Phelipanche ramosa is a major weed holoparasite characterized by a broad host range with a suboptimal development on numerous hosts, suggesting inter- or intra-species specificities. Seeds of P. ramosa germinate after exposure to exogenous chemicals exuded by surrounding host roots such as strigolactones, the concentrations of these germination stimulants varying between hosts. In France, P. ramosa is characterized by genetically differentiated populations presenting varying germination rates and a host specificity. The objective of our study was to investigate the sensitivity of seeds of two P. ramosa populations harvested on tobacco and oilseed rape, to a set of GR24 concentrations, a synthetic strigol analogue. The assessment of the germination rate was based on in vitro experiments. Seeds of P. ramosa were placed in Petri dishes with various concentrations of GR24. The cumulative number of germinated seeds of P. ramosa was counted several times after application of the treatment. Cumulative germination curves were analysed using a three-parameter log-logistic model and a time-to-event approach. The results show that the germination rate of P. ramosa seeds depends on the GR24 concentration and the duration of stimulation, but also that the response to these two factors varies greatly according to the origin of the P. ramosa seeds. The difference in germination speed between P. ramosa populations further shows distinct responses at the intraspecific level, thus suggesting that the specialization of P. ramosa probably occurs at least from the first stage of the holoparasite cycle.

中文翻译：

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两个Phelipanche ramosa (L.) Pomel 种群对一组GR24 浓度和刺激持续时间的种子萌发反应差异

番荔枝是一种主要的杂草全寄生虫，其特征是宿主范围广泛，在许多宿主上发育不理想，表明物种间或物种内的特异性。的种子P. ramosa暴露于周围寄主根部渗出的外源化学物质（如独脚金内酯）后发芽，这些发芽刺激剂的浓度因寄主而异。在法国，P. ramosa其特征在于具有不同发芽率和宿主特异性的遗传分化种群。我们研究的目的是调查两种种子的敏感性P. ramosa在烟草和油菜​​上收获的种群，达到一组 GR24 浓度，一种合成的独脚金类似物。发芽率的评估基于体外实验。的种子P. ramosa被放置在具有不同浓度GR24的培养皿中。累计发芽种子数P. ramosa在应用治疗后数次计数。使用三参数对数逻辑模型和事件时间方法分析累积发芽曲线。结果表明，发芽率P. ramosa种子取决于 GR24 的浓度和刺激的持续时间，而且对这两个因素的反应根据来源的不同而有很大差异。P. ramosa种子。发芽速度的差异P. ramosa种群在种内水平上进一步表现出不同的反应，因此表明P. ramosa可能至少发生在全寄生虫循环的第一阶段。