Author: Pamela Joyce Gorriceta
Gorriceta, Pamela Joyce, 2019 Herbicidal activity of marine sponge associated actinobacteria against herbicide-resistant ryegrass (Lolium rigidum) on greenhouse trial , Flinders University, College of Medicine and Public Health
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The Australian agriculture sector experience a widespread problem caused by weeds resulting in lower quality and quantity of crops. The annual loss reported by the and Development Corporation is set at $3.27 million. one of the most co mm Lolium rigidum known as an GRDC, Grains nual ryegrass is on weed species that cause record loss on Australian crops. It is resistant to co mm ercial herbicides with 11 mode s of action in the market. This species can also withstand different weather conditions to allow for growth year wide. Discovery of novel herbicides from biological sources are making rounds in the research co Marine sponges and their symbiotic mic mm unity. robiota, important contributors of the novel bioactive compounds, are taken our greatly consideration to be employed for potential herbicidal compounds discovery. extracts of the s Therefore, this study aims to 1) to validate the herbicidal activity of the elected 12 candidate actinobacteria strains; 2) to induce the secondary metabolites from 15 newly isolated actinobacteria strains using two different cultivation media; 3) to investigate and compare the herbicidal activity of the metabolites produced by al l the 27 strains under different cultivation conditions; 4) to screen the strains and their metabolites fractions with herbicidal activity. Two rounds of activity investigations were conducted: (1) 12 actinobacteria strains were selected for the first ro und to validate the performance of the selected strains that showed potential herbicidal activity in a previous study; (2) fifteen newly isolated sponge associated actinobacteria were included to screen the strains with potential herbicidal activity. produce the compounds from the previously used actinobacteria, In the validation round, to methanol extracts of inoculated plates using M4 and ISP2 media was employed germination and greenhouse assay test. and the dried methanol extracts were used for In the screening round, liquid media (M4 and ISP2) cultures were employed to evaluate the best inoculation time for an improved compounds production. The germination test from the validation round did not produce significant results in inhibiting the growth of the annual ryegrass, thus no further germination test was employed. Thin layer chromatography (TLC) was additionally applied for 15 s performances in seed germination test. High performance trains showing different liquid chromatography (HPLC) analysis on the active extracts As a result, from ISP in vitro 2 showed different isolation times produce different compounds. germination test sho wed that one of the 27 tested strains had positive effect to inhibit the annual ryegrass seeds. However, the results of its greenhouse trail did not show significant inhibition against the annual ryegrass plant. Moreover, the analysis of the dry weight of the tested annual ryegrass plants also consistently reflected the greenhouse test results. T he best inoculation time is between 5 9 days using ISP2 liquid media. the results from the TLC and confirmation of compound detection using HPLC.
Keywords: Marine actinobacteria, annual ryegrass
Subject: Biotechnology thesis
Thesis type: Masters
Completed: 2019
School: College of Medicine and Public Health
Supervisor: Chris Franco