| Mazie is the largest cultivated crop worldwide and plays key role towards food security around the world. The continuous yield increase of maize is due to genetic improvements in newer varieties. The improvements of main agronomic traits are the core content of maize breeding. Therefore, understanding of main agronomic traits are necessary for promote high yield maize breeding and the molecular biological mechanism analysis. Foundation parents play a key role in varieties replacement and breeding trend change. Ye478 is one foundation parent in China mazie breeding, and the improved Reid germplasm which Ye478 represents are one most important maize breeding germplasm in the North maize zone and the Yellow and Huai River maize zone. It has important theory significance and the practical application value for make more use foundation parent and breeding foundation parent candidates that studies the formation and improved of Ye 478.In this study, an F23 population derived from a cross between two maize elite inbred lines, foundation parent Ye478 and candidate foundation parent 08-641. The F23 population were planted in Nanning, Ya’an and Jinghong, during 2012 and 2013, respectively. The genetic map which includes 471 polymorphic SNP markers was developed using MAPMAKER/EXP version 3.0b. The QTL related to main agronomic traits were detected using QTLNetwork software version 2.1 with a mixed-model based composite interval mapping (MCIM). Base on the information of QTL, we dissect the genetic architecture of main agronomic traits and analyze the favorable alleles pyramiding in two inbred lines. Meanwhile, two testcrossing populations, TP1 and TP2, for explore the formation and improve rules of Ye478 were developed from six Ye478’s related inbred lines and 36 newly bred Ye478’s derived descendents crossed to five testers (Chang7-2, Dan340, Qi319, Mo17 and S37) followed by the North Carolina Design Ⅱ (NCII) mating design. Two testcrossing populations were planted in Ya’an and Jinghong, during 2013 and 2014, respectively. Ultimately, we analyze the formation and improve rules of Ye478 base of phenotypic data, genotype data and QTL information. The main results are as follows:1. Genetic parameters were estimated for main agronomic traits in maize using (08-641×Ye478) F2:3 population, TP1 testcrossing population and TP2 testcrossing population. The results show that plant height related traits and canopy architecture related traits had higher environmental stability than yield related traits. Additive effects were the major genetic component for main agronomic traits, and dominance effects and epistatic effect play a minor role in that. Most of agronomic traits have significant phenotypic correlation and genetic correlation, and correlation coefficient between -0.5 and 0.5, of which correlation coefficient among yield related traits higher than correlation coefficient among plant height related traits and correlation coefficient among canopy architecture related traits.2. The high-density genetic map which includes 471 polymorphic SNP markers was developed using F2:3 population. The map covered all 10 maize chromosomes with a total genome size of 2007.9 cM, and average marker intervals were 4.4 cM. The trials were performed at three experimental stations located in Nanning, Ya’an and Jinghong, during 2012 and 2013, respectively. Analyses of the QTL on each trait for each environment, and a joint analysis across all environments were performed using QTLNetwork software version 2.1 with a mixed-model based composite interval mapping (MCIM). A total of 251 and 119 QTL for all traits were detected based on single environment analysis and joint analysis across all environments,60% QTL detected by using the two QTL mapping procedures were consistent. In total,24 key QTL which controlling agronomic traits development were detected, and there distributed across 17 genome regions on chromosomes 1,2,3,4,5,7 and 8. For QTL × environment interaction (QEI), less than 20% QTL were detected significant QEI in this study. There were 28 pairs of loci with significant (in sequential Bonferroni correction analyses) epistatic effects were detected, and four types effect (AA, AD, DA and DD) were equally important for epistatic interaction.3. The results of the TP1 testcrossing population for analysis Ye478’s related lines phenotypic and GCA improved trend shown that the value of plant height, ear height, internode length above primary ear, leaf length above primary ear, leaf angle above primary ear and ear length in Ye478 between the value of the same trait in Shen5003 and U8112, and Ye478’s GCA for most of traits above or below the same trait in Shen5003 and U8112. Most of favorable alleles for plant height related traits and canopy architecture related traits from Ye478 and half of favorable alleles for yield related trait from Ye478. The favorable alleles associated with plant height in Ye478 from Shen5003, and the favorable alleles associated with leaf angle or ow number of ear in Ye478 from Shen5003 and U8112. Tassel length, leaf angle above primary ear, row number of ear,100-grain weight and grain yield per plant were significantly improved in Ye478’s related lines. The favorable alleles associated with plant height from Ye478 stable pass on to its derived descendents, but the favorable alleles associated with leaf angle or row number of ear from Ye478 present to portion its derived descendents.4. The additive effect value of plant height, leaf length above primary ear, leaf length above primary ear, leaf width above primary ear and leaf angle above primary ear shown segregation distortion in TP2 testcrossing population when Ye478 were improved. Most of SNP markers which close linkage with consensus QTL across multi-environments followed the expected 1:1 ratio in RIL population, but 25% SNP markers shown segregation distortion and those SNP markers main distributed across bin 1.06-1.11 and bin 5.05-5.07. For the consensus QTL across multi-environments in same chromosome, we found only few QTL shown close linkage. It is difficult that prediction the performance of additive effect of newly bred lines in hybridized combination using the QTL information which obtain through trait per se, and trait per se and GCA of trait have different genetic basis. |
PDF Full Text Request