Rice allelopathy

Rice allelopathy has been found since mid 1980's. Currently it is studied worldwide and substantial progress has been made. Numerous compounds have been identified as potent allelochemicals from the rice tissues and root exudates. Furthermore, allelopathic rice (i) not only releases allelochemicals to suppress the growth of neighbouring plant species, but also (ii) detects the presence of interspecific neighbours and responds through increased release of certain allelochemicals and (iii) may modify the soil microorganisms to its advantage by release of allelochemicals. Research to develop the commercial allelopathic rice cultivars is being done world wide. Allelopathic rice cultivars combined with integrated cultural management practices may reduce the quantity of herbicides used. Such an allelopathy-based technique for paddy weed control is most easily transferable to the low-input management systems prevailing in Asian rice farming systems. This review aims to outline the recent advances in rice allelopathy: (a) key allelochemicals exuded from allelopathic rice varieties, (b) interference mechanisms of allelopathic rice varieties with paddy weeds, (c) the fate and impact on microorganisms of rice allelochemicals in paddy soils, (d) inheritance and molecular approaches in rice allelopathy, (e) varietal improvement in rice allelopathy and (f) rice allelopathy-based techniques for paddy weed management.