SPOTS on fruits, at first small, greenish yellow, later brown, gradually enlarge, finally cover the whole fruit surface. The brown spots origin due to rotting of the fruit tissue. On the rotted parts of fruits, warty, grayish-brown tufts of conidia (sporodochia) appear, which break through the skin and are either scattered or more frequently arranged in concentric rings.
SPORODOCHIA (s) grayish-brown, 1-3(-5) mm diam, consist of bottle-shaped conidiophores (cp) with conidia arranged in long, branched chains.
CONIDIA (c) hyaline, ellipsoidal, with slightly sharpened ends, 22 x 13 µm.
PLANT HOST AND DISTRIBUTION. The plant hosts of M. fructigena are species of the genera Malus, Prunus, and Pyrus (Farr et al. 1989).
According to Farr et al. (1989), M. fructigena frequently occurs in Asia, Europe, and northern Africa, but is rare in western hemisphere.
NOTES. The teleomorph of M. fructigena is Monilinia fructigena Honey & Whetzel (Holliday 1989). In Poland, apothecia of Monilinia fructigena have rarely been found (Kochman 1973).
The fungus most closely related to M. fructigena is M. laxa (Ehrenb. ex Pers.) Sacc. & Vogl. (Smith et al. 1988).
Monilia fructigena causes a fruit rot of apples, pears, plums, peaches, and cherries, but occurs mostly on apples (Brooks 1953). In severe infections, 50-75% of the fruit may rot in the orchard (Agrios 1988).
Completely rotted fruits overgrew with the mycelium of M. fructigena frequently remain hanging in trees, where they dry, shrink, and wrinkle (Agrios 1988; Kochman 1973). The skin of the fruits remains as a covering, whereas their inside is first spongy, then hardens, but remains a cork consistency. In this form, the fruits are called "mummies". However, most affected fruits fall to the ground. With time, the mummies transform into black, hardened structures, i. e., pseudosclerotia. In the spring of the next year, the mycelium in the mummified fruits on the tree and the pseudosclerotia in mummified fruits buried in the ground produce new sporodochia with conidia. After a 2-fold overwintering, the pseudosclerotia in mummified fruits produce apothecia with asci and ascospores of Monilinia fructigena. However, the apothecia soon disintegrate, and therefore no ascospores are present when the fruit becomes susceptible.
The susceptibility of the fruit to infection by M. fructigena increases with its maturity. Germ tubes of conidia of the fungus most frequently penetrate fruit through wounds caused by insects, twig punctures, or hail. Occasionally, fruit penetration can take place through stomata or directly through the cuticule.
The fungus grows intercellularly and through secretion of enzymes causes the maceration and browning of the infected tissue. The entire fruit may become completely rotted within a few days.
Agrios G. N. 1988. Plant pathology, 3rd edition, Academic Press, INC. San Diego, New York, Berkeley, Boston, London, Sydney, Tokyo, Toronto.
Brooks F. T. 1953. Plant diseases. Geoffrey Cumberlege. Oxford University Press. London, New York, Toronto.
Farr D. F., Bills G. F., Chamuris G. P., Rossman A. Y. 1989. Fungi on plants and plant products in the United States. APS Press. The American Phytopathological Society. St. Paul, Minnesota. USA.
Holliday P. 1989. A dictionary of plant pathology. Cambridge University Press. Cambridge, New York, New Rochelle, Melbourne, Sydney.
Kochman J. 1973. Fitopatologia. PWRiL. Warszawa.
Smith I. M., Dunez J., Lelliott R. A., Phillips D. H., Archer S. A. 1988. European handbook of plant diseases. Blackwell Scientific Publications.