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 markers.

马铃薯具有约100种在美洲自然生长的相关野生茄属物种。茄属茄属（Solanum jamesii）（jam）原产于美国西南部和墨西哥，具有许多有价值的育种性状，但制作杂种非常困难。我们研究了使用桥梁种茄茄的方法（ver）。对美国马铃薯种质库中所有ver种群的一项调查确定了最优秀的雌性。对于大多数ver，在第一次使用果酱授粉后使用ver的去雄和“良师”双重授粉的标准桥梁穿越技术效率很低，原因是：1）在ver雌性中去雄凹陷的种子集，2）尽管非常小心地去雄，却导致许多偶然的ver自身，并且3）指导者授粉与指导者花粉亲本产生了许多不需要的杂种。因此，我们通过将五代回交到马铃薯中而产生了ver种群细胞质。BC5系的生长和开花非常旺盛，但雄性育性很低，并且完全不自交，可以与果酱花粉大量杂交而不会去雄。即使没有导师花粉，大多数用果酱授粉的verBC5雌蕊也能产生小的果实，平均种子少于一粒正常种子。通过DNA标记证实了所得的幼苗为杂种杂种。