Abstract
Alfalfa (Medicago sativa L.), a perennial and outcrossing species, is a widely planted forage legume for hay, pasture and silage throughout the world. Currently, alfalfa breeding relies on recurrent phenotypic selection, but alternatives incorporating molecular marker assisted breeding could enhance genetic gain per unit time and per unit cost, and accelerate alfalfa improvement. Many major quantitative trait loci (QTL) related to agronomic traits have been identified by family-based QTL mapping, but in relatively large genomic regions. Candidate genes elucidated from model species have helped to identify some potential causal loci in alfalfa mapping and breeding population for specific traits. Recently, high throughput sequencing technologies, coupled with advanced bioinformatics tools, have been used to identify large numbers of single nucleotide polymorphisms (SNP) in alfalfa, which are being developed into markers. These markers will facilitate fine mapping of quantitative traits and genome wide association mapping of agronomic traits and further advanced breeding strategies for alfalfa, such as marker-assisted selection and genomic selection. Based on ideas from the literature, we suggest several ways to improve selection in alfalfa including (1) diversity selection and paternity testing, (2) introgression of QTL and (3) genomic selection.
Highlights
Alfalfa, (Medicago sativa L.) a perennial and outcrossing species, originated in and aroundTranscaucasia and possibly in central Asia; for a comprehensive review of alfalfa’s origins, seeSmall [1] and Russelle [2]
We review the advances in genetic mapping and quantitative trait loci (QTL) detection that have been made in alfalfa and present our view of how genomic tools will impact future alfalfa cultivar development programs
We focus on the use of molecular markers to assess genetic diversity and population structure, to augment selection programs, and to implement genomic selection (GS)
Summary
Alfalfa, (Medicago sativa L.) a perennial and outcrossing species, originated in and around. Alfalfa has significant benefits for sustainable cropping systems because its deep root system and perennial nature limit soil erosion and improve soil tilth. Alfalfa forms a symbiotic association with the soil bacterium Sinorhizobium meliloti, which fixes atmospheric nitrogen (N), providing N for the plant and increasing soil N fertility for subsequent crops in a rotation. We discuss alfalfa germplasm diversity and explain the common breeding methods currently used to develop alfalfa cultivars. We review the advances in genetic mapping and quantitative trait loci (QTL) detection that have been made in alfalfa and present our view of how genomic tools will impact future alfalfa cultivar development programs. We discuss some potential challenges and considerations when applying these tools to alfalfa breeding programs
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