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Oral: Fungicide Resistance


ADEPIDYNTM fungicide: Cross resistance patterns in Alternaria solani.
G. OLAYA (1), R. Linley (2), K. Edlebeck (2), T. Harp (3) (1) Syngenta, U.S.A.; (2) Syngenta, U.S.A.; (3) Syngenta, U.S.A.

ADEPIDYNTM is the first member of a new chemical group among the succinate dehydrogenase inhibitor fungicides (SDHI, FRAC Group 7), the N-methoxy-(phenyl-ethyl)-pyrazole-carboxamides. The common name for ADEPIDYNTM is pydiflumetofen. ADEPIDYNTM has high binding properties to the complex II enzymes that provide a strong fungicidal potency combined with the control of a wide range of plant pathogen species. A variety of mutations are associated with resistance to SDHI fungicides. Cross resistance patterns across SDHI fungicides are complex due to the fact that some mutations confer high levels or resistance and others do not and mutations could lead to different sensitivity shifts in different SDHIs. In Alternaria solani isolates, the in vitro sensitivity revealed incomplete cross resistance patterns between ADEPIDYNTM and boscalid, penthiopyrad, SOLATENOLTM and fluopyram. ADEPIDYNTM exhibited the highest intrinsic activity among these fungicides and across isolates with or without mutations in the sdh subunits (SdhB-H277Y, SdhB-H277R, SdhC-H134R, SdhD-D123E abd SdhD-H133R). ADEPIDYNTM was able to control early blight disease development on inoculation studies done with A. solani isolates sensitive and with different levels of resistance to boscalid and Sdh mutations. Fluopyram was also able to control the disease using higher fungicide rates and disease control with SOLATENOLTM, penthiopyrad and boscalid varied according to the presence or absence of Sdh mutations.