Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2003
Publication Date: 9/1/2003
Citation: Milligan, S.B., Balzarini, M., White, W.H. 2003. Broad-sense heritabilities, genetic correlations, and selection indices for sugarcane borer resistance and their relation to yield loss. Crop Science. 43:1729-1735. Interpretive Summary: The sugarcane borer is the most destructive insect pest of sugarcane in the Americas. Sugarcane plants that are naturally resistant to this insect provide an attractive alternative to pesticides to controlling damaging infestations of the borer. Unfortunately, little knowledge exists on how best to select sugarcane varieties that are resistant to the sugarcane borer. The problem is that borer resistance can be measured in many different ways, but the knowledge of how to incorporate all of these measurements into an effective selection index has been lacking. We measured several different resistance measurements and evaluated them for their economic importance and efficiency of selection. We were able to combine several resistant measurements into a single index that will now allow plant breeders to accurately and effectively select for resistant sugarcane varieties. The results of this research will immediately benefit scientists directly involved in developing new sugarcane varieties. Sugarcane borer resistance can now be more efficiently selected which should improve progress in selecting for this elusive trait. Growers and the general public will ultimately benefit from this research, as less reliance will be placed on expensive and environmentally disruptive pesticides to prevent damage from the sugarcane borer.
Technical Abstract: The sugarcane borer, Diatraea saccharalis (F.), causes significant damage to sugarcane (Saccharum spp. hybrid), rendering cultivar resistance important. Researchers assess borer induced damage using up to five different measures: percent bored internodes, percent exited internodes, pupation success, moth production, and a damage rating. The inheritance of the different damage measures and the best approach to integrate the different variables into a simplified damage-resistance assessment has not been well studied. Furthermore, the relationships of the damage traits to sugar production have not been comparatively assessed. We planted a replicated, two-location test of 28 clones typical of the selection stage screened for borer resistance in the Louisiana sugarcane breeding programs. We recorded the five measures together with sucrose production and its components. Using appropriate variance components, the heriability, expected response to selection, and genetic correlations among the traits were used to construct selection indices of all combinations of the five damage traits studied. We used the regression coefficients of the damage traits on sucrose production as economic weights. The indices indicate that percent bored internodes is the most effective single trait to reduce sugarcane borer damage. If data collection costs are considered, then the subjectively assessed damage rating is the most expeditious of the traits examined. High correlation values among several of the traits lead to the observation that inclusion of more than the bored internodes, exited internodes, and the damage rating in an index are unnecessary.