The Theory And The Practice Of New Cotton Variety Breeding For Disease-resistance And High-quality

The research regards disease-resistant and high-quality of new cotton variety selection as the emphasis point,combining the difficult point of cotton breeding, which analyses theoretically. Purpose lies in approaching to difficult problems of cotton breeding,and finding out a new way to solve disease-resistance and high-quality difficult problems of cotton breeding and cotton industry.The method of the cotton breeding is various.A great number of factors , such as different time, different regions , different breeding goals, different external ecological environment etc.have confirmed the variety of the method of cotton breeding. From systematic selection of early breeding adoption, hybridization selection, mutation breeding, heterosis utilization to the transgenic breeding have been adopted up till now, various methods actually have practicability and theoretical basis.Through summary on various kinds of breeding methods .mentioned above are distinguished and related. The differences lies in : ①Systematic selection that disease-resistant plants are selected under serious disease field is further developed mixture selection method. There are several reasons that systematic selection contributes to cotton breeding for disease-resistance. (1)Because the cotton is often cross-pollination, and frequent naturally hybridizes, the complexity of the hereditary foundation increases, meanwhile the serious disease field offers the selection condition , so one time choice may elect disease-resistant individual. (2)The resistant heredity of the fusarium wilt is controlled by many genes, when a variety is in a complicated colony , these disease-resistant genes may exist in different individuals separately . After one time resistant selection, because of natural hybridization, the disease-resistant herterozygote genes are separated and recombined, it inevitablely lead to accumulative resistant gene. The individual with accumulation resistant gene is chosen by successive selection. It enhances resistance.②Hybridization selection may expand the source of cotton germplasm, it is very important to improve the disease-resistant and high-quality breeding. The cotton varieties with large planting area in Xinjiang in recent years have been bred all by way of crossbreeding, such as early-maturing Xinluzao7 and 8, disease-resistant Xinluzao9 and 13, and high-quality Xinluzaol6. Mutation breeding is to utilize radioactive rays and chemical mutagen to deal with seed , pollen , plant or other organs, to mutate cell hereditary material into sudden change, to produce mutant phenotype of which the fine individual is elected andbred into a new variety. Radiation material should choose cotton variety with high yield and high-quality fiber. After changing specific shortcoming of it, radiational later generation often appears early-maturing, branch compactness, becoming shorter height. According to the characteristics above, changing these characters of cotton easily makes good result. ④Crossbreeding (heteriosis utilization). The first generation (F1) is superior to parents with different heredity which is hteriosis. Hteriosis appears in Fl grow tendency development speed, resistance and adaptability, yield, quality etc are superior to parents respectively. ⑤Transgenic breeding: With fast development and ripeness of biotechnology, transgenic technology has solved the new problem that the routine breeding can't solve. Success of utilizing Bt gene to resist the Heliothis armigera is a milestone in the breeding history of the cotton. This technology is utilized as a kind of ripe breeding technology at home and abroad, such as using resistant the glufosinate tolerance (round up) gene to breed resistant weed killer variety (resistant Heliothis armigera and resistant the weed killer). In the quality and disease-resistant cotton breeding, transgenic technology is in application too.Regards for cotton breeding, systematic selection, hybridization selection, and mutation breeding etc. routine methods are foundation of hybridization breeding procedure and transgenic breeding. Hybridization breeding procedure and transgenic breeding are the perfection and supplement to routine breeding. The various cotton breeding methods, have confirmed the different type of cotton variety, it can better adapt to satisfied with need of cotton production.