UMR ECOSYS INRA, AgroParisTech, Université Paris-Saclay, Thiverval-Grignon, France.
UMR BIOGER INRA, AgroParisTech, Université Paris-Saclay, Thiverval-Grignon, France.
Ann Bot. 2018 Jun 8;121(7):1299-1308. doi: 10.1093/aob/mcy024.
Growing cultivars differing by their disease resistance level together (cultivar mixtures) can reduce the propagation of diseases. Although architectural characteristics of cultivars are little considered in mixture design, they could have an effect on disease, in particular through spore dispersal by rain splash, which occurs over short distances. The objective of this work was to assess the impact of plant height of wheat cultivars in mixtures on splash dispersal of Zymoseptoria tritici, which causes septoria tritici leaf blotch.
We used a modelling approach involving an explicit description of canopy architecture and splash dispersal processes. The dispersal model computed raindrop interception by a virtual canopy as well as the production, transport and interception of splash droplets carrying inoculum. We designed 3-D virtual canopies composed of susceptible and resistant plants, according to field measurements at the flowering stage. In numerical experiments, we tested different heights of virtual cultivars making up binary mixtures to assess the influence of this architectural trait on dispersal patterns of spore-carrying droplets.
Inoculum interception decreased exponentially with the height relative to the main inoculum source (lower diseased leaves of susceptible plants), and little inoculum was intercepted further than 40 cm above the inoculum source. Consequently, tall plants intercepted less inoculum than smaller ones. Plants with twice the standard height intercepted 33 % less inoculum than standard height plants. In cases when the height of suscpeptible plants was doubled, inoculum interception by resistant leaves was 40 % higher. This physical barrier to spore-carrying droplet trajectories reduced inoculum interception by tall susceptible plants and was modulated by plant height differences between cultivars of a binary mixture.
These results suggest that mixture effects on spore dispersal could be modulated by an adequate choice of architectural characteristics of cultivars. In particular, even small differences in plant height could reduce spore dispersal.
将具有不同抗病水平的栽培品种（品种混合物）一起种植可以减少疾病的传播。尽管在混合物设计中很少考虑品种的结构特征，但它们可能会通过雨滴飞溅导致的孢子传播对疾病产生影响，而这种传播通常发生在短距离内。本研究的目的是评估小麦品种混合物中品种高度对导致叶枯病的叶点霉属（Zymoseptoria tritici）飞溅传播的影响。
我们使用了一种建模方法，该方法涉及到对冠层结构和飞溅传播过程的明确描述。该传播模型计算了虚拟冠层对雨滴的拦截以及携带接种物的飞溅液滴的产生、运输和拦截。我们根据开花期的田间测量结果，设计了由感病和抗病植物组成的 3D 虚拟冠层。在数值实验中，我们测试了不同高度的虚拟品种组成的二元混合物，以评估该结构特征对携带孢子的液滴传播模式的影响。
相对于主要接种源（感病植物下部感病叶片）的高度，接种物的拦截量呈指数下降，而且在接种源上方 40 厘米以上的地方很少有接种物被拦截。因此，高大的植物比矮小的植物拦截的接种物更少。高度为标准高度两倍的植物比标准高度植物拦截的接种物少 33%。在感病植物高度增加一倍的情况下，抗性叶片对感病叶片的拦截量增加了 40%。这种对携带孢子液滴轨迹的物理障碍减少了高大感病植物对携带孢子液滴的拦截，并且可以通过二元混合物中品种间的高度差异来调节。
这些结果表明，混合物对孢子传播的影响可以通过适当选择品种的结构特征来调节。特别是，植物高度的微小差异也可以减少孢子传播。
