Interactions of Peronospora tabacina with Roots of Nicotiana spp. in Gnotobiotic Associations

Abstract

Peronospora tabacina is an obligate plant pathogen that causes downy mildew disease on several species of Nicotiana, including N. tabacum (tobacco). The primary objective of this study was to use gnotobiotic associations to describe interactions between the pathogen and roots of either N. tabacum (cv. KY14) or N. repanda. We found that the pathogen was capable of moving systemically from shoots to roots of both host species and emerged from the root tissues as hyphae. We also demonstrated that root-associated hyphae were infectious on roots of nearby plants and resulted in new systemic infections. Following overnight darkness, sporulation of the pathogen was observed on infected roots exposed to air on both host species. We also found that within 2 months in culture, structures resembling resting stages of Peronospora tabacina were produced on hyphae emerging from roots of N. repanda but not N. tabacum. These findings appear relevant to both the epidemiology of the disease and to future studies of this and other downy mildew pathosystems.

Detection and Quantification of Peronospora tabacina Using a Real-Time Polymerase Chain Reaction Assay

“…There are two possible explanations for this result: the presence of vegetative hyphae inside the root tissue ( 14) or the presence of oospores or other kinds of survival stmctures in the roots. There are two possible explanations for this result: the presence of vegetative hyphae inside the root tissue ( 14) or the presence of oospores or other kinds of survival stmctures in the roots.…”

“…Oospores of P. tabacina bave been reported on in vitro plants with sporulation induced under laboratory conditions (14). Oospores of P. tabacina bave been reported on in vitro plants with sporulation induced under laboratory conditions (14).…”

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

“…The polycyclic pathogen can complete an infection cycle in 7–10 days, and thus, an outbreak can spread rapidly. The sexual oospores have been rarely found, and thus, the asexual cycle and re‐introduction of the pathogen each year are needed for an outbreak to occur (Heist, Nesmith, & Schardl, ).…”

“…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.…”

Genetic Dissection of Disease Resistance to the Blue Mold Pathogen, Peronospora tabacina, in Tobacco

“…P. hyoscyami de Bary), is a major foliar disease that causes significant crop losses in tobacco-growing areas around the world. Annual losses exceeding $200 million due to blue mold epidemics have been reported in the United States and Canada [5,6].…”