Identification of Genetic Loci Associated With Crude Protein Content and Fiber Composition in Alfalfa (Medicago sativa L.) Using QTL Mapping

Changfu Yang; Fan Zhang; Xueqian Jiang; Xijiang Yang; Fei He; Zhen Wang; Ruicai Long; Lin Chen; Tianhui Yang; Chuan Wang; Ting Gao; Junmei Kang; Qingchuan Yang

doi:10.3389/fpls.2021.608940

Identification of Genetic Loci Associated With Crude Protein Content and Fiber Composition in Alfalfa (Medicago sativa L.) Using QTL Mapping

Front Plant Sci. 2021 Feb 18:12:608940. doi: 10.3389/fpls.2021.608940. eCollection 2021.

Authors

Changfu Yang¹, Fan Zhang¹, Xueqian Jiang¹, Xijiang Yang¹, Fei He¹, Zhen Wang¹, Ruicai Long¹, Lin Chen¹, Tianhui Yang², Chuan Wang², Ting Gao², Junmei Kang¹, Qingchuan Yang¹

Affiliations

¹ Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China.
² Institute of Animal Science, Ningxia Academy of Agricultural and Forestry Sciences, Yinchuan, China.

Abstract

Forage quality determined mainly by protein content and fiber composition has a crucial influence on digestibility and nutrition intake for animal feeding. To explore the genetic basis of quality traits, we conducted QTL mapping based on the phenotypic data of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin of an F₁ alfalfa population generated by crossing of two alfalfa parents with significant difference in quality. In total, 83 QTLs were identified with contribution to the phenotypic variation (PVE) ranging from 1.45 to 14.35%. Among them, 47 QTLs interacted significantly with environment and 12 QTLs were associated with more than one trait. Epistatic effect was also detected for 73 pairs of QTLs with PVE of 1.08-14.06%. The results suggested that the inheritance of quality-related traits was jointly affected by additive, epistasis and environment. In addition, 83.33% of the co-localized QTLs were shared by ADF and NDF with the same genetic direction, while the additive effect of crude protein-associated QTLs was opposite to that fiber composition on the same locus, suggesting that the loci may antagonistically contribute to protein content and fiber composition. Further analysis of a QTL related to all the three traits of fiber composition (qNDF1C, qADF1C-2, and qlignin1C-2) showed that five candidate genes were homologs of cellulose synthase-like protein A1 in Medicago truncatula, indicating the potential role in fiber synthesis. For the protein-associated loci we identified, qCP4C-1 was located in the shortest region (chr 4.3 39.3-39.4 Mb), and two of the seven corresponding genes in this region were predicted to be E3 ubiquitin-protein ligase in protein metabolism. Therefore, our results provide some reliable regions significantly associated with alfalfa quality, and identification of the key genes would facilitate marker-assisted selection for favorable alleles in breeding program of alfalfa quality improvement.

Keywords: Medicago sativa L.; QTL mapping; crude protein; fiber composition; quality.