Factors affecting the grain yield predicting attributes of spectral reflectance indices in durum wheat: growing conditions, genotype variability and date of measurement

Abstract

The sources of variation (environment, genotype and date of measurement) of spectral reflectance indices describing biomass and its physiological status, and their potential use for providing accurate and non‐destructive estimates of crop phenology and yield, were studied on canopies of several collections of durum wheat genotypes showing adaptation to different Mediterranean environments. Spectral reflectance was measured during grain filling. All spectral indices and grain yields showed significant differences between contrasting environments in terms of water availability. Photosynthetic area indices and senescence indices were good indicators, for all genotype collections, of biomass and phenology, respectively, when comparing a wetter site with a drier site. When crop development was accelerated by growing plants under high temperature, provided by a spring‐sown trial under Mediterranean conditions, all spectral indices showed significant variation within a period of one week through grain filling, reflecting the changes in crop phenology and the onset of senescence. The reported changes in the values, and even the signs, of the correlation coefficients across genotypes between grain yield and some reflectance indices might reflect genotypic differences in response (by avoidance) to high temperature and drought during late grain filling. Spectral reflectance data may help to understand phenological characteristics of durum wheat canopies, such as crop duration, provided the date of measurement is well chosen.