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New breeding approaches for forage crops improvement

Bertrand, A., Claessens, A., Rocher, S., Audy, P. and Castonguay, Y. 2016. New breeding approaches for forage crops improvement. Scientific workshop of the joint laboratory in agriculture science between AAFC and Yangzhou Univeristy Yangzhou 2016/03/24 - 2016/03/24

Abstract

Breeding of open-pollinated species exploits natural gene variability between and within populations. The identification of molecular markers that co-segregate with agronomic traits would facilitate the selection of genotypes with desirable alleles to help accelerate phenotypic selection. The development of marker-assisted selection (MAS) approaches of complex traits in open-pollinated populations of tetraploid species such as alfalfa is a daunting task that requires a good knowledge of plant genomics combined with experience in conventional plant breeding. Freezing tolerance is one of the most important factors that determine the survival of perennial forage crops to severe winter conditions. We developed a recurrent selection scheme entirely performed under controlled conditions to identify genotypes with superior tolerance to freezing (TF). Recurrent selection is a cyclical breeding method that progressively increases the frequency and the optimal assortment of alleles affecting quantitative traits. After several cycles of recurrent selection, the freezing tolerance of alfalfa, ryegrass, and red clover was significantly improved. Bulk segregant analysis of TF populations with contrasted freezing tolerance allowed the identification of functional variants of candidate genes. A recurrent selection scheme was also developed for the improvement of cell wall digestibility in alfalfa including the set-up of a high throughput screening test for that trait. The development of germplasm with superior digestibility and the identification of genes with major impacts on this trait will help increase the beef and dairy sector profitability. Progress in sequencing technologies has brought screening for favorable alleles closer to breeding programs. Next generation sequencing (NGS) technologies such as genotyping-by-sequencing (GBS) will accelerate the identification of DNA polymorphisms (SNPs) linked to genes of interest in frnon-model crop with no reference genome and limited genomic resources like alfalfa. Because of the genome-wide syntheny between Medicago sativa and the model legume Medicago truncatula, the recent release of the Medicago truncatula genome assembly constitutes an invaluable source of information to identify genomic regions and candidate genes putatively involved in trait variation.

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