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首页> 外文期刊>Acta Horticulturae >Resistance to Angular Leafspot Disease of Strawberry: Influence of Seedling Age
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Resistance to Angular Leafspot Disease of Strawberry: Influence of Seedling Age

机译：草莓对角叶斑病的抗性：苗龄的影响

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The bacterium Xanthomonas fragariae (Xf) causes the economically important angular leafspot disease to which a high level of resistance has not been found within the cultivated strawberry Fragaria xananassa. The 2002 introduction of resistance donors'US 4808' and 'US 4809' by the Fruit Laboratory at the Beltsville Agricultural Research Centre, provided sources of resistance at the octoploid level derived from F. virginiana. Moving this resistance through three generations of back crossing to different recurrent F. xananassa parents along with screening progeny (12-week-old seedlings) for resistance with a spray inoculation method, followed by selection based on horticultural traits, has created improved resistant genotypes. Selection from mature plants of seedling populations that had not been screened for ^resistance gave 50% resistant selections - much higher than expected. Therefore, an experiment was designed to determine if some plants develop resistance after 12 weeks of age. Seven controlled crosses were performed in the greenhouse including three resistant (R) x resistant, three resistant x susceptible (S), and one SxS. The S*S cross was included to provide susceptible seedlings, to ensure that the inoculation procedure was effective. Four replicates of seedling sets of 10 to 12 plants per cross were inoculated at 12 or 17 weeks and rated for disease 3 weeks later.The RxR seedlings inoculated at 12 weeks had a mean disease rating of 1.19 compared to 2.28 for seedlings inoculated at 17 weeks. The RxS seedlings inoculated at 12 weeks had a mean disease rating of 2.75 compared to 3.56 for seedlings inoculated at 17 weeks. When seedlings were classified as resistant or susceptible, data analysis showed no significant differences in percent resistant between the inoculation times. These results argue against our hypothesis that older plants show resistance not identified in young seedlings and validate our procedure of screening young seedlings grown to the four to five trifoliate leaf stage. Resistant to susceptible segregation ratios of approximately 3:1 and 1:1 were found in RxR and RxS progeny, respectively, indicating that resistance shows a measure of dominance over susceptibility.
机译：草莓Xanthomonas fragariae（Xf）引起了经济上重要的角状叶斑病，在栽培草莓Fragaria xananassa中尚未发现对它的高抗性。 Beltsville农业研究中心的水果实验室于2002年引入了抗性捐赠者的“ US 4808”和“ US 4809”，这提供了源自维氏假单胞菌的八倍体水平的抗性来源。将这种抗性通过三代回交转移到不同的复发性南美白对虾亲本中，并通过喷雾接种法筛选后代（12周龄幼苗）以寻找抗性，然后根据园艺性状进行选择，从而产生了改良的抗性基因型。从尚未筛选抗病性的幼苗种群的成熟植物中进行选择可获得50％的抗性选择-远高于预期。因此，设计了一个实验来确定一些植物在12周龄后是否产生抗性。在温室中进行了七个对照杂交，包括三个抗性（R）x抗性，三个抗性x易感性（S）和一个SxS。包括S * S杂交以提供易感幼苗，以确保接种程序有效。在第12或17周接种每组10到12株植株的四组重复苗，并在3周后评估病情。在12周接种的RxR苗的平均病害等级为1.19，而在17周接种的苗的平均病害等级为2.28 。在第12周接种的RxS幼苗的平均疾病等级为2.75，而在第17周接种的RxS幼苗的平均疾病等级为3.56。将幼苗分类为抗性或易感性时，数据分析显示接种时间之间抗性百分数没有显着差异。这些结果与我们的假设相反，即年长的植物显示出在幼苗中未发现的抗性，并验证了我们筛选生长到四到五片三叶叶阶段的幼苗的程序。在RxR和RxS后代中分别发现了大约3：1和1：1的抗敏感分离比，这表明抗性显示出对敏感性的控制。

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