Loveless 1964b

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STUDIES OF RHODESIAN ERGOTS

1. CLAVICEPS MAXIMENSIS THEIS A N D CLAVZCEPS PUSILLA

CESAT1

Botany Department, University College of Rhodesia and Nyasaland,

Salisbury

INTRODUCTION

Fungi of the genus Claviceps parasitise the ovaries of many grasses

and a few sedges, forming sclerotia in place of normal grains in the

inflorescence. To these fungi, and to the diseases they cause, the term

"ergot" is applied. The sclerotia are not fruiting bodies of the fungus

but hard compact masses of dormant mycelium that fall to the ground

and tide the fungus over the dry season. They germinate during the

following rains to form stalked stromatic heads in which perithecia

develop. Ascospores are liberated into the air and infect the stigmas of

susceptible plants. The fungus passes into the ovary which gradually

becomes filled with a dense mass of hyphae. On the surface of thismycelial mass a layer of short conidiophores bearing minute conidia is

produced (the Sphacelia stage). The conidia are embedded in a sugary

secretion of the fungus ("honeydew") which sometimes exudes in drops.

The honeydew attracts insects which, when feeding, pick up the conidia

and transfer them to other stigmas where germination and infection

occur. Later in the season the mycelial mass, which has produced the

conidiophores, is progressively transformed into a hard sclerotium. In

most ergot diseases the mature sclerotia are several times longer than

healthy grains, so that they can be seen protruding from the infectedspikelets.

The aim of this series of papers is to provide the minimum specifi-

cations for Rhodesian species of Claviceps that are either new records,

new species, or species that are inadequately described elsewhere.

PREVIOUS RECORDS OF ERGOTS IN RHODESIA

Prior to 1961 only four named species of Claviceps (C . cynodontisLangdon, C.

digitariaeHansford,

C. paspaliStevens and Hall, and C.

sulcata Langdon) and two undetermined species (one on Panicummaximum Jacq. and another on Pennisetum typhoides (Burm.) Stapf and

Hubbard) were definitely known to occur in Rhodesia. Records of the

saprophytic fungus Cerebella andropogonis Cesati on a number of

grasses (Hopkins, 1950) indicated the presence of additional species,

because there is little doubt (Langdon, 1942a) that a record of C.

andropogonis on a grass is a safe indication of previous infection by

Claviceps.

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Since 1961 the author has collected ergotized specimens of Rho-

desian grasses and, in addition to the four named species of Clavicepsmentioned above, has established the presence of two more species, C.maximensis Theis and C. pusilla Cesati. These are new records for

Southern Africa, although the recording of C. rnaxirnensis merely rep-

resents the identification of the ergot on Panicum maximum that was

known to occur but had not previously been determined. This paper

describes C. maximensis and C. pusilla.

Claviceps maximensis Theis, Mycologia 44: 792 (1952).

Panicum maximum Jacq., commonly known as Guinea Grass, is a

valuable fodder grass in the warmer and drier parts of Southern Rho-

desia, where it is usually found growing in the shade of trees. Although

indigenous to Africa, this grass has been introduced to tropical andsubtropical regions throughout the world. It has been known for over

thirty years that Guinea Grass is subject to ergot disease. Sphacelial

stages have been reported from Mauritius (Shepherd, 1927) and India

(Thomas, Ramakrishnan and Srinivasan, 1945). The honeydew sapro-

phyte Cerebella andropogonis Cesati has also been observed in Brazil

(Viegas, 1946) and in Jamaica (Martyn, 1946). The sclerotial stage of an

ergot on Panicunz maximum is recorded from South Africa by Doidge

(1950) and from Southern Rhodesia by Hopkins (1950). In none of the

above records, however, is the causal species of Claviceps stated.

