Sensitivity of Nonexposed and Exposed Populations of Magnaporthe oryzae from Rice to Tricyclazole and Azoxystrobin

Abstract

Kunova, A., Pizzatti, C., Bonaldi, M., and Cortesi, P. 2014. Sensitivity of nonexposed and exposed populations of Magnaporthe oryzae from rice to tricyclazole and azoxystrobin. Plant Dis. 98:512-518.Magnaporthe oryzae is the major pathogen of cultivated rice worldwide, which can cause substantial losses to rice production. Rice blast management is based predominantly on the application of fungicides; however, only a little is known about responses of pathogen populations to the most widely used fungicides. In this work, the baseline sensitivity of the Italian M. oryzae population to tricyclazole and azoxystrobin in terms of mycelium growth was determined, and the possible adaptation of the pathogen population after several years of repeated exposure to fungicide treatments was evaluated. All the analyzed strains demonstrated higher sensitivity and variability to azoxystrobin (concentration of fungicide causing 50% growth inhibition [ED 50 ] = 0.063 mg liter -1 ) than to tricyclazole (99.289 mg liter -1 ). After comparing two additional populations collected from fields repeatedly treated with fungicides to the baseline, no decrease in sensitivity toward these fungicides was observed and no resistant strains were detected. The shift of the pathogen sensitivity toward these fungicides has not occurred, although we observed slightly increased variance associated with ED 50 of azoxystrobin. Therefore, both azoxystrobin and tricyclazole can be used to manage rice blast in Italy but it will be important to continue monitoring M. oryzae population to early detect possible azoxystrobin resistance.

Effect of tricyclazole on morphology, virulence and gene expression of Aspergillus aculeatus for management of soft rot disease in peach

“…Tricyclazole is a melanin biosynthesis inhibitor (Kunova et al 2014). Aspergillus aculeatus belongs to the class of melanized pathogenic fungi, where melanin, as a high molecular weight hydrophobic pigment, has been studied for its role in the virulence of fungal pathogens and as the pathogenicity factor in some fungal plant diseases (Brunskole et al 2009).…”

“…Application of TCZ reduces the virulence of pathogenic fungi B. sorokiniana (Kunova et al . ). Further studies report that TCZ blocks secondary fruit infections caused by Magnaporthe oryzae by blocking sporulation and decreasing pathogenicity of the conidia (Zhang and Zhou ).…”

“…It has been reported that TCZ is associated with the absence of melanin production in the cell wall of Bipolaris sorokiniana, as well as a reduction in the production (and size) of spores (Chand et al 2014). Application of TCZ reduces the virulence of pathogenic fungi B. sorokiniana (Kunova et al 2014). Further studies report that TCZ blocks secondary fruit infections caused by Magnaporthe oryzae by blocking sporulation and decreasing pathogenicity of the conidia (Zhang and Zhou 2004).…”

Rice Blast: A Disease with Implications for Global Food Security

“…Examples include Streptomyces bacteria [148] and the biocontrol agent P. fluorescens Pf7-14, which produces antifungal phenazine-1-carboxylic acid [149]. Fungicides are an option for controlling rice blast, but care should be taken to avoid overuse of similar active ingredients and the development of pathogen resistance [137,[150][151][152].…”

Inhibitory Action of Biofungicide Physcion on Initial and Secondary Infection of Magnaporthe oryzae

“…The sensibility of M. oryzae to tricyclazole was different between different strains . Compared with other strains, the M. oryzae strain P131 are more sensitive to tricyclazole (Kunova et al 2013(Kunova et al , 2014. In our study, the sensitivity of M. oryzae to physcion was assessed only with one strain P131, we will test more strains to assess the bioactivity of physcion comprehensively in the future.…”