Search

Two phenolic compounds were isolated from a filtrate of Valsa ambiensis. Their structures were determined to be a new compound (1) and scytalone (2) by spectroscopic methods. Both had an inhibitory effect on the growth of lettuce roots and hypocotyls.

Leucostoma species that are the causal agents of Cytospora canker of stone and pome fruit trees were studied in detail. DNA sequence of the internal transcribed spacer regions and the 5.8S of the nuclear ribosomal DNA operon (ITS rDNA) supplied sufficient characters to assess the phylogenetic relationships among species of Leucostoma, Valsa, Valsella, and related anamorphs in Cytospora. Parsimony analysis of the aligned sequence divided Cytospora isolates from fruit trees into clades that generally agreed with the morphological species concepts, and with some of the phenetic groupings (PG 1-6) identified previously by isozyme analysis and cultural characteristics. Phylogenetic analysis inferred that isolates of L. persoonii formed two well-resolved clades distinct from isolates of L. cinctum. Phylogenetic analysis of the ITS rDNA, isozyme analysis, and cultural characteristics supported the inference that L. persoonii groups PG 2 and PG 3 were populations of a new species apparently more genetically different from L. persoonii PG 1 than from isolates representative of L. massariana, L. niveum, L. translucens, and Valsella melastoma. The new species, L. parapersoonii, was described. A diverse collection of isolates of L. cinctum, L. persoonii, and L. parapersoonii were examined for genetic variation using restriction fragment length polymorphism (RFLP) analysis of the ITS rDNA and the five prime end of the large subunit of the rDNA (LSU rDNA). HinfI and HpaII endonucleases were each useful in dividing the Leucostoma isolates into RFLP profiles corresponding to the isozyme phenetic groups, PG 1-6. RFLP analysis was more effective than isozyme analysis in uncovering variation among isolates of L. persoonii PG 1, but less effective within L. cinctum populations. Isolates representative of seven of the L. persoonii formae speciales proposed by G. Defago in 1935 were found to be genetically diverse isolates of PG 1. Two large insertions, 415 and 309 nucleotides long, in the small subunit (SSU) of the nuclear rDNA of L. cinctum were identified as Group 1 introns; intron 1 at position 943 and intron 2 at position 1199. The two introns were found to be consistently present in isolates of L. cinctum PG 4 and PG 5 and absent from L. cinctum PG 6 isolates, despite the similarity of the ITS sequence and teleomorph morphology. Intron 1 was of subgroup 1C1 whereas intron 2 was of an unknown subgroup. RFLP patterns and presence/absence of introns were useful characters for expediting the identification of cultures of Leucostoma isolated from stone and pome fruit cankers. RFLP patterns from 13 endonucleases provided an effective method for selecting an array of diverse PG 1 isolates useful in screening plant germplasm for disease-resistance.

The ascomycete order Diaporthales includes a number of plant pathogenic fungi such as Cryphonectria parasitica, the chestnut blight fungus, as well as many asexually reproducing fungi without known...

Paravalsa indica gen. et sp. nov., a member of Valsaceae is described and illustrated. Its relationships with Valsa, Gnomoniella and Xenotypa are discussed.

A survey of stem fungi and associated canker diseases in eucalypts in natural forest and plantations was conducted in Tasmania. A total of 209 samples representing 29 fungal species was obtained. Thirteen of the fungal species detailed in this survey have not been described or previously reported in Australia. The three species most frequently encountered were Endothia gyrosa, Cytospora eucalypticola and Valsa sp., constituting 23.9%, 20.6% and 12.9%, respectively, of the 209 collections. They were ubiquitous, with each species found on more than ten eucalypt species. Fungal species with low incidence but associated with severe cankers were Harknessia cf. eucalypti, Phoma sp., Seiridium eucalypti and Zythiostroma sp.

