2018 ASHS Annual Conference

Heat stress on roses (Rosa x hybrida) negatively affects rose performance and reduces the market value of the crop. The effect of heat on flower size was assessed with a heat shock treatment (44°C for 1 hour) and in the field during the cool (~20°C) and warm (~30°C) seasons of the year for 10 and 9 interrelated diploid rose populations respectively. The elevated temperature caused a decrease in flower size under both conditions for flower diameter (~16-18%), petal number (~23-17%), and flower weight (~17-32%). Flower size showed low to moderate (flower diameter, 0.24-0.38; petal number, 0.12-0.26; flower weight, 0.34-0.53) narrow and moderate (flower diameter, 0.62-0.70; petal number, 0.74-0.91; flower weight, 0.76-0.88) broad sense heritability inferring a major non additive genetic component for flower size. Differences in heat tolerance would indicate that roses respond differentially to the environment (heat stress). Thus in a genetic variance analysis, a high GxE variance would indicate genetic differences in heat stress. Among the three size parameters, flower diameter showed the largest GxE genetic variance. The populations were genotyped using genotyping by sequencing and the SNPs were used to create a consensus map with JoinMap 5. Using the consensus map in FlexQTL, a pedigree based QTL analysis software, for flower petal number, flower diameter, and flower dry weight was done.