Distribution, Host Range and Disease Severity of Pseudoperonospora cubensis on Cucurbits in the Czech Republic

Abstract

Ales leš Lebeda ebeda, Jana ana Pavelkova avelková , Jirı iř í Urban rban and Bozena ožena Sedlakova edlá ková Abstract Cucurbit downy mildew, caused by Pseudoperonospora cubensis, is a major cucumber disease in the Czech Republic. Disease prevalence, host range and disease severity were evaluated from 2001 to 2009. The geographical distribution of P. cubensis was assessed on ca 80-100 locations per year in two main regions of the Czech Republic (central and southern Moravia, and eastern, northern and central Bohemia). Infection by P. cubensis was observed primarily on cucumber (Cucumis sativus) but only on the leaves. During the study, disease prevalence ranged from 66 to 100%. The majority of C. sativus crops were heavily infected at the end of the growing season (second half of August). Generally, P. cubensis was present at high or very high disease severity. The loss of foliage results in the reduction in the quality and quantity of marketable yield of fruit. Pseudoperonospora cubensis was widespread across the whole area of the Czech Republic studied. Very rarely, infection was recorded in muskmelon (Cucumis melo) and Cucurbita moschata. Of other pathogens, the most frequently recorded was the cucurbit powdery mildew (Golovinomyces cichoracearum and Podosphaera xanthii).

Coincidence of virulence shifts and population genetic changes of Pseudoperonospora cubensis in the Czech Republic

“…Since the 1980s, when a wave of severe epidemics significantly impacted cucumber farming in the Czech Republic (Lebeda & Schwinn, ), the pathogen was also observed in Scandinavian countries during 1985–1987 (Lebeda & Cohen, and references therein). Recently, new outbreaks of downy mildew epidemics devastating cucumber ( Cucumis sativus ) crops have been reported in Europe (Lebeda & Cohen, ; Lebeda et al ., ) and the USA (Holmes et al ., ).…”

“…In 2003 new aggressive pathotypes appeared in Israel and Italy, and highly aggressive isolates ravaged cucumber growing areas of North Carolina, Delaware, Maryland and Virginia in the USA in 2004 (reviewed by Lebeda & Cohen, ; Holmes et al ., ). In 2009 a dramatic change in the pathogen population was observed in the Czech Republic, with new pathotypes and infections on new host species ( Citrullus lanatus , Cucurbita moschata , Cucurbita maxima , Cucurbita pepo ), which had not been previously observed, but occurred repeatedly since then (Lebeda et al ., , ,b; Pavelková et al ., ).…”

“…During the main growing season (July–August), infection by propagules from all neighbouring (plus some other) European countries could possibly invade due to the relatively short distances and high pathogen population turnover in Europe. In addition the frequently changing wind currents and the high diversity in cucurbit cultivars grown contribute to the occurrence of various pathotypes in the Czech Republic (Lebeda et al ., , ,b). In 2003 new aggressive pathotypes appeared in Israel and Italy, and highly aggressive isolates ravaged cucumber growing areas of North Carolina, Delaware, Maryland and Virginia in the USA in 2004 (reviewed by Lebeda & Cohen, ; Holmes et al ., ).…”

Field Response of Cucurbit Hosts toPseudoperonospora cubensisin Michigan

“…Downy mildew, caused by the oomycete Pseudoperonospora cubensis (Berk. & M. A. Curtis) Rostovzev, is one of the most serious foliar dis eases of cucurbits (14). Although this pathogen is found in many cucurbit production areas, P. cubensis thrives in areas where elevated humidity and warm growing conditions favor its growth, reproduction, and ability to infect (4,12,26).…”

“…Species within approximately 20 genera have been reported as hosts of P. cubensis; however, Cucumis, Cucurbita, and Citrullus are the most economically important genera affected by cucurbit downy mildew (14). Disease symptoms vary depending on the cucurbit host ( Fig.…”