PICKING A WINNING RACE HORSE, I MEAN – WINNING SUGAR CANE

Authors: White, William; DA SILVA, JORGE - TX AG EXP STATION WESLACO

Submitted to: Sugar Bulletin
Publication Type: Trade Journal
Publication Acceptance Date: 3/16/2005
Publication Date: 4/20/2005
Citation: White, W.H., da Silva, J. 2005. Picking a Winning Race Horse, I Mean - Winning Sugar Cane. The Sugar Bulletin. 83(7):29-31.

Interpretive Summary: Caterpillars of moths such as the Mexican rice borer and sugarcane borer that tunnel into stems of plants are important pests of sugarcane in Louisiana and Texas. Currently, insecticides are widely used to control these pests; however, due to the high costs associated with insecticides and the resulting environmental concerns from their use, alternative control strategies are needed. One of the most promising alternative strategies to insecticides is natural resistance. A drawback to this strategy is the time and cost associated with identifying a resistant plant. When found, a plant that is frequently a low yielding plant. A new genetic tool, called markers, are available that can tell the researcher if the genes for resistance are found in the plants of interest. These markers will allow researchers to accurately identify plants that are resistant to the borers without actually taking the plants to the field. We used 30 markers known to be associated with insect resistance in rice and found one of them associated with susceptibility to the Mexican rice borer and the sugarcane borer. This marker will provide plant breeders with a powerful tool for identifying borer resistance efficiently and accurately in large populations of plant. This will also increase the likelihood of finding borer resistance in a high yielding variety of sugarcane that can be grown by sugarcane farmers. These resistant varieties will save farmer millions of dollars annually and reduce the amount of insecticide being placed into the environment.

Technical Abstract: Lepidopteran stemborers, such as the Mexican rice borer (MRB) Eoreuma loftini and sugarcane borer (SCB) Diatraea saccharalis, are important insect pests of sugarcane (Saccharum spp.) worldwide. Alternative control strategies are needed for both species due to the high costs associated with insecticides and resulting environmental concerns. One of the most promising control strategies is host plant resistance. However, few breeding programs actively breed for insect resistance because of the absence of effective selection procedures. Recent advances in sugarcane molecular biology, such as the development of molecular markers, offer new opportunities for selection and breeding for stemborer resistance. Damage levels of both the MRB and SCB were quantified by the number of emerging shoots killed (deadheart) and percentage of internodes damaged by larvae from a diverse population of 24 sugarcane clones. These clones represented cultivars and elite clones of known and unknown reaction to both borers. The evaluation was conducted under natural infestations in a randomized complete block replicated five times, where genotypes with extreme reactions were identified. Twenty-nine microsatellite (SSR) fragments were evaluated for their association with resistance to both borers. Microsatellite analysis identified informative markers developed from sugarcane disease and insect resistance genes. One of these markers showed a weak association with stemborer susceptibility. Low insect pressure during the initial evaluation is the probable cause for the weak association. If further testing proves the marker to be a strong predictor of resistance, it will provide sugarcane plant breeders with a powerful tool in the effort to breed borer resistant sugarcane.