A molecular approach to breeding for stemborer resistance

Authors: DA SILVA, J - TEXAS A&M UNIV; White, William; SETAMOU, M - USDA, ARS (POST-D0C); SOLIS-GARCIA, N - TEXAS A&M UNIV

Submitted to: International Society of Sugar Cane Technologists Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/21/2004
Publication Date: 1/30/2005
Citation: Da Silva, J.A., White, W.H., Setamou, M., Solis-Garcia, N. 2005. A molecular approach to breeding for stemborer resistance in sugarcane. In: Hogarth, D.M., editor. Proceedings of the XXV Congress of the International Society of Sugar Cane Technologists, January 30 - February 4, 2005, Guatemala City, Guatemala. 25:487-491.

Interpretive Summary: Larvae of moths that tunnel into sugarcane stalk (borers) are important pests of sugarcane worldwide. In the U.S. they are the most important insects pests of sugarcane grown in Florida, Louisiana, and Texas, causing millions of dollars in economic losses and costing millions of dollars to control. Sugarcane plants that are naturally resistant to these insects provide an attractive alternative to insecticides to controlling damaging infestations of these borers. Unfortunately, identifying a sugarcane plant that is resistant to these borers is costly and very time consuming. Recent advances in sugarcane biotechnology, such as being able to identify fragments of genes associated with resistance to borers would allow scientists to quickly and accurately find those plants that are resistant. We located a fragment of the sugarcane gene that appears associated with susceptibility to two borers: the Mexican rice borer and the sugarcane borer. Evidence for the association of this gene fragment and borer susceptibility is presented in this report. Research in underway to validate the presence of this fragment. Ultimately, the results of this research will benefit scientists directly involved in developing new sugarcane varieties. Sugarcane plants found to be susceptible to these borers can be eliminated and only those found to be resistant are kept thus speeding up the release of borer resistant sugarcane varieties. 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: Lepidopteran stemborers, such as the Mexican rice borer (MRB) Eoreuma loftini and sugarcane borer (SCB) Diatraea saccharalis, are important insect pests of sugar cane (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 sugar cane 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 (dead heart) and percentage of internodes damaged by larvae from a diverse population of 24 sugar cane varieties. These varieties represented commercial and elite clones of both 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. Evaluation indicated L97-128 as the most susceptible variety with a mean of 15 dead hearts and 7% damaged internode while several varieties averaged less than one dead heart and less than 1% internodes damage. Twenty-nine microsatellite (SSRs) fragments were evaluated for their association with resistance to both borers. Twenty-three SSRs fragments were obtained from disease and insect resistance genes identified by the Sugar Cane Expressed Sequence Tag Project (SUCEST) and six SSRs fragments were from the Sugar Cane Microsatellite Consortium (SMC). Microsatellite analysis identified informative markers developed from sugar cane disease and insect resistance genes. One of these markers showed a possible association with stemborer susceptibility and is being evaluated further.