Frequency of brown rot fungi on blossoms and fruit in stone fruit orchards in Greece

Abstract

Brown rot is a devastating disease of stone fruits caused by Monilinia spp. This study was conducted to investigate the disease aetiology on blossoms and fruit in peach, apricot, sweet cherry and plum orchards, in Greece. In total, 1433 isolates obtained from orchards located in the main stone fruit production regions of Greece were identified to species based on the presence/size of a cyt b intron. Monilinia laxa and M. fructicola were detected at frequencies of 59 and 41%, respectively, while M. fructigena was absent. Monilinia fructicola was more common on fruit whereas M. laxa occurred in similar frequency on blossoms and fruit. Monilinia laxa was replaced by M. fructicola in fruit infections of peach in both regions investigated and in fruit infections of plum in the Imathia region. Assessments of aggressiveness of 30 isolates of both species on the petals and fruits of the hosts showed that M. fructicola isolates were more aggressive. This suggests that the predominance of M. laxa on the blossoms cannot be explained by higher aggressiveness. Measurements of the effect of temperature on mycelial growth showed that M. laxa isolates had a higher growth rate than M. fructicola at the lowest temperature tested of 5°C, whereas M. fructicola isolates showed higher growth rates at higher temperatures. The observed high frequency of M. fructicola in Greece represents a major threat for stone fruit production. Furthermore, the information obtained about delineation of species and plant organ preference could be useful for the implementation of disease management strategies.

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

“…However, no conidial germination was recorded by these authors when RH was lower than 87%. Our results are in agreement with those of Papavasileiou et al (2015) who found that maximum germination of M. laxa and M. fructicola conidia occurred when the isolates were grown on PDA and the temperature was Fig. 1.…”

“…These results were similar to those of Papavasileiou et al (2015) who reported that the conidia of five M. laxa isolates and five M. fructicola isolates did not germinate on PDA at 35°C. However, Casals et al (2010) reported that the germination of conidia of three different Monilinia isolates, one M. laxa isolate, one M. fructigena isolate, and one M. fructicola isolate, occurred at 35°C, but not at 38°C.…”

“…These results are in accordance with those that were reported by Tamm and Flückiger (1993) and Tian and Bertolini (1999), who found that M. laxa conidia can germinate when the temperature is as low as − 4°C. The ability of M. laxa conidia to germinate at low temperatures has also been reported by Watson et al (2002), Casals et al (2010) and Papavasileiou et al (2015) who reported that M. fructicola conidia can germinate at low temperatures, namely 0 and 5°C. Papavasileiou et al (2015) measured conidial germination of five different M. fructicola and M. laxa isolates 6 days after plating on PDA.…”

“…The ability of M. laxa conidia to germinate at low temperatures has also been reported by Watson et al (2002), Casals et al (2010) and Papavasileiou et al (2015) who reported that M. fructicola conidia can germinate at low temperatures, namely 0 and 5°C. Papavasileiou et al (2015) measured conidial germination of five different M. fructicola and M. laxa isolates 6 days after plating on PDA. They found that (a) germination of the conidia of the two Monilinia species was greater than 70%, and (b) mycelial growth of the M. laxa isolates was greater than that of the M. fructicola isolates after a 6 day incubation period at 5°C.…”

“…do not germinate at 0.87 a w . It has also been reported that (a) the mycelial growth of M. laxa is better than that of M. fructicola isolates at low temperatures on blossoms and fruit (Papavasileiou et al, 2015;Tamm et al, 1995), (b) M. laxa conidia can germinate at temperatures as low as −4°C on fruit (Tian and Bertolini, 1999), and (c) mycelial growth of M. laxa can still occur at 0°C (Tamm and Flückiger, 1993).…”