''Magnaporthe salvinii'' is a

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

known to attack a variety of grass and rice species, including ''

Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yan ...

'' (Asian rice) and ''

Zizania aquatica Wild rice, also called manoomin, Canada rice, Indian rice, or water oats, is any of four species of grasses that form the genus ''Zizania'', and the grain that can be harvested from them. The grain was historically gathered and eaten in both ...

'' (wild rice). Symptoms of fungal infection in plants include small, black, lesions on the leaves that develop into more widespread leaf rot, which then spreads to the stem and causes breakage. As part of its life cycle, the fungus produces

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 ...

that persist in dead plant tissue and the soil. Management of the fungus may be effected by

tilling Tilling can mean: * Tillage, an agricultural preparation of the soil. * TILLING (molecular biology) * Tilling is a fictional town in the Mapp and Lucia novels of E. F. Benson. * Tilling Green, Ledshire, is a fictional village in Patricia Wentwo ...

the soil, reducing its nitrogen content, or by open field burning, all of which reduce the number of sclerotia, or by the application of a

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

Hosts and symptoms

''Magnaporthe salvinii'' (

teleomorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

)'','' also known as ''Sclerotium oryzae'' (

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an ase ...

) and ''Nakataea sigmoidae'' (anamorph)'','' is an

ascomycete Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...

fungal

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

that affects several rice and grass species, including: '' Echinochloa colona'', jungle rice ''Oryza sativa'', common rice ''Zizania aquatica'', annual wild rice '' Zizaniopsis miliacea'', giant cutgrass various turf grasses The first symptom that typically appears is a small, black, irregular lesion on the leaf sheath. Next, the lesion grows and penetrates the inner sheath until the leaf sheath becomes partially or totally rotted. The culm of the plant then shows black or brown discoloration and begins to shrivel. When the plant reaches maturity, the stem breaks due to the weakened, rotted stem. Sclerotia may be seen developing within the dead tissue of the rotted stem.

Disease cycle

''Magnaporthe salvinii'' is an

fungus that infects a plant in a polycyclic manner, through

conidia A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to the ...

that are teardrop-shaped. Once a conidium lands on a leaf, it sticks to the leaf surface and generates a

germ tube A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination. The germ tube differentiates, grows, and develops by mitosis to create somatic hyphae.C.J. Alexopolous, Charles W. Mims, M. Blackwell, ''Introductory Myc ...

, appressorium, and penetration peg to bore through the cuticle of the plant. From there, the penetration peg forms a branched feeding structure analogous to

haustoria In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates t ...

formed in other fungi. As lesions form on the host plant, the pathogen continues to produce

conidiophores A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to ...

and conidia that may be dispersed by rain splash to infect more plants. When conditions become unfavorable, the fungus overwinters in sclerotia inside the dead host plant tissue, or within the soil. The sclerotia can be dispersed through soil by rain and water irrigation. Moist, humid conditions, and high nitrogen fertilization are favorable conditions for the sclerotia, which germinate in wet areas of the leaf or sheath. Once the sclerotia germinate, the

mycelium 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 ...

infects the plant through wounds or natural openings in the plant. Then the fungus produces conidia and repeats its life cycle.

Management

One form of control for this pathogen is

the field to reduce the number of sclerotia. Maximum tilling of the field significantly reduces the viability of the sclerotia in the soil compared to minimum and no tillage. Another useful method of eliminating sclerotia in soil is by open field burning; however, overuse of this method in some areas requires additional practical interventions. Other forms of management to reduce the number of sclerotia are

swathing A swather (North America), or windrower (Australia and rest of world), is a farm implement that cuts hay or small grain crops and forms them into a windrow for drying. They may be self-propelled with an engine, or drawn by a tractor and po ...

and fall incorporation with winter flooding. Additionally, restricting the amount of nitrogen fertilizer added to the soil will reduce germination of sclerotia, since they favor high nitrogen soil. Lastly, an important means of control of this fungal pathogen is the use of fungicide. Quadris is one specific commercial fungicide that is capable of killing ''Magnaporthe salvinii''.

References

External links

Index Fungorum

USDA ARS Fungal Database
Fungal plant pathogens and diseases Rice diseases Magnaporthales {{plant-disease-stub