Marker assisted selection and breeding for desirable thinner pericarp thickness and ear traits in fresh market waxy corn germplasm.

摘要

Kernel pericarp thickness and ear architectural traits are important selection criteria in fresh waxy corn breeding programs as they are associated with consumer sensory and visual preferences. An F2:3 mapping population from the cross between South Korean inbreds BH20 and BH30 was developed in order to estimate genetic relationships among pericarp thickness traits and ear architectural traits, and to identify QTL regions for these traits through univariate and multivariate approaches. High correlations among pericarp thickness traits were detected and QTL regions associated with multiple pericarp thickness traits were identified. Through incorporating principal component analysis (PCA) of pericarp thickness traits and ear traits with QTL analysis, we detected PC-QTL regions that appear to have pleiotropic effects on multiple traits, particularly the pericarp traits on different parts of the kernel. The pericarp thickness QTL information was used to perform marker assisted selection to pyramid favorable QTL, as well as validate pericarp QTL. The MAS population was designed to try and maintain favorable ear traits by making crosses between lines chosen for favorable ear and pericarp thickness phenotypes and lines chosen for favorable QTL alleles for pericarp thickness traits. A few ear traits showed weak but favorable associations with pericarp thickness traits. Evaluation of the MAS population revealed that most selected QTL markers were significant for at least one pericarp thickness trait. Comparing groups of lines in the MAS population sorted by: phenotypes for thinner pericarp; favorable QTL alleles for pericarp thickness; and unfavorable alleles for pericarp thickness from MAS population, we found that in some cases that marker based selection might be effective for reducing pericarp thickness. Pyramiding significant favorable marker alleles showed reduction of pericarp thickness on all kernel regions. Since testcross performance (TP) is ultimately more important than per se line performance (LP), a testcross population was generated for groups of selected lines from MAS population. This was done to enable assessment of the effect of groups of lines and different testers, and to compare LP with TP. Group1 with most favorable alleles showed significantly thinner pericarp than group 2 with fewest favorable alleles in testcross evaluation, regardless of tester. The TP with tester BH1030, which was the thinner pericarp testcross hybrid showed thinner pericarp than TP with tester BH1020. We found evidences that suggested the tester had dominance effects on reducing pericarp thickness in testcross population. In summary, pericarp thickness QTL information was useful for marker assisted selection of favorable loci within Korean germplasm, and therefore offers the potential to be useful for introgression of these favorable loci into more adapted U.S. germplasm. Weak but favorable relationships among pericarp thickness and some ear traits could be used collectively to improve overall features through independent selection in a fresh waxy corn breeding program.