Neofusicoccum parvum, a New Agent of Sequoia Canker and Dieback Identified in Geneva, Switzerland

Fungi were isolated in pure cultures from decaying giant sequoias in Geneva (Switzerland). Isolates were genetically identified by ITS rDNA sequencing. Young giant sequoia trees were artificially infected with a pure culture of Botryosphaeria parva. Henle-Koch’s Postulates demonstrated that Botryosphaeria parva was pathogenic to Sequoiadendron giganteum. When analysing the microorganisms associated to canker and dieback symptoms in a giant sequoias (Sequoiadendron giganteum) in Geneva, the fungus Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, teleomorph Botryosphaeria parva (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, was isolated, whereas such symptoms are commonly associated to Fusicoccum aesculi (teleomorph Botryosphaeria dothidea). These two fungal species belong to the same genus Botryosphaeria of the Botryosphaeriaceae family. Because Neofusicoccum parvum was causing cankers and diebacks in other woody species around the world, we extended the analysis to other trees displaying sequoia dieback symptoms in order to evaluate the involvement of Neofusicoccum parvum in such increasing symptoms in sequoias in Geneva. Dried twigs, trunk, and branch cankers from diseased trees were sampled on several distinct sites. From all samples, isolated fungi in pure cultures showed a phenotype typical of Botryosphaeriaceae species. Isolates were then genetically identified at the species level. Subsequently Neofusicoccum parvum was inoculated to young giant sequoia trees, re-isolated in pure culture from provoked symptoms, and re-identified to fulfil Henle-Koch’s postulates. The identification confirmed that Neofusicoccum parvum was present on all sites, while Fusicoccum aesculi was retrieved only once alone. The inoculation of Neofusicoccum parvum isolates on young sequoias demonstrated for the first time that this fungus was able to develop cankers in Sequoiadendron gigantean. Neofusicoccum parvum could, therefore, be the major cause for dying of giant sequoias in the Geneva Lake area.

Controle da podridão apical da goiaba com tratamentos alternativos em pós-colheita

Objetivou-se avaliar o efeito de produtos alternativos [fosfito de potássio, cloreto de cálcio, fécula de mandioca, 1-metilciclopropeno (1-MCP), etanol seguido de dicloro s. triazinatriona sódica dihidratada (etanol+cloro)] e de hidrotermia, isoladamente e em associação de dois tratamentos, na ocorrência da podridão apical e nas características cor da casca e firmeza da polpa de goiabas ‘Pedro Sato’. Os tratamentos foram avaliados em goiabas naturalmente infectadas, em três estádios de maturação, armazenadas a 22ºC por 8 dias. A eficácia das associações de tratamentos também foi avaliada após 8, 16 e 24 horas da inoculação de Fusicoccum aesculi, Neofusicoccum ribis e N. parvum nos frutos. A incidência da doença foi crescente com o estádio de maturação e inferior nas associações de tratamentos (hidrotermia/fécula, etanol+cloro/1-MCP e etanol+cloro/fécula). Nos frutos inoculados, comprovou-se a eficiência dos tratamentos no controle da doença, com uma maior eficiência da associação hidrotermia/fécula nas inoculações com Neofusicoccum spp. As associações de tratamentos controlaram de forma semelhante F. aesculi. A eficiência de controle decresceu com o aumentou do tempo entre a inoculação e o tratamento. A manutenção da qualidade das goiabas com as associações de tratamentos foram evidenciadas pelo atraso na mudança de coloração da casca e menor redução na firmeza.

First Report of Fusicoccum aesculi Causing Leaf Spots of Paeonia suffruticosa in Henan Province, China

