Lambertella corni‑maris is a species of ascomycete fungus in the family Rutstroemiaceae, order Helotiales. It is the type species of the genus Lambertella and was first described in 1918 by Franz von Höhnel. The species is known primarily as a post‑harvest pathogen of apple fruits, where it causes a disease commonly referred to as “Lambertella rot” or “yellow rot.” It also exhibits mycoparasitic activity, antagonizing the brown‑rot pathogen Monilinia fructigena.
Taxonomy
- Kingdom: Fungi
- Division: Ascomycota
- Class: Leotiomycetes
- Order: Helotiales
- Family: Rutstroemiaceae
- Genus: Lambertella
- Species: Lambertella corni‑maris Höhn. (1918)
Morphological description
When growing on decaying fruit or in culture, L. corni‑maris produces apothecia that are positively phototropic. Immature apothecia are crater‑shaped, becoming saucer‑shaped and eventually flattening as they mature. Their coloration ranges from pale pink to dark brown, depending on age and environmental conditions. Apothecial diameters measured in the field are typically 1–5 mm on apples and 1.5–7.5 mm on pears.
The asci are shortly stalked, clavate, and inoperculate, averaging about 100 µm × 7.5 µm and containing eight ovoid ascospores. Spores are initially hyaline, turning dark brown at maturity, and each spore contains two vacuoles. Paraphyses are numerous, colorless, aseptate, and often equal to or exceed the number of asci.
In vitro, the fungus grows best on media containing glucose and peptone. Optimal growth occurs at pH 4.4 (range 1.6–8.3) and temperatures of 5 °C to 30 °C, with a growth optimum near 20 °C. No growth is observed at temperatures of 30 °C or higher.
Distribution
L. corni‑maris was originally isolated from mummified cherry fruits in Austria. Subsequent records indicate a distribution across western Europe, as well as occurrences in Japan and the Pacific Northwest region of the United States. Occasional reports also exist from other temperate regions, reflecting its association with stored fruit.
Ecology and pathogenicity
The fungus colonizes decaying fruit in the wild but becomes a significant post‑harvest pathogen when apples are wounded during harvest. Infection leads to brown, spongy lesions on the fruit surface, often accompanied by a thick, yellow mycelial growth. The pathogen secretes pectinase, facilitating cell‑wall degradation of the host tissue. In controlled inoculation experiments, non‑wounded apples did not develop disease, indicating that wounds are a primary entry point.
L. corni‑maris also displays antagonistic behavior toward other fungi, notably Monilinia fructigena. It produces secondary metabolites known as lambertellols A and B, which inhibit the germination of M. fructigena hyphae. Under acidic conditions, these compounds are stable and can be converted to lambertellin, further suppressing the competing pathogen. This mycoparasitic activity may contribute to the ecological dynamics of fruit rot diseases and has been implicated in observed strain divergence of M. fructigena in different geographic regions.
Host range
While apples are the principal commercial host, laboratory studies have demonstrated that L. corni‑maris can cause rot on pears, plums, quinces, oranges, lemons, turnips, and parsnips. The fungus does not typically infect young wood of apple, pear, cherry, or plum when inoculated directly.
Economic relevance
Lambertella rot can lead to significant post‑harvest losses in apple production, particularly in regions where the fungus is established. Management strategies focus on minimizing fruit wounds during harvest, maintaining appropriate storage temperatures (below the growth optimum), and applying fungicides where effective. Research continues to evaluate the pathogen’s sensitivity to various fungicidal compounds.
References
(Information summarized from peer‑reviewed literature and the Wikipedia article on Lambertella corni‑maris.)