Theoretical potential of biotechniques in crop improvement

For the past decade, biotechnology has been promising to deliver new methods and new types of variation to the plant breeder, but only in the last 2 or 3 years has this become a reality. A wide array of new molecular biology and genetic manipulation techniques is now available, which should enable plant breeders to produce improved plants more easily and to develop varieties and cultivars with higher and more sustainable yields, improved quality and composition, greater resistance to pests and diseases, and improved tolerance of climatic and edaphic stresses. Opinions on the use of genetic manipulation differ widely, but in our view, any technology that helps extend the range of variation and manipulate the genetic material of the plant has a role to play in developing new and improved crops. Obstacles that still exist in the application of biotechnology, particularly to important cereals and grasses, are likely to be overcome soon. Improvements will result from the application of a range of technologies, from those giving rise to single base changes to those that modify whole genomes. To effect these changes, plant breeders need to understand the potential of biotechnology, and biotechnologists, of the needs of breeders

Comparison and integration of genetic maps generated from F2 and BC1-type mapping populations in perennial ryegrass (Lolium perenne L.)

Linkage maps of perennial ryegrass were constructed from F2 and BC1?type populations using, predominantly, restriction fragment length polymorphism data based on heterologous probes used in mapping other grass species. The maps identified seven linkage groups, which covered a total of 515 cM (F2) and 565 cM (BC1). They were aligned using 38 loci identified in both populations (common loci) and a possible marker order for all mapped loci in either population was identified in an integrated map. The estimated recombination frequencies and map distances between adjacent common loci were compared between the two data sets and regions of heterogeneity identified. Overall, the common markers identified a map distance of 446 cM in the F2 population and 327 cM in the BC1 population, reflecting a higher recombination frequency in the former, although the difference was not evenly spread over the seven linkage groups

Rice pseudomolecule-anchored cross-species DNA sequence alignments indicate regional genomic variation in expressed sequence conservation

BACKGROUND: Various methods have been developed to explore inter-genomic relationships among plant species. Here, we present a sequence similarity analysis based upon comparison of transcript-assembly and methylation-filtered databases from five plant species and physically anchored rice coding sequences. RESULTS: A comparison of the frequency of sequence alignments, determined by MegaBLAST, between rice coding sequences in TIGR pseudomolecules and annotations vs 4.0 and comprehensive transcript-assembly and methylation-filtered databases from Lolium perenne (ryegrass), Zea mays (maize), Hordeum vulgare (barley), Glycine max (soybean) and Arabidopsis thaliana (thale cress) was undertaken. Each rice pseudomolecule was divided into 10 segments, each containing 10% of the functionally annotated, expressed genes. This indicated a correlation between relative segment position in the rice genome and numbers of alignments with all the queried monocot and dicot plant databases. Colour-coded moving windows of 100 functionally annotated, expressed genes along each pseudomolecule were used to generate 'heat-maps'. These revealed consistent intra- and inter-pseudomolecule variation in the relative concentrations of significant alignments with the tested plant databases. Analysis of the annotations and derived putative expression patterns of rice genes from 'hot-spots' and 'cold-spots' within the heat maps indicated possible functional differences. A similar comparison relating to ancestral duplications of the rice genome indicated that duplications were often associated with 'hot-spots'. CONCLUSION: Physical positions of expressed genes in the rice genome are correlated with the degree of conservation of similar sequences in the transcriptomes of other plant species. This relative conservation is associated with the distribution of different sized gene families and segmentally duplicated loci and may have functional and evolutionary implications