Effect of Allelopathic Potential of some Plants Root Exudates Concerning Growth and Pathogenicity of some Fungus on Brassica oleracea Varplant

Abstract

Abstract The study aims to evaluate the effectiveness of allelopathic exudates of five plant species, namely (maize, barley, Sunflower, chard, and mung bean) concerning the release of organic substances exudated from their roots and their effect on the germination and growth of brassica oleracea var plant, as well as their impact on the growth of two isolated fungi, Rhizoctona solani and Pythium ulitmum. According to the laboratory results, chard root exudates had the highest rate of Brassica oleracea var seed germination, reaching 100%, while maize plant exudates had the lowest rate, 23.33%, compared to the control treatment, which was 100%. Sunflower and mung bean plant exudates had germination rates of 50, 43%, respectively, while barley exudates had a germination rate of 90%. Furthermore, the laboratory results also revealed discrepancy in the above-mentioned root exudates regarding the reduction of the diagonal growth of the two fungi, R.solani and P. ulitmum. Obviously, 10-day-old chard root exudates outperformed in reducing the diagonal growth of both fungi, with an average colony diameter of 0.00 cm for P. ulitmum and 1.59 cm for R.solani when compared by the control treatment (water only), which amounted to 9.00 cm. On other hand, Sunflower root exudates had the highest diagonal growth of the two fungi was reaching to 4.86 cm for R.solani and 8.50 cm for P. ulitmum. The chemical analysis of these five plants’ exudates shows that the highest concentration of the terpene compound was obtained by separating this compound from chard root exudates, using HPLC method, which amounted 3.55 55 μg/g. While the least concentration was in the maize treatment, which reached 15 μg/g. Whereas the total phenolic compounds were more concentrated in the root exudates of mung bean, which reached 52.69 μg/g, and the lowest concentration was in the root exudates of Sunflower reaching 7.89 μg/g. With regard to, the ferulic acid compound, the highest rate was observed in the root exudates of mung bean, which amounted to 19.87 μg/g, then, chard control comes in second place in which the concentration reached 10.25 μg/g. while the least concentration of the same compound was in Sunflower root exudates reached 5.69 μg/g. Seemingly, the diversity and variation of concentrations of allopathic compounds exudated from the roots of these plants, which may either negatively or positively affect the germination of Brassica oleracea var plant and the accompanying pathogenic fungi, are considered to be the cause of the varying effect of the understudied plant roots’ metabolites on germination percentages of Brassica oleracea var plant as well as in the reduction of the diagonal growth of the both fungi, R. solani and P. ulitmum.