The pyrenomycete genus Endoxyla (Ascomycotina, Clypeosphaeriaceae) is revised based on the examination of type and authentic material. Five species, E. macrostoma, E. munkii sp. nov., E. operculata, E. parallela and E. xanthostroma sp. nov., are included and a key to the species is given. Endoxyla macrostoma is designated as holotype. Sixteen species and one variety are excluded from Endoxyla and three species are treated as doubtful. The synonymy of Ceratostomella with Endoxyla is rejected and a new combination Ceratostomella hyalostoma is proposed. The taxonomic position of Endoxyla is discussed. The genus Endoxyla was established by Fuckel (1871) for stromatic species possessing immersed ascomata with stout, apically thickened necks, clavate asci, dark, aseptate ascospores and abundant, filiform paraphyses. He referred three species to the genus; Endoxyla macrostoma Fuckel, Sphaeria parallela Fr. and S. operculata Alb. & Schw. Saccardo (1882) formally combined the latter two species in Endoxyla and described the ascospores of E. parallela as aseptate. He included the genus in the section Allantosporae of the Sphaeriaceae, an artificial assemblage of pyrenomycetes characterized by their allantoid ascospores. Winter (1886) treated Endoxyla as a subgenus of Valsa Fr., which he placed in the Valseae. Ellis and Everhart (1892, 1894) maintained Endoxyla as a separate genus in this family and accepted E. macrostoma with aseptate ascospores, E. parallela with uniseptate ascospores, and four species with phragmosporous ascospores including E. fraxini (Ell. & Ev.) Ell. & Ev. Berlese (1902, 1905) included only species with aseptate ascospores in Endoxyla and transferred E. parallela to Endoxylina Romell. He considered Endoxyla to be related to Cryptosphaeria Grev. Von Hohnel (1915) removed the genus from the Valseae and treated Endoxyla as a subgenus

The results of a 10-year study on the mortality of Alnus incana in the Upper Silesia industrial region (Poland) are presented in this paper. Fungi which infected the trees at different stages of the disease were identified. The most common were: Cryptospora suffusa, Hypoxylon fuscum, Peniophora cinerea, P. erikssonii, Pezicula cinnamomea, Tympanis alnea, and Valsa diatrypa.

The following taxa described and illustrated from leaf litter of Laurus nobilis are new host records and new records for the British Isles: Anthostomella spartii, Massarina papulosa and Phacidium aquifolii . Notes are given on collections from Laurus nobilis leaf litter of Micropeltopsis ammophilae (J. P. Ellis) P. M. Kirk & Spooner comb, nov., Microthyrium fagi, Mollisia fuscidula, Mycosphaerella cfr vaccinii, Unguiculella sp. and Valsa coronata , all of which are new host records. Phacidium multivalve is recorded from decaying leaves of Hedera helix , and the anamorphs of this and P. aquifolii are discussed. In addition, a description is given of Mollisiopsis quercina (Sacc.) Spooner & P. M. Kirk comb. nov. and the combination Unguiculella foliicola (Graddon) Spooner & P. M. Kirk comb. nov. is proposed.

Solution of diethyl ether extracts from culture filtrate of Valsa ceratosperma, a causal agent of apple Valsa canker, grown in a medium containing apple bark components caused similar bark necrosis to the canker on naturally infected apple trees. Three toxic substances were purified from culture extracts by column chromatography and were identified by co-chromatography and by ultraviolet absorption spectra. The toxic substances included phloretic acid (p-hydroxypropionic acid), p-hydroxybenzoic acid and protocatechuic acid which are known to be breakdown products of phloridzin. In cut stem bioassay these compounds showed a toxicity only in high concentrations. The toxicities of the compounds were not host specific.

Tremella globospora Reid is described from 32 collections made in British Columbia. The fungus grows directly from within perithecia of species of Valsa and Diaporthe found, in this study, on hosts belonging to seven Angiosperm genera and three of Gymnosperm. Single-spore isolates were made from basidiocarps selected to represent as many variables as possible; both colors (yellow and white) of the basidiocarp, proximity of position on a single twig versus considerable distance between sites, both genera of pyrenomycete host, four genera of seed plants, and collection dates from January to September. Compatibility tests indicated a single species with a modified tetrapolar mating system typical of the genus Tremella. Selected dikaryotic isolates were grown in laboratory culture on simple media, and fertile basidiocarps were produced. Variation in size, color, and consistency of basidiocarps in culture was compared with those in field collections. Clamp connections, branching from the clamp cell, and other microstructures produced in culture are also described. No reaction of T. globospora to Valsa cultures or sterilized Valsa perithecia and extracts was observed.

