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There is growing evidence demonstrating the diversity of foliar endophytic fungi and their ecological roles in the survival of tree seedlings. However, the factors that shape fungal communities in tree seedlings within natural forest ecosystems remain poorly understood. Here, we evaluated the composition of foliar endophytic fungi growing in current-year seedlings of Cornus controversa and Prunus grayana in a cool temperate deciduous forest through a seed-sowing experiment and fungal isolation. The composition of endophytic fungi was affected by canopy tree species, canopy openness, and time after germination. In total, 27 and 22 fungal taxa were isolated from C. controversa and P. grayana seedlings, respectively. The dominant fungal taxa in both seedling species were Colletotorichum spp., and their isolation frequencies were higher under C. controversa canopies than under P. grayana canopies; the frequencies also increased with time after germination. These results suggest that overstory tree species strongly influences the endophytic fungal communities of understory seedlings.

In forests, negative density/distance-dependent seedling mortality (NDD) caused by natural enemies plays a key role in maintaining species diversity [Janzen-Connell (J-C) model]. However, the relative importance of natural enemies in mediating NDD under heterogeneous light conditions has remained unclear. We examined the relative importance of pathogens (i.e., soil pathogens, leaf diseases) on seedling performance in forest understories (FUs) and gaps (gaps) during a 3-year period (results of first year of our study have been previously reported). For the hardwood, Prunus grayana, we investigated seedling mortality, morbidity agents, growth, and root infection by arbuscular mycorrhizal fungi (AMF) beneath conspecific and heterospecific adults in FUs and gaps. Seedling mortality was higher beneath conspecific than heterospecific adults throughout 3 years at both sites, mainly due to continuous leaf disease (i.e., angular leaf spot), whereas damping-off diseases caused mortality only in the first year. Beneath each adult, seedling mortality was higher in FUs than in gaps until second year, but it did not differ between two habitat types in the third year, because leaf diseases caused severe damage even in gaps. Seedling mass was significantly lower beneath conspecific adults. AMF infection of seedlings was also lower beneath conspecific adults, while it was higher in gaps than in FUs beneath both adults. This study demonstrates that the J-C model in a hardwood tree, P. grayana is mainly driven by high NDD seedling mortality caused by airborne leaf diseases, which continuously attack seedlings in a NDD manner regardless of environmental light conditions.

Summary 1.In forest communities, the Janzen–Connell (J-C) hypothesis proposes that species diversity is maintained by non-competitive distance- and/or density-dependent seedling mortality caused by host-specific natural enemies. However, the effects of pathogen associations from nearby conspecifics vs. heterospecifics remain unknown in spatially heterogeneous light environments. 2.Seeds of hardwood species Cornus controversa (Cornus) and Prunus grayana (Prunus) were sown beneath 6–7 Cornus and Prunus adults in both the forest understory (FU) and in gaps (Gap) created by felling all woody vegetation near the focal adults. Seedling growth, mortality, killing agents (e.g. pathogens that cause damping-off and leaf diseases), and root infection by arbuscular mycorrhizal fungi (AMF) were investigated. 3.We found strong habitat effects on the expression of soil fungi beneath both tree species. Seedling mortality caused by soil-borne damping-off pathogens was greater in FU than in Gap, and AMF infection, which enhanced relative seedling growth rate, was greater in Gap than in FU. Seedling mortality caused by damping-off pathogens did not differ between Cornus and Prunus seedlings beneath the adults of conspecific or heterospecific adults in both FU and Gap, suggesting little distance-dependence or host preference in the fungus. 4.Beneath the adults of Cornus and Prunus, the most prevalent leaf diseases were zonate leaf blight and angular leaf spot caused by the airborne pathogenic fungi Haradamyces foliicola and Phaeoisariopsis pruni-grayanae, respectively. Although these pathogens attacked the seedlings of both species, conspecific seedlings (i.e. home) showed more severe leaf damage, earlier leaf shedding and/or less defensive behaviour (cell wall defence) relative to heterospecific seedlings (i.e. away), suggesting negative distance-dependent attack (i.e. host preference) for these leaf diseases. As a result, greater seedling mortality was observed for conspecific seedlings under both FU and Gap treatments. 5.Synthesis. In the temperate forest, the J-C hypothesis is largely mediated through the strong negative influence of airborne leaf diseases rather than through soil-borne damping-off pathogens. We found that airborne diseases demonstrated distance-dependent host preferences, which led to greater conspecific seedling damage regardless of environmental light conditions. This article is protected by copyright. All rights reserved.

