Leptodiscella africana gen. et comb.nov

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  • Notes and Brief Articles 145288 x 9'0 usn; uredosporae singulariter productae, sessiles, oblongae, echinulatae,18'0-21 x 9'0-18'0 ust; germinationis poro non viso. Telia absunt.

    Typus leetus a A. V. Sathe ad Purandar inficiens Adelocaryum coelestinum (Lind!.)Brand. (Boraginaceae), propc Poonum in India die 2.X. 1960 et positus in M.A.C.S.Herbario Mycologico sub numero 269.

    Arthur (1915) considered peridiate uredia as belonging to a separategroup, under the form-genus Uredo. The peridiate nature of uredium,however, has been freely employed to segregate many rust genera, andhence on the basis of the presence of a peridium in the present uredialsorus, its accommodation into a new form-genus is justified. Moreover, asrightly pointed out by Laundon (1967), the imperfect spore forms inUredinales need precise segregation.

    The writer expresses his deep sense of gratitude to Professor M. N.Kamat for his unfailing interest. Thanks are also due to Rev. Dr H.Santapau for Latin diagnoses and to Dr A. B. Sapre for going through themanuscript.

    REFERENCES

    ARTHL'R,]. C. (1915). Uredinalcs of Porto Rico based on collections by F. L. Stevens.Mycologia 7, 318.

    LAUNDON, G. F. (1967). The taxonomy of the imperfect rusts. Trans. Br. mycol. Soc. 50,349-353

    SAPRE, A. B. (1968). Double staining of plant materials in bulk. Stain Technol. 43, 75-77.SATHE, A. V. (1967). Usc of the mixture of ethanol-x-butanol-xylene in paraffin method.

    Experientia 23, 780.A. V. SATHE,

    Maharashtra Associationfor the Cultivation of Science, Poona 4, India

    LEPTODISCELLA AFRICANA GEN. ET COMB.NOV.

    In the original description of Leptodiscus africanus Papendorf (1967) it waspointed out that, although it was closely related to L. terrestris Gerdemann,the type- and only other known species of the form-genus, there were somefundamental morphological and developmental differences. These dif-ferences might eventually make it advisable to erect a new genus forL. africanus if further information and material were to become available.

    In a more or less concurrent report (Ostazeski, 1967) in which anorganism closely related to L. terrestris is described, it is pointed out that thegeneric name Leptodiscus is invalid. A new name, Mycoleptodiscus, is there-fore proposed and an amended description of the genus is provided.

    The announcement of a second species confirming the main diagnosticfeatures of this genus made a critical revaluation of the type of L. africanusessential. Hence a comparative study of Mycoleptodiscus terrestris, M.sphaericus and Leptodiscus africanus was undertaken. The procedure followedwas mainly that recommended by Ostazeski (1967) and further detailssupplied in a private communication.

    According to the latter, sporulation of M. terrestris and M. sphaericusoccurs readily when they are cultured on bean leaves. Dried leaves are

    Trans. Br. mycol. Soc. 53 (I), (1969). Printed in Great Britain10 Myc.53

  • Transactions British Mycological Societyplaced on filter-paper in Petri dishes and after sterilizing for 20 min at104-138 kNJm2 (15-20 IbJin2) and subsequent cooling, sterile distilledwater is added to each dish, pouring gently to float the leaves on the sur-face while at the same time maintaining sterile conditions. The plates areinoculated with a small inoculum from a stock culture either on the leaf, orin the water, or both. Because of a suspected critical requirement foradequate gas exchange, a small bent piece of aluminium is placed over thePetri dishes allowing for free air movement. For successful sporulation itwas also necessary to place the cultures at a distance of 45-60 em from alight source consisting of four fluorescent tubes with a mixture of daylight,cool-white, and white quality tubes on a 6 h on-off cycle giving a measuredintensity of 864-1 188 lx, Between 24 and 28 sporulation can be detected(under magnification) on the leaf surface in about 4-7 days.

    The results confirm the findings of Gerdemann (1953), McVey &Gerdemann (1960) and Ostazeski (1967) and support all the conclusionsof my previous investigation (Papendorf, 1967), thus supplying conclusiveevidence that L. africanus is not a species of the genus Mycoleptodiscus. Italso bears out Ostazeski's contention, stated in a personal communication,that L. africanus most probably is something other than Mycoleptodiscusbecause it lacks two features distinctive for that genus, i.e. sclerotia andthe flat fruiting structures.

    The name Leptodiscella is proposed for this organism.

    Leptodiscella gen.nov.Coloniae sine sclerotibus. Hyphae saepe septatae, hyalinae, plerumque funiculosae.

