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

Summary The expression of self-incompatibility (SI) rejection patterns in 29 accessions of wildBeta 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 inB. vulgaris L. subsp.vulgaris sensu lato seem to be in accordance with an ongoing microevolutionary process that has given rise to the largemaritima complex (viz.B. trojana Pamuk?uoğlu,B. atriplicifolia Rouy, andB. maritima (L.) Arcangeli), in which it seems that the variation is related to geographical origin. The data support the idea that the endemicB. vulgaris subsp.adanensis (Pamuk?uoğlu) Ford-Lloyd & Williams forms a distinct, self-compatible group separated from themaritima complex and also thatB. macrocarpa Gussone should be retained as a separate self-compatible species. For the sectionCorollinae Ulbrich the rejection patterns are in accordance with a division into two subsections (viz.,Lomatogonae andTrigynae) previously suggested on the basis of phenotypical and molecular data. The results fromProcumbentes Ulbrich are interpreted as evidence forB. procumbens Smith andB. webbiana Moquin being more related to each other than toB. patellaris Moquin, reflecting also a similar taxonomic relationship.