''Botryosphaeria dothidea'' is a
plant pathogen that causes the formation of
cankers
A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...
on a wide variety of tree and shrub species. It has been reported on several hundred plant hosts and on all continents except Antarctica.
[Crous, P.W., B. Slippers, M.J. Wingfield, J. Rheeder, W.F.O. Marasas, A.J.L. Philips, A. Alves, T. Burgess, P. Barber, and J.Z. Groenwald. 2006. Phylogenetic lineages in the Botryosphaeriaceae. Studies in Mycology 55:235-253.][Farr, D.F., and A.Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Accessed 21 November 21, 2013. ] ''B. dothidea'' was redefined in 2004, and some reports of its host range from prior to that time likely include species that have since been placed in another genus.
[Phillips, A.J.L., A. Alves, J. Abdollahzadeh, B. Slippers, M.J. Wingfield, J.Z. Groenewald, and P.W. Crous. 2013. The Botryosphaeriaceae: Genera and species known from culture. Studies in Mycology 76:51-167.] Even so, ''B. dothidea'' has since been identified on a number of woody plants—including grape, mango, olive, eucalyptus, maple, and oak, among others—and is still expected to have a broad geographical distribution.
While it is best known as a pathogen, the species has also been identified as an endophyte, existing in association with plant tissues on which disease symptoms were not observed.
[Pérez, C.A., M.J. Wingfield, B. Slippers, N.A. Altier, and R.A. Blanchette. 2010. Endophytic and canker-associated ''Botryosphaeriaceae'' occurring on non-native ''Eucalyptus'' and native ''Myrtaceae'' trees in Uruguay. Fungal Diversity 41:53-69.] It can colonize some fruits, in addition to woody tissues.
[Lazzizera, C., S. Frisullo, A. Alves, and A.J.L. Phillips. 2008. Morphology, phylogeny and pathogenicity of ''Botryosphaeria'' and ''Neofusicoccum'' species associated with drupe rot of olives in southern Italy. Plant Pathology 57:948-956.][Marques, M.W., N.B. Lima, M.A. de Morais Jr., S.J. Michereff, A.J.L. Phillips, M.P.S. Câmara. 2013. ''Botryosphaeria'', ''Neofusicoccum'', ''Neoscytalidium'' and ''Pseudofusicoccum'' species associated with mango in Brazil. Fungal Diversity 61:195–208.][Sutton, T.B. 1990. White rot. Pages 16-18 in: Compendium of Apple and Pear Diseases. A.L. Jones and H.S. Aldwinckle, eds. APS Press, St. Paul, MN.]
Life as a plant pathogen – "Bot rot" of apple
White rot, or "Bot rot", of apple is one of the many plant diseases that have been attributed to ''B. dothidea''.
[Travis, W., J.L Rytter, and A.R. Biggs. (n.d.) White rot. Accessed 22 November 2013. http://www.caf.wvu.edu/kearneysville/disease_descriptions/omwhiter.html ] Recent analysis has confirmed the presence of ''B. dothidea'', along with other ''Botryosphaeria'' species, on ''Malus sp.''.
[Slippers, B., W. A. Smit, P. W. Crous, T. A. Coutinho, B. D. Wingfield, and M.J. Wingfield. 2007. Taxonomy, phylogeny and identification of Botryosphaeriaceae associated with pome and stone fruit trees in South Africa and other regions of the world. Plant Pathology 56:128 –139.] Cankers and other dead wood and bark tissue, as well as mummified fruit (fruit infected by the pathogen and remaining in the orchard) serve as sources of primary and secondary inoculum.
Both pycnidia and pseudothecia are observed on plant tissues, producing conidia and ascospores.
Conidia are produced in greater numbers.
Using spore traps for airborne spores and funnel traps for rainwater, Sutton (1981) determined that, while both conidia and ascospores of ''B. dothidea'' are released from infected pruning waste (dead wood) during rainfall events and conidia are predominantly water-dispersed, ascospores spread in both air and water.
[Sutton, T.B. 1981. Production and dispersal of ascospores and conidia by ''Physalospora obtusa'' and ''Botryosphaeria dothidea'' in apple orchards. Phytopathology 71:584-589.] Conidia and ascospores germinate most readily at 28 to 32 °C (82 to 90 °F).
(''B. dothidea'' has been reported to grow best, in culture, at 25 to 30 °C
7 to 86 °F[Slippers, B., P.W. Crous, S. Denman, T.A. Coutinho, B.D. Wingfield, and M.J. Wingfield. 2004. Combined multiple gene genealogies and phenotypic characters differentiate several species previously identified as ''Botryosphaeria dothidea''. Mycologia 96:83-101.]) Lenticels and wounds provide locations for wood infection
The cankers of white rot appear similar to those of black rot, caused by ''Diplodia seriata'' (formerly ''B. obtusa'').
