Included below is a passage regarding genetic diversity from a response provided by Martina Newell-McGloughlin, director of the international biotechnology program at University of California, Davis.
“Biodiversity is actually enhanced by the adoption of GM crops. Those crops commercialized to date have reduced the impacts of agriculture on biodiversity, through enhanced adoption of conservation tillage practices, reduction of pesticide use and use of more environmentally benign herbicides, and through increasing yields to alleviate pressure to convert additional land into agricultural use.
“With the introduction of GM crops, concern has been raised that crop genetic diversity will decrease because breeding programs will concentrate on a smaller number of high-value cultivars. Studies that have been done to date (cotton in the United States and India, soybeans in the U.S.) find that the introduction of GM crops has not decreased crop diversity. From a broader perspective, GM technology has the potential to actually increase crop diversity by enhancing underutilized alternative crops, and to facilitate more widespread production of heirloom varieties that have fallen out of favor because of their poor agronomic performance, pest/disease susceptibility, lesser adaptability and other undesirable characteristics. Advantageous genes can render them more suitable for widespread commercialization. In addition, transgenic approaches are being used to improve so-called orphan crops, such as sweet potato, cassava, etc., potentially increasing options and improving diversity, especially in sensitive regions.”
If you have additional questions after reading this response, please ask.