Genome-wide association analysis for pollen viability under heat stress in peanut

Peanut is one of the most important crops, providing nutrition and food security to millions worldwide. Pollen viability (PV) is a major determinant of yield in crops and is adversely impacted by heat stress. This study aimed to identify molecular markers associated with sustained PV under heat stress. We evaluated 72 genetically non-redundant genotypes from the U.S. peanut mini-core collection for PV under heat stress and compared them to the PV of "Georgia Green," a runner-type peanut variety used as a control. Seventy-two genotypes were grown under optimal conditions (28/22 °C day/night temperatures with a 16 h photoperiod). Once the plants reached the five-leaf stage, heat stress was applied for two weeks by raising the daytime temperature to 38 °C and the nighttime temperature to 28 °C. Un-opened flowers were collected and assayed for PV through in vitro pollen germination. PI 200441 from Japan exhibited the highest PV, while PI 504614 from Colombia showed the lowest. A genome-wide association study for PPV (percent pollen viability) under heat stress identified a marker on chromosome 20. Haplotype analysis revealed a 6 kb region, designated qPPVA20, containing three candidate genes, two of which (ribosomal protein and copper-transporting ATPase) showed high expression in reproductive organs. The co-localization of qPPVA20 with a previously reported QTL hotspot for heat stress-related traits makes these genes important targets for future validation. Markers associated with seed lipid compositional traits, such as behenate, arachidate, oleate, and eicosenoate content under optimal growth conditions, were also identified, with plans to investigate the impact of heat stress on these QTLs in a future study.