Using Ground-Based Reflectance Measurements as Selection Criteria for Drought- and Aflatoxin-Resistant Peanut Genotypes

Drought stress and aflatoxin contamination continue to challenge peanut (Arachis hypogaea L.) producers across the USA. Thus, the continued development of drought- and aflatoxin-resistant peanut cultivars is essential to maintain productivity under less than ideal growing conditions. Remote sensing of canopy reflectance is a well-established method of evaluating crop condition and shows promise as a tool for rapid selection of drought- and aflatoxin-resistant peanut genotypes. The objective of this study was to evaluate ground-based reflectance measurements to more accurately quantify differences in genotype response to drought conditions. In April 2004 and 2005 several small plots (4 m × 2 m) were established at the Gibbs Farm research facilities in Tifton, GA. Treatments consisted of five peanut genotypes encompassing a range of drought tolerance and yield characteristics. Drought conditions were simulated beginning 90 d after planting and maintained through harvest. Once drought conditions were established, a handheld radiometer was used to acquire twice-weekly reflectance measurements in the visible and near-infrared. Benchmark indices were developed based on the change in remotely sensed vegetation indices as a measure of the change in crop response between nonstressed and drought-stressed conditions. Significant treatment differences in benchmark indices were observed between drought-tolerant, moderately drought-tolerant and drought-intolerant varieties. Benchmark indices were also highly correlated with yield (r = −0.41 to −0.75, α = 0.05) in all three planting environments. However, the relationship between aflatoxin contamination and benchmark indices was less consistent, having a strong correlation with aflatoxin contamination in the second and third planting environments only (r = 0.38–0.73, α = 0.05). These indices could aid plant breeders in more accurately assessing genetic differences, which would accelerate breeding progress and the development of peanut cultivars with resistance to drought and aflatoxin contamination.