Increasing variability in a wheat breeding program

Project Description

This project involves development of advanced cytological approaches to increase the genetic variability released in the CDC wheat breeding programs by utilizing a novel technique that will manipulate the native recombination machinery of the wheat plant.

Conventional wheat breeding still relies mostly on the pedigree method and the variation is produced by genetic recombination (aka crossing-over) between the two parental sets of chromosomes at meiosis in the first generation (F1). Genetic recombination in wheat is restricted to only a small part of the genome, which limits our ability to transfer useful genes from exotic germplasm. However, enormous variation is available in land races and wild relatives of wheat, but only 10% has been captured in modern breeding cultivars, largely because of linkage drag associated with secondary and tertiary gene pools. Although genotyping can reduce linkage drag in cross-breeding, naturally low levels of recombination can slow breeding progress.

Thus, directed modulation of recombination frequency can improve the efficiency of plant breeding programs by expediting attainment of desired combinations of alleles in a genotype-independent manner. In addition, disruption of genetic barriers, is key to enable genetic accessibility of natural variation and introgression of favourable traits from related or wild species into crops. For example, genetic resources as source for FHB resistance in durum and spring wheat and sawfly resistance has been utilized. There are a number of research groups globally working to improve the rate of genetic recombination in wheat to gain full access to the genes available to wheat breeders. However, most strategies focus on genetic transformation events/CRIPSR technologies, which may still be intensely regulated by government agencies. This research involves development of advanced cytological approaches to complement these technologies. This research will also investigate and measure the distribution and frequency of recombination in suitable cytogenetic material that will be developed in the project by utilizing Single Nucleotide Polymorphism (SNP) wheat chips developed at CDC.

Objectives

1. To use alternative strategies to increase the genetic variability released in the CDC wheat breeding programs. Globally, wheat (is a staple food crop supplying 20% of calories. Wheat supports a Canadian farm industry of >$4.5 billion annually and >$11 Billion with value-added processing. Conventional wheat breeding still relies mostly on the pedigree method in which two lines with complementary characteristics are crossed to produce a variable population in the F2 and subsequent generations. From this variable population, improved selections are made and tested. The efficiency of plant breeding is dependent upon natural levels of recombination frequency during meiosis through its effect on breaking or retaining genetic linkage when combining alleles. A breeder largely relies on the utilization of genetic variation available in the elite germplasm pool. The variation is produced by genetic recombination (aka crossing-over) between the two parental sets of chromosomes at meiosis in the first generation (F1). The greater the variability produced, the greater the chances of advancement through breeding. Genetic recombination in wheat is restricted to only a small part of the genome, which limits our ability to transfer useful genes from exotic germplasm. However, enormous variation is available in land races and wild relatives of wheat, but only 10% has been captured in modern breeding cultivars, largely because of linkage drag associated with secondary and tertiary gene pools. Although genotyping can reduce linkage drag in cross-breeding, naturally low levels of recombination can slow breeding progress. Directed modulation of recombination frequency can thus improve the efficiency of plant breeding programs by expediting attainment of desired combinations of alleles in a genotype-independent manner.
2. In addition, disruption of genetic barriers, is key to enable ‘genetic accessibility’ of natural variation and introgression of favourable traits from related or wild species into crops. For example, we have utilized these genetic resources as source for FHB resistance in durum and spring wheat (Ruan et al. 2012), sawfly resistance (Nilsen et al. 2016) and for shorter, stronger straw (Pozniak, personal communication). Technologies to manipulate recombination frequency are thus a strategic goal to enhance crop improvement. There are a number of research groups globally working to improve the rate of genetic recombination in wheat in an attempt to gain full access to the genes available to wheat breeders. However, most strategies focus on genetic transformation events/CRIPSR technologies, which may still be intensely regulated by government agencies. In this research, we propose to develop advanced cytological approaches to complement these technologies.
3. This work is novel in that it will utilize existing genetic stocks available to the CDC and will manipulate the native “recombination machinery” of the wheat plant.