    Conidiophora uni- vel multicellularia, simplicia aut ramosa, saepe aggregata pseudo-stromaticas structuras acervulorum aut sporodochiorum similia formantia. Conidiasingula aut gregaria in hyphis aut conidiophorum cellis, cylindrica extremis rotundis,laevia, tenuitunicata, hyalina aut pallide colorata, in medio l-septata et setulam solamfiliformem a sublatere ad finem singulam ferentia.

    Colonies without sclerotia. Hyphae frequently septate, hyaline, oftenfuniculose. Conidiophores uni- or multicellular, simple or branched, oftenaggregated forming pseudostromatic structures resembling acervuli orsporodochia. Conidia single or in groups on hyphae or cells of conidio-phore, cylindrical with rounded ends, smooth, thin-walled hyaline orfaintly coloured, medially r-septate and bearing a single filamentoussetula sublaterally at each end.

    Type species: Leptodiscella africana (Papend.) Papend. comb.nov.Basionym: Leptodiscus africanus Papend., Trans. Br. mycol. Soc. 50,

    687-690.

    The author appreciates the assistance and valuable comments receivedfrom Dr S. A. Ostazeski.

    Trans. Br. mycol. Soc. 53 (I), (1969). Printed in Great Britain

  • Notes and Brief Articles

    REFERENCES

    GERDEMANN,]. W. (1953)' An undescribed fungus causing a root rot of red clover andother Leguminosae. Myeologia 45, 548-554.

    McVEY, D. V. & GERDEMANN,]. W. (1960). The morphology of Leptodiseus terrestris,and the function of setae in spore dispersal. Myeologia 52, 193-200.

    OSTAZESKI, S. A. (1967)' An undescribed fungus associated with a root and crown rot ofbirdsfoot trefoil (Lotus eornieulatus). Myeologia 59, 970-975.

    PAPENDORF, M. C. (1967). Leptodiseus afrieanus, sp.nov, Trans. Br. mycol. Soc. 50, 687-690.M. C. PAPENDORF,

    Department of Botany, The University, Potchifstroom, Republic ofSouth Africa

    ALTERNARIA HELIANTHI (HANSF.) COMB.NOV.Helminthosporium helianthi, a fungus causing brown spots on Helianthus

    annuus was described by Hansford in 1943 as follows: 'Maculae atro-brunneae, zonatae, in centro cinerescentes, usque ad 10 mm diam, orbicu-lares, saepe confluentes. Conidiophora praecipue epiphylla, fasciculata,olivacea, geniculata, simplicia, 2-5-septata, 70-120 x 8-10 ;.tm. Conidiaelongato-ellipsoidea, olivacea, 2-8-septata, haud constricta, 30-90 x11-16 ;.tm.

    In 1964, Pavgi published a new species of Helminthosporium, H. helianthi,causing brown spots on Helianthus annuus, probably unaware of Hansford'sspecies. In Japan, Takano (1963) reported the occurrence of an Alternaria-or Helminthosporium-like fungus on cultivated plants of the same host, butwithout a description.

    In 1964, one of the authors, N. Nishihara, isolated a Helminthosporium-like fungus from diseased leaves of cultivated Helianthus annuus in theNational Institute of Animal Industry, Chiba Pref. The disease firstappeared in spring and rapidly increased during the following rainyseason. The fungus causes brown spots mostly on leaves of the host plant,but the spots may appear on stems, sepals or petals. On the leaves, lesionsare dark brown with paler margin and yellow' halo', at first small, thenup to 2-3 cm diam, usually irregularly circular in shape (Pl., 13, fig. I); onstems, black, circular, long-ellipsoid or striated; on sepals, at first as abrown black spot, then irregularly circular, with or without indistinctconcentric rings; on petals, at first as a small brown spot, then ellipicalmeasuring 0'5 x 0'2 em and coalescing (PI. 13, fig. 2).

    Through the courtesy of Dr M. B. Ellis, Hansford's type specimen ofHelminthosporium helianthi Hansf. (IMI 5754) was borrowed from theCommonwealth Mycological Institute, Kew. The leaves in the typeshowed scattered brown spots similar to those of the present collection, andafter comparative study of our fungus with the type, it was concluded thatboth fungi were the same. Dr M. B. Ellis (personal communication)refers to collections of H. helianthi in the CMI from Argentina, India,Tanzania, Uganda and Zambia.

    The causal fungus was isolated from diseased leaves in Chiba by using amicromanupulator. The isolate grew and sporulated well on PDA. A

    Trans. Br. mycol. Soc. 53 (I), (1969). Printed in Great Britain10-2