Study On Genetic Diversity Of Tropical Maize Population POB21 And POB32 During Improving In Temperate Zone

In order to study the change of genetics diversity among circles in POB21 and POB32, one experiment was carried at four locations in 2 years. The changing of agronomic traits among different circles was studied in the field at Hainan, Shaanxi, Henan and Beijing during 2004-2005, observing the spike differentiation of POB21C₀ and C₇, POB32C₀ and C₅ and studying the genetic diversity with SSR marks at molecular level. To get the change of genetics diversity during adapting temperate zone on the three level of morphology, anatomy and molecular, it will supply us some theory base about improving and utilizing new exotic germplasm. The results of this thesis indicated that,On the view of agronomic traits, the response among circles is similarity with genetic gain. The time got shorter about days to anthsis, days to silking, the internal of anthsis and silking, plant height and ear height became lower than that of original population C₀. Other traits had improved such as fertile length, rows per ear, 100-kernal weight, the rate of grain-production and yield. The coefficient of variation became small, which showed that genetic variation got lower among circles. Degree of photoperiod-sensitive of some traits decreased with the increasing improved circles. Two large cluster were divided among 14 different circles, one is population POB21 with 8 circles including C₀,C₁,C₂,C₃,C₄,C₅,C₆ and C₇, the other one is POB32 with 6 circles, including C₀,C₁,C₂,C₃,C₄ and C₅.At anatomy level, changing of spike differentiation in tropical maize population POB21and POB32 adapting temperate zone was studied. Comparing with the process of POB21 and POB32 tassel development in original population C₀, the internal of differentiation phase I and III in improvement circle was shorten 8 days and 5 days in POB21C₇, 6 days and 4 days in POB32C₅ respectively. Compare to the process of ear development in POB21C₀ and POB32 C₀, the internal of phase I, III and IV in POB21C₇ was reduced 12 days, 4 days and 4 days and respectively, while 9 days, 3 days and 2 days were reduced in POB32C₅. Along with improvement circle increasing, the gap of the beginning time between tassel and ear was reducing at different spike differentiation phase in POB21 and POB32. Regardless of the internal of spike differentiation, the gap of the beginning time between tassel and ear at different spike differentiation phase, the improvement circle was more similar than original population C₀ in POB21 and POB32.At molecular level, changing of genetic diversity in tropical maize population POB21 and POB32adapting temperate zone was studied. 271 alleles were got by 77 selected primers. There were 3.6 alleles at one locus. Its changing rang was 2-8. The genetic distance of different circles between POB21 and POB32 was longer than that between different circles in POB21 or POB32. Based on the, genetic distance among different circles in POB21 and POB32, 14 different circles were divided into two kinds, which one was POB21 and the other was POB32. There were many different changes on the population genetic structure between POB21Q, and POB21C7, between POB32Q, and POB32C5, such as the index of population genetic diversity, the expected heterozygosity, the number of allele and the allele frequency. The index of genetic diversity deceased between the original population and the improved circles, which indicated that the variation degree in the population deceased during the improvement process of adapting temperate. The gene flow was so smooth that it kept back the genetic variation caused by genetic drift in the population.In order to assess the genetic diversity between POB21C0 and POB21C7, POB32Q, and POB32C5, the sampling capacity from one population was first studied. This study focused on the changes in genetic diversity index, allele number, genotype and genetic distance among samples with different capacity. The objectives were to get the suitable sample capacity for studying population. When genetic diversity index or grouping heterosis group was studied in populations, 10 plants or so were chosen randomly in POB21 and POB32;When the allelic number, genotype, and genetic distance between plants in population, the sample capacity was over 30 in POB21 and POB32.In the conclusion, improvement of spike differentiation was anatomic base for the suitability improvement in tropical maize population adapting temperate zone, and the sampling capacity in different researching objective was different. On the view of response among circles, genetics gain and clustering, it was effective improving the suitability of tropical maize population adapting temperate with controlling bi-parental mass selection.