Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 302

Utilizing a traditional hybrid corn production methodology, two inbred lines are typically required to produce an F₁ hybrid. At the present time, apomictic hybrids would likely utilize one or both inbred lines that would carry the necessary genes and genetics to develop a true breeding, apomictic F₁ hybrid corn cultivar. Land, labor, and storage space are also required to maintain these inbred lines. If true breeding, apomictic hybrids can be developed, the yearly seed increase of inbreds, the generation of hybrids, the necessary time allowed for such production, land, fertilizer, and required field isolations necessary for producing a hybrid corn line could be omitted. With apomictic hybrid corn, seed generated from that crop would reproduce seed and individuals possessing the identical genetics of the parental hybrid. As such, the development of an apomictic seed crop from an apomictic hybrid would lead to a substantial savings in cost and time to commercial producers and hopefully a decrease in seed price to farmers.

Under present agricultural patents and plant variety protection legislation, farmers are able to retain a limited amount of their produced seed for their own use. This could be particularly advantageous to poorer farmers in developing countries. In addition, farmers who live in remote regions where government or commercial seed suppliers are not available could essentially guarantee themselves a yearly supply of quality hybrid seed. These farmers would not be dependent on government or commercial seed suppliers once a suitable cultivar was introduced into their area and could provide farmers greater control regarding the production and use of their locally generated product. However, farmers utilizing such “on the farm seed production rational” need to be aware of seed quality issues as well as the enforceable and legal ramifications of selling and or distributing such seed protected by licence, patent, or PVP. Growers should also be aware that the lack of genetic diversity or uniformity that is embedded in their apomictic seed crop could eventually make that variety susceptible to a particular disease infestation. Retaining and sowing an apomictic seed crop over the long term could eventually result in major disease infestations and a dramatic reduction in crop yield.

At this time, it is difficult to visualize how the application of cytogenetics, molecular genetics, mapping, and genetic engineering, coupled with traditional breeding procedures, will be readily integrated to incorporate apomixis into maize and develop a apomictic hybrid corn cultivar anytime in the near future. Some have given the development of apomictic hybrid corn an approximate twenty‐year horizon; others much longer. As has been discussed above, the research process to be utilized to develop apomictic corn, or other species is time consuming, difficult and generates several legal, social, breeding and genetic issues that will need to be resolved. Though the transfer of apomixis holds much promise, it will be some time before a commercial apomictic maize hybrid will reach the marketplace.