Relationship between the incidence of latent infections caused by Monilinia spp. and the incidence of brown rot of peach fruit: factors affecting latent infection

Abstract

Five field experiments were performed in commercial orchards located in Lleida (Spain) over three growing seasons, 2000-2002, in order to estimate the relationship between the incidence of latent infection caused by Monilinia spp. in peaches and the incidence of post-harvest brown rot. No latent infection was recorded at popcorn and the maximum incidence occurred pre-harvest; in some orchards a second peak was detected during the pit hardening period. Monilinia laxa is the most prevalent species isolated from peaches with brown rot. There was a positive correlation between the incidence of latent infection and that of post-harvest brown rot. The average incidence of latent infection during the crop season explained 55% of the total variation in the incidence of post-harvest brown rot. The effect of temperature (T) and duration of wetness (W) on the incidence of latent infection in peach and nectarine orchards was analysed using multiple regression. The regression analysis indicated that T and W jointly explained 83% of the total variation in the incidence of latent infection. The model predicts no latent infections when T<8°C, and >22 h wetness are required when T=8°C but only 5 h at 25°C are necessary for latent infection to occur. The incidence of brown rot and latent infection of peaches caused by M. laxa under controlled experimental conditions were also affected by T and W, as well as by fruit maturity and inoculum concentration. Latent infections were produced in fruit when T was not suitable for the development of brown rot symptoms. In these experiments more than 4-5 h of daily wetness were required after embryo growth in fruit sprayed to runoff with an inoculum concentration higher than 10 4 conidia ml −1 of M. laxa for brown rot and latent infections to develop. The fitted model obtained from the field data was able to predict the observed data obtained under controlled environmental conditions.

The Crop Load Affects Brown Rot Progression in Fruit Orchards: High Fruit Densities Facilitate Fruit Exposure to Spores but Reduce the Infection Rate by Decreasing Fruit Growth and Cuticle Cracking

“…We assumed a fruit to be susceptible to infection from the time t i at which P(FD) = 0.1, with FD assumed to be a linear function of time, until the time of fruit harvest t H . We assumed as favorable those days when precipitations occurred and mean temperature was comprehended between 22 and 26 • C in accordance to previous studies indicating that conidia reproduction preferably occurs in wet conditions (Tamm and Flückiger, 1993;Xu and Robinson, 2000;Gell et al, 2008;Holb, 2008) and that it is impaired at "extreme" temperatures that are likely to be met in those days with mean daily temperature <22 or >26 • C (Tamm and Flückiger, 1993;Holb, 2008). Eventually we computed how many favorable days for brown rot spreading occurred in 2014 and 2015, (i.e., number of rainy days with mean temperature between 22 and 26 • C in the time period t i -t h ).…”

Pest risk assessment ofMonilinia fructicolafor the EU territory and identification and evaluation of risk management options

“…Under unfavourable weather conditions, the primary infections may remain latent in the blossoms and/or immature fruit (Emery et al, 2000;Gell et al, 2008), and persist as latent infections throughout the growing season until the weather conditions become conducive to disease expression Luo et al, 2001b;Luo and Michailides, 2003). The occurrence of latent infections is very important for the epidemiology of the disease as several studies have shown (Emery et al, 2000;Luo et al, 2001a and b;Northover and Cerkauskas, 1994).…”

“…The incidence of latent infections on immature fruit and the incidence of brown rot on fruit at harvest and post-harvest are also influenced by the quantity of inoculum, the fruit phenological state (Biggs and Northover, 1988;Emery et al, 2000;Gell et al, 2008;Luo and Michailides, 2003;Ogawa et al, 1995), and the environmental conditions (temperature and wetness duration) Luo and Michailides, 2003;Wade and Cruikshank, 1992). Temperature and wetness duration are considered the most crucial factors affecting fruit infection by M. fructicola (Biggs and Northover, 1988a;Michailides, 2001, 2003).…”

“…changes with the degree of fruit ripeness (Fideghelli, 1993;Gell et al, 2008;Lee and Bostock, 2007;Luo et al, 2001a;Luo and Michailides, 2003;Northover and Biggs, 1990) or the cultivar of the host (Feliciano et al, 1987;Gradziel and Wang, 1993;Wagner et al, 2005).…”

Fruit maturity and post-harvest environmental conditions influence the pre-penetration stages of Monilinia infections in peaches

“…Most studies on appressorial formation by M. fructicola have focused on the surface properties of the fruit, the stage of fruit maturity, and the signaling pathways that are required for surface attachment and appressorial formation (Cruickshank and Wade, 1992;Lee and Bostock, 2006). The incidence of brown rot increases as fruit approaches maturity (Gell et al, 2008;Lee and Bostock, 2007;Villarino et al, 2011): immature fruit are more resistant to infection than mature fruit (Gell et al, 2008;Bostock, 2006, 2007;Xu et al, 2007).…”