Heterosis Group And Heterotic Patterns Of CIMMYT Maize Germplasm Populations

By the test, we studied the heterosis and combining ability of 2 maize populations, which were crossed with four key domestic temperate maize inbreeds (Mo 17, B73, Huangzaosi and Dan340) by NCII mating design. The 88 (22.4) combinations were planted in Ya'an farm in 2003. Based on the special combining ability (SCA) and heterosis for grain yield, the 2 maize populations were clustered heterotic groups, and their heterosis utilizing models were proposed. The main results were summarized as following:1. This study evaluated the major agronomic traits, which were yields and combining ability of the 2 maize populations. The results indicated that the 2 populations had adapted to the Ya'an ecological environment, which were valuable maize germplasm and could be used to develop the genetic foundation of existing maize germplasm. But the plant is higher, the site of spike is a little higher and the rachis is wider for the populations compared with Ghuandan13. So, those traits must be focused for selection in the future.2. Clustering analysis was taken based on plant yields SCA as genetic distances. The individuals were approximately classified into 5 groups: group I including Mo 17, 2-6, group II including 1-1, 1-2, 1-3, 1-6 , B73, groupIII including huangzaosi, 1-5, groupIV including Dan340,2-5 and group V including 1-4,1-7,2-1, 2-2, 2-3, 2-4.3. The genetic distances (GD) of individuals were calculated based on agronomic and economic traits. GD range (from 3.053 to 7.734) and average GD (4.800) showed more genetic morphology among the two populations. Population La Posta was classified into Sipingtou heterotic group, and population Pob 28 was classified into Reid heterotic group. Not only are in the populations, but also between the ones, wider GD range and higher average GD showed higher genetic morphology among the populations and the individuals. That implies there are heterotic groups in the individuals.4. Genetic distances of 22 individuals and 4 inbreeds were calculated based on SSR analysis data. The higher average GD (0.614) and the bigger range of variance (from 0.204 to 0.980) showed higher genetic morphology among the studied materials. In the result, 22 individuals and 4 inbreeds were classified into 4 groups: group I including Huangzaosi,Dan340, group II including Mo 17, group 3 including the individuals 13-22 and group IV including the individuals 1-12, B73. The result approximately agreed with the result of SCA cluster, but there were still some difference.5. In the three cluster methods, namely agricultural and economic traits cluster, SCA cluster, and SSR cluster. Agronomic and economic traits cluster and SCA cluster were easy to be influenced by environment; SSR cluster could not only eliminate environment influence on3studied materials, but also especially amplify DNA fragment connecting with yield trait. So the results of SSR were more accurate and reasonable than the other methods.6. According to the composition of yield characters, we think that there are difference heterotic groups in the same population, which exists the new heterotic pattern. We should extend the range of the selection in order to select the excellent individuals. Then we can select inbreeds from them.