Lambertella corni-maris

Lambertella corni-maris was first described in 1918, and named for Lambert Gelbenegger.[4] The genus Lambertella was created for the discovery of L. corni-maris.[3]

When found on apples or grown on rotting fruit in the lab, L. corni-maris forms apothecia. The apothecia are positively phototropic, though light does not affect growth.[3] They vary in shape and color depending on maturity. They begin crateriform, then saucer-shaped, then flatten as they mature. They range from pale pink to dark brown, varied by location and age.[1] Apothecia found on apples ranges from 1 to 5 mm, while those found on pears ranged from 1.5 to 7.5 mm.[1]

Asci are shortly stalked, clavate, and inoperculate.[1][3] The average size of asci is 100 x 7.5 μm.[1] Asci contain eight ovoid spores, which begin colorless, and turn dark brown as they mature. Spores are unicellular and contain two vacuoles.[1] Paraphyses are colorless, aseptate and unbranched, and numerous, either equal to or exceeding the number of asci.[1][3]

Lambertella corni-maris has several unique features noted when grown on agar. Its most favorable medium contains glucose and peptone as sources of carbon and nitrogen.[1] Optimum pH for growth is 4.4, though growth occurs from pH 1.6-8.3.[1] The species tends to grow towards areas higher in acidity.[1] It can grow in temperatures ranging from 5° to 30° C, and the optimum temperature is 20° C.[1][5] No growth occurs at 30° C or above.[6] While it is most often found on apples in the wild, under lab conditions it can cause disease on the fruits of pear, plum, quince, orange, lemon,[2] as well as turnip and parsnip.[1] It did not attack when inoculated in young wood of apple, pear, cherry, and plum.[1]

Lambertella corni-maris was first discovered in Austria on cherry fruits.[7] It is distributed throughout western Europe, and has also been noted in Japan, and the Pacific northwest United States.[1][2][3][5][6]

Lambertella corni-maris causes the disease postharvest rot, found most often on apples. Several proposed names for this disease are yellow rot,[2] or Lambertella rot.[6] It likely infects fruit through wounds that occur during harvest,[6] as in the lab, non-wounded apples did not develop yellow rot.[2] The excretion of the cell wall degrading enzyme pectinase allows L. corni-maris to attack fruits.[1] It causes brown spongy lesions on apple fruits, and may also grow thick yellow mycelia.[2]

Lambertella corni-maris displays antagonism to many species of fungi and bacteria.[7] It can live alone as an apple fruit pathogen, but will also replace Monilinia species on fruit.[5] L. corni-maris displays allelopathic activity against Monilinia fructigena, which is a species that causes brown rot on apples.[5] In this interaction, L. corni-maris secretes the antibiotic lambertellols A and B.[5] The lambertellols are produced both in the presence and absence of the host M. fructigena.[7] Lambertellol production also increases under acidic conditions, or in the presence of M. fructigena, which has been found to make its surroundings acidic.[7] Lambertellols A and B inhibit hyphal germination of M. fructigena.[8] In acidic conditions, lambertellols A and B become stable, allowing them to diffuse towards the host. A and B then decompose into lambertellin, which inhibits the host and allows infection by L. corni-maris.[9] This interaction has been reported to occur on potato sucrose agar and on apple fruits.[9] The antagonistic biotic environment caused by L. corni-maris may have driven genetic divergence between Japanese and European strains of M. fructigena[10].