Molecular biology and plant breeding

Abstract

The use of modern molecular biological techniques has played a significant role in elucidating various aspects of the molecular organization of plant genes. Most of the information gained concerns characters and phenomena that are of relevance to plant breeding. It has been shown at the molecular level that cereal and legume seed storage proteins are controlled by complex multigenic nuclear loci. The analysis of movable nuclear genes, exemplified by the Ds-Ac transposable elements in maize, has given insight into the nature of these elements and the genetic changes that occur at their insertion and deletion sites. The characterization of the heterogeneous mitochondrial DNA and the uniform chloroplast DNA has helped to elucidate the molecular basis of cytoplasmic male sterility, RuBP carboxylase enzyme synthesis and herbicide resistance, In N2 fixation, the emphasis has been put on the molecular dissection of N2-fixing genes in bacteria and the interactions between symbiotic and host DNAs. It has been possible to develop vectors of Agrobacterium tumefaciens Ti-plasmids which lack oncogenes for DNA transfer. Cauliflower and gemini viruses as well as liposomes are also potential systems for DNA transport to protoplasts which can be regenerated into plants. Furthermore, it has been shown that certain molecular biological techniques are useful for screening purposes in genetic analysis and plant breeding work.