To examine whether the Janzen–Connell hypothesis is valid in temperate forests, we investigated the density, growth, mortality, and agents of mortality of seedlings and the density, size, and age of saplings of Prunus grayana Maxim. at three distances (0–3, 6–10, and 16–26 m) from conspecific adults in a temperate forest in Japan. An inoculation experiment was also conducted to test the host range of a leaf pathogen. The probability of mortality was highest at 0–3 m during the first 2 years of growth. Mortality mainly resulted from distance-dependent attack by two types of pathogen that caused damping-off epidemics and spot symptoms on leaves. The leaf pathogen was identified as Phaeoisariopsis pruni-grayanae Sawada, which infected many more seedlings of Prunus grayana than of the two other tree species tested in an inoculation experiment. The vertical and diameter growth was lowest at 0–3 m and highest at 16–26 m in both seedlings and saplings. As a result, the greatest number of large and older saplings was observed at 16–26 m. Our results demonstrate that the Janzen–Connell mechanism operates in a beech-dominated forest in the temperate region of Japan.

Prunus is a large and economically important genus with considerable morphological variation. The evolution of vegetative and reproductive characters are examined here by parsimony reconstruction on trees obtained from data of ITS, trnL-trnF, trnS-trnG, and 25 morphological characters of 37 species of Prunus and representatives of eight other genera of Rosaceae. Prunus grayana is supported as the sister species to the rest of Prunus and the common ancestor of Prunus is reconstructed as having deciduous and serrated leaves, leafy racemes and fruit with well-developed pericarp. All diagnostic characters used in classification of the raceme-bearing species show some degree of convergent evolution and do not reflect phylogenetic relatedness. Some character states, such as evergreen foliage and entire leaf margin, are likely adaptations to environments with higher humidity and mean temperature. However, these hypotheses need to be tested by including species formerly classified in genus Pygeum, which were not available for this study. A clade consisting of subgenera Prunus, Amygdalus, Emplectocladus and section Microcerasus (formerly in subgenus Cerasus) is characterized by having axillary buds organized in groups of three, two of which give rise to flowers or inflorescences and one to a vegetative shoot. Fruits with thin pericarps are common in Prunus but they arose more than once independently. Dry fruits also evolved more than once, and only in species of Prunus living in arid environments, suggesting that this feature is another example of adaptation. Maddenia hypoleuca is nested within Prunus and the morphological characters used to segregate it from Prunus have been misinterpreted or are also found in species of Prunus previously classified in genus Pygeum.

Simple sequence repeat (SSR) markers were developed for Prunus verecunda and Prunusgrayana to help understand the seed dispersal pattern of each species. We isolated and characterized nine microsatellite loci (four from P. verecunda and five from P. grayana). In P. verecunda, the number of alleles detected and the expected heterozygosity of five loci ranged from 11 to 24 and 0.59 to 0.92, respectively. In P.grayana, the number of alleles detected and the expected heterozygosity of five loci ranged from 4 to 14 and 0.62 to 0.86, respectively. These results show that the markers described here will be useful in studying the seed dispersal pattern of Prunus species.

Oviposition and larval development of Halyomorpha halys on Prunus grayana trees in a coppice were investigated in Akita Prefecture, in the northern part of Japan from 2001 to 2003. Overwintered adults were observed on the trees from early June to late July. Most of the females had mature eggs and egg batches were found on the leaves in early June. Many larvae were observed on the trees from mid-June to mid-September, and progeny adults after mid-August. In 2004, 2nd instar larvae were reared on fruits collected from P. grayana trees in the laboratory; the ratio of developing into 3rd instar (developmental ratio) was 25–40% in June to early July, and increased to more than 80% in late August with fruit maturation. P. grayana trees, which grow widely throughout Akita Prefecture, bear many fruits until mid-September. This suggests that P. grayana is certainly a main food source supporting H. halys reproduction, at least in Akita Prefecture.

Prunus grayana (subg. Padus) was found to serve as the uredinial-telial host of two distinct Tranzschelia species in Japan. Tranzschelia pruni-spinosae has been known to occur on P. grayana, and the other species was previously overlooked. The latter fungus was experimentally proven to form its spermogonial and aecial stages on Hepatica nobilis var. japonica f. variegata and f. magna. The fungus was similar in morphology and host relationships to Tranzschelia arthurii, whose spermogonial and aecial stages occur on H. nobilis var. acuta and uredinial and telial stages on Prunus serotina and Prunus virginiana (subg. Padus) and Prunus americana (subg. Prunophora) in North America. However, the spores at all stages in the life cycle of the Japanese fungus were significantly smaller than those of the North American fungus. Because of this, a new species, Tranzschelia asiatica, was proposed for the geographically separated fungus. This species is expected to occur in East Asia outside of Japan, but this is not yet confirmed. Key words: rust fungus, Uredinales, Rosaceae, Prunus, Ranunculaceae, Hepatica.

