|Richard Jr, Edward|
Submitted to: American Society of Sugar Cane Technologists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 10, 2006
Publication Date: August 10, 2006
Citation: White, W.H., Tew, T.L., Richard Jr, E.P. 2006. Association of sugarcane pith, rind hardness, and fiber with resistance to the sugarcane borer. Journal American Society Sugar Cane Technologists. 26:87-100. Interpretive Summary: Varietal resistance is an important component of the integrated pest management program for controlling damaging infestations of the sugarcane borer, Diatraea saccharalis (F.), in Louisiana sugarcane (Saccharum hybrids). Developing borer-resistant varieties is, however, hindered to some extent by a general lack of knowledge of how to effectively select for resistance. We investigated the association of sugarcane pith, a trait frequently associated with borer resistant phenotypes from our recurrent selection for borer resistance program, and sugarcane borer resistance within a population of sugarcane progeny selected from a single biparental cross. The population consisted of 15 individuals with pith and 15 individuals without pith. These individual selections were planted in a replicated test to evaluate their response to borer damage as measured by percent bored internodes and damage ratings. Damage was measured in both the plant-cane and first-ratoon crops. We found that the subpopulation with pith sustained significantly less damaged internodes (pith = 12.5%; no pith = 15.6%) and had significantly lower damage ratings (pith = 3.7; no pith = 4.0) than the subpopulation without pith. However, within each subpopulation there were individuals that were both resistant and susceptible suggesting that factors other than the presence or absence of pith were involved in resistance. Two of these other factors that we investigated were target-internode rind hardness and total fiber. We found that both were more closely associated with resistance than pith and that pith was only loosely correlated to rind hardness and total fiber. We conclude from this study that repetitive phenotypic selection in the early stages of variety development for low insect damage may result in varieties with high total fiber and rind hardness and with a higher frequency and level of pith.
Technical Abstract: Planting sugarcane varieties with natural resistance to the sugarcane borer is an attractive alternative to pesticides for controlling damaging infestations of this important insect pest. Unfortunately some of the plant traits (i.e. plant stalk fiber) that have been identified as conferring resistance to the borer are also associated with lower sugar yields. Another trait that is frequently associated with lower sugar yields is stalk pith; however, it is not certain whether pith is also associated with borer resistance. Pith is the white, low-density, low moisture tissue sometimes present in stalks of some varieties of sugarcane. In this study we investigated the association of pith and insect resistance by comparing the amount of borer damage in sugarcane selections with pith and without pith. The study was conducted in the field under artificially induced insect infestations and individuals of the subject population all originated from the same genetic background (i.e. they were siblings of the same parents). We found that varieties with pith to be significantly less damaged than those without pith. This is the first time that an association of pith and borer resistance has been demonstrated experimentally. Unfortunately we found that the varieties with pith also have higher stalk fiber; a trait that can contribute to lower sugar yields. This information is of primary interest to plant breeders as it means that borer resistant varieties will have to be crossed to high yielding varieties to obtain borer resistance and retain high sugar yields and that there is also a need for identifying new traits that confer resistance, but are not associated with low sugar yields.