| The effect of temperature on spinach seed germination was evaluated using a total of nine spinach genotypes and seven temperatures: 10, 15, 20, 25, 30, 32, and 35 °C in growth chambers. Genetic variation was observed. 'Donkey', 'Marabu', and 'Raccoon' showed higher seed germination percentage with over 70% at 30 and 32 °C, indicating the three spinach genotypes had heat-tolerance for germination. However, all spinach genotypes except 'Ozarka II' had lower germination percentages of less than 30% while 'Ozarka II' had 63% at 35 °C, indicating 'Ozarka II' may be a source of heat-tolerance for seed germination.;Seed germination may be useful as an early screening method for heat-tolerant spinach genotypes. The whole-plant experiment was conducted using two temperatures, 20 and 32 °C, in growth chambers. Variation was observed among spinach cultivars for leaf area and shoot dry weight at 32 °C. 'Samish' was the only cultivar to have no significant difference between 20 and 32 °C for leaf area, while the leaf area for 'Ozarka II', 'Donkey', and 'Marabu' decreased from 20 to 32 °C. This may indicate that 'Samish' is heat-tolerant. However, significant differences were not observed among cultivars for shoot dry weight. The results from whole-plant growth at high temperature did not parallel those of the seed germination study, and the evidence does not indicate that seed germination can be used as a screening tool for heat tolerant cultivars.;Bolting, tallness, and erectness are important morphological traits in spinach breeding. A total of 288 USDA spinach accessions were used as the association panel in this research. Single nucleotide polymorphisms (SNPs) discovered through genotyping by sequencing (GBS) were used for genotyping. Three SNP markers, AYZV01001038_398, AYZV01031624_1060, and AYZV01088923_95 were found to be associated with bolting. Eight SNP markers, AYZV01011130_540, AYZV01180397_2162, AYZV01069590_19842, AYZV01105690_376, AYZV01058838_64, AYZV01152613_2532, AYZV01113619_2197, and AYZV01003134_248 were associated with tallness. Four SNP markers, AYZV01137843_229, AYZV01158294_79, AYZV01023368_256, and AYZV01097131_197 were associated with erectness. These SNP markers may be used in spinach molecular breeding to select spinach bolting, tallness and erectness through marker-assisted selection. |
