Influence of Temperature and Leaf Wetness Duration on Infection of Strawberry Leaves by Mycosphaerella fragariae

Abstract

In controlled environment studies, the influence of temperature and wetness duration on infection of strawberry leaves by Mycosphaerella fragariae was quantified by inoculating plants with a conidial suspension and incubating them at various combinations of temperature (5 to 35 degrees C) and leaf wetness duration (0 to 96 h). Infection was expressed as the number of lesions per square centimeter of leaf surface and relative infection was used to develop an infection model. Younger leaves were more susceptible to infection. Regardless of temperature and duration of leaf wetness, only few lesions developed on the oldest (19 to 21 days old) and intermediate leaves (12 to 15 days old), respectively (maximum of 1.7 and 2.3 lesions per cm(2)) as compared to the youngest leaves (5 to 7 days old; maximum of 12.6 lesions per cm(2)). On the youngest leaves, lesions developed at all temperatures except at 35 degrees C, and the number of lesions, for all leaf wetness durations, increased gradually from 5 to 25 degrees C and decreased sharply from 25 to 30 degrees C. For temperatures of 15 and 20 degrees C, the number of lesions increased gradually when leaf wetness duration increased from 12 to 96 h. At 25 degrees C, the number of lesions increased with increasing leaf wetness from 12 to 48 h and then at a higher rate from 48 to 96 h. The optimal temperature for infection was 25 degrees C. For most temperatures, a minimum of 12 h of leaf wetness was necessary for infection (more than 1 lesion per cm(2)). Relative infection was modeled as a function of both temperature and wetness duration using a modified version of the Weibull equation (R (2) = 0.98). The resulting equations provided a precise description of the response of M. fragariae to temperature. The model was sufficiently flexible to account for most characteristics of the response of M. fragariae to wetness duration. The model was used to construct a risk chart that can be used to estimate the potential risk for infection based on observed or forecasted temperature and leaf wetness duration.

Differential Regulation of Superoxide Dismutase Activity in Selected Strawberry Lines Exposed to Mycosphaerella fragariae

“…Three further minor isoforms of SOD showed a strong increase in activity during the hypersensitive reaction (Ádám et al, 1995). In previous studies, the most severe infection of strawberry leaves by M. fragariae was found to occur within 12 to 96 h of leaf wetness and inoculation (Elliott, 1988;Carisse et al, 2000). With the growth of conidia, total SOD activity in the four strawberry cultivars increased and then peaked 2 d after inoculation, a pattern that presumably reflects the oxidative effects of M. fragariae.…”

“…With increased emphasis on the development and use of resistant cultivars, leaf spot, although still an important foliar disease, is now of less concern (Maas, 1984). Strawberry cultivars differ in their sensitivity to leaf spot; host and environmental conditions during infection are factors that affect the lesions produced by M. fragariae (Delhomez et al, 1995;Carisse et al, 2000). Joliette is HR (highly resistant) and Kent HS (highly susceptible) (Delhomez et al, 1995;Khanizadeh et al, 1996).…”

Suitability of certain strawberry genotypes for breeding of new cultivars tolerant to leaf diseases based on their combining ability

“…In 2013, SCA effects with values significantly different from zero (P \ 0.05) were found for Table 5 Estimates of SCA effects for the severity of plant infection with leaf spot, leaf scorch and powdery mildew for 78 sibling families from a half-diallel mating design among 13 dessert strawberry cultivars from testing these progenies in Skierniewice Euphytica recorded. It is considered, that the optimum conditions for M. fragariae infection and rapid appearance of the characteristic spots on strawberry leaves are high air humidity and temperature in the range 20-25°C occurring at the same time (Howard et al 1985, Carisse et al 2000. Carisse et al (2000) had observed germination of up to 92 % of spores of the fungus M. fragariae at 25°C, while at 5, 15 and 35°C the spore germination percentage was 15, 40 and 2 %, respectively.…”

Leaf spot and leaflet removal in day-neutral strawberry cultivars under different cultivation conditions, in organic management

“…The infection is eased under air temperature about 25 ºC and long periods of leaf wetting. Young leaves are more susceptible (Carisse et al, 2000).…”