Association Mapping for Fiber-Related Traits and Digestibility in Alfalfa (Medicago sativa).

Zan Wang,Xuemin Wang,Haiping Qiang,Zhengli Zhang,Haiming Zhao,Guibo Liu,Yingjun Zhang,Hongwen Gao,Ruixuan Xu

doi:10.3389/fpls.2016.00331

Abstract

Association mapping is a powerful approach for exploring the molecular genetic basis of complex quantitative traits. An alfalfa (Medicago sativa) association panel comprised of 336 genotypes from 75 alfalfa accessions represented by four to eight genotypes for each accession. Each genotype was genotyped using 85 simple sequence repeat (SSR) markers and phenotyped for five fiber-related traits in four different environments. A model-based structure analysis was used to group all genotypes into two groups. Most of the genotypes have a low relative kinship (<0.3), suggesting population stratification not be an issue for association analysis. Generally, the Q + K model exhibited the best performance to eliminate the false associated positives. In total, 124 marker-trait associations were predicted (p < 0.005). Among these, eight associations were predicted in two environments repeatedly and 20 markers were predicted to be associated with multiple traits. These trait-associated markers will greatly help marker-assisted breeding programs to improve fiber-related quality traits in alfalfa.

Highlights

Alfalfa (Medicago sativa) is one of the most important forage crops in the world due to its high biomass and choice nutritional profiles and it provides reliable sources of protein and minerals to animals
One of the limitations of association mapping studies is the easy detection of false positives associations caused by the existence of the genetic structure in the populations studied (Flint-Garcia et al, 2005)
Association analysis was conducted for five fiber-related traits in four environments using the GLM−simple model, the Q model, and the Q + K model

Summary

Introduction

Alfalfa (Medicago sativa) is one of the most important forage crops in the world due to its high biomass and choice nutritional profiles and it provides reliable sources of protein and minerals to animals. The main objective, in many alfalfa quality breeding programs is to improve the digestibility (Buxton and Redfearn, 1997) for poor stem digestibility would cause major loss in animal feeding values (Mowat et al, 1965). A research indicated minor improvement in alfalfa stem digestibility would impact agriculture economically (Jung and Allen, 1995). In these sense, efforts in traditional breeding of improving the quality traits as well as yield, resistance, and agronomic traits are necessary. The feeding quality traits are usually quantitative, i.e., controlled by multiple genes. Understanding the genetic architecture of these traits on the molecular level is of necessity for efficient molecular breeding

Methods

Results

Conclusion