Abstract
Sugarcane aphid [(Melanaphis sacchari (Zehntner)] emerged in the United States in 2013 as a new pest infesting sorghum (Sorghum bicolor (L.) Moench). Aphid population and plant damage are assessed by field scouting with mean comparison tests or repeated regression analysis. Because of inherently large replication errors from the field and interactions between treatments, new data analytics are needed to rapidly visualize the pest emergence trend and its impact on plant damage. This study utilized variable importance in the projection (VIP) and regression vector statistics of partial least squares (PLS) modeling to deduce directional relationships between aphid population and leaf damage from biweekly field monitoring (independent variable) and chemical composition (dependent variable) of 24 sweet sorghum cultivars. Regardless of environment, aphid population increase preceded the maximum damage rating. Greater damage rating at earlier growth stage in 2015 than 2016 led to an overall higher damage rating in 2015 than 2016. This trend in damage coincided with higher concentrations of trans-aconitic acid and polyphenolic secondary products in stem juice in 2016 than 2015, at the expense of primary sugar production. Developed rapid data analytics could be extended to link phenotypes to perturbation parameters (e.g., cultivar and growth stage), enabling integrated pest management.
Highlights
Sorghum (Sorghum bicolor (L.) Moench) is a marginal land crop having a unique ability to grow on semi-arid soils[1]
New analytics are in demand to rapidly and objectively interpret (1) aphid population and damage time courses having large replication errors, (2) relationships between aphid population and crop damage, and (3) influence of host genotypes and environmental factors on (1) and (2)
Our previous report developed partial least squares (PLS) calibration and prediction models based on UV/visible spectra of sweet sorghum juice and bagasse[22]
Summary
Sorghum (Sorghum bicolor (L.) Moench) is a marginal land crop having a unique ability to grow on semi-arid soils[1]. Sweet sorghum juice is composed of fermentable sugars and chemical feedstocks (carboxylate and polyphenolic secondary products). Both primary and secondary products could be used to produce high market value specialty bio-based products including plastics[3], green pesticides[4], nematicides[5], and antioxidant food additives[6]. Spectra for juice samples were used to predict trans-aconitic acid concentration, while spectra from the methanol extract of bagasse were used to predict the relative concentrations of polyphenol-like fluorescent fingerprints[22] Both phenolics[21,23,24] and trans-aconitic acid[25] have been proposed to act as defensive phytochemicals or phytohormonal signals upon leaf damage by aphids and other plant-feeding arthropods
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