Genetic Basis of Potato Tuber Defects and Identification of Heat-Tolerant Clones

Abstract

Heat stress during the potato growing season reduces tuber marketable yield and quality. Tuber quality deterioration includes external (heat sprouts, chained tubers, knobs) and internal (vascular discoloration, hollow heart, internal heat necrosis) tuber defects, as well as a reduction in their specific gravity and increases in reducing sugars that result in suboptimal (darker) processed products (french fries and chips). Successfully cultivating potatoes under heat-stress conditions requires planting heat-tolerant varieties that can produce high yields of marketable tubers, few external and internal tuber defects, high specific gravity, and low reducing sugars (in the case of processing potatoes). Heat tolerance is a complex trait, and understanding its genetic basis will aid in developing heat-tolerant potato varieties. A panel of 217 diverse potato clones was evaluated for yield and quality attributes in Dalhart (2019 and 2020) and Springlake (2020 and 2021), Texas, and genotyped with the Infinium 22 K V3 Potato Array. A genome-wide association study was performed to identify genomic regions associated with heat-tolerance traits using the GWASpoly package. Quantitative trait loci were identified on chromosomes 1, 3, 4, 6, 8, and 11 for external defects and on chromosomes 1, 2, 3, 10, and 11 for internal defects. Yield-related quantitative trait loci were detected on chromosomes 1, 6, and 10 pertaining to the average tuber weight and tuber number per plant. Genomic-estimated breeding values were calculated using the StageWise package. Clones with low genomic-estimated breeding values for tuber defects were identified as donors of good traits to improve heat tolerance. The identified genomic regions associated with heat-tolerance attributes and the genomic-estimated breeding values will be helpful to develop new potato cultivars with enhanced heat tolerance in potatoes.

Keywords: Solanum tuberosum; genome-wide association study; genomic selection; high temperature stress; quality; tuber deformities.

Figure 1

Pearson’s correlations for yield and tuber-defect traits measured in 217 potato genotypes across Texas environments [Dalhart (2019 and 2020) and Springlake (2020 and 2021)].

Figure 2

Location of significant QTLs on potato chromosomes for yield components and tuber external and internal defects based on evaluations of 217 potato genotypes across Texas environments [Dalhart (2019 and 2020) and Springlake (2020 and 2021)]. The QTLs are color-coded and the closest SNP to each peak is indicated.

Figure 3

Boxplot of the predicted reliabilities (y axis) for the yield and tuber-defect traits (x axis) measured in 217 potato genotypes in Dalhart (2019 and 2020) and Springlake (2020 and 2021).

Figure 4

Phenotypes of potato tuber defects. Horizontal panel (A) represents external defects: (1) heat sprouts, (2) chained tubers, (3) knobs, and (4) growth cracks. Horizontal panel (B) represents internal defects: (1) internal heat necrosis, (2) vascular discoloration, and (3) hollow heart.