2.1.5. Testing for mixed mating systems

Many plants can set fruit both from self and cross pollen, resulting in a mixed mating system that ensures fruit- or seed-set under autogamy and xenogamy, although one or another may predominate. This test will tell us the extent to which a plant is responsive to either mating scheme.

  1. Choose a given number of flower buds prior to anthesis. The number of buds may vary with availability and ease of access, but larger samples produce more reliable results.
  2. Protect three fourths of these buds with pollination bags (see section 2.1.1.) and leave the other one fourth unbagged as the control. Identify each treatment with weather-resistant tags.
  3. After anther dehiscence and when the stigmas are receptive, remove all bags and hand pollinate one third of the flowers each with its own pollen (using paint brushes), one third with pollen from another flower of the same plant, and the final third with pollen from multiple plants. After that, bag the flowers again to prevent flower visitors or wind pollination. Leave bags on flowers until they are no longer receptive, then remove the bags.
  4. At the end of the season, check whether any fruit developed from the bagged flowers. If all or most bagged flowers have developed into fruits, the plant species has a mixed mating system and the proportion of fruit- or seed-set obtained from the bagged treatments in comparison to the control treatment will tell whether there is a preference for self-pollination, geitonogamy or xenogamy. In the case of mixed breeding systems, honey bees can be highly effective pollinators.