Making hybrids with the wild potato Solanum jamesii

Authors: Bamberg, John; KIELAR, ABRAHAM - UNIVERSITY OF WISCONSIN; DEL RIO, ALFONSO - UNIVERSITY OF WISCONSIN; DOUCHES, DAVID - MICHIGAN STATE UNIVERSITY

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2021
Publication Date: 4/30/2021
Citation: Bamberg, J.B., Kielar, A., Del Rio, A.H., Douches, D. 2021. Making hybrids with the wild potato Solanum jamesii. American Journal of Potato Research. 98:187-193. https://doi.org/10.1007/s12230-021-09828-1.
DOI: https://doi.org/10.1007/s12230-021-09828-1

Interpretive Summary: Potato is the top vegetable crop in the USA and world, with many wild related species available for breeding. One of these is Solanum jamesii, native to the southwest USA. It has many potent disease, pest, and stress resistances, but has never been successfully hybridized with the cultivated potato. Using stocks from the US Potato Genebank in Sturgeon Bay, Wisconsin, we found a new way to cross jamesii to an intermediate species, Solanum verrucosum with relative ease. This opens the door to the next step - crossing those hybrids with cultivated potato to bring valuable jamesii traits into potato breeding for the first time.

Technical Abstract: Potato has about 100 related wild Solanum species growing naturally in the Americas. Solanum jamesii (jam), native to the southwest USA and Mexico, has many valuable traits for breeding, but making hybrids is extremely difficult. We investigated the approach of using the bridge species Solanum verrucosum (ver). A survey of all ver populations in the US Potato Genebank identified the best females. The standard bridge crossing technique using emasculation of ver and “mentor” double pollination after first pollinating with jam was very inefficient for most ver because: 1) emasculation depressed seedset in ver females, 2) despite very careful emasculation many accidental ver selfs resulted, and 3) mentor pollination produced many unwanted hybrids with the mentor pollen parent. We therefore produced populations of ver by backcrossing five generations into tuberosum cytoplasm. The BC5 lines are very vigorous in growth and flowering, but having very low male fertility and complete self-incompatibility they can be mass crossed with jam pollen without emasculation. Even with no mentor pollen, most pistils of verBC5 pollinated with jam produce a small fruit with an average of less than one normal seed. Resulting seedlings were confirmed ver-jam hybrids by DNA marker.