Self-incompatibility reactions in wild species of the genus Beta and their relation to taxonomical classification and geographical origin

The expression of self-incompatibility (SI) rejection patterns in 29 accessions of wild Beta species was studied at the anatomical level. Three different SI-related pollen tube rejection patterns were observed: (1) The pollen germinate from many pores and the pollen tubes are very short, often with swollen tips. (2) The pollen germinate and grow along the stigmatic papillae, where the self-incompatibility response takes place at the basis of the stigmatic papillae. (3) The pollen germinate and the pollen tubes grow with a distinct direction towards the style; the self-incompatibility response is observed at the border between the stigma and the style. In general the patterns observed in B. vulgaris L. subsp. vulgaris sensu late seem to be in accordance with an ongoing microevolutionary process that has given rise to the large maritima complex (viz. B. trojana Pamukcuoglu, B. atriplicifolia Rouy, and B. maritima (L.) Arcangeli), in which it seems that the variation is related to geographical origin. The data support the idea that the endemic B. vulgaris subsp, adanensis (Pamukcuoglu) Ford-Lloyd & Williams forms a distinct, self-compatible group separated from the maritima complex and also that B. macrocarpa Gussone should be retained as a separate self-compatible species. For the section Corollinae Ulbrich the rejection patterns are in accordance with a division into two subsections (viz., Lomatogonae and Trigynae) previously suggested on the basis of phenotypical and molecular data. The results from Procumbentes Ulbrich are interpreted as evidence for B. procumbens Smith and B. webbiana Moquin being more related to each other than to B. patellaris Moquin, reflecting also a similar taxonomic relationship.