Cephaleuros parasiticus
A plant-pathogenic green alga causing red rust of tea.
Cephaleuros parasiticus is a plant pathogenic green alga (Chlorophyta) that causes red rust disease in several commercially important crops, most notably tea. It is notable for penetrating the epidermis of host plants, a trait that distinguishes it from most other pathogenic Cephaleuros species, which are limited to subcuticular growth. The alga has sometimes been misidentified as Cephaleuros virescens, but its ability to invade cortical tissue and produce red rust symptoms sets it apart.
Quick Facts
- Genus
- Cephaleuros
- Species
- parasiticus
Facts from the source article.
Lore & Background
Cephaleuros parasiticus consists of irregularly branching prostrate filaments that form a round mass just beneath the leaf epidermis. From these filaments, rhizoidal growth penetrates between palisade cells and grows near stomata. Sporangiophores, which bear asexual reproductive structures, occur singly or in tufts of 3–7 and cause the death of stomata. Each sporangiophore has 4–11 cells with a terminal head cell bearing whorls of sporangiate-laterals containing zoosporangia. Gametangia are produced beneath the upper epidermis or alongside sporangiophores in the lower epidermis. One variety, var. nana, differs from the typical variety by producing more irregular lesions, shorter sporangiophores (usually two cells), and an additional whorl of sporangiophores on the head cell.
Reader's Guide
The significance of Cephaleuros parasiticus lies in its increasing economic impact on tea plantations, particularly in the Indian subcontinent and Sri Lanka, and to a lesser extent in China. It can necessitate large-scale replanting, and up to one-quarter of tea plantations in Bangladesh may be affected. The alga has been a recognized concern since at least 1907. Management is challenging because detergents and fungicides are mostly ineffective. Copper-based fungicides sprayed up to three times during summer, especially during sporulation, can control the disease. A mixture of urea and muriate of potash, applied via spraying, reduces severity, and potash combined with bordeaux spraying has been shown to lessen yield losses. Tolerant cultivars are under development, but no resistant cultivars exist. Cultural practices such as eliminating weed shade and maintaining soil health are important. Mechanical harvesters increase losses by wounding plants, which facilitates pathogenesis. Pruning infected branches aids recovery.
Did You Know?
- Cephaleuros parasiticus penetrates the plant epidermis, unlike most pathogenic Cephaleuros species that are limited to subcuticular growth.
- The alga has a latent period of roughly a year before fruiting during rainy periods.
- It disperses via both motile zoospores and wind-borne sporangia.
- One variety, var. nana, has shorter sporangiophores (usually two cells) and produces more irregular lesions.
Frequently Asked Questions
What is Cephaleuros parasiticus?
It is a green algal pathogen (Chlorophyta) that infects host plants and triggers a condition known as red rust, with tea being its most economically significant target crop.
How does Cephaleuros parasiticus differ from other Cephaleuros species?
Unlike most relatives in the genus, which only grow beneath the cuticle, this species actually breaches the epidermis and invades deeper cortical tissue, making it a true penetrating pathogen rather than a surface dweller.
What kind of lesions does Cephaleuros parasiticus produce on its hosts?
Infected plants develop characteristic red rust symptoms, with individual lesions reaching up to 25 mm in diameter, and the disease can take roughly a full year to manifest after initial infection.
What are the key morphological features of Cephaleuros parasiticus?
Its sporangiophores are composed of 4 to 11 cells and cluster in tufts of either a single sporangiophore or groups of 3 to 7. The species is further divided into two recognized varieties: var. parasiticus and var. nana.
When was Cephaleuros parasiticus first formally described, and has it been confused with other species?
The earliest publication describing this species dates back to 1907, though it has at times been misidentified as Cephaleuros virescens before its distinct ability to invade cortical tissue and produce red rust symptoms was properly recognized.
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