There are several reports (e.g. Shepherd, 1927) of the occurrence

of a sphacelial stage of ergot on plants of Panicum maximum growing

in the same locality as ergotized plants of Paspalum, a genus that is

well known to include many host species of Claviceps paspali Stevens

and Hall. It was presumably on such circumstantial evidence that

Sprague (1950) listed C. paspali as the species probably responsible for

the ergot of Panicum maximum. However, by cross-inoculation experi-

ments with the sphacelial stages from Panicum maximum and Paspalunzplicatulum Michx., Theis (1952) showed that the ergot on Panicum maxi-

mum in Puerto Rico is distinct from Claviceps paspali. He described the

ergot on Panicum maximum as a new species, Claviceps maximensisTheis. The following is Theis' description of C. rnaxirnensis:

"Sclerotia 2-9 mm. long, 1 mm. wide, brown to gray brown, white

inside, straight to slightly curved or twisted, tapering upward, tip usually

with a cap of dried sphacelial-stage hyghae, longitudinally furrowed,

replacing host ovaries, host glumes remaining attached; germinating in

approximately 20 days, bearing 1 to 5 stromata: stipes variable in

length, 0.4-0.6 mm. in diameter, smooth, pale green becoming yellow as

the capitulum matures, flexuous; capitulum 0.7 to 1.0 mm. in diameter,

subglobose, light yellow becoming brown as it matures, overlapping

point of attachment with stipe, surface uneven due to slightly projecting

perithecia; perithecia flask-shaped, immersed in the capitulum and dis-

tributed over the entire upper surface, neck projecting slightly, ovate,

240-280 p long and 120-160 p wide; asci hyaline, cylindrical, 2.5-3.0 x105-139 p , tapered toward point of attachment, apex with a hyaline

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cap, 8-spored; no paraphyses; ascospores hyaline, filiform, 0.5 x 95-126

p: conidia hyaline, elliptical, aseptate 10-30 x 3.5-11.0 p from con-

voluted hyphae in ovary of flower" (Theis, 1952, p. 792).

In May 1961 severe infection with ergot occurred in a demonstration

plot of Panicum maximum at the Botany Garden of the University

College of Rhodesia and Nyasaland, Salisbury. Since it cannot be

assumed that the species of Claviceps associated with a particular host

is the same in all parts of the world, it was decided to identify the

species responsible for this outbreak. The characters of the conidia

(Photo 2) and sclerotia (Photo l), which were readily determined at the

time of the outbreak, closely resembled those of C . maximensis . It is

not possible, however, to make a final determination without also

observing the stromata produced by germination of the sclerotia.A large

number of sclerotia were therefore collected in May 1961 and kept dryin the laboratory until the onset of the rainy season. In mid-November

1961 these sclerotia were sown on soil in shallow flower pots that were

left in the open. Germination began at the end of December, and by

mid-January 1962 (i.e. two months after sowing) many mature stromata

(Photos 3 and 4) were available for establishing the identity of the

ergot. In all essential characters, including the method of germination

of the sclerotia, the colour of the stipes and capitula, and the shape and

size of the perithecia, the strornata agreed with Theis' type description

of C . maximensis. From conidial, sclerotial and stromatic characters,

and on a host basis, it may therefore be concluded that the ergot species

responsible for the above-mentioned outbreak is C. maximensis.

This identification of the ergot affecting Panicum maximum in

Rhodesia with a species described from Puerto Rico raises the question

as to whether Claviceps maximensis is indigenous to Puerto Rico. Anyconsideration of the origin of a species of Claviceps must take into

account the origin of its host. Because Panicum maximum is known to

be indigenous to Africa, it would seem likely that Claviceps maximensisis also indigenous to Africa and was introduced into Puerto Rico as

sclerotia with imported seed. The possibility of infection of Panicummaximum by ascospores from sclerotia introduced by chance into Puerto

Rico does not presuppose an unlikely series of events. In the south-

western part of Puerto Rico large acreages are devoted to pastures of

P. maximum, and the yearly epiphytotics of Claviceps maxim~nsis hat

now occur in this area (Theis, 1952) indicate how well the local con-

ditions suit the ergot. Assuming that sclerotia of C . maximensis were

introduced into Puerto Rico at some previous date, the first sclerotia

to germinate after their introduction would have available an abundance

of host plants and, in view of the suitability of local conditions to thisergot, the initial infections should not have been difficult to establish.

Establishment of ergot disease by such accidental introductions is known

to have occurred with C . purpurea (Fr.) Tul. and C . paspali in Australia.

In the case of C . paspali even the approximate date of introduction is

known. Since it is well known that Panicum maximum has in the past

been introduced from Africa into many warm countries, it is very

reasonable to suppose that sclerotia of C . maximensis went with it.

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The mycological and ecological evidence certainly supports the case

for regarding C. maximensis as indigenous to Africa.

Clavicepspusilla Cesati, Comm. Soc. Crittog. Ital. 1: 64 (1861).