Tree peony (Paeonia suffruticosa) is regarded as the national flower of China and is cultivated throughout the country. In early August 2010, a moderately severe leaf spot was observed on tree peony cultivated in a garden of Zhengzhou, Henan Province, where approximately 15% of trees were diseased. In 2011, a less damaging leaf spot was also observed in another area of the city with approximately 10% of trees diseased. Early symptoms appeared as small, round, pale-brown lesions on the leaves. Lesions expanded into 5- to 20-mm-diameter spots that were elliptical or irregular, brown to dark brown. A fungus was consistently isolated from the leaf spots on potato dextrose agar (PDA) in grey-black colonies, but produced few pycnidia. Black pycnidia were ostiolate, globose, papillate, formed in uniloculate or multiloculate stromata that were immersed in the leaf, and became erumpent at maturity. Conidiophores or conidiogenous cells were hyaline and cylindrical. Conidia were hyaline, granular, fusoid to ellipsoid, aseptate, with a sub-truncate base, and 20 to 28 × 4.5 to 7.5 μm (mean dimensions of 50 conidia: 24.5 × 5.2 μm). The pathogen was identified as Fusicoccum aesculi, anamorphic stage of Botryosphaeria dothidea, on the basis of morphology (2). The identity of the fungus was confirmed to be F. aesculi by DNA sequence analysis of the internal transcribed spacer (ITS) region (GenBank Accession No. JQ323001), which was 100% identical to those of other F. aesculi isolates (GenBank Accession Nos. GU997686.1 and GU723469.1) (1). Pathogenicity tests were done by inoculating each of 10 leaves on one 7-year-old tree with a mycelial plug (0.5 cm diameter) harvested from the periphery of a 7-day-old colony. An equal number of leaves on the same tree, serving as controls, were mock-inoculated with plugs of PDA medium. Inoculated leaves were covered with plastic for 24 h to maintain high relative humidity and incubated at about 25°C. The plugs were removed after 48 h. After 7 days, 80% of the inoculated leaves showed symptoms identical to those observed in the field under natural conditions, whereas controls remained symptom-free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was F. aesculi. Pathogenicity tests were repeated on the other two trees by the same methods with the same results. To our knowledge, this is the first report of F. aesculi infecting P. suffruticosa in China. References: (1) S. Mohali et al. Mycol. Res. 110:405, 2006. (2) B. C. Sutton. The Coelomycetes. CABI Publishing, New York, 1980.

Identification and Characterization of Botryosphaeria spp. Causing Gummosis of Peach Trees in Hubei Province, Central China

Peach (Prunus persica) is one of the most important and widely grown fruit trees in China; however, perennial gummosis on trunks and branches is a major problem in peach orchards of Hubei Province, one of the most important peach production areas of China. In order to identify the gummosis-causing agents, diseased trunks and branches were collected from 11 peach orchards in Hubei Province. Fungal isolates were obtained from these samples, yielding three species: Botryosphaeria dothidea (anamorph Fusicoccum aesculi), B. rhodina (anamorph Lasiodiplodia theobromae), and B. obtusa (anamorph Diplodia seriata). They were identified based on conidial morphology and cultural characteristics, as well as analyses of nucleotide sequences of three genomic regions: the internal transcribed spacer region, a partial sequence of the β-tubulin gene, and the translation elongation factor 1-α gene. Fusicoccum aesculi was found in all 11 orchards but L. theobromae was found only in Shayang County in the Jingmen region and D. seriata only in Gong'an County in the Jingzhou region. Via artificial inoculation using mycelia on wounded twigs or branches, these three species were all found to be pathogenic, causing dark lesions on the twigs and branches and, sometimes, gum exudation from diseased parts. Isolates of L. theobromae were the most virulent and caused the largest lesions and most copious gummosis, and D. seriata had less gum than the other two species. This report represents the first description of L. theobromae and D. seriata as causal agents of gummosis on peach in China.

Botryosphaeriaceae Species Associated with Avocado Branch Cankers in California

Members of the family Botryosphaeriaceae cause branch cankers and dieback on California avocado trees. More intensive pruning, a practice associated with high-density planting that is becoming more common in the California avocado industry, may increase the occurrence of branch canker. This study was undertaken to identify and characterize the Botryosphaeriaceae spp. involved in the branch canker disease complex in order to develop future management strategies. From 2008 to 2009, branch cankers were sampled from four or five trees from each of eight avocado groves in five California counties. Six Botryosphaeriaceae spp. were identified based on morphology as well as phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) and a partial sequence of the β-tubulin gene. These six species included Neofusicoccum australe, N. luteum, N. parvum, an unknown Neofusicoccum sp., Fusicoccum aesculi, and Dothiorella iberica. Members of the Botryosphaeriaceae were isolated from all avocado-growing regions sampled in California; however, incidence and distribution of species varied. This report is the first description of the isolation of D. iberica from avocado branch cankers in California.