The hot and the classic.

Allelopathy is the direct influence of a chemical released from one living plant on the development and growth of another. Many researchers have speculated that allelopathy might prove useful in controlling weeds and increasing grain yields. Selection for genotypes with enhanced allelopathic potentials has been carried out in several field crops, and evidence has accumulated that crop cultivars differ significantly in their ability to inhibit the growth of certain weed species. Although traditional breeding methods have not been successful in producing highly allelopathic grain crops with good yields, genetic engineering has the potential for overcoming this impasse (Duke et al., 2001). Conceivably, genetic engineers could enhance the production of allelochemicals already present in a crop or impart the ability to produce new compounds. With either strategy, there are potential problems that must be overcome with regard to tissue-specific promoters, autotoxicity, metabolic imbalances, and proper movement of the allelopathic compound to the rhizosphere. Thus, there is a considerable amount of research to do in all the subdisciplines surrounding this problem. This article highlights some recent developments in this field.