Girdling of limbs by cankers can result in yellowing ("chlorosis") of leaves on affected branches in the spring.
While the precise time of fruit infection is unclear, symptoms of fruit rot appear approximately four to six weeks before harvest.
The name "white rot" comes from the light brown color of the surface of affected red-skinned apples.
Classification and characteristics
''Botryosphaeria dothidea'' is the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...
of the genus ''
Botryosphaeria
''Botryosphaeria'' is a genus of pathogenic fungi in the family Botryosphaeriaceae. There are 193 species, many of which are important disease-causing agents of various important agricultural crops.
Species
*'' Botryosphaeria abietina''
*'' Bot ...
''.
While the International Botanical Congress recently emended the
International Code of Nomenclature for algae, fungi, and plants to state that one fungal species should be called by one name, the sexual (teleomorphic) and asexual (anamorphic) stages of single fungal species have often been called by different names. ''B. dothidea'' was the name given to the teleomorphic form, and ''Fusicoccum aesculi'' has been identified the anamorph of ''B. dothidea'', as currently defined.
[Agrios, G.N. 2005. Plant Pathology. 5th ed. Elsevier.] Phillips et al. (2013) chose to use the genus name ''Botryosphaeria'', rather than ''Fusicoccum'', since ''Botryosphaeria'' is commonly used and is the type genus of the family Botryosphaeriaceae.
Fries first published a description of ''B. dothidea'' as ''Sphaeria dothidea'' in ''Systema Mycologicum'' in 1823.
[International Mycological Association. MycoBank. Accessed 21 November 2013. http://www.mycobank.org/] Cesati and De Notaris described the genus ''Botryosphaeria'' and moved the species formerly known as ''S. dothidea'' into the new genus.
After determining that a type specimen consistent with the original description of ''Sphaeria dothidea'', on ash, did not exist, Slippers et al. (2004) designated an epitype specimen to go along with a non-sporulating neotype from the collection of Fries, who published the original description of the species.
Slippers et al. (2004) then revised the description of ''B. dothidea''. The name is believed to have previously encompassed a species complex, and references to it in older literature might represent species now otherwise identified.
Like other members of the Dothideomycetes, the sexual stage of ''B. dothidea'' has bitunicate asci, which are borne in cavities ("ascomata") formed through a process known as "
ascolocular development".
[Schoch, C.L., R.A. Shoemaker, K.A. Seifert, S. Hambleton, J.W. Spatafora, and P.W. Crous. 2006. A multigene phylogeny of the Dothidiomycetes using four nuclear loci. Mycologia 98:1041-1052.] In the case of ''B. dothidea'', these ascomata are pseudothecia.
The asci in the pseudothecia produce ascospores that can then infect plants. Like other species in the order Botryosphaeriales, ''B. dothidea'' ascomata have "multilayered dark brown walls" and contain septate
pseudoparaphyses which are transparent or translucent (hyaline).
[Alexopoulos, C.J., C.W. Mims, and M.M. Blackwell. 1996. Introductory Mycology. 4th ed. John Wiley & Sons.] Pseudothecia are sometimes located alone and other times clustered together.
In the asexual stage, conidia, which can also infect plants, are produced in pycnidia.
The pycnidia and pseudothecia of ''B. dothidea'' look very similar.
Microconidia have also been reported in at least one ''B. dothidea'' isolate.
Microconidia are small, asexual spores that often act as male gametes or gametangia (spermatia) in a process of cytoplasmic fusion (plasmogamy)
According to a key provided in Phillips et al. (2013), ''B. dothidea'' can be distinguished from six other members of the genus by conidia that are typically longer than 20 μm, have a length to width ratio greater than 4.5, and occur on hosts other than ''Vaccinium'' species.
These conidia are "narrowly...or irregularly fusiform," have thin walls, and are generally transparent or translucent (hyaline) and aseptate but sometimes form up to two septa and/or darken when they are older. Differentiating between species based on morphology depends on observing multiple samples, to get an idea of prevailing character states, and doing so at the appropriate developmental stage.
Sequencing is considered an important companion to morphological identification
References
External links
Index FungorumMycoBankUSDA ARS Fungal Databases
{{Taxonbar, from=Q4948837
Fungal plant pathogens and diseases
Grapevine trunk diseases
Fungi described in 1823
dothidea