Factors influencing external fruit rot of cucumber caused by Didymella bryoniae

Abstract

Several factors influencing the occurrence and extent of external fruit rot caused by Didymella bryoniae on cucumbers in the post harvest period were studied.The minimum, optimum and maximum temperatures for growth of the fungus on fruits were circa 10, 23 and 35 ~ respectively. The influence of the temperature on the growth of the fungus in vitro and in vivo was about similar. The fitness of the fungus diminished by storing inoculated fruits at about the maximum temperature for growth of the fungus for one day, but this temperature influenced fruit quality negatively. Storing at 10 to 12 ~ is more advisable.Isolates of D. bryoniae showed variation in virulence. There was a linear relationship between growth on fruits and growth in vitro of these isolates, but no correlation was found with disease incidence on plants.The degree of fruit rot was increased by more severe wounding, by storing in the dark instead of in the light and by higher nitrogen fertilization of the crop. Relative humidity during storage had no effect on fruit decay. It is very likely that the amount and composition of available nutrients for fungus growth determine the degree of rotting of the fruits.Wkh the present cultivars, external fruit rot can be best controlled by reducing the changes of wounding in the pre-and post-harvest period.

Cell wall-degrading enzymes of Didymella bryoniae in relation to fungal growth and virulence in cantaloupe fruit

“…Steekelenburg (1982) reported that there was a linear relationship between the growth of 11 D. bryoniae isolates on potato dextrose agar and virulence on cucumber fruit. In the present study, our data agreed with the report of Steekelenburg (1982).…”

“…Fungal virulence factors include any microbial characteristic that determines the capacity for virulence in the host. Steekelenburg (1982) reported that variation in virulence of D. bryoniae isolates on cucumber fruit was correlated with the extent of fruit rot and in vitro radial growth of the fungus. Keinath et al (1995) tested pathogenicity of 19 D. bryoniae isolates collected from different locations in the United States and found that 17 of them were pathogenic to watermelon and cantaloupe plants.…”

Epidemiological aspects of Didymella bryoniae, the cause of stem and fruit rot of cucumber

“…1) and in a growth chamber indicate that the minimum temperature for fructification of D.bryoniae is between 5, and 10 ~ This implies that ascospores can be present in glasshouse air throughout the year and are absent outdoors only during a few winter months. In vitro and in vivo, the minimum temperature for growth of the fungus was also between 5 and 10 ~ ( Van Steekelenburg, 1982;Wiant, 1945). Besides a temperature above this minimum, moisture is needed for fructification of the fungus on plant debris.…”

Integrated pest management of disease and arthropod pests of greenhouse vegetable crops in Ontario: Current status and future possibilities

“…Wounding caused by rough handling of fruit during harvesting and storage is the most important factor influencing fruit infection (Steekelenburg 1982). Storing fruit in the light compared to darkness reduces the incidence of post-lnrvest fruit rot.…”

“…Storing fruit in the light compared to darkness reduces the incidence of post-lnrvest fruit rot. High relative humidity during storage ofthe fruit has no effect on disease incidence but storage temperatures of 10-12"C decrease disease incidence comoared to storage even lor 8 h at 20"C ancl then placement at 11'C (Steekelenburg 1982 High concentrations of N reduce disease caused by P. aphanidermatum whereas high concentrations of P and K do not (Rajan and Singh 1973). Calcium and alfalfa meal, incorporated into growth media, significantly suppress damping-off caused by P. splendens Braun in cucumbers (Kao and Ko 1986a,b (Chen et al 1987 Chen et al (1987) (Elad et al 1980).…”