Screening potato genotypes for antioxidant activity, identification of the responsible compounds, and differentiating Russet Norkotah strains using AFLP and microsatellite marker analysis
Hale, Anna Louise
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Total antioxidant activity and total carotenoid levels were evaluated for more than 100 common potato (Solanum tuberosum, L.) cultivars grown in the United States, advanced breeding lines from several Western U.S. breeding programs, and 47 related, tuber-bearing species. An initial assessment of variability for antioxidant activity provided baseline information to be used for potential potato promotion and for the development of new varieties with greater human health benefits. Wide variability in antioxidant levels provided evidence of genetic control of this trait, indicating that it could be possible to breed for enhanced levels of antioxidant compounds in potato. Accessions, varieties, and advanced breeding lines identified in the broad screen as having high antioxidant activity and high total carotenoid levels, were fine screened via HPLC to determine specific phenolic and carotenoid compounds present in potato. The objective of the study was to identify parents for use in the Texas breeding program to develop potato varieties containing increased levels antioxidant compounds. In the broad screen for total antioxidant activity, the 47 related, tuber-bearing species showed a wider range of variability than the cultivated varieties and breeding lines. Based on the DPPH assay, antioxidant activity ranged from 103-648 uM trolox equivalents in the cultivated varieties and advanced breeding lines, while that of the wild species was 42-892. HPLC analysis revealed that the phenolic content of the species, and their cultivated counterparts, was primarily composed of caffeic and chlorogenic acids. Other phenolics identified were p-coumaric acid, rutin hydrate, vanillic acid, epicatechin, t-cinnamic acid, gallic acid, and salicylic acid. The highest phenolic content discovered in the accessions was five-fold higher than the highest of the cultivated genotypes. Carotenoid analysis revealed lutein in the accessions, but the yellow-flesh breeding lines were much higher in carotenoids. In addition to the work conducted on antioxidants, an attempt was made to separate intraclonal variants of the potato cultivar Russet Norkotah. Eleven microsatellite primers and 112 AFLP primer combinations failed to produce any reproducible polymorphisms. The inability to detect differences between the clones could be due to the tetraploid nature of the clones or epigenetic differences not detected by the procedures utilized in this study.