This species was described on Bothriochloa ischaemum (L.) Keng.

(= Andropogon ischaemum L.) in Italy by Cesati in 1861. Cesati's

description was short and dealt only with characters of the stromata.

Apart from a mention of its occurrence on the same host in Yugoslavia

(Ranojevic, 1914), there is no further reference to this fungus until

1941 when Langdon (1941) recorded it on three native species of grass

in Australia. Subsequently, as a result of further field collections and

inter-host infection experiments, Langdon (19423 and 1950) increased the

known host range of Claviceps pusilla in Australia to thirteen native

species belonging to the following seven genera: Bothriochloa (5 spp.),

Capillipedium (1 sp.), Cymbopogon (1 sp.), Dichanthium (2 spp.),

Heteropogon (1 sp.), Themeda (2 spp.) and Vetiveria (1 sp.). Langdon(1950) also collected Claviceps pusilla from New Guinea in 1943 on

Capillipedium and Themeda, both genera that are included in the

Australian list of host genera.

Although it is necessary to obtain information on both the imperfect

and perfect states of a species of Claviceps before an authentic deter-

mination can be made, it is nevertheless safe to identify certain wellrecognized species from distinctive features of the conidia and sclerotia,

considered in conjunction with the host range. Claviceps pusilla is such

a species because its conidia have a very characteristic and unusual

shape, being mostly triangular in outline (Photo 6 ) . Sphacelial stages

of ergot fungi with triangular conidia have been reported from India

and other Asian countries, and on the same or allied hosts which are

known to be infected by C. pusilla in Australia. On this evidence Lang-

don (1942b and 1950) suggested that C. pusilla may also be present in

Asia. This suggestion was subsequently confirmed by Langdon (1952),

when he germinated sclerotia from ergotized plants of Themeda cym-baria (Roxb.) Hack. that were sent to him from India. It may be con-

cluded, therefore, that Claviceps pusilla is widespread in the warmer

regions of Europe, Asia and Australia.

As a result of the author's recent collections of Rhodesian ergots,

the known distribution of C. pusilla may now be extended to include

south-central Africa. Of the twenty odd species of ergotized grasses

so far collected in Rhodesia, C. pusilla has been identified as being

responsible for the ergot disease of five species belonging to three

different genera. The host species (of which herbarium specimens have

been filed in the Central African Herbarium, Salisbury) are:

Heteropogon contortus (L.) Beauv. ex Roem. and Schult.

Bothriochloa glabra (Roxb.) A. Camus

Hyparrhenia collina (Pilg.) Stapf

Hyparrhenia sp. aff. H. collina (Pilg.) Stapf

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Hyparrhenia cymbaria (L.) StapflH. variabilis Stapf, an inter-

mediate form related to both these species.

These five grasses all belong to the tribe Andropogoneae, which

conforms with the known host restriction of Claviceps pusilla in Europe,

Asia and Australia. Indeed, in the case of the first two of the above-

mentioned hosts, either the same species (Heteropogon contortus) or

other species of the same genus (Bothriochloa) are well known to be

hosts of Claviceps pusilla in Australia. The discovery in Rhodesia of

C. pusilla on three species of Hyparrhenia (Photo 5) is, however, interest-

ing from three points of view. First, this is the first record of Hyparr-henia as a host genus of C . pusilla. Second, it is noteworthy that all

the three mentioned species of Hyparrhenia belong to the same section,

the Cymbariae, of this large genus, although in the. field they grow in

association with other species of Hyparrhenia belonging to other sections

of the genus. Third, another species of ergot, Claviceps inconspicuaLangdon, has been described by Langdon (1949) from Australia on

Hyparrhenia filipendula (Hochst.) Stapf (which belongs to the section

Filipendulae of Hyparrhenia). The recognition of Hyparrhenia as a

host of Claviceps pusilla in Rhodesia thus provides a striking example

of the association of one host genus with different species of Clavicepsin different parts of the world.

