Evaluation of Inhibitory Effects of Marigold (Tagetes Erecta) and It’s Associated Bacteria on Fungal Pathogens of Ginger (Zingiber Officinale)

Lee, Xiao Qing (2019) Evaluation of Inhibitory Effects of Marigold (Tagetes Erecta) and It’s Associated Bacteria on Fungal Pathogens of Ginger (Zingiber Officinale). Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Marigold, in particular Tagetes erecta L. (Asteraceae), is widely planted and used in India for many reasons including repellent effects for insects, fungi, bacteria, and viruses. This might be due to the production of a thiophene which was also known as alpha-terthienyl that is uncommonly abundant in Tagetes sp. tissues. The fungi suppression ability of marigold was further explored in this study to help ginger farmers facing hindrances in production caused by fungal pathogens Pythium sp. and Fusarium sp. In addition, this could help farmers to reduce production costs and preserving environment. This study is aimed at determining and quantifying plant extracts from various plant parts of marigold. The extracts were then used to determine the inhibitory effects towards fungal pathogens of ginger which served as second objective. The potentials of bacteria isolated from marigold plant extracts as biological control agent of ginger plant pathogens were also examined. Fungal inhibition test with marigold extracts using disk-diffusion technique was performed and observed frequently up to 7 days. Results showed that the plant extracts could not inhibit the growth of fungi regardless of concentration and various plant parts. However, dual culture test to determine the inhibitory potential of associated bacteria yielded encouraging results. Of the 9 bacterial isolates, bacteria B1,C1,D1,F1,F2,H1 and H2 showed inhibitory potential to Pythium sp. and bacteria B1,C2,D1,E1,F1,F2,H1 and H2 are able to inhibit Fusarium sp. The significant level of bacteria C1 and H2 have highest significant difference in supressing Fusarium sp. while there are no significant different of bacteria in supressing Pythium sp. Biochemical test using potassium hydroxide has showed that majority of the bacteria were Gram positive with only 1 Gram negative. All bacterial isolates were subjected to identification via molecular means. Identification results showed that most of the bacteria belonged to Bacillus sp. Bacillus sp. bacteria are known to be useful in various industries including biological control. The bacterial isolates have shown potential to be further studied as biological control agent and will be kept for future research.