Evaluation of the Impacts of Potassium Bicarbonate, Moringa oleifera Seed Extract, and Bacillus subtilis on Sugar Beet Powdery Mildew

Baher A El-Nogoumy; Mohamed A Salem; Gabr A El-Kot; Salem Hamden; Mohamed D Sehsah; Abeer H Makhlouf; Yasser Nehela

doi:10.3390/plants11233258

Evaluation of the Impacts of Potassium Bicarbonate, Moringa oleifera Seed Extract, and Bacillus subtilis on Sugar Beet Powdery Mildew

Plants (Basel). 2022 Nov 27;11(23):3258. doi: 10.3390/plants11233258.

Authors

Baher A El-Nogoumy¹, Mohamed A Salem^{2

3}, Gabr A El-Kot⁴, Salem Hamden⁴, Mohamed D Sehsah⁵, Abeer H Makhlouf⁶, Yasser Nehela⁷

Affiliations

¹ Microbiology Department, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
² Department of Chemistry, Faculty of Science & Arts, King Khalid University, Abha 62529, Saudi Arabia.
³ Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo 11284, Egypt.
⁴ Department of Agricultural Botany, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt.
⁵ Plant Pathology Research Institute, Agricultural Research Center, Giza 12619, Egypt.
⁶ Faculty of Agriculture, Minufiya University, Shibin El-Kom 32511, Egypt.
⁷ Department of Agricultural Botany, Faculty of Agriculture, Tanta University, Tanta 31511, Egypt.

Abstract

Powdery mildew disease, caused by Erysiphe betae, is one of the most threatening diseases on sugar beet plants worldwide. It causes a great loss in the root yield, sugar percentage, and quality of produced sugar. In the current study, we aimed to evaluate the susceptibility of 25 sugar beet cultivars to infection with powdery mildew disease under Egyptian conditions. Moreover, we evaluated the impacts of three eco-friendly materials, including potassium bicarbonate (KHCO₃; at 5 and 10 g L^-1), Moringa oleifera seed extract (25 and 50 g L^-1), and the biocontrol agent, Bacillus subtilis (10⁸ cell suspension) against E. betae in two successive seasons 2020 and 2021. Our findings showed that there were significant differences between these 25 cultivars in their susceptibility to the disease under study. Using the detached leaves technique in vitro, B. subtilis showed strong antifungal activity against E. betae. Moreover, both concentrations of KHCO₃ and moringa seed extract significantly reduced the disease severity. Under field conditions, tested treatments significantly reduced the severity of powdery mildew disease and prevented E. betae from producing its conidiophores and conidia. Scanning electron microscope examination of treated leaves demonstrated the presence of the decomposition of fungal hyphae, conidiophores, conidia, and the occurrence of plasmolysis to fungal cells and spores on the surface of the leaves. Furthermore, these treatments greatly improved the percent of sucrose and soluble solids content, as well as the enzymatic activity of peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase. It is noteworthy that treatment with moringa seed extract gave the best results, followed by potassium bicarbonate, then B. subtilis cell suspension. Generally, it is recommended to use the substances used in this research to combat powdery mildew to minimize or prevent the use of chemical fungicides harmful to public health and the environment.

Keywords: Bacillus subtilis; Erysiphe betae; Moringa oleifera; PAL; antioxidant; potassium bicarbonate; salicylic acid; scanning electron microscope; sugar beet.

Grants and funding

The ACP of this manuscript was funded by the Deanship of Scientific Research at King Khalid University for funding the APC through the Program of Research Groups under grant number (RGP. 2/106/43).