PCR-based monitoring of recent isolates of tobacco blue mold from Europe reveals the presence of two genetically distinct phenotypes differing in fungicide sensitivity

Abstract

Bioassays testing the fungicide sensitivity against metalaxyl of Peronospora tabacina isolates collected in German tobacco fields in 2005 revealed the presence of two phenotypes, resistant and sensitive. DNA fingerprints using SSR and minisatellite primers allowed separation of the samples into two groups. The differences in amplification patterns coincided with the sensitive and resistant reaction of the isolates in metalaxyl bioassays. New primers were developed which allowed PCR-based detection of P. tabacina and differentiation of the metalaxyl-sensitive and the metalaxyl-resistant phenotype, respectively.

PCR-based detection of sunflower white blister rust (Pustula helianthicola C. Rost & Thines) in soil samples and asymptomatic host tissue

“…Besides possible soil contamination with other oomycetes such as Pustula spinulosa from infected Cirsium arvense or Bremia lactucae from Sonchus sp., Plasmopara halstedii may have contributed to the COX2 amplicons. The latter pathogen often co-occurs with white blister rust in sunflower fields and frequently infects the same host individual simultaneously (Spring 2009). But also soil-borne Phytophthora or Pythium species are a potential source of the cox2 amplicons.…”

Biological Characteristics and Assessment of Virulence Diversity in Pathosystems of Economically Important Biotrophic Oomycetes

“…sporulation or necrosis), are affected by the experimental conditions, by the fitness of the two partners, and by subjective criteria of the operator in rating the symptoms. Third, field isolates of biotrophic oomycetes may consist of a mixture of different pathotypes (for examples see Gulya et al, 1991;Gobbin et al, 2003;Zipper et al, 2009). This impedes correct interpretation of a bioassay until a genetically homogenous strain of the pathogen has been developed and propagated from a single spore or sporangium.…”

“…Since the initial epidemics of 1979 and 1980 with the "new form" of P. tabacina, the disease became established throughout the tobacco growing regions of the world (Sukno et al, 2002a;Ristaino et al, 2007) including Europe where it causes regular epidemics in Germany with high economic losses (Zipper et al, 2009). Control of the disease at this time essentially relied on single-site of action fungicides (e.g.…”

“…Bruck et al (1982) determined that three of the fourteen isolates tested from North Carolina (USA) were resistant to metalaxyl. Isolates resistance to this fungicide were later identified from Texas (USA) in 1983 and Mexico in 1985 (Wiglesworth et al, 1988), as well as in Germany in 2002 (Krauthausen et al, 2003), and France and Italy (Zipper et al, 2009). In fact, the predictions of Lucas (1980) were accurate: the "overuse" of metalaxyl, which is a site-specific acylanaline fungicide, selected for naturally occurring resistant individuals that had temporarily become the dominant genotype in the field.…”

Production and characterization of amphihaploid hybrids between Nicotiana wuttkei Clarkson et Symon and N. tabacum L

“…The blue mold pathogen is notorious for mutations and the ability to develop new races (Masiak 1982;Zipper et al 2009) and, according to the recent molecular studies (Milla et al 2005), all important resistant cultivars probably derive their resistance from a single source (N. debneyi) even if previously reported otherwise. The hybridization of N. wuttkei with N. tabacum may also be important for basic studies in plant biology, gaining increased understanding of phylogenetic relationships among species, and for investigating aspects of evolution of the genus Nicotiana.…”