Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2016
Publication Date: 6/15/2016
Citation: Zhao, D., Gordon, V.S., Comstock, J.C., Glynn, N.C., Johnson, R.M. 2016. Assessment of sugarcane yield potential across large numbers of genotypes using canopy reflectance measurements. Crop Science. 56:1747-1759.
Interpretive Summary: Approximately 12000 and 1500 genotypes (clones) are planted annually in first and second clonal stages (Stages I and II) of the Canal Point breeding and cultivar development program (CP program). Evaluation and selection of sugarcane clones for yield potential in Stage I are based on visual vigor ratings of clones and stalk juice Brix. Yield assessment of Stage II is based on millable stalk population, mean stalk weight, and juice sucrose content. In addition to requirement of technical skills and accuracy concerns for vigor ratings, collections of real yield data from the selection fields and in a laboratory are labor intensive and time consuming. Therefore, development of methodologies that rapidly and properly estimate these characteristics will help scientists improve selection efficiency. Canopy reflectance indices have been used to monitor plant growth and estimate yields in many field crops. This technology may be used to evaluate yield potential across clones in the early stages of a sugarcane breeding program. A 3-year field study was in Stage II of the CP program using 156 to 164 clones to determine if there were any putative relationships between reflectance indices and yield traits. Of yield traits (i.e., stalk population, stalk weight, cane yield, sucrose content, and sucrose yield), stalk population and cane yield were most highly correlated with reflectance at 800 and 980 nm and normalized different vegetation index (NDVI). The best time of measuring canopy reflectance for yield estimation across the tested clones was in late tillering to early grand growth (March-April). Therefore, canopy reflectance measurements could be a useful tool for estimating yield potential across large numbers of clones in sugarcane breeding programs.
Technical Abstract: Canopy reflectance indices have been used to monitor plant growth and estimate yields in many field crops. Little is known if canopy reflectance of sugarcane (a complex hybrid of Saccharum spp.) can be used to estimate growth and yield potential across large numbers of genotypes (clones) in the early stages of a breeding program. The objectives of this study were to identify clonal variation in sugarcane canopy reflectance and yield components and to determine if there were any putative relationships between canopy reflectance or reflectance indices and yield variables. In Stage II of the Canal Point sugarcane breeding and cultivar development program, canopy reflectance data were collected five to six times from each of 156 to 164 randomly selected clones during the growing seasons in 2011-2013 using a multispectral radiometer. Normalized difference vegetation index (NDVI) and other reflectance indices were calculated using the reflectance values. Yield traits, including stalk population, mean stalk weight, cane yield, commercial recoverable sucrose (CRS), and sucrose yield, were determined on mature plants in late October. Stalk population and cane yield were most highly correlated with reflectance at the wavebands centered 800 and 980 nm and NDVI (r = 0.50-0.68****), while CRS was not related to canopy reflectance. The best time to measure canopy reflectance for yield estimation across clones was from March to April (tillering stage). Canopy reflectance measurements at the early growth stage can be used as a screening tool to estimate yield potential for large numbers of clones in sugarcane breeding programs.