cultivated sunflower gene pool. Thus, development of cultivars that are both flooding‐tolerant and highly productive should be straightforward. Results further indicate that estimates of pleiotropic costs from GWA analyses explain, in part, patterns of diversity loss in crop genomes.

Gene banks for wild and cultivated sunflower genetic resources

“…Populations of wild H. annuus from wet habitats also exhibit tolerance to flooding (Torres and Diedenhofen, 1981). However, considerable variation for flooding tolerance can be found in the cultivated sunflower gene pool, so it is unlikely to be necessary to tap wild resistance alleles for this trait (Gao et al, 2019). Likewise, tolerance to heavy metal soils has been reported in wild species, most notably H. exilis (Sambatti and Rice, 2007), but substantial variation already exists among sunflower cultivars (Rizwan et al, 2016).…”

HeliantHOME, a public and centralized database of phenotypic sunflower data

“…The plants were dried at ~60°C for at least 3 days, or until biomass reached a constant weight, then weighed (in g) Roots traits ARN (Number of adventitious roots) All new roots from hypocotyl longer than 1 mm were counted Detailed methodological description of the traits measured for the SAM population in a GWAS flooding experiment carried out by Gao et al . in 2019 17 . …”

“… Detailed methodological description of the traits measured for the SAM population in a GWAS flooding experiment carried out by Gao et al . in 2019 17 . …”

Exceeding expectations: the genomic basis of nitrogen utilization efficiency and integrated trait plasticity as avenues to improve nutrient stress tolerance in cultivated sunflower (Helianthus annuusL.)

“…The SAM population includes both heterotic groups (i.e., male [RHA] and female [HA] lines) as well as both major market types (i.e., oil and non-oil [confectionery] lines). The SAM population has been used extensively for GWAS studies (Masalia et al ., 2018; Gao et al ., 2019; Temme et al ., 2020; Stahlhut et al ., 2021) because of the substantial genetic/trait diversity contained within the population, relevant commercial uses, and the availability of whole genome re-sequencing data for the entire population.…”