Understanding how disease foci arise from single source lesions has not been well studied. Here, single wheat leaves were inoculated with Puccinia striiformis f. sp. tritici urediniospores, and all wheat leaves within two intersecting 0.3 × 3.0 m transects were sampled in eight replicates over three years. The lesions observed on each of the top three leaves on plants within 1.5 m from the source lesion were three-dimensionally mapped. The total number of lesions within a 1.5 m radius was estimated by dividing the number of lesions observed within each 0.025 m-wide annulus by the fraction of the annulus sampled. The estimated total number of lesions produced within 1.5 m of a single source lesion ranged from 27 to 776, with a mean of 288 lesions. Eighty percent of the lesions were recorded within 0.69 m of the source infection. The proportion of total lesions observed at a given distance from the source was fitted well by the Lomax and Weibull distributions, reflecting the large proportion of lesions arising close to the source, and when fitted to an inverse-power distribution had a slope (b) of 2.5. There were more lesions produced on leaves higher in the canopy than on lower leaves, with more lesions being detected above than below the point of inoculation. Simultaneous measurement of lesion gradients and spore dispersal in the final year of the study suggests that this pattern is due to greater susceptibility of upper leaves, rather than increased dispersal to upper leaves.

中文翻译：

---

条锈菌局部扩散。小麦病原菌


了解病灶如何由单一来源病变产生尚未得到充分研究。在这里，用条锈菌 f 接种单片小麦叶子。 sp。三年内，对小麦 urdiniospores 和两个相交的 0.3 × 3.0 m 横断面内的所有小麦叶子进行了八次重复采样。对距离源病斑 1.5 m 范围内的植物顶部三片叶子上观察到的病斑进行三维绘图。通过将每个 0.025 m 宽的环带内观察到的损伤数量除以采样的环带的比例来估计 1.5 m 半径内的损伤总数。估计单个源病灶 1.5 m 内产生的病灶总数为 27 至 776 个，平均为 288 个病灶。 80% 的病灶记录在距感染源 0.69 m 的范围内。在距源给定距离处观察到的总损伤的比例与 Lomax 和 Weibull 分布很好地拟合，反映了靠近源产生的损伤的大部分，并且当拟合到逆幂分布时具有斜率 (b) 2.5。冠层较高的叶子比下部的叶子产生更多的病斑，在接种点上方检测到的病斑比接种点下方的病斑多。研究最后一年对病斑梯度和孢子扩散的同时测量表明，这种模式是由于上部叶片的敏感性更高，而不是上部叶片的扩散增加。