GENETIC-RELATIONSHIPS BETWEEN FIBER AND SUGARCANE YIELD COMPONENTS

Sugarcane (Saccharum spp.) fiber, the dry, water-insoluble component of the stalk, is an important quality component because of its inverse relationship to juice extraction and milling efficiency. Sugarcane cultivars in temperate regions are enhanced with S. spontaneum L. germplasm to provide increased vigor and cold tolerance. Unfortunately, S. spontaneum L. clones typically have low recoverable sucrose and high fiber content. Our objective was to estimate genetic and genotype x environment (G x E) interaction variances for sugarcane fiber content, not previously reported for a temperature sugarcane population. Twenty-two clones from the first replicated testing stage of the Louisiana Sugarcane Variety Development Program (LSVDP) were studied in a first and second ratoon crop at three locations. Genotype x crop (G x C), genotype x location (G x L), and genotype x crop x location (G x C x L) variances were much smaller than genetic and error variances. Heritability of fiber on a single-plot basis was 0.71 and 0.91 when heritability was based on three locations, two replicates, and one crop. From path analysis, the direct effect of fiber content on recoverable sucrose was -0.203, indicating a weak inverse relationship between these two traits. Fiber content was significantly correlated with stalk diameter, r(g) = -0.585, indicating that indirect selection for larger stalk diameter should decrease fiber content. Direct selection for optimum fiber content by evaluating clones in a single crop and/or location would be effective. Evaluation at different locations and during different crops, however, would offset the relatively large error variance, thereby increasing the statistical power to determine differences among clones for fiber.