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Molecular markers pinpoint genes for disease resistance in tomato

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Tainan, Taiwan
February 20, 2009

Source: AVRDC - The World Vegetable Center Newsletter

Tomato (Solanum lycopersicum) is a high value crop and a valuable source of vitamin A in human diets. However, yields in the tropics average less than 15 t/ha, far lower than those in developing countries in temperate areas. Diseases are a major cause of low tomato yields in the tropics; especially Tomato yellow leaf curl virus (TYLCV) and bacterial wilt (BW). TYLCV is spread by the sweet potato whitefly after it feeds on infected plants. Farmers often spray pesticides to control the disease, causing harm to themselves and the environment. The BW pathogen (Ralstonia solanacearum) lives in the soil and infects tomato and many other plant species. It causes plants to wilt and die, often just before harvest. BW is so severe in some regions that farmers are not able to grow tomato at all.

“Disease-resistant varieties are the most effective, cheapest, and easiest way to control diseases to benefit
small-scale farmers, but resistance is often unstable and does not work equally well against all pathogen strains or in all environments,” says Dr. Peter Hanson, Tomato Breeder and the Center’s Global Theme Leader for Breeding. “Together with partners from the University of Hannover and funded by Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) we are developing tomato lines for the tropics with stable BW and TYLCV resistance. We identify and use resistance genes from wild and cultivated tomato species and we apply molecular markers to develop disease resistant tropical tomato varieties.”

The use of molecular markers increases the efficiency of plant breeding for disease resistance by facilitating the selection of multiple resistance genes. Molecular markers have been applied to select tomato populations for two TYLCV resistance genes. Hybrids with TYLCV resistance genes from this project demonstrated promising
resistance in north India during trials in October 2007. Hybrids and inbred lines with multiple TYLCV resistance genes, resistance to BW, heat tolerance, and good fruit quality have been under evaluation in 2008 trials in India, Vietnam, Cambodia, Thailand, Mali, and Niger. Additional TYLCV and BW genes for resistance are being
mapped for future breeding activities.

“Improved varieties will benefit small-scale producers and can create additional employment opportunities along the commodity chain,” says Hanson. “Tomato varieties resistant to TYLCV and BW will increase yield by 30%
or more and allow farmers to reduce pesticide applications for whitefly control, reducing their production costs and improving product and environmental safety.” Rich in micronutrients, tomatoes also help improve the nutritional status of consumers in the tropical lowlands beyond the typical limits of tomato cultivation. The tomato varieties developed through the project are international public goods and will be disseminated by AVRDC – The World Vegetable Center through public and private sector institutions worldwide.

 

 

 

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