The effects of canopy gaps on seedling emergence and growth ofCornus controversa andPrunus grayana were studied in a 21-year-oldCryptomeria japonica plantation. The seeds of the two species were sown in December 1995 and their fate was followed until March 2000.P. grayana germinated in 1996, butC. controversa germinated in 1997. In both species studied, more than 70% of the seedlings survived in the forest edge until the end of the experiment, although none survived in the forest understory in the first growing season. In the gap, the survival rate was higher inP. grayana than inC. controversa. In this experiment, some trees were cut to enlarge the area of the gap, in which the growth rate increased markedly forC. controversa seedlings, but not forP. grayana seedlings after the cutting. These two species showed substantial differences in the patterns of seedling emergence, survival and growth in aCr. japonica plantation which had a canopy gap.

Two new phenolic glucosides, pruyanaside A and pruyanaside B, have been isolated from the heartwood of Prunus grayana . Their structures have been shown by the spectral evidence to be 2′-β- d -glucopyranosyloxybenzyl 2-(6- O -benzoyl-β- d -glucopyranosyloxy)benzoate and 2′-(6- O -benzoyl-β- d -glucopyranosyloxy)benzyl 2-β- d -glucopyranosyloxy-6-hydroxybenzoate.

In a chemical examination of the bark ofPrunus grayana, three new phenylpropanoid glucosides, grayanoside A, grayanoside B and grayanin, have been isolated. The structures of these compounds have been established to be 2-(4-hydroxyphenyl)ethyl-(6-O-feruloyl)-β- D -glucopyranoside, 2-(3,4-dihydroxyphenyl)ethyl-(6-O-feruloyD-β- D -gluco and (2R)-[(6-O-caffeoyl)-β- D -glucopyranosyloxy]benzeneacetonitrile, respectively, on the basis of the spectroscopic studies and the chemical evidence.

A caeomatoid rust fungus on Prunus grayana is proved to be an aecial anamorph of Blastospora itoana, whose uredinial and telial stages occur on Smilax nipponica and S. riparia. The Caeoma stage is determined as C. radiatum. Aciculate aeciospores and completely echinulate urediniospores separate B. itoana from B. smilacis with verrucose aeciospores and incompletely echinulate urediniospores.

A new bitter phenylpropanoid glucoside, 2-(4-hydroxyphenyl)-ethyl-(6- O -caffeoyl)-β- D -glucopyranoside and a new bitter tannin-related compound, 3,4,5-trimethoxybenzoyl-β- D -glucopyranoside, have been isolated together with known compounds, 2-(3,4-dihydroxyphenyl)-ethyl-(6- O -caffeoyl)-β- D -glucopyranoside, 2-(3,4-dihydroxyphenyl)-ethyl-β- D -glucopyranoside and 6- O -caffeoyl- D -glucopyranose, from the bark of Prunus grayana . The structures of these compounds have been established on the basis of spectroscopic studies and chemical evidence.

The cherry spruce rust caused by Thekopsora areolata (Fr.) Magnus results in significant losses in spruce seed production in the forest industry. The pathogen is present in Asia and Europe but absent from North America where it has been considered as a potential threat and listed as a quarantine organism by the United States Department of Agriculture. A comprehensive list and in-depth information regarding the alternate hosts of this pathogen are important for conducting epidemiological studies and for optimal disease control. Prunus padus L. is the main alternate host reported for T. areolata. In this study, we investigated the susceptibility of domestic and exotic Prunus spp. and other potential alternate host-plant species native to Scandinavia to T. areolata infection through a field survey and aeciospore inoculation experiments in the greenhouse and laboratory. No new susceptible species were found. In Sweden, a new record of Prunus grayana Maxim. with low susceptibility to T. areolata was found. In addition, we updated the list of currently confirmed alternate hosts of T. areolata according to field observations and inoculation results. Prunus padus and Prunus serotina Ehrh., as well as their hybrids and subspecies of Prunus padus, are highly susceptible, while Prunus depressa Pursh, Prunus grayana, Prunus spinosa L., and Prunus tenella Batsch are considered slightly susceptible.