Association of sugarcane pith, rind hardness, and fiber with resistance to the sugarcane borer.

Abstract

Varietal resistance is an important component of the integrated pest management program for controlling damaging infestations of the sugarcane borer in Louisiana sugarcane. Developing borer-resistant varieties is, however, hindered to some extent by a general lack of knowledge of resistance selection strategies. We investigated the association of sugarcane pith with sugarcane borer resistance within a population of progeny selected from a biparental cross. The population consisted of 15 clones selected with pith and 15 clones selected without pith. These selections were planted in a replicated experiment to evaluate their response to borer feeding. Damage was measured as percent bored internodes and damage ratings in both the plant-cane and first ratoon crop. We found that the subpopulation with pith sustained fewer damaged internodes (pith = 12.5 %; no pith = 15.6 %) and had lower damage ratings (pith = 3.7; no pith = 4.0) than the subpopulation without pith; however, these differences were not significant when selection was considered a random effect in our statistical model. Pith in the upper portion of the stalk was negatively correlated with damaged internodes and ratings in first ratoon. Within each subpopulation, there were individuals that were both resistant and susceptible suggesting that factors other than the presence or absence of pith were contributing to resistance. Two other factors that were investigated, targetinternode rind hardness and fiber content, were more closely associated with resistance than pith. Fiber content was correlated with resistance in all cases. Pith was not correlated to rind hardness and fiber content. Phenotypic selection in the early stages of variety development for low insect damage may result in varieties with high fiber content and rind hardness, and possibly with higher levels of pith. Accumulating these traits through repetitive phenotypic selection during recurrent selection may account for the lower sugar yields often observed in borer resistant selections.