''Pythium graminicola'' is a

plant pathogen Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

infecting

cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...

Host and symptoms

''Pythium graminicola'' infects a wide range of hosts, including:

bent grass ''Agrostis'' (bent or bentgrass) is a large and very nearly cosmopolitan genus of plants in the grass family, found in nearly all the countries in the world. It has been bred as a GMO creeping bent grass. Species , Plants of the World Onlin ...

turmeric Turmeric (), or ''Curcuma longa'' (), is a flowering plant in the ginger family Zingiberaceae. It is a perennial, rhizomatous, herbaceous plant native to the Indian subcontinent and Southeast Asia that requires temperatures between and high ...

cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...

barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...

wheat Wheat is a group of wild and crop domestication, domesticated Poaceae, grasses of the genus ''Triticum'' (). They are Agriculture, cultivated for their cereal grains, which are staple foods around the world. Well-known Taxonomy of wheat, whe ...

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

bean A bean is the seed of some plants in the legume family (Fabaceae) used as a vegetable for human consumption or animal feed. The seeds are often preserved through drying (a ''pulse''), but fresh beans are also sold. Dried beans are traditi ...

pea Pea (''pisum'' in Latin) is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name ''Pisum sativum' ...

s, and

sugarcane Sugarcane or sugar cane is a species of tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with stout, jointed, fib ...

. In particular ''Pythium graminicola'' is an important pathogen of graminaceous plants. As with many '' Pythium'' diseases, the most common symptom of ''Pythium graminicola'' is root/seed rot, which can then cause

damping off Damping off (or damping-off) is a horticultural disease or condition, caused by several different pathogens that kill or weaken seeds or seedlings before or after they germinate. It is most prevalent in wet and cool conditions. Symptoms There ar ...

. However, ''Pythium graminicola'' can also infect above ground tissue causing stalk rot in

maize Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

, foot rot of beans, leaf blight of grasses and feeder root necrosis in rice, sugarcane and maize. Diagnosis of ''Pythium graminicola'' can be made through observation of the above symptoms and the presence of

oomycete The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

structures, such as

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

Disease cycle

The life cycle of ''Pythium graminicola'' is essentially the same as the generalized ''Pythium'', soil borne pathogen life cycle. In the sexual state of ''Pythium graminicola'' an

antheridium An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. The androecium is al ...

and an

oogonium An oogonium (: oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. In the mammalian fetus Oogonia are formed in large ...

combine to make an oospore. An oospore has a thick

cell wall A cell wall is a structural layer that surrounds some Cell type, cell types, found immediately outside the cell membrane. It can be tough, flexible, and sometimes rigid. Primarily, it provides the cell with structural support, shape, protection, ...

and can survive and overwinter either in the soil or on plant debris. These oospores act as the primary innoculum by remaining dormant for up to ten years and the germinating when conditions are right. Oospores can be disseminated by wind, or, if in the soil, can infect host seedlings causing systemic infection. The oospores that infect plants then create sporangia, the asexual state of ''Pythium graminicola'', which acts as a secondary innoculum, making the disease cycle polycyclic. Sporangia can be disseminated by wind and produce

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s, which act as the infection agent. Zoospores can swim a short distance in water using

flagellum A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

helping them to reach the host plant. Zoospores infect the host plant by adhering to the plant surface and then germinating into the host plant with

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...

e. ''Pythium'' infects and spreads through roots very fast. Penetration occurs quickly, and the cell wall does not act as an important barrier to keep ''Pythium graminicola'' from infecting the plant.

Management

There are several current practices used to manage ''Pythium graminicola'', including: chemical control,

biological control Biological control or biocontrol is a method of controlling pests, whether pest animals such as insects and mites, weeds, or pathogens affecting animals or plants by using other organisms. It relies on predation, parasitism, herbivory, or o ...

, use of genetic resistance, and control through cultural practices. Chemical control involves using specific pesticides such as benomyl, captafol, captan, carboxin, metalaxyl, propamocarb hydrochloride, and etridiazole to try and kill surviving oospores in the soil. Seeds can also be dipped into chemicals to protect them from seed rot and avoid damping off. Biological control involves using microorganisms that protect the plant roots by producing antifungal metabolites and competing with the pathogen for nutrients. There are already commercially available biological control products for ''Pythium'' root rot created from isolates of '' Trichoderma'' spp. and '' Gliocladium'' spp., which are antagonists of ''Pythium''-induced soil-borne diseases. Genetic resistance involves finding species of plant that are not susceptible to ''Pythium graminicola''. Cultural practice is a broad category that essential includes any practice that does not use the above controls methods. An example of cultural practice is avoiding growing crops in environments that the disease thrives in. Another example would be using

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by Decomposition, decomposing plant and food waste, recycling organic materials, and man ...

s with specific compositions, such as composts prepared from brewery sludge, Endicott biosolids, and some animal

manure Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nut ...

s, to suppress damping-off and root rot.

References

{{Taxonbar, from=Q7263880 Water mould plant pathogens and diseases Cereal diseases graminicola Oomycete species Protists described in 1928