High‐Throughput Sensing of Aerial Biomass and Above‐Ground Nitrogen Uptake in the Vegetative Stage of Well‐Watered and Drought Stressed Tropical Maize Hybrids

Abstract

The measurement of agronomical parameters of maize (Zea mays L.) indicating its biomass and nutritional status provides important information to understand its responses to the environment. The detection of significant differences among maize hybrids would be very useful in plant breeding programs screening for N uptake and drought tolerance. The aim of the study was to assess the efficacy of high‐throughput sensing measurements to determine the aerial biomass and N uptake of tropical maize hybrids grown in well‐watered (control) and drought stress treatments. Experiments were conducted at the National Corn and Sorghum Research Center in Thailand in the years 2007 through 2009. High‐throughput canopy reflectance measurements using spectral indices from the literature and newly developed for this study were performed regularly along with biomass samplings until flowering. The relationship of the spectral indices with each of aerial biomass and N uptake had coefficients of determination of up to 0.8 and were also able to distinguish between drought stress levels. Through most sampling dates and stress levels, varieties were similarly classified in their amount of aerial biomass and N uptake by destructive and noncontacting measurements. Our results support the possibility of incorporating these methods in the development of high‐throughput phenotyping techniques that could prove to be potentially useful for future plant breeding.

Assessing maize foliar water stress levels under field conditions using in-situ spectroscopy

“…The normalised difference water index (NDWI) has been another widely used index for monitoring water status of vegetation both through multispectral (Jackson et al, 2004) and hyperspectral (Eitel et al, 2006;Elsayed et al, 2011;Winterhalter et al, 2011) remote sensing. It is measured by a ratio of difference between the reflectance value at 860 and 1240 nm wavelengths (Gao, 1996).…”

“…The index is measured of wavelengths both from the NIR region of the electromagnetic spectrum and its application in detecting water content has been widely used (Govender et al, 2009). However, other wavelengths have been used to develop ratios which have also illustrated important as a result of crop types or management conditions in monitoring water status (Winterhalter et al, 2011).…”

“…Maize (Zea mays) being an important field crop that relies on water availability for enhanced productivity has been tested in monitoring with this technology (Elsayed et al, 2011;Winterhalter et al, 2011;Genc et al, 2013). It is clear that water status assessment varies across crop types and geographical locations as a result of varying water budgets.…”

Stay-Green and Associated Vegetative Indices to Breed Maize Adapted to Heat and Combined Heat-Drought Stresses

“…Vegetative indices, which are the ratios and differences between radiation reflected at specific wavelength bands, relate to different canopy traits such as biomass, chlorophyll content, senescence (or stay-green), and plant water status [24]. Different vegetative indices have the potential to be used to address canopy senescence in maize; (i) the Normalized Difference Vegetative Index (NDVI) is based on the distinctive reflectance characteristics of the canopy in the red and near-infrared (NIR) region of the spectrum, thereby relating to leaf chlorophyll content and crop biomass [25]; (ii) the greenness (GRE) is associated with chlorophyll content [26]; (iii) the Hypespectral biomass and structural index (HBSI) relates to biomass and leaf area index [27]; and (iv) the crop water mass index (CWMI) was shown to be significantly related to the canopy water content of maize [28].…”

“…Ground-based methodologies have been used in the past; carrying hand held instruments [29] and attaching the sensor system on a platform mounted on a tractor [30] or on a forklift [28]. Ground-based methods, however, are time consuming and may be operator-biased.…”