Botryosphaeria ribis is a species of fungus in the family Botryosphaeriaceae. It is recognized as a plant pathogen that infects a wide range of woody hosts, causing cankers, dieback, and fruit rot.
Taxonomy
- Kingdom: Fungi
- Phylum: Ascomycota
- Class: Dothideomycetes
- Order: Botryosphaeriales
- Family: Botryosphaeriaceae
- Genus: Botryosphaeria
- Species: B. ribis
The species was originally described by (Peck) Sacc. in the late 19th century, with the epithet “ribis” referring to its association with plants of the genus Ribes (currants and gooseberries).
Morphology
- Teleomorph (sexual stage): Produces dark, globose to subglobose stromata on infected plant tissue. Within these stromata are immersed perithecia that release eight ascospores per ascus. Ascospores are hyaline, ellipsoid, and typically 5–10 µm in length.
- Anamorph (asexual stage): The asexual morph is often identified as Fusicoccum spp., producing hyaline, aseptate conidia on short conidiogenous cells.
Host Range and Symptoms
Botryosphaeria ribis has a broad host spectrum, including but not limited to:
- Fruit trees: Apple (Malus domestica), pear (Pyrus communis), peach (Prunus persica).
- Stone fruit and ornamental trees: Plum, cherry, and almond.
- Berry crops: Currants and gooseberries (Ribes spp.).
- Other woody plants: Walnut, oak, and eucalyptus.
Typical disease manifestations are:
- Cankers: Sunken, often elongated lesions on branches and trunks that may exude gum.
- Dieback: Progressive death of shoots and twigs distal to the infection site.
- Fruit rot: Soft, watery decay of fruits, especially under wet conditions.
Distribution
B. ribis has a cosmopolitan distribution, reported from North America, Europe, Asia, and parts of Oceania. Its prevalence is heightened in regions experiencing climatic stress (e.g., drought, temperature extremes) that predispose hosts to infection.
Disease Cycle
- Inoculum Sources: Overwintering pycnidia or stromata on dead woody material serve as primary inoculum.
- Dispersal: Ascospores are released during wet periods and disseminated by wind or rain splash.
- Infection: Wounds, lenticels, or natural openings permit spore entry.
- Colonization: The fungus colonizes the vascular cambium, leading to canker formation.
- Secondary Spread: Conidia produced in the asexual stage can cause secondary infections within the same growing season.
Management Strategies
- Cultural Controls: Prune and destroy infected branches during dormancy; maintain proper tree vigor through irrigation and balanced fertilization.
- Sanitation: Remove fallen infected debris to reduce inoculum reservoirs.
- Chemical Controls: Fungicide applications (e.g., protectants containing copper or systemic strobilurins) may be employed preventatively, especially in high‑risk orchards.
- Resistant Cultivars: Selection of less susceptible cultivars where available can mitigate impact.
Economic Impact
In commercial orchards, B. ribis can lead to significant yield reductions due to pre‑harvest fruit rot and post‑harvest quality loss, as well as increased costs associated with tree removal and replanting.
Research and Genomics
Molecular studies, including ITS rDNA sequencing, have been used to confirm species identity and elucidate phylogenetic relationships within Botryosphaeriaceae. Whole‑genome sequencing of related Botryosphaeria species provides insight into pathogenicity genes, though a complete genome for B. ribis remains limited.
Botryosphaeria ribis is a well‑documented fungal pathogen of woody plants, notable for its broad host range, worldwide occurrence, and capacity to cause economically important diseases in horticultural and forest systems.