Unveiling the potential antifungal role of essential oils in the management of Rhizoctonia solani causing sheath blight of rice

The present study aimed to investigate the fungicidal/fungistatic effects of essential oils (EOs) from 14 different plant species against Rhizoctonia solani. Bio-efficacy tests were carried out in a glasshouse and under field conditions during three consecutive years of kharif 2016–2018 by spraying essential oils on healthy rice plants followed by inoculation of R. solani. In vitro results revealed that, three essential oils i.e., Thyme (Thymus vulgaris L.), Cedarwood (Cedrus atiantica), Oregano (Oreganum vulgare) inhibit the mycelial growth by 100, 81.66 and 68.33 per cent respectively. Greenhouse and field experiments showed that Thyme (Thymus vulgaris L.), Cedarwood (Cedrus atiantica), Oregano (Oreganum vulgare) oils show significantly lower values of the disease index (PDI). During three consecutive years field evaluationsof essential oils (Eos) of Thyme (Thymus vulgaris L.), Cedarwood (Cedrus atiantica) and Oregano (Oreganum vulgare) oils recorded lowest PDI when compared with untreated control plot. Gas Chromatography-Mass-spectrometry (GC–MS) results showed limonene (18.38 per cent, peak 11) followed by cymene (12.28 per cent, peak 10), himachalene (16.07 per cent, peak 58) and atlantone (12.02 per cent, peak 79) in cedarwood oil. In oregano oil, limonene (70.55 per cent) was found to be the main compound. Studies on the efficacy of essential oils on yield and per cent yield increase under field conditions have shown that application of essential oils (EOs) such as Thyme (Thymus vulgaris L.), Cedarwood (Cedrus atiantica), and Oregano (Oreganum vulgare) resulted in a yield of 5, 523, 4,506 and 4, 935 kg/ha, respectively, with a per cent yield increase of 55.4, 26.57 and 38.62 per cent, respectively, during Kharif 2015, 2016 and 2017 with slight variations.