High throughput phenotyping of canopy water mass and canopy temperature in well-watered and drought stressed tropical maize hybrids in the vegetative stage

The high throughput determination of the water status of maize (Zea mays L.) in precision agriculture presents numerous benefits, but also shows the potential for improvement. On the former count, the differentiation of maize hybrids could be used in screening drought tolerance in plant breeding, whereas, on the latter count, the monitoring of plant water status by non-destructive high-throughput sensing carried out on GPS based vehicles could enable the fast evaluation of various traits over a large area, improving the management decisions of farmers. The aim of this study was to assess the ability to measure the canopy water mass (CWM; amount of water in kgm⁻²) of several tropical maize hybrids using high throughput sensing. Experimental field trials were conducted in Thailand (National Corn and Sorghum Research Center) in the years 2007–2009, where seven hand sown tropical high yield hybrids were analyzed under four furrow irrigation treatments. High throughput canopy reflectance and thermal radiance measurements, as well as biomass samplings were done on a regular basis until flowering. Both a large number of spectral indices from literature and newly developed for this study were validated. Selected spectral indices and IR-temperature were highly correlated with CWM and able to show the different drought stress levels. Several indices showed global coefficients of determination of over 0.70 and it was possible to differentiate and classify the hybrids into three consistent groups (above, below, or average performance) under control and stress environments. The results of this study show that it is indeed possible to both detect CWM and discriminate between groups of hybrids using non-destructive high throughput phenotyping, and that this technology presents a potentially useful application for breeding in the future.