Allelopathy in agro-ecosystems: a critical review of wheat allelopathy-concepts and implications

Allelopathy is an important mechanism of plant interference mediated by the release of plant-produced secondary metabolites or decomposition products of microbes to the aerial or soil environment. It plays a key role in natural as well as cultivated ecosystems. Allelochemicals are released into the soil rhizosphere by a variety of mechanisms, including volatilization, decomposition of residues, and root exudation. Along with inhibitory/stimulatory effects of allelochemicals, several other ecological roles of these chemicals, including plant defense, nutrient chelation, and regulation of soil biota, have been reported. Wheat is extensively studied and used as an allelopathic crop, and numerous chemicals are reported to be released from the wheat living plants and decomposing residues. In this review, we presented a contemporary synthesis of the existing data that how wheat allelopathy can be exploited: (a) to biologically control the insects, pests, and diseases, (b) to enhance the soil quality by adding nutrients for crop plants during decomposition from residues and ameliorate soil environment for microbes, (c) to increase the crop diversification by rotation while reducing the weeds and pests infestation, (d) to develop the low-cost biological pesticides with a novel mode of action from crop plants, and (e) to confer tolerance against abiotic stresses. Based on our hypothetical concepts and previous evidences, we briefly discussed the mode of action of allelochemicals, and extent and rate of their production based on crop growth stage. We also addressed the interaction of root exudates and allelochemicals with soil biotic and abiotic components to explore the role of allelopathy in rhizosphere ecology.