Construction of high-density linkage maps and identification of quantitative trait loci associated with verticillium wilt resistance in autotetraploid alfalfa (Medicago sativa L.)

Authors: Yu, Long-Xi; ZHANG, FAN - Chinese Academy Of Agricultural Sciences; CULMA, CESAR MEDINA - Washington State University; LIN, SEN - Washington State University; NIU, YI - Washington State University; ZHANG, TIEJUN - Chinese Academy Of Agricultural Sciences; YANG, QINGCHUAN - Chinese Academy Of Agricultural Sciences; SMITH, MARK - S&w Seed Company; Hu, Jinguo

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2019
Publication Date: 5/1/2020
Citation: Yu, L., Zhang, F., Culma, C., Lin, S., Niu, Y., Zhang, T., Yang, Q., Smith, M., Hu, J. 2020. Construction of high-density linkage maps and identification of quantitative trait loci associated with verticillium wilt resistance in autotetraploid alfalfa (Medicago sativa L.). Plant Disease. 104(5):1439-1444. https://doi.org/10.1094/PDIS-08-19-1718-RE.
DOI: https://doi.org/10.1094/PDIS-08-19-1718-RE

Interpretive Summary: Alfalfa (Medicago sativa L.) is an important legume forage grown worldwide. Alfalfa is called “Queen of Forage” due to its high production and nutrition values. The present study reports the identification of quantitative trait loci (QTL) associated with Verticillium wilt (VW) resistance in a biperental population of alfalfa. Five QTL for VW resistance have been mapped in a high density genetic map. They were located in four chromsomes. With further validation, these QTLs and closely linked markers can be used in maker-assisted selection (MAS) in breeding programs to improved disease resistance.

Technical Abstract: Verticillium wilt (VW) of alfalfa is a devastating disease and causes forage yield reductions of up to 50% in the northern United States and Canada. The best method for controlling the disease is through the development and use of resistant varieties. To understand the genetic base of VW resistance in alfalfa, in the present study, we used a full-sib population segregating for VW resistance for mapping QTL for the disease resistance. High density linkage maps for both resistant and susceptible parents were constructed using single-dose alleles (SDAs) of SNP markers generated by GBS (Genotyping by sequencing). Five QTL associated with VW resistance were mapped in 4 linkage groups. The QTL (qVW-8C) located on LG 8C contributed a major effect to VW resistance while the rest QTL had minor effects. The identification of multiple loci for VW resistance suggests its polygenetic inheritance in alfalfa. Two putative candidates, NBS-LRR disease resistance genes were identified in the QTL intervals of qVW-6D-2 and qVW-8C, respectively. The result agreed with our previous studies where similar resistance loci were identified. The results provide insight into the mechanistic basis of VW resistance in alfalfa. The closely linked markers or candidate genes identified in the present and previous studies can be used in marker-assisted selection to develop alfalfa varieties with enhanced resistance to VW when they are validated.