Abstract
BackgroundPlant digestibility of silage maize (Zea mays L.) has a large influence on nutrition intake for animal feeding. Improving forage quality will enhance the utilization efficiency and feeding value of forage maize. Dissecting the genetic basis of forage quality will improve our understanding of the complex nature of cell wall biosynthesis and degradation, which is also helpful for breeding good quality silage maize.ResultsAcid detergent fiber (ADF), neutral detergent fiber (NDF) and in vitro dry matter digestibility (IVDMD) of stalk were evaluated in a diverse maize population, which is comprised of 368 inbred lines and planted across seven environments. Using a mixed model accounting for population structure and polygenic background effects, a genome-wide association study was conducted to identify single nucleotide polymorphisms (SNPs) significantly associated with forage quality. Scanning 559,285 SNPs across the whole genome, 73, 41 and 82 SNPs were found to be associated with ADF, NDF, and IVDMD, respectively. Each significant SNP explained 4.2 %–6.2 % of the phenotypic variation. Underlying these associated loci, 56 genes were proposed as candidate genes for forage quality.ConclusionsOf all the candidate genes proposed by GWAS, we only found a C3H gene (ZmC3H2) that is directly involved in cell wall component biosynthesis. The candidate genes found in this study are mainly involved in signal transduction, stress resistance, and transcriptional regulation of cell wall biosynthetic gene expression. Adding high digestibility maize into the association panel would be helpful for increasing genetic variability and identifying more genes associated with forage quality traits. Cloning and functional validation of these genes would be helpful for understanding the molecular mechanism of the fiber content and digestibility. These findings provide us new insights into cell wall formation and deposition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0919-9) contains supplementary material, which is available to authorized users.
Highlights
Plant digestibility of silage maize (Zea mays L.) has a large influence on nutrition intake for animal feeding
In the present study, a genome-wide association study for forage quality traits was conducted with nearly 560 thousand Single nucleotide polymorphism (SNP)
Underlying a significant associated SNP on chromosome 6, a C3H gene, which catalyzes a key step in the lignin pathway, was proposed as a candidate gene for all the three forage quality traits
Summary
Plant digestibility of silage maize (Zea mays L.) has a large influence on nutrition intake for animal feeding. Dissecting the genetic basis of forage quality will improve our understanding of the complex nature of cell wall biosynthesis and degradation, which is helpful for breeding good quality silage maize. Forage maize is a type of high-energy silage that supplies dry matter, organic matter and cell walls of whole plants for ruminants. Improving the feeding value is a major objective in forage maize breeding by increasing forage digestibility, especially cell wall digestibility. Variations in cell wall structure and composition have an essential effect on plant digestibility. Among the cell wall components, lignins are important for structure integrity of stalk tissues, and contribute to the mechanical support of plants [6]. Association and cross linkages between lignins with other cell wall components greatly increase the resistance to degradation or stover fermentation.
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