Neem Leaf Extracts and Azadirachtin Trigger a Moderate Early Defense Response in Sunflowers Infected with Downy Mildew Caused by <i>Plasmopara halstedii</i> (Farl.) Berl. et de Toni
This study examined the effectiveness of neem leaf extract (NLE) and azadirachtin (AZA) against two isolates of <i>Plasmopara halstedii</i>, which causes downy mildew in sunflowers. We also explored their physiological and histopathological effects. The pre-inoculation treatments include...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Agriculture |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2077-0472/15/12/1248 |
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| Summary: | This study examined the effectiveness of neem leaf extract (NLE) and azadirachtin (AZA) against two isolates of <i>Plasmopara halstedii</i>, which causes downy mildew in sunflowers. We also explored their physiological and histopathological effects. The pre-inoculation treatments included 10% and 20% NLE and 0.01% and 0.1% AZA, compared to a mefenoxam-treated control and a non-treated control. All treatments significantly reduced the disease rate compared to the inoculated controls (which had a 73–76% disease rate). The 10% NLE treatment showed the strongest effect against isolate 1 (0% damping-off), while the 20% NLE treatment was most effective against isolate 2 (4% damping-off). Neem treatments also significantly improved plant height; for instance, 20% of NLE-treated plants inoculated with isolate 2 reached approximately 15 cm, compared to about 8 cm in the inoculated controls. Histological analyses indicated limited hyphal spread and low levels of cortical necrosis in neem-treated plants, particularly with 0.1% AZA treatment. This suggests a moderate initial defense response without extensive hypersensitive cell death. Neem treatments were comparable to mefenoxam treatments. These results highlight the potential of neem-derived products, particularly 10% NLE and 0.1% AZA, for the integrated management of sunflower downy mildew through both direct pathogen suppression and enhanced host resistance. |
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| ISSN: | 2077-0472 |