Resistance to the SDHI Fungicides Boscalid, Fluopyram, Fluxapyroxad, and Penthiopyrad in Botrytis cinerea from Commercial Strawberry Fields in Spain

Abstract

Gray mold, caused by the necrotrophic fungus Botrytis cinerea., is one of the most economically important diseases of strawberry. Gray mold control involves the application of fungicides throughout the strawberry growing season; however, B. cinerea isolates resistant to multiple classes of site-specific fungicides have been recently reported in the Spanish gray mold population. Succinate dehydrogenase inhibitors (SDHI) constitute a relatively novel class of fungicides registered for gray mold control representing new alternatives for strawberry growers. In the present study, 37 B. cinerea isolates previously characterized for their sensitivity to boscalid and amino acid changes in the SdhB protein were used to determine the effective concentration that reduces mycelial growth by 50% (EC50) to fluopyram, fluxapyroxad, and penthiopyrad. The present study was also conducted to obtain discriminatory doses to monitor SDHI fungicide resistance in 580 B. cinerea isolates collected from 27 commercial fields in Spain during 2014, 2015, and 2016. The EC50 values ranged from 0.01 to >100 μg/ml for fluopyram, <0.01 to 4.19 μg/ml for fluxapyroxad, and, finally, <0.01 to 59.65 μg/ml for penthiopyrad. Based on these results, as well as findings from a previous publication, the discriminatory doses chosen to examine sensitivities to boscalid, fluopyram, fluxapyroxad, and penthiopyrad were 100, 15, 1, and 6 μg/ml, respectively. Over the course of the 3-year monitoring period, the overall frequencies of resistance to the four SDHI were 56.9, 6.9, 12.9, and 24.6%, respectively. The frequency of boscalid-resistant isolates decreased from 73 to 41% over the years; however, the fluopyram-resistant isolates increased from 5 to 10% after 1 year of registration. Four SDHI resistance patterns were observed in our population, which included patterns I (30%; resistance to boscalid), II (13.8%; resistance to boscalid and penthiopyrad), III (5.7%; boscalid, fluxapyroxad, and penthiopyrad), and IV (7.9%; resistance to boscalid, fluopyram, fluxapyroxad, and penthiopyrad). Patterns I and II were associated with the amino acid substitutions H272R and H272Y; pattern III was associated only with the H272Y mutation; and, finally, pattern IV was associated with the N230I allele in the SdhB subunit. For gray mold management, it is suggested that the simultaneous use of boscalid and penthiopyrad should be limited to one application per season; however, fluxapyroxad and, especially, fluopyram could be used as valid SDHI alternatives for gray mold control, although they should be applied with caution.

Growing a circular economy with fungal biotechnology: a white paper

“…However, even with the solutions available from the agricultural industry, crop losses remain high in soybean and a wide range of other crops [93]. In many cases, the losses seen are due to fungi that have developed resistance to existing control strategies [94][95][96]. The speed with which many species of fungi evolve and become resistant to existing control strategies means that there is a constant need to identify agents with novel modes of action.…”

Characterization of Botrytis cinerea resistance to fungicides in California strawberry production

“…Specific mutations within the sdhB region are associated with different resistance patterns among the SDHI fungicides (Hu et al 2016b;Leroux et al 2010). Mutations within sdhB conferred the same resistance patterns as shown previously except that this study includes isofetamid (Fernández-Ortuño et al 2017). The P225F mutation that conferred resistance to boscalid, fluopyram, isofetamid, and penthiopyrad has also been associated with resistance to fluxapyroxad (Hu et al 2016b).…”

Cytological and Gene Profile Expression Analysis Reveals Modification in Metabolic Pathways and Catalytic Activities Induce Resistance in Botrytis cinerea Against Iprodione Isolated From Tomato

“…There were one hundred and twelve different isolates of B. cinerea collected from different locations of Tian Dong, Tian Yang County, Baise City, Guangxi province, a southern region of China during 2016–2018 ( Supplementary Table S1 ). Single spore isolation was accomplished from diseased leaves and fruits, as described by Fernández et al [ 30 ]. All isolates were stored at 20 °C on dried filter paper [ 31 ].…”