The high and low molecular weight glutenin subunit polymorphism of Algerian durum wheat landraces and old cultivars

The high molecular weight (HMW) and B-zone low molecular weight (B-LMW) glutenin subunit composition of 45 Algerian durum wheat (Triticum turgidum L. var. durum) landraces and old cultivars were examined by sodium-dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Nine accessions were heterogeneous and presented two or three genotypes. All together, 33 glutenin patterns were detected, including 12 for HMW and 15 for B-LMW glutenin subunits. Twenty-four different alleles were identified for the five glutenin loci studied, Glu-A1 (3), Glu-B1 (6), Glu-A3 (8), Glu-B3 (5) and Glu-B2 (2). Five new alleles were found, three at Glu-A3 and two at Glu-B3. At the Glu-1 loci, the Glu-A1c-Glu-B1e allelic composition was predominant (31%). For the B-LMW glutenins, the most common allelic composition was Glu-A3a-Glu-B3a-Glu-B2a (36%). The collection analysed shows a high percentage of glutenin alleles and allele combinations related to high gluten strength, together with some others that have not been tested so far. This information could be useful to select local varieties with improved quality and also as a source of genes to develop new lines when breeding for quality. © 2005 Blackwell Verlag

Contribution of genetic resources to grain storage protein composition and wheat quality

The technological quality of wheat flour is defined by a range of dough characteristics relevant to the breadmaking processes and practices of individual countries and for particular products. The influence of storage protein diversity on wheat quality has been widely documented in the last three decades. The present chapter focuses on several aspects of wheat quality that merit more attention. The huge genetic diversity of wheat storage proteins means that all the possible allelic combinations and their interactions are too numerous to be tested in terms of their influence on the major quality parameters. However it is still relevant to describe the variation in rheological and viscoelastic properties of gluten in relation to its component proteins, glutenin and gliadin. Although gluten plays a major role in determining the properties of dough, the abundance of the two major storage protein fractions does not solely explain the observed variation in those properties. We therefore examine the influence of some genetic factors, including those affecting the protein composition, on the variation in the glutenin polymer sizes. Some examples will be given to illustrate how end-use quality can be improved by taking advantage of the available genetic resources in parallel with molecular genome analyses with the dual aim of widening the scope of characteristics that can be harnessed in breeding and ensuring consistent wheat quality in changing agro-climatic situations. The known alleles of the major genes are highlighted in the context of the challenges that the research community is facing regarding wheat allele nomenclature, exchange of gene bank material and the numerous quality attributes of interest. Finally, important research objectives are proposed for breeding future wheats with grain protein quality and technological properties tailored for different food products

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