Self‐incompatibility (SI) in flowering plants potentially represents a major obstacle for sexual reproduction, especially when the number of S‐alleles is low. The situation is extreme in the commercially important olive tree, where in vitro pollination assays suggested the existence of a diallelic SI (DSI) system involving only two groups (G1 and G2). Varieties belonging to the same SI group cannot fertilize each other, such that successful fruit production is predicted to require pollination between varieties of different groups. To test this prediction, we explored the extent to which the DSI system determines fertilization patterns under field conditions. One hundred and seventeen olive cultivars were first genotyped using 10 highly polymorphic dinucleotide Simple Sequence Repeat (SSR) markers to ascertain varietal identity. Cultivars were then phenotyped through controlled pollination tests to assign each of them to one of the two SI groups. We then collected and genotyped 1440 open pollinated embryos from five different orchards constituted of seven local cultivars with known group of incompatibility groups. Embryos genotype information were used: (i) to assign embryos to the most likely pollen donor genotype in the neighbourhood using paternity analysis, and (ii) to compare the composition of the pollen cloud genetic among recipient trees in the five sites. The paternity analysis showed that the DSI system is the main determinant of fertilization success under field open pollination conditions: G1 cultivars sired seeds exclusively on G2 cultivars, and reciprocally. No self‐fertilization events were observed. Our results demonstrate that DSI is a potent force determining pollination success among varieties within olive orchards used for production. They have the potential to improve management practices by guiding the selection of compatible varieties to avoid planting orchards containing sets of varieties with strongly unbalanced SI groups, as these would lead to suboptimal olive production.

中文翻译：

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双等位自交不亲和性是橄榄园施肥模式的主要决定因素

开花植物的自交不亲和性（SI）可能是有性生殖的主要障碍，特别是当 S 等位基因数量较低时。这种情况在具有重要商业价值的橄榄树中最为极端，体外授粉测定表明存在仅涉及两个类群（G1 和 G2）的双等位基因 SI (DSI) 系统。属于同一 SI 组的品种不能相互受精，因此预计成功的果实生产需要不同组的品种之间授粉。为了检验这一预测，我们探索了 DSI 系统在田间条件下确定施肥模式的程度。首先使用 10 个高度多态性二核苷酸简单序列重复 (SSR) 标记对 117 个橄榄品种进行基因分型，以确定品种身份。然后通过受控授粉测试对品种进行表型分析，将它们分配到两个 SI 组之一。然后，我们从五个不同的果园收集了 1440 个开放授粉胚胎并进行了基因分型，这些果园由七个具有已知不亲和性群体的当地品种组成。使用胚胎基因型信息：（i）使用亲子分析将胚胎分配给附近最可能的花粉供体基因型，以及（ii）比较五个地点的受体树之间的花粉云遗传组成。亲子关系分析表明，DSI 系统是田间开放授粉条件下受精成功的主要决定因素：G1 品种仅在 G2 品种上交配种子，反之亦然。没有观察到自体受精事件。我们的结果表明，DSI 是决定用于生产的橄榄园内品种授粉成功的强大力量。他们有潜力通过指导选择相容品种来改善管理实践，以避免种植含有SI组严重不平衡品种的果园，因为这会导致橄榄产量不理想。