The species of Valsa and Cytospora found on hardwoods in North America are reevaluated, based on morphological studies of type specimens, herbarium specimens, and fresh collections. Three sections are accepted in Valsa: sections Valsa, Monostichae Nits., and Cypri Urban, distinguished by the number, size, and arrangement of perithecia, the distribution of ostioles in the disc, and the size of ascospores. Four sections are accepted in Cytospora: sections Cytospora, Torsellia (Fr.) Gvrit., Cytophoma (Hoehn.) Gvrit., and Cytosporopsis (Hoehn.) Gvrit., based on the number and shape of the locules. Correlations between the teleomorphic and anamorphic sections Valsa–Cytospora, Monostichae–Torsellia, and Cypri–Cytophoma are reaffirmed. Six species of Valsa on North American hardwoods are accepted, and two new subspecies are proposed: V. ambiens subsp. ambiens and V. ambiens subsp. leucostomoides (Peck) Spielman. Six species of Cytospora are accepted.

リンゴ腐らん病病斑の進展の過程を時期別に病態組織学的に観察した。リンゴ樹の休眠期には,病原菌は樹皮組織内を単独の菌糸で進展し,菌糸進展部に先行した組織では細胞の収縮と軽微な褐変が認められた。5月にも単独菌糸が樹皮組織内を進展するが,菌糸進展部における寄主組織の褐変は顕著となった。気温が高くなるにつれて,組織の褐変はさらに顕著となり,健全組織との間の2∼3層から数10層の細胞壁はリグニン化し,さらにその外側に傷痍木栓組織が形成された。このような一連の変化によって,病原菌の菌糸は集合しやがて木栓組織を突破する。菌糸の集団的な樹皮組織の進展と木栓組織の新生が繰り返され,その結果,病斑の進展は緩慢になる。最も樹体活性の高い8月には菌糸の進展に対し寄主組織は速やかに反応し,3∼7層の厚膜コルク化細胞より成る木栓組織を形成し,これにより病原菌の進展はほぼ完全に阻止された。しかし,10月になると,罹病組織と木栓組織の間隙内で増殖した集塊状菌糸は木栓組織形成の不十分な部分から健全組織内へ再び進展した。リンゴ休眠期に人為的に樹皮に付傷した場合,5月中旬まで木栓組織の形成は認められないが,夏期に付傷したときは2週間後に木栓組織が形成された。すなわち,傷痍木栓組織の発達の速さや程度は季節によって著しく異なり,それによって発病およびその後の病斑進展が左右される。

Susceptibility of peach tree wounds infected with Cytospora canker to invasion by lesser peachtree borer (LPTB), Synanthedon pictipes (Grote & Robinson), was investigated. Treatments were 1) impact wounds on the scaffold limbs, 2) impact wounds treated with 1% naphthalene acetic acid (NAA) to induce gumming, and 3) impact wounds infected with Cytospora canker. Each treatment was made at three different times during spring 1983. Both date wounds were made and wound treatment had a significant effect on number of wounds becoming infested with LPTB. Wounds made in early April were less susceptible to infestation by borers than wounds made in late May; wounds made in late April were intermediate in susceptibility. Wounds infected with Cytospora at the beginning of the experiment were infested with LPTB earlier and to a greater extent than either untreated wounds or wounds treated with NAA. As the experiment progressed. many of the untreated or NAA-treated wounds that did not heal became infected with Cytospora , after which 35–38% of them were invaded by LPTB. In only one instance did a wound become infested with borers before its infection with Cytospora ; otherwise, establishment of borers either followed or, in a few cases, coincided with infection of wounds with the disease. Relationship of structure of Cytospora -infected wounds to LPTB egg deposition and larval entry is discussed. On smooth-barked, otherwise healthy peach trees, such as those used in this experiment, infection of wounds by Cytospora is important to the establishment and spread of LPTB infestations in peach orchards.

In a survey of peach canker in widely separated areas of southern Ontario, Valsa leucostoma Fr. was recovered more frequently and consistently than V. cincta and other suspect pathogens. V. cincta predominated on only a few varieties. While some evidence was found of a seasonal influence and of effects of maturity and varietal specificity on the relative frequency of Valsa species, inconsistencies occurred. Infection of nursery stock was established, and to a considerable extent this may determine the subsequent occurrence of canker fungi in infected trees. The pathogenicity of the two Valsa species was a function of temperature. At temperatures of 60 °F and above, V. leucostoma was more pathogenic than V. cincta on young trees. At temperatures below 50 °F the latter was more pathogenic. Coniothyrium fuckelii Sacc. proved weakly pathogenic, and Fusicoccum amygdali Delacr. was not a factor of canker in southern Ontario.

