In Vitro Determination of Sensitivity of Fusarium fujikuroi to Fungicide Azoxystrobin and Investigation of Resistance Mechanism

Abstract

Rice bakanae disease (RBD) caused by Fusarium fujikuroi is a widespread and destructive disease of rice. It is urgent to introduce a new class of fungicide to manage the fungicidal resistance problem and effectively control the disease. Azoxystrobin (AZO) is an active fungicide with a broad antifungal spectrum, while its activity against F. fujikuroi is not well investigated. In this study, the baseline sensitivity of F. fujikuroi to AZO was established by testing the sensitivity of 100 isolates, collected from Anhui Province of China. The mechanism of resistance to AZO was also investigated. AZO exhibited a strong activity against the 100 F. fujikuroi isolates with EC50 values of 0.822 ± 0.285 and 0.762 ± 0.283 μg/mL for mycelial growth and conidial germination, respectively, and both of the baseline sensitivity curves were validated as unimodal curves. To investigate the resistance mechanism, six mutants with resistance factor (RF) values >50 were generated from wild-type sensitive strains through UV mutagenesis, and sequence analysis showed that mutation G143A in cyt b conferred the resistance to AZO. Mycelial growth, conidia production, pathogenicity, and ATP production were decreased in all six resistant mutants as compared to the parental strains, indicating the fitness penalties in this phenotype of resistance mutation. In addition, the cross-resistance assay showed that there was no cross-resistance between AZO and carbendazim, prochloraz, phenamacril, or pydiflumetofen. AZO can be an efficient candidate to control RBD in China with moderate to low fungal resistance risk, but continuous resistance monitoring should be performed during the application of this fungicide.

Target and non‐target site mechanisms of fungicide resistance and their implications for the management of crop pathogens

“…For QoIs, there are some examples of QoI‐resistant plant pathogens in which a fitness cost has been associated with G143A/S, F129L mutations in the cyt b gene, such as Fusarium fujikuroi , 173 Magnaporthe oryzae , 177,178 Monilinia fructicola , 179 Plasmopara viticola , 20,183 Pyricularia oryzae , 186 Ustilago maydis , 189 and Zymoseptoria tritici 191 (Table 3). There were also reports of no fitness costs in QoI‐resistant field isolates, such as Alternaria alternata , 159 Alternaria alternata pathotype tangerine , 160 Botrytis cinerea , 162,214 Colletotrichum acutatum , 167,168 Erysiphe necator , 172 Magnaporthe grisea , 176 Phakopsora pachyrhizi , 18 Plasmopara viticola , 16,184,185 and Z .…”

Nanoparticles of Fe3O4 Loaded with Azoxystrobin and Pectin to Enhance Resistance of Rice to Sheath Blight

“…Azoxystrobin (AZOX) is a potent, broad-spectrum methoxyacrylate fungicide effective against various fungal diseases, including net spot, downy mildew, rice blast, and sheath blight . Despite its excellent agricultural application prospects due to its advantages of low toxicity and environmental friendliness, AZOX faces challenges like low utilization rate, reduced drug sensitivity, and the need for repeated applications. , Therefore, to address these limitations, we propose utilizing iron-based mesoporous material as a core and pectin as a shell to construct an AZOX delivery system. This system aims to enhance the utilization rate and improve the inhibitory effect on sheath blight.…”

Multiple Mutations in SDHB and SDHC2 Subunits Confer Resistance to the Succinate Dehydrogenase Inhibitor Cyclobutrifluram in Fusarium fujikuroi

“…Fusarium fujikuroi (teleomorph: Gibberella fujikuroi) is one of the dominant pathogens of rice bakanae disease (RBD), a destructive seed-borne disease widely distributed in all rice-growing areas throughout the world. , RBD has occurred in various rice-producing areas of China, such as Hunan, Jiangxi, Guangxi, and Jiangsu provinces, resulting in 30–95% yield loss. − The infected rice seedlings are slenderer and weaker, with abnormally elongated leaf sheaths, poorly developed roots, and severely reduced grains. , Furthermore, F. fujikuroi also produces harmful toxins, such as fumonisins, that affect the quality of the rice and harm the health of humans and animals. ,, …”