Potential Allelopathic Effect of Wheat Straw Aqueous Extract on Bermudagrass Noxious Weed

Residues of several crops, including wheat, have a promising allelopathic effect on noxious weed species and thus represent eco-friendly alternatives to harmful, widely applied herbicides. The current investigation deals with the effects of wheat straw aqueous extract on the growth and biochemical aspects of bermudagrass ( Cynodon dactylon L.) as a model of harmful weeds for the wheat crop. The prepared aqueous extract from wheat straw was subjected to high-performance liquid chromatography (HPLC) analysis to identify and quantify phenolic and flavonoid components. In addition, the allelopathic effect of different concentrations of the extract on the germination, seedling growth, and biochemical aspects of bermudagrass was assessed. Our findings showed a significant decrease in bermudagrass seed germination percentage (ranging from 29.6 to 82.4%) and germination index (ranging from 10.07 to 32.43) in response to the extract treatments and a significant decline in all morphological growth parameters of the seedling. HPLC analysis of the extract showed the presence of seven phenolic acids and six flavonoids. The most prevalent phenolics included pyrogallol (13.75 µg/g), ferulic acid (9.82 µg/g), gallic acid (8.5 µg/g), and isoferulic acid (4.47 µg/g), while the predominant flavonoids included catechin (11.04 µg/g), luteolin (8.26 µg/g) and quercetin (7.74 µg/g). The highest extract concentrations (75% and 100%) showed a corresponding decline in the leaf content of chlorophylls a and b but a significant increase in the content of free amino acids, total protein and soluble carbohydrates. Superoxide dismutase (SOD) activity exposed a concentration-dependent reduction, while the activities of both catalase (CAT) and ascorbate peroxidase (APX) were reduced only with the highest extract concentration. The principal component analysis (PCA) showed a high correlation among the morphological growth parameters, indicating that these elements either have a common ground of variance or are inter-correlated. Accordingly, our findings suggest the possibility of combating bermudagrass weeds using the aqueous extract of wheat straw.