Numerous microorganisms, antagonistic toward canker fungi, Cytospora cincta Sacc. (Leucostoma cincta (Fr.) v.H.) and C. leucostoma (L. persoonii (Nit) v.H.) were recovered from the outer bark of peach. In unsterilized outer bark, fungi predominated in a population of antagonists that included bacteria and actinomycetes. In surface-sterilized outer bark, antagonistic bacteria predominated. A predominance of antagonists in the spring- and fall-infection periods suggests that they contribute to the control of canker. The important but relatively low proportion of strong antagonists in the microflora of resistant Standard Elberta and Sunhaven varieties may explain in part the prevalence of canker on all varieties of peach. Their absence in favor of weak antagonists on Dixired at this time may contribute to its higher susceptibility (canker counts) than that of Standard Elberta, Sunhaven, and Redhaven varieties.

Two species of Valsa have been isolated more or less consistently from cankers of various ages, and from "die-back" twigs on the peach. In culture, one species, identified as Valsa leucostoma (Pers.) Fr., is hair-brown and has small dark pycnidia exuding cirri when mature. On the host, its stroma is compact in texture, contains no host cells and is delimited beneath by a black zone of carbonized fungal and host cells. Ascospores of V. leucostoma measure 10–17 by 2–4.5 μ. The other species, which has been assigned to V. cincta Fr., is whitish to olive buff in culture and has large light-colored pycnidia containing, though rarely exuding, spores. On the host, the stroma of V. cincta is comparatively loose in texture, contains host cells and is delimited from the cortex of the host by a thin, black zone, sometimes only marginal. Ascospores of V. cincta measure 14–28 by 4–7 μ. In both species, the pycnospores range from 5 to 10 μ in length and 1 to 2 μ in width. These organisms, along with Sclerotinia fructicola (Wint.) Rehm., were used in series of infection experiments at frequent intervals over a period of two years. Similar series of checks were also provided. Periodical observations and measurements furnished detailed case histories of all wounds concerned. V. cincta was found to be a virulent wound-parasite, able not only to infect freshly made wounds during the late autumn, winter and spring, but also to give rise to perennial cankers. Infection with this organism rarely occurred during June, July and August. V. leucostoma proved in these experiments to be almost, if not quite, incapable of initiating cankers on the peach. S. fructicola parasitized the tissues of branches and produced considerable necrosis during the first three weeks after inoculation during the growing season. Subsequently the lesions proceeded to heal. The degree of infection and the amount of resultant necrosis in wounds inoculated with S. fructicola during the dormant season were dependent upon the conditions of temperature and humidity then prevailing. S. fructicola, while capable of inducing lesions on the stem, cannot be regarded as the cause of typical peach canker. Some of the factors influencing infection by the three organisms mentioned above are briefly discussed.

Innate resistance, described as the resistance of tissues under the outer bark of peach to perennial canker, Leucostoma cincta (Fr.) v. Hohnel (Valsa cincta), was unrelated to the field performance of Standard Elberta, Sun-haven, Redhaven and Dixired cultivars and unsuitable as an index of performance in the orchard. The physiological state of trees, the environment, and the kind and depths of wounds influenced the amount of infection and canker growth achieved. Appreciably higher percentage infection and canker growth were achieved at wounds made during the post-dormant period than during dormancy of trees. In dormant trees of three cultivars, resistance to infection was highest at cortex wounds. For Redhaven a relatively low resistance of the cortex to infection and canker growth suggested that minor injuries may play an important part in its field performance. In post-dormant trees of all cultivars, resistance to canker growth was highest at cortex wounds.

Valsa myinda Cooke and Ellis is correctly placed in the genus Valsa. The specimens described under the name Cryptodiaporthe myinda (Cooke and Ellis) Wehmeyer belong to a different species that is properly placed in the genus Cryptodiaporthe and for which there is no valid species name available. Cryptodiaporthe acerinum sp. nov. is therefore proposed for this fungus, with collections available from New York, New Jersey, West Virginia, and Ontario. All of the collections of these two species are on Acer.

