Effects of fruit maturity and wetness on the infection of apple fruit by Neonectria galligena

Abstract

Neonectria galligena can cause European canker of apple as well as fruit rot. Healthy unwounded fruits on potted trees of cvs Cox, Bramley and Gala were inoculated with conidia of N. galligena to investigate the effects of wetness duration and fruit maturity on rot development. Overall, the incidence of fruit rot was influenced more by fruit maturity at the time of inoculation than by duration of wetness (6-48 h). Young fruit were most susceptible to infection, with 50% of fruit infected when inoculated up to 4 weeks after full bloom. The susceptibility decreased initially until c. 2 months after full bloom and then increased gradually until harvest. Almost all preharvest symptoms (eye rot) developed only on the fruit inoculated up to 4 weeks after full bloom. All other rots were observed after six-month postharvest storage under controlled atmospheric conditions. However, the relative proportion of preharvest eye rots and postharvest storage rots varied greatly among three years. The effect of wetness duration was only significant for fruit inoculated in their early stages of development but not for those inoculated near harvest. Regression models were developed to describe the observed effects of fruit maturity and wetness on the incidence of total nectria rots.

Seasonal susceptibility of apple trees to <i>Neonectria ditissima</i> wound infections

“…For many pathosystems, infections are only successful if minimum conditions of temperature and wetness periods are provided. The availability of wounds is a necessary condition for infection of N. ditissima in apple trees and the wound age, organ and type of wound (natural or artificial) also affect pathogen infection (Xu et al 1998;Xu & Robinson 2010). In some experiments it was not possible to prove the relationship between the wetness duration and the infection of the disease (Xu et al 1998;Latorre et al 2002;Xu & Robinson 2010).…”

“…Also, no symptoms of the disease were observed in the inoculations performed on the flowers. According to Xu & Robinson (2010), susceptibility of apple fruit occurs mainly between full bloom and 4 weeks after. Although it is common to observe symptoms in fruit in infected orchards, no symptoms were observed in flowers in the present experiment or during fruit development.…”

“…The availability of wounds is a necessary condition for infection of N. ditissima in apple trees and the wound age, organ and type of wound (natural or artificial) also affect pathogen infection (Xu et al 1998;Xu & Robinson 2010). In some experiments it was not possible to prove the relationship between the wetness duration and the infection of the disease (Xu et al 1998;Latorre et al 2002;Xu & Robinson 2010). In this study, inoculations were performed under field conditions, in fresh wounds, and and natural precipitation was recorded only after 5 inoculation dates, so, in general, there was no additional moisture after inoculation.…”

Cut-off shoots method for estimation of partial resistance in apple cultivars to fruit tree canker caused byNeonectria ditissima

“…This pathogen can infect apple by either conidia or ascospores during all growth stages and attack trunks, branches, shoots and fruit. The main avenue for infection is leaf scars, but damage occurs also in pruning wounds, cracks and frost injuries (Metzler et al 2002;Plante et al 2002;Mccracken et al 2003;Xu & Robinson 2010).…”

Lower Temperatures More Effective than Atmosphere Modification in Controlling Botrytis and Nectria Rots in Stored Apples

“…Conidia of N. galligena are believed to enter apple fruits through lenticels only (Swinburne 1971). Recent work also suggested that conidia may infect fruit via stomata based on the observations that young fruitlets, on which lenticels may not have formed, were most susceptible to N. galligena (Xu and Robinson 2010). Invading fruit from colonised flower parts in the calyx ends might be another route.…”