Applied Genetics and Genomics in Alfalfa Breeding

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.

Salicornia europaea L. Na+/H+ antiporter gene improves salt tolerance in transgenic alfalfa (Medicago sativa L.)

“…Alfalfa, a perennial and outcrossing species, is one of the most valuable forage crops with high-protein content and biomass production and has been widely cultivated as an economic crop worldwide. However, it is moderately tolerant to salinity and can only be cultivated in moderate salt-alkaline soils, which limit the growth range of alfalfa (Suárez et al, 2009;Li and Brummer, 2012;Zhang et al, 2012). The expression of foreign genes, such as GmDREB1, SsNHX1, AhBADH, and TaNHX2, increases salt tolerance in transgenic alfalfa plants compared with that of wild-type plants (Jin et al, 2010;Liu et al, 2011;Zhang et al, 2012).…”

Assessment of the genetic variation in alfalfa genotypes using SRAP markers for breeding purposes

“…The breeding strategy is based on the partial exploitation of heterosis in alfalfa proposed for the development of semihybrids by crossing genetically divergent germplasm and identifying heterotic groups (Brummer, 1999;Milic et al, 2013;Annicchiarico et al, 2017). One potential source of a heterotic combination within an alfalfa combination would be crossing between genetically distant populations (Li and Brummer, 2012). Therefore, we assumed that local Tunisian germplasm, which has a long history of growing in the relatively isolated environment of the oasis, can be valuable heterotic populations in semi-hybrids with selected, geographically distant populations.…”

10.5937/ratpov50-5059 = Heterosis in alfalfa breeding

“…Main goals in alfalfa breeding are biomass yield (for hay or biofuel), forage quality: protein, neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent lignin (ADL) content, leaf to stem ratio (Milić et al 2011a), but also persistence, adaptability and stability of newly created populations/cultivars (Katić et al 2008, Veronesi et al 2010, Milić et al 2011c. Breeding alfalfa for yield has not been very successful compared to other species (Lamb et al 2006, Brummer 2008, Veronesi et al 2010, Li & Brummer 2012. The progress of alfalfa breeding has been slow, most notably due to its complex genetic structure (autotetraploidy), allogamy and tetrasomic inheritance present in alfalfa, and besides this plant architecture, hermaphroditic flowers and meadow conditions (Scotti & Brummer 2010).…”

“…Alfalfa breeding programs are based on recurrent phenotypic selection with or without progeny testing, to accumulate desirable alleles at high frequency into a population (Li & Brummer 2012). The tetraploid species usually express severe inbreeding depression.…”