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Helminthosporium dictyoseptatum S. Hughes 1980

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Helminthosporium dictyoseptatum S. Hughes, New Zealand J. Bot. 18 69 (1980)

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S. Hughes
S. Hughes
1980
69
ICN
Helminthosporium dictyoseptatum S. Hughes 1980
NZ holotype
species
Helminthosporium dictyoseptatum

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dictyoseptatum

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Helminthosporium dictyoseptatum S. Hughes 1980

Auckland Province, Walker's Bush, Henderson Valley, Waitakere Range, 30.I.1963, F. J. Morton, PDD 20506 (type) (DAOM 109608).

Colonies black, effuse, hairy. Mycelium immersed, composed of branched, septate, pale brown to dark brown hyphae 3.5-9 µm wide, forming immersed or partially immersed subglobose to flattened stromata up to 100 µm wide, but larger by confluence, composed of brown to dark brown cells up to 16 µm wide.
Conidiophores scattered or crowded, arising singly from small aggregations of a few cells or in groups of two or more from the stromata; they are simple, flexuous, subcylindrical, dark brown to black below, pale brown to dark brown toward the apex, thick-walled (up to 3 µm), smooth or distally roughened, septate at 40-63 µm intervals for most of their length with the cells-more or less progressively shorter toward the apex where they are mostly 14¬-30 µm long. Conidiophores are up to 2 mm long, 18-23 µm wide just above the swollen base and 15-21 µm wide toward the apex; pores in the conidiophores indicate the position at which the solitary conidia developed.

The distal cell of the condiophore bears a con¬spicuous terminal "pore" and usually 1 or 2 sub-apical pores; one or sometimes two similar pores are found in 1-6 other cells toward the apex of the con¬idiophore. Pores are 1.8-2.5 µm wide. Conidia obclavate, often conspicuously rostrate, smooth toward the base and apex, elsewhere with the exospore reticulate-foveate to irregularly so, golden brown to brown, paler toward the apex and dark brown or occasionally black around the immediate base which may be slightly denticulate. The lateral wall is 7-9 µm thick below but thinner toward the apex; usually the conidia have 3 or 4, thick (up to 5.5 µm), main transverse septa, each often with a thin central darker lamella. Below the lower two or three main septa thin-walled trans¬verse septa are formed so that conidia are finally 14-to 18-septate; 4-14 scattered, thin-walled, longitudinal or oblique septa arise so that mature conidia are essentially dictyoseptate. Conidia measure 92-145 x 29-38 µm with the rostrum c. 5.5 µm wide and 15-115 µm long; the rostrum may extend into simple or once branched pale brown germ tube with cells up to 100 µm long.

On dead twigs.

Coloniae effusae, atrae, pilosae. Mycelium immersum, ex hyphis septatis, ramosis, pallide brunneis vel atrobrunneis 3.5-9 µm crassis compositum. Stromata immersa vel partim superficialia, subglobosa vel depressa, usque ad 100 µm lata, ex cellulis brunneis vel atrobrunneis ad 16 µm latis composita.
Conidiophora oriunda sive pluraliter ex stromata sive singula ex cellulis perpaucis aggregatis, simplicia, flexuosa, subcylindrica, septata (cellulis plerumque 40-63 µm longis sed apicem versus cellulis 14-30 µm longis), basim versus atrobrunnea vel atra laeviaque, apicem versus pallidiora, crasso-tunicata (ad 3 µm) interdum asperata, usque ad 2 mm longa, supra basim 18-23 µm crassa, apicem versus 15-21 µm crassa, cellula terminali poris 1-3 in apice conidiiferis praedita, cellulis subterminalibus 1-5 etiam poris 1 vel 2 lateralibus conidiiferis praeditis. Conidia ad poros conidiophori oriunda, obclavata saepe rostrata, basim et apicem versus laevia, ceteris inconspicue subreticulate-foveata, aureo-brunnea vel brunnea, apicem versus pallidiore, ad basim interdum denticulata et atrobrunnea vel atra, lateraliter crasso-tuni¬cata (ad 9 µm), ad maturitatem dictyoseptata, septis 14-18 transversalibus, septis 4-14 longitudinalibus vel obliquis, dispersis. Conidia 92-145 x 29-38 µm, rostro ca 5.5 µm crasso,15-45 µm longo, germinante elongascente.

Holotypus in ramulis emortuis, Nova Zelandia, "Auckland Province, Walker's Bush, Henderson Valley, Waitakere Range", 30.I.1963, F. J. Morton, PDD 20506 (DAOM 109608).

Only one species of Helminthosporium, H. ahmadii Ellis (1961) with conidia 25-30 µm wide, approaches this robust New Zealand species: but in H. ahmadii the conidiophores are shorter and narrower and the conidia are narrower, smooth and lack longitudinal septa. Occasional longitudinal septa in the conidia of the type species of Helminthosporium, H. velutinum, are rare. Nevertheless, in view of the several other characters that H. dictyoseptatum shares with H. velutinum the dictyoseptation of conidia in the new species is not regarded as sufficient to exclude the species from this genus.

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Helminthosporium dictyoseptatum S. Hughes 1980
Helminthosporium dictyoseptatum S. Hughes (1980)
Helminthosporium dictyoseptatum S. Hughes 1980
Helminthosporium dictyoseptatum S. Hughes (1980)
Helminthosporium dictyoseptatum S. Hughes 1980
Helminthosporium dictyoseptatum S. Hughes (1980)

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Helminthosporium dictyoseptatum S. Hughes 1980
New Zealand
Auckland

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1cb18c8d-36b9-11d5-9548-00d0592d548c
scientific name
Names_Fungi
21 December 1992
17 December 2018
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