Characteristics of self-incompatibility in Schlumbergera truncata and S. x buckleyi (Cactaceae)

The influence of self-incompatibility (SI) on fruit set, seed set, and pollen tube growth was investigated in Schlumbergera truncata (Haworth) Moran and S.xbuckleyi (T. Moore) Tjaden. Four Schlumbergera clones were crossed in a complete diallel to verify the presence of SI. Fruit did not set when the clones were selfed or when two of the clones were crossed reciprocally, but all other outcrosses yielded fruit which contained 100–200 seeds each. Compatible outcrosses were characterized by large numbers of pollen tubes in the style and ovary cavity at 72 h after pollination. When pistils were selfed or incompatibly crossed, pollen tubes were inhibited in the upper third of the style and few pollen tubes reached the base of the style by 72 h after pollination. Schlumbergera exhibits several characteristics often associated with sporophytic SI systems (tricellular pollen and dry stigmas with elongate papillae), together with those commonly observed in gametophytic SI systems (stylar inhibition of incompatible pollen tubes and absence of reciprocal differences in outcrosses).Publication no. 3174 of the Massachusetts Agricultural Experiment Station