INRA-EMMAH-CAPTE, Route de l'aerodrome, Avignon, France.
HIPHEN, Rue Charrue, Avignon, France.
J Exp Bot. 2018 Apr 27;69(10):2705-2716. doi: 10.1093/jxb/ery071.
Leaf rolling in maize crops is one of the main plant reactions to water stress that can be visually scored in the field. However, leaf-scoring techniques do not meet the high-throughput requirements needed by breeders for efficient phenotyping. Consequently, this study investigated the relationship between leaf-rolling scores and changes in canopy structure that can be determined by high-throughput remote-sensing techniques. Experiments were conducted in 2015 and 2016 on maize genotypes subjected to water stress. Leaf-rolling was scored visually over the whole day around the flowering stage. Concurrent digital hemispherical photographs were taken to evaluate the impact of leaf-rolling on canopy structure using the computed fraction of intercepted diffuse photosynthetically active radiation, FIPARdif. The results showed that leaves started to roll due to water stress around 09:00 h and leaf-rolling reached its maximum around 15:00 h (the photoperiod was about 05:00-20:00 h). In contrast, plants maintained under well-watered conditions did not show any significant rolling during the same day. A canopy-level index of rolling (CLIR) is proposed to quantify the diurnal changes in canopy structure induced by leaf-rolling. It normalizes for the differences in FIPARdif between genotypes observed in the early morning when leaves are unrolled, as well as for yearly effects linked to environmental conditions. Leaf-level rolling score was very strongly correlated with changes in canopy structure as described by the CLIR (r2=0.86, n=370). The daily time course of rolling was characterized using the amplitude of variation, and the rate and the timing of development computed at both the leaf and canopy levels. Results obtained from eight genotypes common between the two years of experiments showed that the amplitude of variation of the CLIR was the more repeatable trait (Spearman coefficient ρ=0.62) as compared to the rate (ρ=0.29) and the timing of development (ρ=0.33). The potential of these findings for the development of a high-throughput method for determining leaf-rolling based on aerial drone observations are considered.
叶片卷曲是玉米作物对水分胁迫的主要反应之一，可在田间进行视觉评分。然而，叶片评分技术无法满足育种者对高通量表型分析的高要求。因此，本研究探讨了叶片卷曲评分与通过高通量遥感技术确定的冠层结构变化之间的关系。2015 年和 2016 年在受水分胁迫的玉米基因型上进行了实验。在开花期前后的全天进行叶片卷曲的视觉评分。同时拍摄数字半球形照片，以使用计算的漫射光合有效辐射截获分数（FIPARdif）评估叶片卷曲对冠层结构的影响。结果表明，叶片大约在 09:00 时开始因水分胁迫而卷曲，大约在 15:00 时达到卷曲的最大值（光照时间大约为 05:00-20:00）。相比之下，在同一时间，处于充分供水条件下的植物没有出现任何明显的卷曲。提出了一个冠层卷曲指数（CLIR）来量化叶片卷曲引起的冠层结构的日变化。它可以对基因型之间在清晨叶片未卷曲时观察到的 FIPARdif 差异进行归一化，还可以对与环境条件相关的年度效应进行归一化。叶片卷曲评分与由 CLIR 描述的冠层结构变化非常强相关（r2=0.86，n=370）。通过变化幅度、叶片和冠层水平上的发展速率和时间来描述卷曲的日时间进程。在两年实验中都有的八个基因型的结果表明，CLIR 的变化幅度是最具可重复性的特征（Spearman 系数 ρ=0.62），而发展速率（ρ=0.29）和发展时间（ρ=0.33）则相对较差。考虑到基于空中无人机观测确定叶片卷曲的高通量方法的发展潜力，对这些发现进行了探讨。
