Insertional Mutagenesis Using T-DNA Tagging

A soil bacterium, Agrobacterium, transfers the T-DNA containing genes that encode the proteins involved in biosynthesis of plant growth factors and bacterial nutrients. Because none of the genes carried by the T-DNA are required for the transfer, foreign DNA can be inserted into the plant chromosome by putting the sequences between two T-DNA borders and using the Agrobacterium transfer system. Utilising this naturally occurring property, efficient transformation protocols have been developed for Arabidopsis (Bechtold et al., 1993) and rice (Hiei et al., 1994). It is now feasible to rapidly generate the thousands of transformants necessary for investigating genome-wide mutagenesis (Clogh and Bent 1998; Jeon et al., 2000).

Concepts of QTL Analysis and Genomic Selection

The use of molecular genetic markers for selection and genetic improvement is based on genetic linkage between these markers and a quantitative trait locus (QTL) of interest. Thus, linkage analyses between markers and QTLs and between the proper multiple markers are essential for genetic selection from genomic information. It must be made clear that by definition, a QTL refers only to the statistical association between a genomic region and a trait.

Biometrics Applied to Molecular Analysis in Genetic Diversity

Studies about genetic diversity have been of great importance for the purposes of genetic improvement and to evaluate the impact of human activity on biodiversity. They are equally important in the understanding of the microevolutionary and macroevolutionary mechanisms that act in the diversification of the species, involving population studies, as well as in the optimization of the conservation of genetic diversity. They are also fundamental in understanding how natural populations are structured in time and space and the effects of anthropogenic activities on this structure and, consequently, on their chances of survival and/or extinction. This information provides an aid in finding the genetic losses generated by the isolation of the populations and of the individuals, which will be reflected in future generations, allowing for the establishment of better strategies to increase and preserve species diversity and diversity within the species.

How to Choice The Best Molecular Marker for Plant Breeding

The choice of the most appropriate molecular marker for genetic and plant breeding studies must be made on the basis of the ease of developing a useful technique coupled with the efficiency of data evaluation, interpretation, and analysis. The chosen marker must provide easy access and availability, rapid response and high reproducibility, and allow information exchange between laboratories and between populations and/or different species; it must also permit automation of data generation and subsequent analysis. Other desirable characteristics include a highly polymorphic nature, codominant inheritance (permitting the identification of homozygous and heterozygous individuals), frequent occurrence in the genome, and neutral selection (selection free from interference by management practices and environmental conditions). In addition to the characteristics of the marker, the goals of the project, the availability of financial, structural, and personal resources, convenience, and the availability of facilities for the development of the assay, as well as the genetic trait of the species under study, should all be considered.