Biological activity and synergistic effects of terpineol and d-limonene against Sclerotium rolfsii,the causal agent of peanut southern blight
To clarify the biological activity and application potential of terpineol and d-limonene from plant essential oils in fighting peanut southern blight caused by Sclerotium rolfsii,their inhibitory activities were tested using the mycelial growth rate method.The optimal mixing mass ratio of terpineol and d-limonene for controlling S.rolfsii was screened in the laboratory,and the synergistic effect was evaluated using co-toxicity coefficient method and pot experiments.The results showed that the strongest inhibitory activity of terpineol and d-limonene against S.rolfsii was achieved with EC50 values of 49.23 μg/mL and 60.87 μg/mL,respectively.At 500 μg/mL and 1 000 μg/mL,terpineol completely inhibited mycelial growth,sclerotium formation and re-germination when treatment lasted for 15 and 30 days.However,under same treatment conditions,d-limonene did not inhibit mycelial growth for a longer period and did not inhibit sclerotium formation and re-germination.Compared with the single agent,the inhibition rates of combination of terpineol and d-limonene against S.rolfsii at specific concentrations with different mass ratios were elevated.The synergistic effect of terpineol combined with d-limonene in mass ratios of 1∶4 and 1∶2 was the most significant,with co-toxicity coefficients of 147.87 and 216.57,respectively.Potted experiments showed that the control effect of the combination of terpineol and d-limonene in mass ratios of 1∶4 and 1∶2 was higher than that of a single agent,indicating that this combination can be developed and utilized as a new plant-derived fungicide.
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