''Mycosphaerella musicola'' is a

fungal 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 ...

plant pathogen, which is the causal agent of Yellow Sigatoka

leaf spot A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesion ...

disease on

banana A banana is an elongated, edible fruit – botanically a berry (botany), berry – produced by several kinds of large herbaceous flowering plants in the genus ''Musa (genus), Musa''. In some countries, Cooking banana, bananas used for ...

plants.

Characteristics

Sigatoka leaf spot disease (SD) is a disease of bananas and is caused by the

ascomycetous 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 ...

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

, ''Mycosphaerella musicola''. This pathogen can be distinguished morphologically from '' Mycosphaerella fijiensis'', which causes black leaf streak disease (BLSD), by the characteristics of the

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 th ...

and

conidiophore 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 ...

. The

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the Biological life cycle, life cycles of fungi in the Phylum, phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a Asc ...

of ''M. musicola'', '' Pseudocercospora musae'', lacks the thickened cell walls that are present at the base of the conidia of ''Paracercospora fijien'', the anamorph of ''M. fijiensis'', and are shorter and less wavy. The conidiophores of ''P. musae'' are bottle-shaped and much smaller than the elongated conidiophores of ''P. fijiensis'' which are often bent and bear conspicuous conidial scars. The two species can also be differentiated by molecular methods.INIBAP

Distribution

''Mycosphaerella musicola'' was first reported from Java in 1902 and by 1962 was found in most banana growing regions of the world. Although it is spread over short distances by conidia and ascospores, over long distances it is the movement of infected germplasm such as diseased leaves and suckers that is likely to be responsible. In the Pacific islands and in lowland areas of South America and Africa, symptoms of SD are now rarely seen and BLSD has largely supplanted it. SD is more adapted to cooler regions and often predominates at altitudes over 1200 metres while BLSD is rarely seen at such elevations.

Life cycle

When spores of ''M. musicola'' are deposited on a susceptible banana leaf they germinate within three hours if there is a film of water present or if the humidity is very high. The optimal temperature for germination of the conidia is between 25-29 °C and for the ascospores, 25-26 °C. The germ tube grows

epiphytically An epiphyte is an organism that grows on the surface of a plant and derives its moisture and nutrients from the air, rain, water (in marine environments) or from debris accumulating around it. The plants on which epiphytes grow are called phoroph ...

over the

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...

for about five days before penetrating the leaf via a

stoma In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bo ...

.Meredith DS (1970) 'Banana leaf spot disease(Sigatoka) caused by Mycosphaerella musicola Leach.' (Commonwealth Mycological Institute, Kew, Surrey, England) Once inside the leaf the invasive hypha forms a vesicle and fine hyphae grow through the

mesophyll A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...

layers into an air chamber. More hyphae then grow into the palisade tissue and continue on into other air chambers, eventually emerging through stomata in the streak that has developed. Further epiphytic growth occurs before the re-entry of the hypha into the leaf through another stoma repeats the process.PaDIL
/ref> Both conidia and

ascospore An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera o ...

s are important for dispersal of M. musicola with the ascospores being involved in the movement of the pathogen over longer distances than the conidia.Stover RH (1971) Leaf spot of bananas caused by Mycosphaerella musicola: Role of conidia in epidemiology. Phytopathology 60, 856-860. The deposition of ascospores by wind currents is generally near the tips of the leaves resulting in a distinctive pattern of infection on the leaf extremities. When conidia are the source of the

inoculum In biology, inoculum refers to the source material used for inoculation. ''Inoculum'' may refer to: * In medicine, material that is the source of the inoculation in a vaccine * In microbiology, propagules: cells, tissue, or viruses that are used to ...

and these are dislodged by rain, a distinctive line of streaks is produced as water trickles down the leaf blade.

Symptoms

It is not always easy to differentiate between the symptoms of SD and BLSD. The first sign of disease in SD is the appearance of small yellow streaks on the upper side of leaves while in BLSD small, dark brown streaks appear on the lower surface of leaves. These streaks enlarge and coalesce forming necrotic lesions with light gray centres and yellow perimeters. Large areas of leaf can be damaged causing a lowering of

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in ...

ability, a reduction in crop yield and premature ripening of the fruit. BLSD is the more serious of the diseases as the symptoms emerge on younger leaves and it affects many

cultivar A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...

s that have developed

resistance Resistance may refer to: Arts, entertainment, and media Comics * Either of two similarly named but otherwise unrelated comic book series, both published by Wildstorm: ** ''Resistance'' (comics), based on the video game of the same title ** ''T ...

to SD, including the

plantain Plantain may refer to: Plants and fruits * Cooking banana, banana cultivars in the genus ''Musa'' whose fruits are generally used in cooking ** True plantains, a group of cultivars of the genus ''Musa'' * ''Plantaginaceae'', a family of flowerin ...

subgroup.

References

External links

Index Fungorum

USDA ARS Fungal Database

Sigatoka Leaf Spot Diseases

PaDIL
{{Taxonbar, from=Q6947206 musicola Fungal plant pathogens and diseases Banana diseases Fungi described in 1902 Leaf diseases