International Journal of Environmental Science and Development

Abstract—Gynura pseudochina (L.) DC. is a native Zn and Cd hyperaccumulative plant. It can be applied to rehabilitate an old zinc mine by cooperating with a select Zn/Cd tolerant plant endophyte that contains plant growth-promoting properties. Therefore, this research aims to study the inoculation effects of selected Zn/Cd tolerant endophytic bacteria on the growth and phenolic profiles of G. pseudochina growing in Zn plus Cd contaminated soil. Curtobacterium sp. GLD03, Stenotrophomonas sp. GSD10 and Chryseobacterium sp. GTID13 were separately inoculated on tubers before growing in nutrient-rich commercial soil supplemented with Zn (1000 mg L-1) and Zn (50 mg L-1) for two months. The excess Zn and Cdresulted in phytotoxicity (yellow and dead leaves) and a decrease in dry weight. GSD10 had a direct impact on Zn andCd accumulation in the underground (tubers and roots) part,while GLD03 and GTID13 tended to promote Zn and Cdaccumulation in shoots. Interestingly, GLD03 and GTID13seemed to degrade phenolic compounds in leaves. The totalphenolic content (TPC) and total flavonoid content (TFC)decreased by 68-76% and 70-80%, respectively, whencompared to the non-inoculated plants. The TPC and TFC ofGTID13 decreased by 20% and 12%, respectively. HPLC andLC-MS/MS analysis confirmed the results. Moreover, thephenolic profile of GTID13-inoculated plants was not differentfrom that of uninoculated plants. Caffeoylquinic acid andcaffeic acid likely played a key role in reducing Zn/Cd stress.The other involved compounds were salicylic acid, ethylchlorogenate, dicaffeoylquinic acid, ferulic acid, and methyl3,4-dicaffeoylquinate. The results obtained can be used asinformation for selecting endophytes to be applied in the field.

Keywords—bioaugmentation, cadmium, endophyte, phenolic compounds, Zinc

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Cite: Ruttanakorn Munjit, Aphidech Sangdee, Dawn Alnold, Nitra Nuengchamnong, and Woranan Nakbanpote, "Effect of Zn/Cd Tolerant Endophytic Bacterial Inoculation on Phenolic Profiles of Gynura pseudochina (L.) DC. Grown in Zn and Cd Contaminated Soil, " International Journal of Environmental Science and Development vol. 15, no. 6, pp. 315-325, 2024.

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