Emasculation technique reduces seedset in Solanum verrucosum

Authors: Bamberg, John

Submitted to: American Journal of Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2019
Publication Date: 12/12/2019
Citation: Bamberg, J.B. 2019. Emasculation technique reduces seedset in Solanum verrucosum. American Journal of Potato Research. http://doi.org/10.1007/s12230-019-09754-3.
DOI: https://doi.org/10.1007/s12230-019-09754-3

Interpretive Summary: Potato is an important US and world food crop, so breeding improved varieties is a high priority. Fortunately, potato has many wild relatives that can contribute traits, but sometimes making inter-specific hybrids is difficult. One difficulty is when the target mother plant easily self-pollinates before the male pollen from the target father is applied to the flower. The normal solution is to physically emasculate by removing the male parts from the target mother's flowers. We showed that this results in significantly lower seed production even in crosses with mothers that produce much seed. The implication is that more difficult crosses expected to produce only a few seeds might be failing completely due to physical emasculation, so alternatives to standard emasculation should be sought.

Technical Abstract: The potato crop has much exotic related germplasm, so optimizing the techniques for obtaining hybrid seeds from interspecific crosses is of interest to potato researchers and breeders, especially when the cross of interest is very difficult and few hybrid seeds are expected per pollination. A model plant of Solanum verrucosum (a particularly useful wild bridge species) was selected to have very uniform and robust flower and seed production in natural crosses as a backdrop for detecting effects of different emasculation techniques. For three uniform buds in single inflorescences, one was pollinated naturally (N) after no emasculation, one was emasculated by gently opening the corolla and plucking out only the immature anthers (A) with a tweezer, and one had total (T) removal of the sepals, corolla and anthers with a tweezers. Pollen of a highly fertile diploid tuberosum male was applied uniformly to all three buds within an inflorescence one day later. No pistil abortion occurred, excluding that as a limiting factor for getting hybrid seed. But both average fruit weight and average seeds per fruit were highly significantly reduced by emasculation in the pattern T < A < N, suggesting that the increasing physical trauma of emasculation progressively reduces seedset in S. verrucosum. In contrast, in similar crosses made within tuberosum cultivar females, pistil abortion was the only significant factor limiting hybrid seedset. We conclude that it could be valuable to find alternatives to physical emasculation for preventing selfing.