Effect of Climatic Factors on Powdery Mildew Caused by Sphaerotheca macularis f. sp. Fragariae on Strawberry

Abstract

Powdery mildew of strawberry is caused by the obligate pathogenic fungus Sphaerotheca macularis f. sp. fragariae. The disease affects the leaves, flowers and fruit of this crop. This study examined the effects of different environmental factors on disease cycle components (germination, conidiation and survival) in strawberry to determine which conditions limit the progress of the disease. The optimal environmental conditions for conidial germination and conidial germ tube length ranged between 15 and 25°C with relative humidity (RH) higher than 75%, but less than 98%. High light intensity reduced germination and hyphal growth. The viability of conidia on infected leaves was examined at temperatures ranging from 15 to 35°C at 80-85% RH. Conidia survival declined over time, but a certain percentage of conidia remained active after 5 months incubation. The rate of conidial germination was significantly higher on young leaves than on older leaves. This observation was consistent across all four tested cultivars. Conidiation at 70-75% RH was similar to that at 80-85%, but greater than that at ‡95% RH. The shortest time from inoculation to appearance of the first disease symptoms was 4 days, at 20 and 30°C with RH above 75%. In growth chambers, temperatures of 10 and 30°C, RH above 95%, radiation of 7000 lux and the use of a more tolerant cultivar were all detrimental to disease development. In general, the environmental conditions required for germination and dispersal of powdery mildew are conducive to disease progress under strawberry production conditions in Israel. Furthermore, viability and survival of the pathogen during and between seasons appears to be dependent on asexual inoculum production.

Genomic identification, phylogeny, and expression analysis of MLO genes involved in susceptibility to powdery mildew in Fragaria vesca

“…Sphaerotheca macularis f. sp fragariae) (Boesewinkel, 1979;Xiao et al, 2001;Foulongne et al, 2003;Turechek et al, 2004). PM in strawberry is caused by the obligate pathogenic fungus S. macularis f. sp fragariae, and affects leaves, flowers, and fruit (Amsalem et al, 2006). These four fungi cause similar PM symptoms (Pessina et al, 2014).…”

Effect of grapevine training systems on susceptibility of berries to infection by Erysiphe necator

“…The average light intensity was 50 percent higher in the "free" canopy around bloom time and increased to four-fold of that in the VSP trellising in the following weeks. Radiation, and especially UV radiation, was shown to inhibit the development of several fungi, both biotrophs (Rotem et al 1985;Jacob et al 2008;Amsalem et al 2006) and necrotrophs (Stevenson and Pennypacker 1988), the former including E. necator (Willocquet et al 1996). Light is also assumed to affect the chemical composition of grapes.…”

Spray treatments combined with climate modification for the management of Leveillula taurica in sweet pepper

“…In tomato we found that some of the cultivars were more resistant to O. neolycopersicy than others (Jacob et al 2008). In a crop such as strawberry (Amsalem et al 2005) different resistance sources are available. On the contrary, in the present work there was no significant difference in resistance.…”

“…In various studies, temperatures allowing for powdery mildew development have been shown to range from 15-25°C, with an optimum of approximately 20°C in strawberry (Amsalem et al 2005;Okayama et al 1995) or 22-23°C in rose (Xu 1999a,b). Temperatures of 10°C and 30°C and above have been shown to be detrimental to the pathogen and disease incidence was significantly reduced under these conditions (Amsalem et al 2005;Elad et al 2007;Jhooty and McKeen 1965;Peries 1962).…”

“…Temperatures of 10°C and 30°C and above have been shown to be detrimental to the pathogen and disease incidence was significantly reduced under these conditions (Amsalem et al 2005;Elad et al 2007;Jhooty and McKeen 1965;Peries 1962). In tomato disease did not develop at 28°C (Jacob et al 2008) Disease also did not develop at temperatures >30°C in studies of rose or grape powdery mildews (Delp 1954;Wheeler 1978).…”