STUDIES OF RHODESIAN ERGOTS 1. CLAVICEPS MAXIMENSIS THEIS A N D CLAVZCEPS PUSILLA CES AT1 Botany Departmen t, University College of Rhodes ia and Nyasal and, Salisbury INTRODUCTION Fungi of the genus Claviceps par asi tis e the ovaries o f many grasses and a few sedges, forming sclerotia in pl ace o f 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 mass es of dorman t myceli um that fa ll 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 fil led w ith a dense mass of hyphae. On the su rface o f thi s mycelial mass a layer of short conidiophores bearing minute conidia is produced (the Sphacelia stage). The conidia are embedded in a sugary secreti on o f the fungus ("ho ney dew ") which someti mes 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 most ergot diseases the mature sclerotia are several times longer than healthy grains, so that they can be seen protruding from the infected spikelets. The aim o f this series of papers is to provide the minimum specifi - cations for Rhodesian species of Claviceps that are either new records, n ew species, or spec ies that are inadequately described elsewhere. PREVIOUS RECORDS OF ERGOTS IN RHODESIA Prior to 1961 only four named species of Claviceps ( C . cynodontis Langdon, C. digitariae Hansford, C. paspali Stevens and Hall, and C. sulcata Langdon) and two undetermined species (one on Panicum maximum Jacq. and another on Pennisetum typhoides (Burm.) Stapf and saprophytic fungus Cerebella andropogonis Cesati on a number of grasses (Hopkins, 1950) indicated the presence o f additi onal species, because there is little doubt (Langdon, 1942a) that a record of C.
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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
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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.
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