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Development of Leaf Spectral Models for Evaluating Large Numbers of Sugarcane Genotypes

Duli Zhao, Neil C. Glynn, Barry Glaz, Jack C. Comstock, Richard M. Johnson
Crop science 2012 v.52 no.4 pp. 1837-1847
Saccharum, canes, carbon, carbon nitrogen ratio, chlorophyll, crop yield, early selection, genetic variation, genotype, growing season, juices, leaves, mature plants, models, nitrogen, plant breeding, reflectance, spectral analysis, sucrose, sugarcane, thyrotropin, Florida
Leaf reflectance has been used to estimate crop leaf chemical and physiological characteristics. Sugarcane (Saccharum spp.) leaf N, C, and chlorophyll levels are important traits for high yields and perhaps useful for genotype evaluation. The objectives of this study were to identify sugarcane genotypic variation in leaf hyperspectral reflectance, leaf chemical (chlorophyll, N, and C), and yield (juice sucrose content, commercial recoverable sucrose [CRS], cane yield in tonnes of cane per hectare [TCH], and sucrose yield in tonnes of sucrose per hectare [TSH]) traits and to determine relationships between leaf reflectance and these chemical and yield traits. In Stage II of the Canal Point, FL, sugarcane cultivar development program, we measured spectral reflectance and chemical traits on three leaves of the top visible dewlap from each of 87 genotypes in December 2008 and 208 and 124 genotypes in May, July, September, and October 2009 and 2010, respectively. Yield traits were determined on mature plants. Genotypic variation of leaf reflectance mainly occurred in 540 to 1200 nm. Leaf relative chlorophyll, N, C, and C to N ratio varied among genotypes and during the growing season. Highly significant calibrations were developed for leaf chemical traits using leaf reflectance (P < 0.0001). Correlations of juice sucrose, CRS, TCH, and TSH with leaf reflectance were poor. Measurement of leaf reflectance is a promising tool for estimating leaf chemical traits but not for predicting yield traits across a large number of diverse genotypes in early selection stages of a sugarcane breeding program.