''Helicobasidium longisporum'' (syn: H. ''mompa'') is a

Basidiomycete Basidiomycota () is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basi ...

fungal pathogen of plants, which is the cause of violet root rot. The name Violet root rot refers to the dark purple color of the

mycelial Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...

mats formed on the infected plants, usually at or below the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

line. It can cause total rot and structural failure of roots and subterranean storage organs. Impact of violet root rot on crop loss is often due to stunting of above ground plant growth and decreased vigor, and in extreme cases, whole plant death. It does not directly infect above ground organs. Violet root rot can also damage or cause the death of subterranean storage organs such as potato

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

s or carrots.

Disease cycle

''Helicobasidium longisporum'' is a

soil borne pathogen A soil borne pathogen is a disease-causing agent which lives both in soil and in a plant host, and which will tend to infect undiseased plants which are grown in that soil. Common soil borne pathogens include ''Fusarium'', ''Pythium'', ''Rhizoctoni ...

. The pathogen overwinters both as

sclerotia A sclerotium (; (), is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until favor ...

and via mycelium;

basidiospore A basidiospore is a reproductive spore produced by Basidiomycete fungi, a grouping that includes mushrooms, shelf fungi, rusts, and smuts. Basidiospores typically each contain one haploid nucleus that is the product of meiosis, and they are pro ...

s are not known to play a significant role in the disease cycle. Fall sclerotia production is initiated by nutrient deficits, in the early growing season when the host and moisture are present again the sclerotia will resume growth and infection of the host. Sclerotia are dispersed through movement in

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...

or rain water, particularly of note where flood irrigation is used. ''H. longisporum'' will grow as an independent, whitish mycelium for the first part of the growing season, gradually darkening from pink to a dark violet brown as infection progresses mid-season. Infection occurs via an external infection cushion from which penetrating

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 or ...

e infest the

lamellae Lamella (plural lamellae) means a small plate or flake in Latin, and in English may refer to: Biology * Lamella (mycology), a papery rib beneath a mushroom cap * Lamella (botany) * Lamella (surface anatomy), a plate-like structure in an animal * ...

of root tissues, where it causes damage. The dark pigment found in ''H. longisporum'' is helicobasidin and can be toxic to some plants and microorganisms.

Hosts and symptoms

The most indicative sign is the presence of dark fungal mats on the effected plant’s roots and stem near the soil line, and the presence of mycelium on the soil. ''H. longisporum'' is an opportunistic parasite of subterranean plant organs. Symptoms of infection include foliage

chlorosis In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

, premature

abscission Abscission () is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a ...

, wilting, and severe reduction of root mass. Infected soil may be identified by the conspicuous nature of the webbed mycelium, which transitions from white to dark violet over the growing season. It is not highly specialized and infects a wide range of hosts, among them including

apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

(''Malus domestica),''

mulberry ''Morus'', a genus of flowering plants in the family Moraceae, consists of diverse species of deciduous trees commonly known as mulberries, growing wild and under cultivation in many temperate world regions. Generally, the genus has 64 identif ...

(''Morus spp.)'',

Grape A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus ''Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters. The cultivation of grapes began perhaps 8,000 years ago, ...

s (''Vitus spp.)'',

Potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

(''Solanum tuberosum)'',

Plum A plum is a fruit of some species in ''Prunus'' subg. ''Prunus'.'' Dried plums are called prunes. History Plums may have been one of the first fruits domesticated by humans. Three of the most abundantly cultivated species are not found i ...

(''Prunus spp.)'', Tea,

beets The beetroot is the taproot portion of a beet plant, usually known in North America as beets while the vegetable is referred to as beetroot in British English, and also known as the table beet, garden beet, red beet, dinner beet or golden beet ...

soy The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu and ...

, and

cotton Cotton 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 cellulose, and can contain minor perce ...

. It is suspected to infect many more hosts and is not selective.

Management

This disease is not highly present outside of China, Japan, India, the Korean Peninsula and Taiwan, and is mostly controlled through cultural means. Resistant varieties can be an effective method to stifle disease progress, as well as early maturing annual crops which avoid infection altogether. Harvesting before the fungus has a chance to infect the crop is also a viable option. As

cereal A cereal is any Poaceae, grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, Cereal germ, germ, and bran. Cereal Grain, grain crops are grown in greater quantit ...

grains are not affected by ''H. longisporum'', long

rotations Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...

with grains can reduce incidence. The fungus requires ample moisture, warm soil temperatures (20-30 °C) and low pH to thrive, drip irrigation and regular

lime Lime commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Botany ...

applications can serve to reduce the fungal presence.

References

{{DEFAULTSORT:Helicobasidium Longisporum Fungal plant pathogens and diseases Teliomycotina Fungi described in 1917