Comar Alexis, Burger Philippe, de Solan Benoit, Baret Fr D Ric, Daumard Fabrice, Hanocq Jean-Fran Ois
ARVALIS Institut du végétal, 3 rue Joseph et Marie Hackin, 75116 Paris, France.
INRA - INPT, UMR 1248 AGIR, F-31320 Castanet-Tolosan, France.
Funct Plant Biol. 2012 Nov;39(11):914-924. doi: 10.1071/FP12065.
A semi-automatic system was developed to monitor micro-plots of wheat cultivars in field conditions for phenotyping. The system is based on a hyperspectral radiometer and 2 RGB cameras observing the canopy from ~1.5m distance to the top of the canopy. The system allows measurement from both nadir and oblique views inclined at 57.5° zenith angle perpendicularly to the row direction. The system is fixed to a horizontal beam supported by a tractor that moves along the micro-plots. About 100 micro-plots per hour were sampled by the system, the data being automatically collected and registered thanks to a centimetre precision geo-location. The green fraction (GF, the fraction of green area per unit ground area as seen from a given direction) was derived from the images with an automatic segmentation process and the reflectance spectra recorded by the radiometers were transformed into vegetation indices (VI) such as MCARI2 and MTCI. Results showed that MCARI2 is a good proxy of the GF, the MTCI as observed from 57° inclination is expected to be mainly sensitive to leaf chlorophyll pigments. The frequent measurements achieved allowed a good description of the dynamics of each micro-plot along the growth cycle. It is characterised by two periods: the first period corresponding to the vegetative stages exhibits a small rate of change of VI with time; followed by the senescence period characterised by a high rate of change. The dynamics were simply described by a bilinear model with its parameters providing high throughput metrics (HTM). A variance analysis achieved over these HTMs showed that several HTMs were highly heritable, particularly those corresponding to MCARI2 as observed from nadir, and those corresponding to the first period. Potentials of such semi-automatic measurement system are discussed for in field phenotyping applications.
开发了一种半自动系统，用于在田间条件下监测小麦品种的微区，以进行表型分析。该系统基于一台高光谱辐射计和2台RGB相机，从距冠层顶部约1.5米的距离观察冠层。该系统允许从天底和倾斜视图进行测量，倾斜视图的天顶角为57.5°，垂直于行方向。该系统固定在由拖拉机支撑的水平梁上，拖拉机沿着微区移动。该系统每小时对约100个微区进行采样，由于厘米级精度的地理位置，数据被自动收集和记录。通过自动分割过程从图像中得出绿色部分（GF，从给定方向看单位地面面积的绿色面积比例），辐射计记录的反射光谱被转换为植被指数（VI），如MCARI2和MTCI。结果表明，MCARI2是GF的良好代理指标，从57°倾斜角度观察到的MTCI预计主要对叶片叶绿素色素敏感。频繁的测量能够很好地描述每个微区在生长周期中的动态变化。它具有两个时期：第一个时期对应营养阶段，VI随时间的变化率较小；随后是衰老期，其特征是变化率较高。通过双线性模型简单描述了动态变化，其参数提供了高通量指标（HTM）。对这些HTM进行的方差分析表明，几个HTM具有高度遗传性，特别是那些对应于从天底观察到的MCARI2的指标，以及那些对应于第一个时期的指标。讨论了这种半自动测量系统在田间表型分析应用中的潜力。
