Correlation Analysis Of Genetic Distance Based On AFLP Marker And Heterosis On Photosynthetic Traits Maize

Use of heterosis was an important way to improve crop yield and improve crop quality, quickly and accurately predict heterosis was beneficial to breeding of strong hybrid combinations. For a long time, people aim at exploring the genetic basis of heterosis and its prediction for better use of heterosis. The development of molecular markers in heterosis study provides a new means to effectively improve the breeding efficiency. Molecular markers can be used either parental genetic distance (GD) estimates, but also for the study of mechanism of heterosis provides an effective technology platform, because it can show genetic differences from the whole genome. Most of the current studies focused on the relationship between genetic distance and general combining ability (GCA), heterosis of yield traits, but few studies of the relationship between genetic distance and heterosis on photosynthetic characteristics.A total of 20 AFLP primer combinations were used to the study of genetic distance among 8 maize inbred lines. Analysis the relationship of genetic distance and general combining ability, genetic distance and special combining ability(SGA), genetic distance and total combining ability (TCA) by a 9*9 complete diallel cross design. Measured the net photosynthetic rate (Pn), stomatal conductance (Cond), transpiration rate (Trmmol) and intercellular CO2 concentration (Ci). Analyze the heterosis on photosynthetic traits maize. Study the correlation of genetic distance and combining ability, genetic distance and heterosis. The main results were summarized as follows:1. In this experiment, genetic distance was computed for 8 maize inbred lines based on AFLP molecular markers. These genetic distances among 8 parents ranged from 0.21 to 0.46, with an average of 0.36. From the genetic distance, speculating relationships of 8 inbred lines were not too far. The cluster analysis resolved 8 parental inbred lines into four major groups, the first group was H5, H7 and H8, the second group was HI and H6, the third group was H3 and H4, the fourth group was H2. AFLP analysis was applied to the genetic diversity of species, assisted breeding, genetic mapping, germplasm kinship, AFLP molecular markers can be used to identify genetic distance, genetic diversity and genetic relationship of parent, and further delineated heterosis, enhanced the potential of heterosis.2. Combining ability analysis of major yield traits on 8 inbred lines showed that the same trait with different parents, have very different GCA effect values, the same parent with different traits, GCA also have very different. The combinations of high SCA has at least one parent with high GCA, parents of high GCA may not be able to group with a hybrid combination of high SCA. The same trait of the TCA effects of different combinations there is significant difference in value. TCA of the same combination with different characters have obvious differences. The combination of high TCA may be have a high GCA value, or a high SCA value, but it must ensure that both have relatively high sum. Those show that the advantages of hybrid combination was not only depending on the GCA effects, but also on the SCA effects, The role of the general combining ability and specific combining ability was parallel, should not substitute for each other and make use of the general combining ability basically be able to comprehensively reflect the true inbred lines, which have the ability to heterosis.3. Analysis of significant difference of heterosis of reciprocal cross among 4 photosynthetic traits shows that Pn and Cond were more obvious heterosis, no significant difference in the mid-parent heterosis and over-parent heterosis of reciprocal crosses on 4 photosynthetic traits. Select the excellent hybrid combinations should pay attention to the parental reciprocal configuration investigated.4. Correlation analysis of genetic distance and the main yield traits corresponding to the SCA, TCA among 8 inbred lines show that SCA of the main yield traits and genetic distance was no significant correlation except grain number per row, correlation coefficients range were between 0.08～0.32. Genetic distance and TCA of ear weight, ear width, ear row number, axle width and ear weight was significant or highly significant correlation, Show that the genetic distance have better prediction to TCA.Therefore, in future, maize breeding should be placed on general combining ability of the goal traits, and accorded to the general combining ability to make judgment.5. Correlation analysis of genetic distance and heterosis on photosynthetic traits in 8 inbred lines show that most of the trends show a positive correlation in the mid-parent heterosis and over-parent heterosis of photosynthetic traits, But did not reach significant level, prediction of heterosis was not very accurate. This shows that with the genetic distance to predict the possibility of maize heterosis was still to be further study, but also need a lot of research work.