Abdallah Donia, Baraket Ghada, Perez Veronica, Salhi Hannachi Amel, Hormaza Jose I
Faculté des Sciences de Tunis, Département Biologie, Université de Tunis El Manar, 2092 Tunis, Tunisie.
Laboratorio de Agrobiología Juan José Bravo Rodríguez (Cabildo Insular de La Palma), Unidad Técnica del Instituto de Productos Naturales y Agrobiología (IPNA-CSIC), 38700 S/C La Palma, Canary Islands, Spain.
Hortic Res. 2020 Oct 1;7:170. doi: 10.1038/s41438-020-00392-z. eCollection 2020.
Self-incompatibility (SI) to self-compatibility (SC) transition is one of the most frequent and prevalent evolutionary shifts in flowering plants. L. (Rosaceae) is a genus of over 200 species most of which exhibit a Gametophytic SI system. Peach [ (L.) Batsch; 2 = 16] is one of the few exceptions in the genus known to be a fully self-compatible species. However, the evolutionary process of the complete and irreversible loss of SI in peach is not well understood and, in order to fill that gap, in this study 24 peach accessions were analyzed. Pollen tube growth was controlled in self-pollinated flowers to verify their self-compatible phenotypes. The linkage disequilibrium association between alleles at the -locus and linked markers at the end of the sixth linkage group was not significant ( > 0.05), except with the closest markers suggesting the absence of a signature of negative frequency dependent selection at the -locus. Analysis of SFB1 and SFB2 protein sequences allowed identifying the absence of some variable and hypervariable domains and the presence of additional α-helices at the C-termini. Molecular and evolutionary analysis of SFB nucleotide sequences showed a signature of purifying selection in SFB2, while the SFB1 seemed to evolve neutrally. Thus, our results show that the SFB2 allele diversified after and (almond) divergence, a period which is characterized by an important bottleneck, while SFB1 diversified at a transition time between the bottleneck and population expansion.
自交不亲和性（SI）向自交亲和性（SC）的转变是开花植物中最频繁和普遍的进化转变之一。李属（蔷薇科）是一个拥有200多个物种的属，其中大多数表现出配子体自交不亲和系统。桃[（蔷薇科）巴施；2n = 16]是该属中已知的少数几个完全自交亲和的物种之一。然而，桃中自交不亲和性完全且不可逆丧失的进化过程尚未得到很好的理解，为了填补这一空白，本研究分析了24份桃种质。通过自花授粉花朵中花粉管的生长来验证它们的自交亲和表型。除了与最接近的标记显示在S-位点不存在负频率依赖选择的特征外，S-位点等位基因与第六个连锁群末端的连锁标记之间的连锁不平衡关联不显著（P > 0.05）。对SFB1和SFB2蛋白序列的分析表明，不存在一些可变和高变结构域，并且在C末端存在额外的α-螺旋。SFB核苷酸序列的分子和进化分析表明，SFB2存在纯化选择的特征，而SFB1似乎是中性进化。因此，我们的结果表明，SFB2等位基因在桃和扁桃分歧后多样化，这一时期的特征是重要的瓶颈效应，而SFB1在瓶颈效应和种群扩张之间的过渡时期多样化。
