FUNDAMENTALS FOR TAXONOMIC STUDIES OF FUSARIUM1 By H. W. WOLLEN WEBER,2 Pathologist, Biologische Reichsanstalt für Land- und Forstwirtschaft; C. D. SHERBAKOFF,3 Pathologist, Agricultural Experiment Station, University of Tennessee; and O. A. REINKING, Pathologist, United Fruit Company; with the cooperation of HELEN JOHANN, Assistant Pathologist, Office of Cereal Investigations, Bureau of Plant Industry, and ALICE A. BAILEY, