A Review of Apothecial Production by Monilinia Fungi in Japan

Abstract

The literature on apothecial production by Monilinia spp. is reviewed with particular attention given to Japanese work. Four stages of apothecial development are distinguished? stromatal development, stromatal maturation, apothecial initiation, and apothecial differentiation. Information is given on growth conditions which have been found suitable in laboratory studies for apothecial production by M. fructicola, M. fructigena, M. mali, and M. oxycocci. The temperature, light and moisture regimes, substrates, and incubation times used were similar to those that are encountered in the field in regions of Japan where apothecia are frequently found. The effect of weather conditions and of fruit size and time of ripening of hosts on apothecial production is discussed. The Monilinia fungi are characterized by the production of monilioid spores and stromatic tissue on which apothecia are borne (Honey, 1928). Members of the genus are pathogens of the Rosaceae and Ericaceae and some cause considerable economic losses to crops. Honey (1936) divided the genus into two sections based on the presence or absence in conidial chains of disjunctors (small structures which develop between mature conidia and facilitate spore dispersal). Those that do not possess disjunctors were included in the Junctoriae and those with dis? junctors, in the Disjunctoriae. There are about 30 known species of Monilinia of which nine have been recorded in Japan. Details of the Japanese Monilinia spp. are summarized in Table I. Most studies have been made on the species comprising the Junctoriae because of their economic importance as serious pathogens of apples, pears, and stone fruits. The diseases on fruits are usually referred to collectively as since brown lesions develop on infected tissues, particularly those of fruits. The biology and control of the Monilinia spp. causing brown rot have been reviewed by Wormald (1954) and more recently by Byrde and Willetts (1977), while Harada (1977) has published a report of his detailed studies on the Japanese species of Monilinia. In a more recent article, Batra (1983) reported an investigation of Monilinia spp. on Ericaceae. The sexual spore of Monilinia spp. is the ascospore produced in an apothecium. There are numerous reports in the literature of the discovery in the field of apothecia of most ofthe species. However, there are only a few reports of successful apothecial formation by these fungi in the laboratory, and consequently the factors involved in the initiation and differentiation of ascocarps of Monilinia are not well understood. Also most of the successful studies have been carried out in Japan and details ofthe work are not readily available to many western workers. The purpose of this article is to review the data available on apothecial pro? duction by Monilinia fungi, with particular reference to the Japanese species. Attempts are made to interpret the findings using published information on