Comparison of two strategies to introgress genes for resistance to common scab from diploid Solanum chacoense into tetraploid cultivated potato

Authors: Jansky, Shelley; Haynes, Kathleen; DOUCHES, DAVID - Michigan State University

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2018
Publication Date: 1/7/2019
Citation: Jansky, S.H., Haynes, K.G., Douches, D. 2019. Comparison of two strategies to introgress genes for resistance to common scab from diploid Solanum chacoense into tetraploid cultivated potato. American Journal of Potato Research. (2019) 96:255–261. https://doi.org/10.1007/s12230-018-09711-6.
DOI: https://doi.org/10.1007/s12230-018-09711-6

Interpretive Summary: Common scab is a serious disease for potato growers. It produces lesions on tubers, leading to losses in marketable yield as infected tubers are graded out. The best control strategy is the development of resistant cultivars, but no major cultivars have high levels of resistance. We have identified strong resistance in a wild potato relative and this study was undertaken to compare two breeding strategies for introducing resistance into cultivated germplasm. One strategy generates more adapted germplasm, but we expected it to produce progeny with lower levels of resistance. However, we found that both strategies produced offspring with similar levels of resistance. Consequently, we can combine adaptation with high levels of resistance. This research will benefit potato breeders by providing guidance on breeding strategies. Ultimately, this will lead to cultivars with stronger resistance to common scab.

Technical Abstract: Wild potato relatives are important sources of novel genes useful for potato improvement. Since most wild potato species are diploid and most cultivars are tetraploid, it is typically necessary to employ ploidy manipulations to access wild potato germplasm. A common strategy is unilateral sexual polyploidization (USP), in which a tetraploid cultivated clone is crossed with a diploid that produces 2n gametes. The diploid parent may be a wild plant selected for a trait of interest. Alternatively, the wild plant may be crossed to a cultivated diploid and, after selection, the diploid hybrid is then crossed to the tetraploid parent. This study was designed to compare the two strategies for the introgression of common scab resistance from the wild diploid Solanum chacoense (chc) into cultivated potato. There were no differences between introgression methods for tuber surface area covered by scab. Scab lesions were significantly more severe when a hybrid was used as the diploid parent, but this difference is likely not large enough to be important in a breeding program. Reciprocal cross differences were not significant. However, location x clone interactions were detected for both surface area and lesion type. This study revealed that, while hybridization strategy did not play a major role in developing germplasm with chc-based resistance to common scab, it is critical to consider production environment when screening for resistance.