10 research outputs found
IBD risk loci are enriched in multigenic regulatory modules encompassing putative causative genes.
GWAS have identified >200 risk loci for Inflammatory Bowel Disease (IBD). The majority of disease associations are known to be driven by regulatory variants. To identify the putative causative genes that are perturbed by these variants, we generate a large transcriptome data set (nine disease-relevant cell types) and identify 23,650 cis-eQTL. We show that these are determined by âŒ9720 regulatory modules, of which âŒ3000 operate in multiple tissues and âŒ970 on multiple genes. We identify regulatory modules that drive the disease association for 63 of the 200 risk loci, and show that these are enriched in multigenic modules. Based on these analyses, we resequence 45 of the corresponding 100 candidate genes in 6600 Crohn disease (CD) cases and 5500 controls, and show with burden tests that they include likely causative genes. Our analyses indicate that â„10-fold larger sample sizes will be required to demonstrate the causality of individual genes using this approach
Cereal landraces for sustainable agriculture. A review
Modern agriculture and conventional breeding and the liberal use of high inputs has
resulted in the loss of genetic diversity and the stagnation of yields in cereals in less
favourable areas. Increasingly landraces are being replaced by modern cultivars which are
less resilient to pests, diseases and abiotic stresses and thereby losing a valuable
source of germplasm for meeting the future needs of sustainable agriculture in the context
of climate change. Where landraces persist there is concern that their potential is not
fully realised. Much effort has gone into collecting, organising, studying and analysing
landraces recently and we review the current status and potential for their improved
deployment and exploitation, and incorporation of their positive qualities into new
cultivars or populations for more sustainable agricultural production. In particular their
potential as sources of novel disease and abiotic stress resistance genes or combination
of genes if deployed appropriately, of phytonutrients accompanied with optimal
micronutrient concentrations which can help alleviate aging-related and chronic diseases,
and of nutrient use efficiency traits. We discuss the place of landraces in the origin of
modern cereal crops and breeding of elite cereal cultivars, the importance of on-farm and
ex situ diversity conservation; how modern genotyping approaches can help both
conservation and exploitation; the importance of different phenotyping approaches; and
whether legal issues associated with landrace marketing and utilisation need addressing.
In this review of the current status and prospects for landraces of cereals in the context
of sustainable agriculture, the major points are the following: (1) Landraces have very
rich and complex ancestry representing variation in response to many diverse stresses and
are vast resources for the development of future crops deriving many sustainable traits
from their heritage. (2) There are many germplasm collections of landraces of the major
cereals worldwide exhibiting much variation in valuable morphological, agronomic and
biochemical traits. The germplasm has been characterised to variable degrees and in many
different ways including molecular markers which can assist selection. (3) Much of this
germplasm is being maintained both in long-term storage and on farm where it continues to
evolve, both of which have their merits and problems. There is much concern about loss of
variation, identification, description and accessibility of accessions despite
international strategies for addressing these issues. (4) Developments in genotyping
technologies are making the variation available in landraces ever more accessible.
However, high quality, extensive and detailed, relevant and appropriate phenotyping needs
to be associated with the genotyping to enable it to be exploited successfully. We also
need to understand the complexity of the genetics of these desirable traits in order to
develop new germplasm. (5) Nutrient use efficiency is a very important criterion for
sustainability. Landrace material offers a potential source for crop improvement although
these traits are highly interactive with their environment, particularly developmental
stage, soil conditions and other organisms affecting roots and their environment. (6)
Landraces are also a potential source of traits for improved nutrition of cereal crops,
particularly antioxidants, phenolics in general, carotenoids and tocol in particular. They
also have the potential to improve mineral content, particularly iron and zinc, if these
traits can be successfully transferred to improved varieties. (7) Landraces have been
shown to be valuable sources of resistance to pathogens and there is more to be gained
from such sources. There is also potential, largely unrealised, for disease tolerance and
resistance or tolerance of pest and various abiotic stresses too including to toxic
environments. (8) Single gene traits are generally easily transferred from landrace
germplasm to modern cultivars, but most of the desirable traits characteristic of
landraces are complex and difficult to express in different genetic
backgrounds.Maintaining these characteristics in heterogeneous landraces is also
problematic. Breeding, selection and deployment methods appropriate to these objectives
should be used rather than those used for high input intensive agriculture plant breeding.
(9) Participatory plant breeding and variety selection has proven more successful than the
approach used in high input breeding programmes for landrace improvement in stress-prone
environments where sustainable approaches are a high priority. Despite being more complex
to carry out, it not only delivers improved germplasm, but also aids uptake and
communication between farmers, researchers and advisors for the benefit of all. (10)
Previous seed trade legislation was designed primarily to protect trade and return royalty
income to modern plant breeders with expensive programmes to fund. As the desirability of
using landraces becomes more apparent to achieve greater sustainability, legislation
changes are being made to facilitate this trade too. However, more changes are needed to
promote the exploitation of diversity in landraces and encourage their use