Detection and Early Diagnosis of Peronospora tabacina Adam in Tobacco Plant with Systemic Infection

Abstract

A disease characterized by the absence of sporulation on leaves and evident necrosis underneath the bark tissues affected adult tobacco plants during 2005 in south Italy. In the field, diagnosis was based mainly on recognition of symptoms, often non-specific, resulting in the application of the wrong control strategy. Two current diagnostic methods based on microscopic observations were compared with polymerase chain reaction (PCR) technique. DNA extraction protocol was modified by replacing sonication with a further lysis step at 60°C and PCR was performed using primers that amplified a specific DNA fragment (230 bp). Microscopy methods were able to detect the pathogen in 50% and 6% of cases, respectively, while PCR was able to detect Peronospora tabacina in all diseased plants. Elimination of sonication in DNA extraction rendered the method easier to perform and avoided the possibility of DNA fragmentation. The results demonstrated that PCR makes the diagnosis fast and reliable while microscopy gives discontinuous results, is time-consuming and not applicable for monitoring.

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

“…PCR-based diagnosis of tobacco blue mold infection has already been described in 1994 (Wiglesworth et al 1994) and has been renewed recently using ITS DNA (Ristaino et al 2007). The aim of these studies was either to detect early infections (Caiazzo et al 2006) or differentiation from other tobacco pathogens (Ristaino et al 2007). The results presented here, show for the first time, that metalaxyl-sensitive and resistant fungicidephenotypes of P. tabacina can be determined by means of specific PCR-primers.…”

“…1b). The sonication as described by Wiglesworth et al (1994) turned out to be an appropriate method for DNA extraction from minute sample amounts, despite the risk of DNA fragmentation as discussed by Caiazzo et al (2006).…”

The Effect of Static Magnetic Field on Growth and Biochemical Indices of Five Fungal Genera

“…R. oryzae quickly fills a Petri dish (agar surface) with a typically cotton candy like colony, initially white that turns grey to yellow brown. The reverse is white to pale [25].…”

Population structure and migration of the Tobacco Blue Mold Pathogen, Peronospora tabacina, into North America and Europe

“…Movement of plant pathogens in planting material is a common means by which pathogens emerge in new geographic regions. A third possible source of inoculum could include survival of the pathogen as oospores on roots, stems or host debris in the field (Caiazzo, Tarantino, Porrone, & Lahoz, 2006;Heist et al, 2002;LaMondia & Aylor, 2001;Lucas, 1980;Spurr & Todd, 1982). The pathogen can also survive and spread in infected tobacco seedling beds or in transplants in greenhouses.…”