Botrytis pseudocinerea Is a Significant Pathogen of Several Crop Plants but Susceptible to Displacement by Fungicide-Resistant B. cinerea Strains

Abstract

cBotrytis cinerea is one of the most important pathogens worldwide, causing gray mold on a large variety of crops. Botrytis pseudocinerea has been found previously to occur together with B. cinerea in low abundance in vineyards and strawberry fields. Here, we report B. pseudocinerea to be common and sometimes dominant over B. cinerea on several fruit and vegetable crops in Germany. On apples with calyx end rot and on oilseed rape, it was the major gray mold species. Abundance of B. pseudocinerea was often negatively correlated with fungicide treatments. On cultivated strawberries, it was frequently found in spring but was largely displaced by B. cinerea following fungicide applications. Whereas B. cinerea strains with multiple-fungicide resistance were common in these fields, B. pseudocinerea almost never developed resistance to any fungicide even though resistance mutations occurred at similar frequencies in both species under laboratory conditions. The absence of resistance to quinone outside inhibitors in B. pseudocinerea was correlated with an intron in cytB preventing the major G143A resistance mutation. Our work indicates that B. pseudocinerea has a wide host range similar to that of B. cinerea and that it can become an important gray mold pathogen on cultivated plants. Botrytis cinerea Pers.:Fr. is one of the most important plant pathogens worldwide, causing gray mold rot on far more than 200 plant species, including cultivated fruits, vegetables, and ornamental flowers. In addition to its wide host range, typical features of B. cinerea are a necrotrophic, macerating mode of infection, abundant production of asexual macroconidia on the surface of colonized host tissue, and formation of melanized sclerotia for long-term survival and sexual reproduction. Control of gray mold often relies on the use of fungicides although the efficacy of such treatments is threatened worldwide by the abundance of fungicide-resistant B. cinerea field strains (1). Based on gene sequence comparisons, the genus Botrytis has been divided into two phylogenetically separate clades (2). Clade 1 includes B. cinerea and B. pseudocinerea as well as the host-specific species B. fabae, B. calthae, and B. sinoviticola; all of these infect only dicot plants. Clade 2 is phylogenetically more diverse and currently comprises 23 host-specific Botrytis species that infect predominantly monocots (2-4).B. cinerea shows considerable variability in mycelial growth phenotype, conidiation, and sclerotium formation. Numerous studies have also documented a high degree of genetic variability within the species. Based on the analysis of PCR-restricted fragment length polymorphism (RFLP) patterns, fungicide resistance, and the detection of transposable elements, Giraud et al. provided evidence of the existence of genetically distinct groups within B. cinerea (5, 6). In particular, the presence or absence of the long terminal repeat retrotransposon Boty (7) and of the DNA transposon Flipper (8) was used to divide isolates into different transposon types, e...

Spread of Botrytis cinerea Strains with Multiple Fungicide Resistance in German Horticulture

“…Resistance to benzimidazoles was also very common, even though this fungicide has not been in use for many years. Genetic characterization with species-specific PCR primers (Plesken et al, 2015a) revealed eight isolates to belong to B. pseudocinerea ; six of them were sensitive to all fungicides and two were resistant only to benzimidazoles. Isolates belonging to B. cinerea groups N and S showed a random distribution, with no evidence of any host preference or differences in fungicide resistance frequencies (Table S2).…”

“…Formerly thought to be caused by one species called Botrytis cinerea Pers. :Fr., gray mold is now known to be due to a complex of cryptic species (Walker et al, 2011; Plesken et al, 2015a). In addition, the core species of B. cinerea can be separated into genetically more or less distinct groups (N and S) which were shown to be enriched differentially in response to fungicide treatments (Leroch et al, 2013; Plesken et al, 2015a).…”

“…Resistance to individual botryticides has been reported in Germany and other countries since the 1970s, affecting all major fungicide classes (Leroux et al, 2002; Hahn, 2014). In the past 5 years, increasing frequencies of Botrytis strains with multiple fungicide resistance (MR strains) have been reported in different parts of the world especially from strawberries (Amiri et al, 2013; Fernández-Ortuño et al, 2015), but also from raspberries (Weber, 2011; Plesken et al, 2015a), grapes (De Miccolis Angelini et al, 2014; Panebianco et al, 2015) and tomatoes (Konstantinou et al, 2015). …”

Detection of sdhB Gene Mutations in SDHI-Resistant Isolates of Botrytis cinerea Using High Resolution Melting (HRM) Analysis

“…The isolates possessing the P225L and P225T mutations were originating from Germany. All the isolates were identified as B. cinerea using a duplex PCR assay developed by Plesken et al (2015). A complete list of the isolates used in the study and their origin is provided in Table 1 .…”

Cryptic Species: A Leitmotif of Contemporary Mycology Has Challenges and Benefits for Plant Pathologists

“…Botrytis pseudocinerea appears, like B. cinerea, to have a wide host range but is subject to replacement by fungicide-resistant strains of B. cinerea, and appears to produce fungicide-resistant strains less frequently than B. cinerea (Plesken et al 2015). Both host range and fungicide susceptibility/resistance play strong roles in disease management.…”