Toxicity and Resistance Potential of Selected Fungicides to Galactomyces and Penicillium spp. Causing Postharvest Fruit Decays of Citrus and Other Crops

Abstract

McKay, A. H., Förster, H., and Adaskaveg, J. E. 2012. Toxicity and resistance potential of selected fungicides to Gaiactomyces and Pénicillium spp. causing postharvest fruit decays of citrus and other crops. Plant Dis. 96:87-96.A diverse collection of isolates of Gaiactomyces citri-aurantii and G. geotrichutn, the causal pathogens of sour rots of citrus and other fruit crops, respectively, was evaluated for sensitivity to demethylationinhihiting (DMI) fungicides of the triazole group. Propiconazole was found to be highly effective in reducing mycelial growth of both species in vitro. For 1.^9 isolates of G. citri-aurantii, a mean effective concentration for 50% reduction of mycelial growth (EC^o value) of 0.34 ng/ml was determined; whereas, for 33 isolates of G. geotrichum, this value was 0.14 ng/ml. In a comparison of additional DMI fungicides, mean ECsd values for 60 isolates of G. citri-aurantii and 20 isolates of G. geotrichutn. were 0.27 and 0.17 pg/ml for cyprocona/ole, 0.25 and 0.14 pg/ml for trtetconazole, and 1.16 and 0.73 ng/ml for tebuconazole, respectively. Propiconazole was also highly active against mycelial growth of iniazalil-sensitive isolates of Pénicillium digitatum, the pathogen that causes green mold of citrus, with a tnean ECsn value of 0.008 |ag/tnl for 63 isolates. Imazalil-resistant isolates of this fungus were cross-resistant to propiconazole. When G. citri-aurantii and P. digitatum were grown at selected pH values between 3 and 9, inhibition by propiconazole occurred over the entire pH range. The fungicide was most effective at pH 5 when compared with the nonfungicide-amended control grown at the same pH. In laboratory mass platings of single-spore isolates sensitive to propicona/ole onto selective media, isolates with an up to 81.6-fold dectease in sensitivity to the fungicide were recovered lor P. digitatum. 1-or (/. geotrichutn, isolates with an approximately twofold decrease in sensitivity were obtained. No isolates with reduced sensitivity were recovered for G. citri-aurantii. Propiconazole is currently being registered lor postharvest use on citrus and other crops, and the inlomiation provided will he valuable in monitoring of fungicide resistance and in designing effective fungicide application strategies.

Imazalil resistance in Penicillium digitatum and P. italicum causing citrus postharvest green and blue mould: Impact and options

“…Multiple resistance have been reported for IMZ, TBZ and SOPP (Holmes and Eckert, 1999). Imazalil and PPZ fall in the same DMI class, and cross resistance has been shown between these two fungicides (Mckay et al, 2012b). Some indication of potential negative cross resistance was also observed where the IMZ resistant isolates were markedly better controlled with GRA, PYR and AZO than their respective control of the sensitive isolates.…”

Soil Microbial Functional and Fungal Diversity as Influenced by Municipal Sewage Sludge Accumulation

“…A molecular analysis of the fungi that were isolated from the municipal sewage sludge indicated that this sludge could be dangerous for plants due to the presence of M. circinelloides and G. citri-aurantii . These fungal species are common plant pathogens [ 41 , 42 ]. Worldwide citrus sour rot, which is caused by Geotrichum citri-aurantii , has been reported as an important postharvest disease in citrus fruit [ 42 ].…”

“…These fungal species are common plant pathogens [ 41 , 42 ]. Worldwide citrus sour rot, which is caused by Geotrichum citri-aurantii , has been reported as an important postharvest disease in citrus fruit [ 42 ]. In addition, M. circinelloides causes disease in fruit [ 41 ] and tomatoes [ 43 ].…”

Transcriptome analysis of fungicide-responsive gene expression profiles in two Penicillium italicum strains with different response to the sterol demethylation inhibitor (DMI) fungicide prochloraz

“…The resulted economic losses are so great that aroused enormous attentions all over the world [1]. The sterol demethylation inhibitor (DMI) fungicides, such as imazalil and prochloraz, have been widely applied to control citrus molds [2][3][4][5][6]. However, resistance to these DMI fungicides has frequently occurred for the Penicillium molds in the past decade, especially for P. digitatum isolates with high DMIresistance [5,7], considerably reducing the efficacy of the fungicides.…”