Lignocellulosic Composition Not Associated with Stem Borer Resistance in Select Louisiana Sugarcane Cultivars

Abstract

The two most economically damaging insect pests of sugarcane in Louisiana are the sugarcane borer (SCB) and the newly invasive Mexican rice borer (MRB), both of which can be managed in part with cultivar resistance. High stalk fiber levels is a well-documented aspect of stem borer resistance but is inversely correlated with recoverable sugar levels. However, lignocellulosic components such as hemicellulose, cellulose, and lignin are associated with resistance to other borer species in poaceous crops, potentially indicating mechanisms that may provide resistance without substantial trade-offs in yield. The goal of this study was to determine whether lignocellulosic composition varied among four cultivars—HoCP 85-845, HoCP 04-838, Ho 07-613, and HoCP 00-950—selected based on known variation in SCB and MRB resistance and total fiber content. We estimated lignocellulosic composition as well as Brix throughout the growing season and the total stalk fiber and recoverable sugar content at harvest for both plant cane and first ratoon crop years. We found that the Brix content throughout the growing season, as well as total fiber and sugar content at harvest, were significantly associated with the cultivar, aligning with previously documented trends in borer resistance (i.e., higher Brix and lower total fiber indicate a more susceptible cultivar). While lignocellulosic composition during the growing season was not associated with cultivar or resistance to either borer species, it was significantly impacted by sampling month and crop year. These data indicate the potential influence of alternative resistance mechanisms and interactions with abiotic conditions.