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BACKGROUND Common purslane (Portulaca oleracea) and annual ryegrass (Lolium rigidum) are important infesting weeds of field crops. Herbicides are mostly used for weed suppression, while their environmental toxicity and resistance in weeds against them demand considering alternative options, such as the use of allelopathic crops for weed management. Wheat is an important allelopathic crop and present research focused on the identification and quantification of benzoxazinoids (BXZs) and polyphenols (phenolic acids and flavonoids) of the wheat accession ‘Ursita’ and to screen its allelopathic impact on P. oleracea and Lolium rigidum through equal‐compartment‐agar (ECA) method. RESULTS Weed germination, radicle length, biomass and photosynthetic pigments were altered following co‐growth of weeds with Ursita for 10‐day. Root exudates from Ursita reduced (29–60%) the seedling growth and photosynthetic pigments of Lolium rigidum depending on co‐culture conditions of planting density. Weed pressure caused significant increase in the production of phenolic acids (vanillic, ferulic, syringic and p‐coumaric acids) and root exudation of BXZs, in particular benzoxazolin‐2‐one (BOA), 2‐hydroxy‐7‐methoxy‐1,4‐benzoxazin‐3‐one (HMBOA), 2‐hydroxy‐1,4‐benzoxazin3‐one (HBOA) and 2,4‐dihydroxy‐1,4‐benzoxazin‐3‐one (DIBOA) in wheat tissues (shoots, roots) and exudate in root rhizosphere agar medium in response to co‐cultivation with Lolium rigidum and P. oleracea, depending on weed/crop density. CONCLUSION The work revealed that Ursita is allelopathic in nature and can be used in breeding programs to enhance its allelopathic activity. Meanwhile, there are opportunities to explore allelopathic effect of wheat cultivars to control P. oleracea and Lolium rigidum under field conditions. © 2022 Society of Chemical Industry.

Screening suitable allelopathic crops and crop genotypes that are competitive with weeds can be a sustainable weed control strategy to reduce the massive use of herbicides. In this study, three accessions of common buckwheat Fagopyrum esculentum Moench. (Gema, Kora, and Eva) and one of Tartary buckwheat Fagopyrum tataricum Gaertn. (PI481671) were screened against the germination and growth of the herbicide-resistant weeds Lolium rigidum Gaud. and Portulaca oleracea L. The chemical profile of the four buckwheat accessions was characterised in their shoots, roots, and root exudates in order to know more about their ability to sustainably manage weeds and the relation of this ability with the polyphenol accumulation and exudation from buckwheat plants. Our results show that different buckwheat genotypes may have different capacities to produce and exude several types of specialized metabolites, which lead to a wide range of allelopathic and defence functions in the agroecosystem to sustainably manage the growing weeds in their vicinity. The ability of the different buckwheat accessions to suppress weeds was accession-dependent without differences between species, as the common (Eva, Gema, and Kora) and Tartary (PI481671) accessions did not show any species-dependent pattern in their ability to control the germination and growth of the target weeds. Finally, Gema appeared to be the most promising accession to be evaluated in organic farming due to its capacity to sustainably control target weeds while stimulating the root growth of buckwheat plants.

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