Abstract
Rice false smut (RFS), caused by Villosiclava virens, is an emerging devastating disease of rice panicles worldwide and produces yield loss and mycotoxin residues in rice. In this study, 18 plant essential oils (PEOs) were selected to evaluate antifungal activity via fumigation and contact methods against the mycelial growth and conidial germination of V. virens. The primary compositions of PEOs with stronger fungistatic activity were analyzed using gas chromatography (GC)-mass spectrometry (MS), and the changes in the mycelial morphology were observed using scanning electron microscopy (SEM). Antifungal tests showed that cinnamon bark oil and cinnamon oil had stronger fumigation and contact effects on V. virens than the other oils tested. The primary active composition in both cinnamon bark oil and cinnamon oil was trans-cinnamaldehyde, which exhibited contact activities with EC50 values of 2.13 and 35.9 μg/mL against mycelial growth and conidial germination, respectively. The hyphae surface morphological alterations caused by cinnamon bark oil, cinnamon oil and trans-cinnamaldehyde included shriveling, vacuolation and exfoliation. In conclusion, cinnamon bark oil and cinnamon oil have the potential to prevent and control RFS, and trans-cinnamaldehyde is a promising natural lead compound for new fungicide discoveries to control RFS contamination and mycotoxin residues in rice.
Highlights
Rice false smut (RFS) caused by Villosiclava virens is becoming one of the most economically important grain diseases in China with its incidence growing to 76% due to the expanded planting of hybrid rice cultivars, overuse of nitrogenous fertilizers and an apparent change in climate[1,2,3]
Artemisia argyi oil, camphor oil, Ligusticum wallichii oil, myristica oil, Platycladus orientalis oil and tea seed oil showed less than 50% inhibition against mycelial growth of V. virens
It is interesting that L. cubeba oil had stronger fumigation activity while L. wallichii oil showed stronger contact activity against mycelial growth and conidial germination of V. virens
Summary
Rice false smut (RFS) caused by Villosiclava virens is becoming one of the most economically important grain diseases in China with its incidence growing to 76% due to the expanded planting of hybrid rice cultivars, overuse of nitrogenous fertilizers and an apparent change in climate[1,2,3]. Cinnamon bark and cinnamon oils showed the strongest inhibitory effect on the conidial germination in both the fumigation and contact activity assays with EC50 values less than 0.5 μL/L air and 33.1 and 30.9 μg/mL, respectively.
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