The Effects Of Population Size And Pollination Methods On The Genetic Integrity Of Cotton Germplasm

Cotton is often cross-pollinated crops, and its genetic integrity maybe affected by the differentpopulation size and pollination methods and other factors during the seed regeneration. Theoretically,alarger amount of breeding colony and self-pollination helps a lot in reducing the probability of geneticdrift, however as the limitations of manpower, material resources and other factors, it is hard to increasethe amount of breeding population and to use pollination methods in practice. To solve the problem, weanalyzed the effect of different regeneration population sizes and pollination methods on geneticintegrity of AoL23/757,Zhongmiansuo19and Hongtao based on morphological markers, agronomictraits and SSR markers. The main conclusions of this study are as follows:1. Genetic alteration of different population sizes with50,100,200and300plants ofAoL23/757(okra-leaf),Zhongmiansuo19and Hongtao(red leaf) was analyzed by using agronomic traitsand morphological markers. we sowed these3germplasms in order of hongtao,zhongmiansuo19andaoL23/757,with3replication. The results showed that the genetic characteristics differences among fourbreeding groups of50,100,200,300plants was not significant.Genetics similarity coefficient of AoL23/757,Zhongmiansuo19and Hongtao with4different sizesof regeneration populations was analyzed using SSR markers. The polymorphism informatiom content(PIC) and effective number of alleles (Ne) of the SSR markers suggested that the genetic differencesbetween original population and the population with sizes of50,100,200and300plants was notsignificant. The results of PIC value and Ne value was affected by types of marker character and thehomozygosity. Combined with the results of morphological markers, the genetic differences was notsignificant with50-300plants, if manpower, economic situation allows, the appropriate regenerationpopulation size should be more than50. But for heterozygous varieties, the regeneration populationshould not be too large or too small, because the genetic heterozygosity in the population increases asthe regeneration population increases. In short,different pollination sizes did not affect the geneticintegrity of cotton significantly.2. Genetic alteration of AoL23/757(okra-leaf) and Zhongmiansuo19was analyzed usingagronomic traits and morphological markers. We planted these2varieties next to each other, treatedzhongmiansuo19flowers of individual plant with self-pollination and natural pollination separately.Then we investigated the rate of mixed plants with okra-leaf etc. in the population of zhongmiansuo19next year. The results indicated that there’s some okra-leaf appeared in the natural pollination populationof zhongmiansuo19and no okra-leaf in self-pollinated population.Genetics similarity coefficient of original population, self-pollinated plants and natural pollinatedplants was analyzed using SSR markers. The PIC and Ne value suggested that different pollinationmethods affected the genetic integrity of zhongmiansuo19significantly. Compared to the originalpopulation, the genetic similarity of self-pollinated plants was higher than that of natural pollinatedplants. Combined with the results of morphological markers, self-pollinated plants maintained bettergenetic integrity than natural pollinated plants, so we should use self-pollination during upland cottonregeneration.In short,different pollination methods affected the genetic integrity of cotton significantly.