Physiological and biochemical responses of basil to some allelopathic plant residues and dodder infestation

In the present study, the effects of three allelopathic plant residues, namely Syrian bean-caper (Zygophyllum fabago L.), marigold (Calendula officinalis L.), and jimsonweed (Datura stramonium L.) on two cultivar of sweet basil (Ocimum basilicum L.) plants infested by dodder (Cuscuta campestris Yunck.) were examined using factorial experiment in randomized complete block design with three replications. Means comparison revealed that the degree of sensitivity to allelopathic plant residues and dodder infestation in Iranian cultivar (Mubarake) of the basil was more than that of the Italian cultivar. In the plants, infested by dodder, a significant increase in the content of total soluble sugars, peroxidase activity, catalase, superoxide dismutase, ascorbate peroxidase and the initial fluorescence (F-0) was observed, while a noticeable decrease in their height, shoot dry weight, relative water content, pigment-protein content, the variable fluorescence (Fv) and the maximum quantum efficiency (Fv/Fm) of PSII was recorded. Depending on the allelopathic plants used in this study, the effect of the residues on dodder infestation and basil growth varied significantly. While the use of Z. fabago and D. stramonium residues positively correlated with the suppression of dodder emergence, D. stramonium residue use showed a negative impact on basils' growth. In contrast, the usage of C. officinalis residues could not diminish dodder infestation, and in dodder-infested basils it decreased plant performance, RWC, pigment and protein content and the maximum quantum efficiency (Fv/Fm) of PSII. Meanwhile, the application of Z. fabago residues to dodder-infested basil plants decreased dodder emergence rate and increased basil plants' height, dry weight of shoot, relative water content, pigment and protein content, and the maximum quantum efficiency (Fv/Fm) of PSII. Our findings suggest that as an environment-friendly treatment, Z. fabago residues could be used for controlling dodder infestation in basil plants.