Genetic Resources of Tomato (Lycopersicon esculentum var. esculentum) and Wild Relatives

Authors: Robertson, Larry; Labate, Joanne

Submitted to: Genetic Improvement of Solanaceous Crops, Vol 2: Tomato
Publication Type: Book / Chapter
Publication Acceptance Date: 3/30/2006
Publication Date: 1/20/2007
Citation: Robertson, L.D., Labate, J.A. 2007. Genetic Resources of Tomato (Lycopersicon esculentum var. esculentum) and Wild Relatives. Genetic Improvement of Solanaceous Crops, Vol 2: Tomato. p. 25-75.

Interpretive Summary: Cultivated tomato (Lycopersicon esculentum Mill.) is an important vegetable, with a worldwide area of 4 million hectares and a production of 108.5 million tons. In the United States tomato accounts for 14.5% of the economic value of fresh market vegetable production and 50.7% of the economic value of processed production of vegetables. Domestication of tomato is relatively recent, within the past 400 years. L. esculentum is thought to have originally been domesticated in maize fields by ancient Mexicans, with Peru as the center of diversity for the genus. There are more than 75,000 accessions of tomato conserved in genebanks around the world. Genebanks maintain large collections of the wild relatives in addition to the cultivated tomato. The cultivated tomato has undergone a narrowing of its germplasm base. The major utilization of tomato germplasm for crop improvement in the past 20 years has been the use of wild species as sources of genetic variation. This has led to a major utilization of wild species introgressions which have resulted in an increase in genetic diversity in the cultivated tomato. Wild species have been used as sources of variation for disease and insect resistances and/or tolerances, abiotic stress tolerances, and for fruit quality.

Technical Abstract: Cultivated tomato (Lycopersicon esculentum Mill.) is an important vegetable, with a worldwide area of 4 million hectares and a production of 108.5 million tons. Tomato area has increased by 38% and production has increased by 45% in the past ten years, with most of this increase in China, which has increased production from 8.5 to 25.5 million tons, propelling it to the number one tomato producer in the world. Other leading tomato producers are the United States, Turkey, India, and Egypt. In the United States tomato accounts for 14.5% of the economic value of fresh market vegetable production and 50.7% of the economic value of processed production of vegetables. Domestication of tomato is relatively recent, within the past 400 years. L. esculentum is thought to have originally been domesticated in maize fields by ancient Mexicans, with Peru as the center of diversity for the genus. Tomato spread to Europe in the early 1500s and thereafter became widely dispersed. Tomato has eight (nine by some authorities) related wild species relatives which are extensively utilized for crop improvement. There are more than 75,000 accessions of tomato conserved in genebanks around the world, with the largest of these at AVDRC, TGRC, and the USDA genebank at Geneva, NY. These genebanks maintain large collections of the wild relatives in addition to the cultigen. Several collections are also available of related Solanum taxa and Lycopersicon introgression populations. While cultivated tomato is self-pollinated, the other taxa provide a mixture from self-pollinated to obligate cross-pollinated, with self compatibility and self-incompatibility. This has led to development of methodologies and standards for maintenance of tomato germplasm to minimize the effects of genetic drift, mutation, and selection. The cultivated tomato has undergone a narrowing of the germplasm based caused by genetic bottlenecks and selection. The major utilization of tomato germplasm for crop improvement in the past 20 years has been the use of wild species as sources of genetic variation. This has led to a major utilization of wild species introgressions which have resulted in an increase in molecular genetic variation in and around regions that have been introgressed from wild species. Wild species have been used as sources of variation for disease and insect resistances and/or tolerances, abiotic stress tolerances, and for fruit quality.