The growing human population faces a problem and demands greater crops, more productive and better adapted to specific agroclimatic-conditions. Plant breeders are are crucial in worldwide efforts to understand gene functions and interactions. Higher quality and productivity has to be achieved through “science-based” rather than “traditional” agriculture. Biotechnology and plant breeding offer this possibility when applied appropriately.
Wheat is one of the most important food crops in the world and breeders have been using related species as genetic donors with the aim of widen the genetic basis of this crop to get, for example, wheat cultivars better adapted to specific agro-climatic conditions, carrying resistance to pests, etc.
This ERC project is ambitious and a challenge within the framework of wheat breeding. It is focused to deep in our knowledge on chromosome pairing during meiosis in cereals and to transfer into wheat desirable agronomic traits from related wild species such as Hordeum chilense, a wild barley carrying desirable genes, among others, codifying for high carotene content on chromosome 7Hch or resistance to Septoria tritice on chromosome 4Hch. This breeding goal can be approached by promoting inter-specific recombination between wheat chromosomes and those from H. chilense in the background of the ph1 mutant, carrying a deletion for the Ph1 locus. Results from this project could be applied directly to generate new wheat varieties more productive and better adapted to our regional requirements to be use openly by the farmers.
Goals
- A plant breeding programme to widen the genetic basis of durum wheat by introgressing desirable agronomic traits from the wild barley Hordeum chilense, such as resistance to diseases (Septoria tritice through the introgression of chromosome 4Hch of H. chilense) or an increased pigment content (via the introgression of chromosome 7Hch).
- Identify and analyse in rice meiotic proteins involved on each stage during meiosis (especially at early prophase) as a tool to improve the knowledge about the proteins implicated in chromosome associations to manipulate these.
State of the art
The increasing human population demands greater crops, more productive and better adapted to specific agroclimatic-conditions. Plant breeders are key in worldwide efforts to unzip gene functions and interactions, so higher quality and productivity can only be achieved through “science-based” rather than “traditional” agriculture. Wheat is one of the most important food crops in the world and it is key to understand its genetics for plant breeding purposes. Wheat has a complex (polypoloid) genome and despite of this, hexaploid and tetraploid wheats behave as diploids during meiosis (the process occurring in organisms with sexual reproduction to generate the gametes), which means that each chromosome, when has to associate with another one at early meiosis, only recognises its identical (homologue) and not the related chromosomes (homeologues), and this is control by several pairing homologous (Ph) genes. The strongest effect is associated with the Ph1 locus. In the absence of Ph1 locus (ph1 mutants), the chance of pairing between related chromosomes is increased. Thus it is possible to exploit ph1 mutants as a tool for wheat breeding programs to promote inter-specific recombination between wheat chromosomes and those from a related species such as Hordeum chilense, and transfer into wheat desirable agronomic traits from this wild barley, like resistance to diseases or the increment in antioxidant content. Therefore, increasing the knowledge of this phenotype will also contribute to complete the breeding goals of this proposal.
The introgression of genetic material from wild relatives or distantly related species into wheat germplasm is a classical and effective approach for broadening the genetic basis of this crop. Hordeum chilense is polymorphic wild barley from South America which has a high potential for wheat breeding, given its high crossability with this and other members of the Triticeae tribe and its agronomically interesting characteristics for introgression into wheat including: resistance to the root-knot nematode Meloidogyne naasi on chromosome 1HchS; tolerance to salt on chromosomes 1Hch, 4Hch and 5Hch; resistance to Septoria on chromosome 4Hch; and high carotenoid pigment content and resistance to common bunt, both located on chromosome 7Hch. The fertile amphiploid Triticum turgidum-H. chilense called ×Tritordeum has been synthesised. Chromosome addition lines of H. chilense in bread wheat have been also developed and serve as a tool for the transfer of wild barley genes to wheat, but it is not the most efficient approach, making necessary the reduction of the introgression size.
Chromosome engineering methodologies, based on the manipulation of pairing control mechanisms and induced translocations, have been employed to transfer into wheat specific disease and pest resistance genes from members of the wheat tribe. New technologies based on the manipulation of pairing mechanisms have been used and translocations between members of the tribe have been introduced. The use of extra-specific genetics variability has a limitation. The introgression of the gene of interest has associated a chromosomal region which is necessary to eliminate or reduce by backcrossing to recover the genomic structure of the original cultivar. This point can be facilitated using mutants for chromosome pairing in wheat, such as the ph1 mutants. The in situ hybridisation joint to the use of DNA markers are also useful tools to characterise alien chromatin and helps to identify desirable genotypes more precisely and, thereby, facilitates gene transfer into wheat.
The analysis of the homologous pairing during meiosis in a crop like wheat or rice will be an important advance in the strategies to improve cereals genetically, allowing the manipulation of meiotic recombination between non-homologous chromosomes from related species, in our case wheat and barley. It is necessary to promote homoeologous pairing in wheat so far, through the manipulation of the Ph1 gene, analyse where the introgressed chromatin have been integrated and their stability trough different stages of the cell cycle and different plant generations. Understand and control those factors which cause instability and rearrangement will be a goal in breeding lines to be used for crop development.
