Bioactivity Of Extracts From Helianthus Tuberosus Leaves Against Insects And Plant Fungual Pathogens

The study of plant-source pesticides is of great importance due to the development of green food and environmental protection. Nowadays, the plants of compositae genus play an important role in the study on plant-source pesticides as well as application as insecticide and germicide in ancientry. The Jerusalem artichoke (Helianthus tuberosus L.), which is representative plant of Helianthus species and compositae genus, was widely distributed in the most parts of China, since it has a strong adaptability. However, there is little study on the bioactivity of extracts from Jerusalem artichoke leaves. Therefore, this study has a great meanings in developing new plant-source pesticides, in taking full advantage of this abundant plant resource and in protecting environment. In this paper, the effects of four extracts of Helianthus tuberosus leaves on the development of cotton bollworm (Heliothis armigera) and the growth of four plant pathogenic fungi are discussed and the results are listed as follows:1. The extraction rates were significantly different in extracting solvents with Soxhlet extraction, and the magnitude order: water>ethyl acetate>ethyl ether, petroleum ether.2. Three extracts (with petroleum ether, ethyl ether and ethyl acetate) from Helianthus tuberosus leaves significantly effected the development (larva weight, larva period, pupa weight, pupating rate and corrected mortality) of cotton bollworm (Heliothis armigera), and the effect of ethyl acetate extracts is much better than extracts of other solvents, suggesting that the ethyl acetate is the optimal extracting solvent to distill the active compounds from Helianthus tuberosus leaves.3. Four extracts (with petroleum ether, ethyl ether, ethyl acetate and water) from Helianthus tuberosus leaves significantly inhibited the growth of four plant pathogenic fungi (Rhizoctonia solani, Gibberella zeae, Alternaria solani and Botrytis cinerea), and the magnitude order of effect: ethyl acetate>ethyl ether>petroleum ether>water. Therefore, the ethyl acetate is the optimal extracting solvent to distill the active compounds from Helianthus tuberosus leaves. 4. The measurement of virulence showed that the inhibitory effects of ethyl acetate extracts from Helianthus tuberosus leaves on Gibberella zeae and Botrytis cinerea were far less than those to Rhizoctonia solani and Alternaria solani.5. The ethyl acetate extracts from leaves of eight varieties of Helianthus tuberosus (NY. 1, NY. 2, NY. 3, NY. 4, NY. 5, NY. 6, NY. 7 and NY. 8) significantly inhibited the growth of three plant pathogenic fungi (Rhizoctonia solani, Alternaria solani and Botrytis cinerea) . It is demonstrated that the NY. 5 and NY. 4 are the optimal varieties apt to extract active compounds.6. The ethyl acetate extracts from the leaves of Helianthus tuberosus under irrigation with seawater mixed with fresh water at certain concentrations (0%, 10%, 25%, 50%, 75% and 100%) significantly inhibited the growth of Rhizoctonia solani; and there are no significant differences among treatments. Therefore, Helianthus tuberosus could be cultivated in mudflat of seashore and be irrigated by seawater to obtain the active compounds in the leaves of Helianthus tuberosus.