Infection risk of Monilinia fructicola on stone fruit during cold storage and immersion in the dump tank

Abstract

Monilinia spp. is the main pathogen responsible for postharvest losses of stone fruit.Several studies have examined the conditions for Monilinia spp. infection in the field, but very limited information is available about postharvest. Storing fruit for 24 hours in cold room and water dump fruit in a water tank are the most common handling operations during the postharvest of fruit. Then, the aim of this study was to investigate the risk of Monilinia fructicola infection for peaches and nectarines during cold storage and water dump operations. The storage of fruit with the presence of M. fructicola conidia on their surface for up to 30 days at 0 or 4 ºC and 98% Relative Humidity (RH), did not suppose an important risk of infection since only 3.3% of fruit were already infected. M. fructicola was not able to infect fruit at 20 ºC when the RH was around 60%, however, it was possible to develop disease if fruit was already infected before the treatment applications. Conidia of M. fructicola present on the surfaces of nectarines was not able to infect fruit stored at 0 ºC and 100% RH for 24 hours and then immersed in the water dump tank, nevertheless it was able to infect 26.3% of peaches in the same conditions. When fruit was immersed in the dump tank with water containing the presence of viable conidia of M. fructicola, and then fruit was incubated at 20 ºC and 60 or 100% for 7 days, the infection recorded was between 66.7 and 90%, respectively. In addition, water dump operation free from M. fructicola conidia favours optimal conditions to develop infections produced on fruit before the treatment applications. Therefore, postharvest water dump would provide optimal conditions to infect inoculated and non-inoculated fruit, increasing the need for water disinfection.

Impact of Postharvest Handling on Preharvest Latent Infections Caused by Monilinia spp. in Nectarines

“…Monilinia growth was very low at 0 °C. M. fructicola conidia on fruit surface at 0 °C and 100% RH or 4 °C and 100% RH for up to 30 d caused a very low risk of infection, with only a 3.3% and 3.8% brown rot rate of incidence, respectively [ 26 ]. Monilinia spp.…”

“…development and their latent infections, although it is also dependent on relative humidity (RH), wetness duration, and water availability [ 9 , 21 , 39 , 41 ]. During stone fruit postharvest, humidity must be well controlled and kept constant at 60% in order to avoid new brown rot infections, although at this relative humidity, fruit would lose its firmness and quality, reducing their shelf life [ 26 ]. Previously, we reported that high relative humidity levels increase the number of active infections by M. fructicola and especially M. laxa conidia in in vitro experiments [ 5 ].…”

“…Surface disinfection is an important practice to avoid secondary infections in the postharvest handling of stone fruit [ 26 ]. On the other hand, disinfection of fruit by dumping in water with chlorine will sanitize fresh produce and may reduce decomposition by lowering the effective fungal concentration of conidia [ 49 ].…”

“…Degree-days above 0 °C was cumulative daily thermal time, considering that 0 °C is set as the temperature at which Monilinia spp. cannot grow [ 26 ]. DD = Σ [(Trc × trc) + (Twd × twd) + (Tec × tec)]/24, where DD: Degree-days above 0 °C.…”

Phenotyping Brown Rot Susceptibility in Stone Fruit: A Literature Review with Emphasis on Peach

“…In addition, the two species significantly differ in infection and colonization speed, whereby M. fructicola is more aggressive, causing larger fruit lesions and having shorter periods of both incubation and latency [37]. However, the risk of Monilinia infection is significantly reduced at low temperatures [38].…”