Macrophomina phaseolina

Macrophomina phaseolina
Macrophomina phaseolina spores growing on Pinus
Scientific classification
Kingdom: Fungi
Division: Ascomycota
Class: Dothideomycetes
Order: Botryosphaeriales
Family: Botryosphaeriaceae
Genus: Macrophomina
Species: M. phaseolina
Binomial name
Macrophomina phaseolina
(Tassi) Goid. (1947)
Synonyms

Botryodiplodia phaseoli (Maubl.) Thirum. (1953)
Dothiorella cajani (Syd., P.Syd. & E.J.Butler) Syd., P.Syd. & E.J.Butler (1925)
Dothiorella phaseoli (Maubl.) Petr. & Syd. (1927)
Dothiorella philippinensis (Petr.) Petr. (1927)
Fusicoccum cajani (Syd., P.Syd. & E.J.Butler) Samuels & B.B.Singh (1986)
Macrophoma cajani Syd., P.Syd. & E.J.Butler (1916)
Macrophoma corchori Sawada (1916)
Macrophoma phaseoli Maubl. (1905)
Macrophoma phaseolina Tassi(1901)
Macrophoma sesami Sawada (1922)
Macrophomina phaseoli (Maubl.) S.F.Ashby, (1927)
Macrophomina philippinensis Petr. (1923)
Rhizoctonia bataticola (Taubenh.) E.J.Butler, (1925)
Rhizoctonia lamellifera W.Small (1924)
Sclerotium bataticola Taubenh. (1913)
Tiarosporella phaseoli (Maubl.) Aa (1977)
Tiarosporella phaseolina (Tassi) Aa (1981)

Macrophomina phaseolina is a Botryosphaeriaceae fungus that is a plant pathogen that causes charcoal rot on many plant species including Zea mays and Pinus elliottii.

Occurrence, distribution and symptoms

Macrophomina phaseolina (Tassi) Goidanich causes seedling blight, root rot, and charcoal rot of more than 500 crop and non-crop species (Smith and Carvil 1977). It has a very wide distribution covering most of the tropics and subtropics, extending well into temperate zones having occurrence as far north as the United Kingdom and as far south as New Zealand (Songa 1995). It is an important pathogen of crops particularly where high temperatures and water stress occurs during the growing season. The typical symptoms of the disease are like those described by Smith and Carvil (1977) for soybean: “In soybean, charcoal rot disease symptoms appear in midsummer during high temperature and low soil moisture when the plant is stressed. Initial infections occur at seedling stage but remain latent until the soybean plant approaches maturity. Plants may wilt and die. Sloughing of cortical and tap root tissues occur with characteristic black speckled appearance due to the presence of sclerotia.” Necrotic spots may also appear on the leaves of some plants due to a translocatable toxin (Chan and Sackston 1973, Day 1993) that may be responsible for the rot symptoms sometimes without being able to see other signs. Such toxins from cultures and diseased plants have been shown to produce typical rot symptoms (Dhingra and Sinclair 1974, Day 1993).

Signs of the disease

The disease is well characterised by the presence of numerous black microsclerotia varying from 100 μm to 1 mm in stems, leaves and roots and 50 μm -300 μm in culture (Holliday 1980). Under the microscope they appear as round to ovate black dots which, when lighted from above, have relatively large, smooth, rounded bumps on their surface, a bit like an artichoke. Clear images of microsclerotia were obtained by using optical and electron microscopes.

M.phaseolina by Scanning Electron Microscope (SEM).
M.phaseolina germination (SEM).
New Hyphae of M.phaseolina. Lens: 100x oil immersion.
Close up of M.phaseolina. Lens: 40x.

The mature sclerotia (sclerotia are a special type of spore) are jet black and do not transmit light, hence the SEM.

Pycnidia may also sometimes be seen. These are black and globose varying from 100 μm to 250 μm in length with a truncate ostiole (Dhingra and Sinclair 1978, Mihail 1992), the spores of which are pointed at one end. The hyphae are septate, usually containing numerous vesicles.

Nomenclature

The Nomenclature already given looks good it similar apart from a few prefixes . This work was done in 1997 and the changes will be as a result of updates. These changes need to be verified. What follows is an explanation of how it goes. M. phaseolina is of the deuteromycetes, the ‘fungi imperfecti’ normally being without an observable sexual stage, but many such fungi have been shown to be anamorphs with sexual teleomorphs so they are generally grouped as mitosporic fungi (Hawksworth et al. 1995). In the case of M. phaseolina a teleomorph has been described as Orbilia obscura by Ghosh, Muckerji & Basak 1964 (Holliday 1980) but this has not been confirmed (Mihail 1992). Mitosporic fungi are Coelomycetes (enclosed conidia) so for M. phaseolina it goes something like this:

Fungi; Mitosporic fungi (Coelomycetes); Sphaeropsidales (pycnidial); Sphaerioidaceae; Macrophomina Petrak; Macrophomina phaseolina (Tassi) Goid. Synonyms historically are: Macrophoma phaseolina Tassi (1901), Macrophoma phaseoli Maubl. (1905), Sclerotium bataticola Taub (1913), Rhizoctonia bataticola (Taub) Briton-Jones (1925), Macrophomina phaseoli (Maubl.) Ashby (1927), Macrophomina phaseolina (Tassi) Goid. (1947). (From Day 1993). Some of these are still in use along with the present convention of Macrophomina phaseolina (Tassi) Goid. (1947) but are more likely to be seen in some of the older literature on the subject.

Decoding the genome

The genome of Macrophomina phaseolina has been sequenced.. Macrophomina was the source of the first endoglucanase genes cloned from a plant pathogenic fungus. Cloning and expression provided the first evidence that plant pathogenic fungal endoglucanases can lack the linker and cellulose binding domains found in saprophyte encoded endoglucanases.[1][2]

External links

References

  1. Wang, Haiyin; Jones, Richard (1995). "A unique endoglucanase-encoding gene cloned from the phytopathogenic fungus Macrophomina phaseolina.". applied and Environmental Microbiology 61: 2004–2006.
  2. Wang, Haiyin; Jones, Richard (1995). "Cloning, characterization and functional expression of an endoglucanase-encoding gene from the phytopathogenic fungus Macrophomina phaseolina.". Gene 158: 125–128.

Songa, A.(1995). Variation and Survival of Macrophomina phaseolina in Relation to Screening Common Bean (Phaseolus vulgaris L.) for Resistance. A. Songa. PhD thesis. pp 7-32, 89-90. University of Reading 1995.

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