In more than 60 families of angiosperms, the self- and cross-fertilization is avoided through a complex widespread genetic system called self-incompatibility (SI). One of the major puzzling issues concerning the SI is the evolution of this system in species with complex polyploid genomes. Among plums, one of the first fruits species to attract human interest, polyploid species represent enormous genetic potential, which can be exploited in breeding programs. However, molecular studies in these species are very scarce due to the complexity of their genome. In order to study the SFB gene [the male component of gametophytic self-incompatibility system (GSI)] in plum species, 36 plum accessions belonging to diploid and hexaploid species were used. A total of 19 different alleles were identified; 1 of them was revealed after analyzing sequences. Peptide sequence analysis allowed identifying the five domains features of the SFB gene. Polymorphism analysis showed a subtle difference between domesticated and open pollinated Tunisian accessions and suggested a probable influence of the ploidy level. Divergence analysis between studied sequences showed that a new specificity may appear after 5.3% of divergence at synonymous sites between pairs of sequences in Prunus insititia, 6% in Prunus cerasifera, 8% and 9% in Prunus domestica and Prunus salicina respectively. Furthermore, sites under positive selection, the ones more likely to be responsible for specificity determination, were identified. A positive and significant Pearson correlation was found between the divergence between sequences, divergence time, fixed substitutions (MK test), and PSS number. These results supported the model assuming that functionally distinct proteins have arisen not as a result of chance fixation of neutral variants, but rather as a result of positive Darwinian selection. Further, the role that plays recombination can not be ruled out, since a rate of 0.08 recombination event per polymorphic sites was identified.

在60多个被子植物科中，通过称为自我不相容性（SI）的复杂广泛的遗传系统避免了自我受精和交叉受精。关于SI的主要令人困惑的问题之一是该系统在具有复杂多倍体基因组的物种中的进化。在李子（最早引起人类关注的水果之一）中，多倍体物种具有巨大的遗传潜力，可在育种计划中加以利用。然而，由于其基因组的复杂性，这些物种的分子研究非常匮乏。为了研究李子物种中的SFB基因[配子体自交不亲和系统（GSI）的雄性成分]，使用了36种李子种，分别属于二倍体和六倍体。总共鉴定出19个不同的等位基因。分析序列后发现其中1个。肽序列分析允许鉴定SFB基因的五个结构域特征。多态性分析显示，驯化和开放授粉的突尼斯种质之间存在细微差异，并可能对倍性水平产生影响。研究序列之间的差异分析表明，在5.3％的序列对同义位点之间，在5.3％的差异之后可能会出现新的特异性。樱桃insititia，在6％红叶李，8％和9％国内李和李蚧分别。此外，确定了在阳性选择下的位点，这些位点更有可能负责确定特异性。发现序列之间的差异，差异时间，固定取代（MK检验）和PSS数之间存在显着正相关的Pearson相关性。这些结果支持该模型，其假设功能上不同的蛋白质的产生不是由于中性变体的偶然固定，而是由于积极的达尔文式选择。此外，由于鉴定出每个多态性位点的重组事件发生率为0.08，因此不能排除重组的作用。