Summary. 1 Diaporthe perniciosa, first isolated by Marchal from rots in stored fruits, has proved to be parasitic and one of the causes of “die back” in stone fruit trees. 2 The various strains of D. perniciosa isolated from “die back” on peach and different varieties of plums have proved to be parasitic, morphologically identical, and cause definite wilt and “die back” on peach, plum, apricot and nectarine. Cross inoculations of the same organisms on two year old wood of Prince of Wales plum have so far not brought about typical symptoms of “die back,” but considerable disturbance, accompanied by gumming, has occurred at the points of inoculation. A strain obtained from apricot, which shows morphological differences, has also been proved to be capable of causing “die back” on peach and apricot. All the controls remained healthy. 3 The progress of D. perniciosa in the host tissue is slow; infection occurs a considerable time, in some cases years, before any external symptoms appear. The mycelium permeates the internal tissues more especially the medullary rays, cortical tissues, phloem cambium, and vessels. 4 D. perniciosa has a pycnidial or Phomopsis stage with “a” and “b” spores, and a perithecial or Valsa stage with numerous eight-spored asci. The pycnospores emerge as whitish tendrils or globules through numerous lenticel-like slits in the bark; the perithecial necks are long and protrude mostly through the same slits as the tendrils, and the ascospores are given off either through the ostiolum at the tip of the neck of the perithecium, or may burst through any part of the neck. 5 The external symptoms are sunken areas and longitudinal slits in the bark; elongated strands of numerous lenticel-like transverse slits through which tendrils and perithecial necks emerge; rapid wilt and browning of the trees in summer, or premature yellowing and fall of the leaves in the autumn. 6 The internal tissues are discoloured and secondary thickening arrested. 7 The pycnidial stage occurs on living or more or less moribund bark, the perithecial stage on the parts which are dead. 8 D. perniciosa shows a certain degree of polymorphism on the host plant; on artificial media this polymorphism is much more marked. 9 The Phomopsis stage of D. perniciosa grows and sporulates well on artificial media, but perithecia develop sparingly in cultures from pycnospores. 10 Cultures of mass infections of ascospores of D. perniciosa have given rise in some cases to the Phomopsis stage with “a” and “b” spores; in others no “b” spores could be found. Mono-ascospore cultures develop the pycnidial stage very sparingly, and no “b” spores have been observed in any of the cultures. Large numbers of perithecia develop in mono-ascospore cultures on various media.

The sudden-death disease of the clove tree is invariably associated with the fungus Valsa eugeniae. The pathogenicity of this fungus has been investigated experimentally, and it has been shown that it is a primary parasite on mature clove trees, that saplings are resistant to it, and that seedlings are immune. It has been experimentally demonstrated that water-borne spores of the fungus can invade the absorbing and the fibrous roots of the clove tree. The slow-decline disease, which affects clove saplings only, is associated with a slow and progressive root-rot over a period of many years. Valsa is also invariably associated with this disease, which occurs only in areas which have been replanted after the previous stand has been killed by sudden death. It is thought that slow decline is the symptom-expression of Valsa attack on young trees when these still retain some measure of juvenile resistance to it.

An outbreak of balsam fir dieback in Ontario, which was first reported in 1954, reached its peak throughout the Province in 1955 and gradually receded during subsequent years. The dieback, which involved leaders, branches, and occasionally entire trees, appeared when those parts died as the result of their proximal invasion by a fungus. Cankering usually accompanies necrosis; fruiting bodies may be produced immediately or may not appear until the spring following canker formation. The three fungi most commonly found in association with dieback, Thyronectria balsamea (Cke. & Pk.) Seel., Dermea balsamea (Pk.) Seav., and Valsa abietis Fr., were shown to be independently capable of inducing typical dieback and cankering when inoculated into wounds on transplanted trees. It was further shown that adult balsam fir borer beetles (Monochamus spp.), which regularly feed on and injure twigs and branches of healthy trees, usually carry viable material of one or more of the three common fungi. The ability of the beetles to kill twigs was confirmed and it was shown that, although dieback frequently develops from wounds made by fungus-infested beetles, no dieback ensued in the absence of fungi. The outbreak is believed to have been caused by the interaction of several factors (climate, fungi, site, and insects) on the host trees.