Cephaleuros parasiticus
From Wikipedia, the free encyclopedia
| Cephaleuros parasiticus | |
|---|---|
.jpg) | |
| Cephaleuros parasiticus on guava | |
Scientific classification  | |
| Clade: | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Ulvophyceae |
| Order: | Trentepohliales |
| Family: | Trentepohliaceae |
| Genus: | Cephaleuros |
| Species: | C. parasiticus |
| Binomial name | |
| Cephaleuros parasiticus | |
Cephaleuros parasiticus is a plant pathogenic member of the chlorophyta, or green algae. It infects several commercially important crops including tea. Unlike the majority of pathogenic Cephaleuros species, it penetrates the epidermis of plants and is not constrained to subcuticular growth. It has sometimes been misidentified as Cephaleuros virescens.[1] Cortex penetration and the name red rust of tea are marked differentiators of C. parasiticus from its relative C. virescens, which does not penetrate the epidermis. It has been renamed several times as more phylogenetic information has become available.[2]
Symptoms and hosts
Cephaleuros parasiticus consists irregularly branching prostrate filaments, which form a round mass just underneath the epidermis of a leaf. From the prostrate filaments, a rhizoidal growth is produced which penetrates between the palisade cells and grows near the stomata.[3]
Sporangiophores (which bear the asexually reproductive structures) occur singly or in tufts of 3-7, leading to the death of the stomata which they grow near. They consists of four to 11 cells, with a terminal head cell that has numerous whorls of "sporangiate-laterals". Sporangiate-laterals contain the zoosporangia which produce zoospores. Gametangia are produced beneath the upper epidermis, and/or with the sporangiophores in the lower epidermis.[3]
One variety is known and is named var. nana. It differs from the typical variety (var. parasiticus) in that the lesions produced are more irregular, the sporangiophores are shorter (usually with two cells), and the head cells may produce an additional whorl of sporangiophores.[3]
Red rust is known to infect other plants, including mango, coffee, citrus, and guava. It should not be confused with either the fungal coffee leaf rust, a basidiomycete rust; or with coffee red leaf spot, caused by the related C. virescens. Similar symptoms and pathogenesis seem to be present on all hosts.[4]
Cephaleuros parasiticus can penetrate the epidermis, although spores more readily spread through wounds. It proceeds to invade the cortical tissue in the stem.[1] On the upper surface of the leaf, the spot is dark red-brown to purple-black, up to 25 mm in diameter. At first, the spot is yellow to green and irregularly cushion-like, but then becomes white from the dead epidermis cells. The lower surface of the spot is equally sized, with dark brown dead leaf tissue.[3] In leaves, the rust causes chlorosis and variegation, which might be surrounded by anthocyanescence.[5] In humid conditions, red-orange filamentous growth may emerge on wounds;[6] these are the crowded sporangiophores.[3] The most extreme symptoms produce necrotic patches on the stem.[7] Repeated infection cycles result in permanently reduced yields mortality, especially in younger plants.
Life cycle
The algae has a latent period of roughly a year following the initial infection of damaged tissue. After this time, it will begin fruiting during rainy periods. It disperses as both motile zoospores, and also through wind-borne sporangium. Wind and rain are mechanisms of this dispersal.[1]