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

Abstract

SummaryThe 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 lato seem to be in accordance with an ongoing microevolutionary process that has given rise to the large maritima complex (viz. B. trojana Pamukquo~lu, 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 (Pamukquo~lu) 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.

Taxonomy of Beta Section Beta

“…maritima a higher level of heterozygotic genotypes pointed to allogamous reproduction. These results generally are in agreement with studies of Bruun et al (1994) on self-incompatibility, although the latter investigators observed incompatibility in B. patula and sometimes self-compatibility in B. vulgaris subsp. maritima.…”

Chloroplastic and nuclear diversity of wild beets at a large geographical scale: Insights into the evolutionary history of the Beta section

“…This lack of heterozygosity could also be explained by the low level of diversity in the subspecies. However, the hypothesis of selfing conforms to the cytological pattern observed on self‐pollen germination in B. v. adanensis (Bruun et al., ). Further studies on a larger sampling and including a population level, in particular by contrasting parapatric versus allopatric situations, are necessary to estimate current gene flow that could occur between the subspecies, and the level of self‐fertilization in B.v. adanensis .…”

“…Within Beta vulgaris , while B.v. maritima populations are found on a large geographical area, along both the Atlantic coasts of Western Europe and most of the Mediterranean coast, B. v. adanensis is restricted in the eastern part of the Mediterranean Basin (Aegean islands, Turkey and Syria). In addition, subspecies of the Beta section differ in their mating system: B.v. maritima is allogamous and self‐incompatible, while B. macrocarpa and B. v. adanensis have been described as self‐compatible (Bruun et al., ; Letschert, ).…”

“…Mediterranean Basin (Aegean islands, Turkey and Syria). In addition, subspecies of the Beta section differ in their mating system: B.v. maritima is allogamous and self-incompatible, while B. macrocarpa and B. v. adanensis have been described as self-compatible (Bruun et al, 1995;Letschert, 1993).…”

Low level of gene flow from cultivated beets (Beta vulgaris L. ssp. vulgaris) into Danish populations of sea beet (Beta vulgaris L. ssp. maritima (L.) Arcangeli)

“…Inbreeding will affect the heterozygote frequency for a population at all its loci, whereas a Wahlund effect only will affect allele frequencies at loci where the subpopulations have different allele frequencies (Hedrick 1999). Sea beets are mostly self-incompatible and are predominantly pollinated by wind (Brun et al 1995;Van Dijk et al 1997) and may therefore receive pollen from other neighbouring populations of beets. In addition, they spread their seeds by the movement of sea water (Tjebbes 1933).…”