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CROP BREEDING & GENETICS

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

USDA-ARS, Southeast Watershed Research Lab., P.O. Box 748, Tifton, GA 31793

^* Corresponding author (dgs{at}tifton.usda.gov).

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 x 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, = 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, = 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.

Abbreviations: BI, benchmark indices • GNDVI, greenness normalized difference vegetation index • LAI, leaf area index • MIR, middle infrared • NDVI, normalized difference vegetation index • NIR, near infrared • NRI, nitrogen reflectance index • OSAVI, optimized soil-adjusted vegetation index • RS, remote sensing • SAVI, soil adjusted vegetation index • SRC, spectral response curve • TSAVI, transformed soil-adjusted vegetation index • TSWV, tomato spotted wilt virus • VIS, visible.