<p style="text-align: justify;"><big><b>General Description</b></big></p>

<p style="text-align: justify;">This description has been adapted from a monograph published by the Animal and Plant Health Inspection Service (APHIS) of the United States Department of Agriculture (USDA). The commercial tomato belongs to a species referred to as <i>Lycopersicon esculentum</i>. Lycopersicon is a relatively small genus within the large and diverse family Solanaceae, consisting of approximately 90 genera. The genus is currently thought to consist of cultivated tomato, <i>L. esculentum</i>, and eight closely related wild Lycopersicon species (Rick 1976). Lycopersicon species are native to Ecuador, Peru, and the Galapagos Islands; however, most evidence suggests that the site of domestication was Mexico (Taylor 1986).</p>

<p style="text-align: justify;"><big><b>Outcrossing</b></big></p>

<p style="text-align: justify;">Tomato can be crossed by hand-pollination to all wild Lycopersicon species with varying degrees of success. The genus has been divided into two subgenera, the one easily crossed with commercial tomato (esculentum complex), and those that cannot be easily crossed (peruvianum complex). Hybridization between these two subgenera usually leads to early embryo breakdown, which results in seed that is not viable. This problem can be circumvented by embryo culture and other laboratory techniques, albeit at great effort. The closest genetic relatives of tomato are in the genus Solanum. Hybrids have been obtained between <i>L. esculentum</i> and <i>S. lycopersicoides</i>, but these hybrids are usually sterile (Stevens &amp; Rick 1986). No other member of the genus, including <i>S. nigrum</i>, a common weed in tomato fields, has yielded viable hybrids (Taylor 1986). All commercial tomato cultivars are exclusively self-compatible and exclusively inbreeding. As is true for most self-pollinating plants, the viability of exposed tomato pollen is limited. The distance required between foundation seed fields is 200 feet which in practical terms is the effective distance tomato pollen can travel under field conditions and remain viable (Anonymous 1971; Rick 1976).</p>

<p style="text-align: justify;"><big><b>Other Means of Gene Flow</b></big></p>

<p style="text-align: justify;">The transformed tomato has gained no measurable selective advantage over nontransformed tomato in its ability to be disseminated or to become established in the environment. The risk of horizontal movement of these genes from the genetically engineered tomato plants into the genetic environment is negligible because the genes are incorporated into the plant genome. No mechanism is known to exist in nature capable of transferring the genetic material from the tomato genome to another organism which tomato does not fertilize.</p>

<p><big><b>References</b></big></p>

<ol>
	<li>Rick, C. M. (1976). Tomato (family Solanaceae). In: Evolution of Crop Plants, pp. 268-273. Simmonds, N. W. (ed.), Longman Publications, New York.</li>
	<li>Stevens, M. &amp; Rick, C. M. (1986). Genetics and breeding. In: The Tomato Crop. A Scientific Basis for Improvement, pp. 35-109. Atherton, J. and Rudich, G. (eds.), Chapman and Hall, New York.</li>
	<li>Taylor, I. B. (1986). Biosystematics of the Tomato. In: The Tomato Crop. A Scientific Basis for Improvement, pp. 1-34. Atherton, J. and Rudich, G. (eds.), Chapman and Hall, New York.</li>
</ol>
