Factors determining the length of the incubation period of Monilinia fructicola (wint.) Honey in fruits of Prunus spp.

Abstract

The length of the median incubation period of Monilinia fruticola (Wint.) Honey was determined on fruits of several Prunus species at various maturity, injury, and inoculum levels; the median incubation period being defined as the interval between application of conidia to fruits and the first appearance of sporodochia on 50% of fruits. Results were expressed as the time required for 20% and 50% of fruits to produce sporodochia. The following points were demonstrated: (1) Differences in the median incubation period between varieties for similar inoculum dosage were greatest when fruits were least matured and non-injured. (2) These differences became less apparent as inoculum dosage increased, as fruits matured, and as skin injuries increased. (3) Green fruits could be infected by high inoculum dosages when non-injured and by low inoculum dosages when injured. (4) Ripe fruits could be infected by low inoculum dosages whether non-injured or injured. (5) Free ("precipitated") moisture was necessary for infection. High relative humidity (R.H.) maintained this moisture after application of spore suspensions, thus permitting infection, whilst low R.H. allowed this moisture film to dry out, preventing infection. (6) After infection occurred, the R.H. level did not appear to affect the sporulation intensity.The above results are discussed in relation to the concept of inoculum potential, as defined by Garrett (1956), and to the development of epiphytotics and other aspects of the epidemiology of the brown rot fungus.

Effects of temperature and relative humidity on conidial germination and viability, colonization and sporulation ofMonilinia fructigena

“…Thus, it appears that the differences in numbers of conidia produced in the previous experiments were probably due to the indirect effect of temperature via its effect on colonization. This was supported by Corbin's (1962) work on M. fructicola where RH did not affect sporulation intensity on fruits once infection was established. It is well known that overwintered mummified fruits of brown rot need free water to sporulate (Corbin & Cruickshank, 1963; Byrde & Willetts, 1977).…”

“…Little is known about the epidemiology of brown rot on apple in comparison to brown rot on stone fruit caused by M. fructicola and M. laxa (Corbin, 1962; Corbin et al ., 1968; Biggs & Northover, 1988; Tamm & Fluckiger, 1993; Northover & Cerkauskas, 1994; Northover & Biggs, 1995; Michailides & Morgan, 1997). In general, apple cultivars are susceptible to M. fructigena (Sharma & Kaul, 1988) and the incidence of brown rot is associated with wounds on the fruit (Moore, 1950; Byrde & Willetts, 1977; Xu et al ., 1998; Xu & Robinson, 2000).…”

Quiescent fruit infections of peach, apricot, and plum in New Zealand caused by the brown rot fungus Sclerotinia fructicola

“…These differences between adjacent trees could only occur with short range splash-droplet dispersal, since wind dispersal would have eliminated them. In addition, splash dispersal supplies the free water necessary for spore germination and penetration, and a sufficient concentration of spores to achieve infection (Corbin 1963) during a relatively non-susceptible stage in fruit development. Thus, adjacent infected orchard blocks are unlikely to provide spores for quiescent infection in an orchard with no blossom blight present.…”

Contribution à l'étude des voies de pénétration de parasites fongiques des nectarines Monilia laxa (Ascomycète-Discomycète) et Rhizopus stolonifer (Zygomycète-Mucorale)

“…La contamination de blessures par des spores de R. stolonifer ou par des conidies de M. laxa, conduit à la pourriture du fruit, même si l'inoculation survient plusieurs semaines avant maturité (Corbin, 1962;Nguyen-The et Souty, 1985 (Bessis, 1972;Pucheu-Plante et Mercier, 1983). Il en serait de même pour Phytophtora cactorum sur pomme (Mourichon et Bompeix, 1979 (Bessis, 1972), dont le rôle dans la germination des conidies de B. cinerea à la surface des baies semble bien établi (Doneche, 1986 (Dickman et al, 1982) -ainsi que des substances antifongiques préexistantes à l'infection dans le fruit ou induites par le parasite -par exemple, la pomme vis-à-vis de Nectria galligena (Swinburne et Brown, 1975;Seng et aL, 1985).…”