CO 2 assimilation and protection of PSII by a reduction of light harvesting capacity. The data further suggests that stress tolerant cultivars suppress cell death and maintain growth and development via fine tuning of hormone signaling, and primary and secondary metabolism. This study highlights potential targets for the development of stress tolerant potato cultivars.

Since potato production has been expanded into warmer regions, breeding heat-tolerant potato varieties has also been considered among the top priorities in most breeding programs in recent years. Identification of traits related to heat tolerance in potato is crucial for selection of heat-tolerant genotypes. The objective of this study was to evaluate the responses of 17 potato genotypes to high temperature stress for identifying some candidate traits associated with heat tolerance. Haulm dry weight (HDW), leaf area index (LAI), photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), SPAD value, and mean tuber weight (MTW) of potato genotypes at control conditions were significantly and positively correlated with tuber yield of genotypes grown under high temperature conditions, whereas canopy temperature (CT) was negatively associated with tuber yield. Classification of potato genotypes based on heat tolerance was done by principal component analysis with yield-correlated traits. The classification results showed high similarities with the yield performance of genotypes grown under high temperature conditions. The HDW, LAI, Pn, Gs, Tr, CT, and SPAD of potato genotypes grown under normal conditions might be useful traits to screen for heat-tolerant genotypes.

Having knowledge on genetic similarity and DNA profile of potato genotypes facilitates a breeder's decision for parent selection and provides accurate variety identification. Fingerprinting and identification of genetic similarity among 151 potato genotypes were achieved using an inter-primer-binding sites (iPBS) retrotransposon marker system. Our study is the first application of iPBS markers for fingerprinting and distinguishing large numbers of Solanum tuberosum genotypes. Initially, 16 potato genotypes were screened using 45 iPBS retrotransposon markers to identify polymorphisms. Seventeen of these primers were selected for fingerprinting the whole set of accessions due to strong, reproducible and polymorphic bands. The 17 iPBS primers produced 290 scorable bands of which 224 were polymorphic. The number of bands per primer ranged from 10 to 26 with an average of 17.1. The number of polymorphic bands per primer was between 6 and 21. The polymorphism percentage per primer ranged from 46.2 to 100.0% with an average of 77.2% per primer. The mean polymorphism information content (PIC) values of iPBS primers varied from 0.12 to 0.31 per primer. Genetic similarity based on Jaccard's coefficient of potato genotypes ranged from 0.61 to 0.93 with an average of 0.73. The data produced herein may be used for selection of appropriate parents and variety description in the future. The findings of the present study suggest that iPBS retrotransposons are powerful and easy DNA markers for fingerprinting the large samples of potato germplasm.

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