Allelopathy as a tool for weed management

Several studies have demonstrated that many plants have strong allelopathic effects enabling them to reduce growth of other plants growing simultaneously or subsequently in the fields. Exuded or secreted substances derived from their normal metabolism called allelochemicals inhibit certain plants, while, others are not affected at all. This differential effect is due to the same paradigm governing herbicide selectivity, which is also implicit in the selectivity of the allelochemicals. Crops with strong allelopathic effect may become ail additional important tool for weed management. Practically allelopathy is used widely in those areas where cover crops are planted in rotation with other crops and effectively smother or suppress several weeds. Now, it is also known that various cultivars have an allelopathic potential making possible the control of sonic major weeds during the crop cycle. One of these crops is rice. Evaluation of the allelopathic potential of rice germplasm indicates that there are some lines quite aggressive against troublesome weeds such as Echiochloa crusgalli and Cyperus difformis, In this context, breeders should be able to combine the characteristics of these allelopathic lilies with those high yielding varieties. In China it has been found that there is no correlation between the allelopathic traits and main agronomic characters of high yielding varieties, and this makes possible to effectively breed allelopathic lines with high-yield potential. Allelopathic rice varieties should be Suitable for direct seeding as well as for transplanting. Another possibility to explore in the near future. is to improve crop varieties with less allelopathic potential by incorporating desired genes encoding the synthesis of allelochemicals. Therefore allelopathy may also be another component of desired improved weed management. It will not solve all weed problems in any field, but may help considerably to reduce the population of sonic weeds in the fields.