Although, as previously mentioned, the type description of Clavi-ceps pusilla by Cesati is inadequate, Langdon (1950) has redescribed

this fungus on the basis of extensive field and laboratory studies. Inorder to make Langdon's description readily available to local botanists,

it is reproduced here in full:

"Sclerotia dark brown to black, cylindrical, tapering slightly and

rounded at the ends; surface minutely wrinkled, with several shallow

longitudinal furrows. Stromata one to several on each sclerotium. Stipespale straw colour, glabrous, with a waxy appearance, 3-15 mm. long,

sometimes reaching 30 mm. in old age; tufts of white hyphae persistent

round the base, but most prominent during early stages of development

of the stromata. Capitula globose, dark straw colour, prominently papil-

late at maturity, 0.5-1.0mm. diameter; a collar-like appendage surrounds

the base of the capitulum at its junction with the stipe. Peritheciasubglobose, 220-300 x 125-165 p. Asci cylindrical, rounded at the apex,

tapering at the base, hyaline, 55-160 p. Ascospores 8, filiform, hyaline,

almost equalling the ascus in length. Conidia hyaline, granular, some-

times biguttulate, mostly triangular in general outline, some elliptic,

10-15.5x 5.0-7.5p" (Langdon, 1950, p. 3).

The only respect in which the Rhodesian material was found to

differ from the above description is a slightly greater range in size of

the conidia (8-14.5-(15.5)x 3.5-8.0 p as compared with Langdon's

figures of 10-15.5 x 5.0-7.5 p). However, in view of the slight variation

observed in the dimensions of conidia from different hosts, there can

be no doubt that the Rhodesian material belongs to this widespread

species Claviceps pusilla.

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REFERENCES

Doidge, E. M. (1950). The South African fungi and lichens. Bothdia5: 149.

Hopkins, J. C. F. (1950). A descriptive list of plant diseases in SouthernRhodesia and list of bacteria and fungi. Mem. Dept. Agric. No. 2(rev. 2nd edition). Govt. Stationery Office, Salisbury.

Langdon, R. F. (1941). Occurrence of ergot in Queensland, with specialreference to Claviceps pusilla Cesati. J. Australian Inst. Agric. Sci.7:85-87.

(1942.a). The genus Cerebella Cesati-its biologic statusand use. Phytopathology 32: 613-617.

(1942b). Ergot of native grasses in Queensland. Proc.Ro y. Soc. Queensland 54: 23-32.

(1949). A new ergot from Queensland. Proc. Roy. Soc.Queensland 61: 3 1-35.

(1950). Studies in Australian ergots 1. Claviceps pusillaCesati. Un iv. Queens'and Papers (Biolog y)2 (12): 1-12.

(1952). The geographical distribution of Claviceps

pusilla. Australian J . Sci.14:

164-165.Martyn, E. B. (1946). Ann. Rep. Dept. Agric. Jamaica, for year ended

March 3 1, 1945.

Ranojevic, N. (1914). Anndes mycologici 12: 393-421 (cited in Langdon,R. F. (1950). Univ. Queensland Papers (Biology) 2 (12): 1-12).

Shepherd, E. F. S. (1927). Ann. Rep. Mauritius Dept. Agric. for theyear 1926.

Sprague, R. (1950). Diseases of cereals and grasses in North Am erica.

The Ronald Press Company, New York.

Theis, T. (1952). An undescribed species of ergot on Panicum m axim umJacq. var. Common Guinea. Mycologia 44: 789-794.

Thomas, K. M., Ramakrishnan, T. S. and K. V. Srinivasan. (1945). Thenatural occurrence of ergot in South India-11. Proc. Indian Acad.Sci. Sect. B . 22: 191-192.

Viegas, A. P. (1946). Alguns fungos do Brasil. 13. Hifomicetos. Bragan-tia, S . Paulo 6: 353-442.

ACKNOWLEDGEMENTS

I wish to thank Mr. J. B. Phipps, formerly of the Government Her-barium, Salisbury, for invaluable help in identifying ergotized grasses,and Mr. J. Brewer of the Botany Department, U.C.R.N., Salisbury, fortechnical assistance during the progress of this work.

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TAB.VIII. 1, Ergotized and healthy spikelets of Panicz im max imum; 2, Conidiaof Claviceps rnaxmensis; 4, Stroma of Claviceps maximensis showing collar-likeappendage surrounding point of attachment of capitulum with stipe; 5, Spikeletsof intermediate form of Hyparrhenia cym bari a lH . variabi li s infected b y C lav ic epspusilla. Sphacelial stage on right, mature sclerotium on left; 6 , Conidia of

Claviceps pusilla showing characteristic triangular shape.

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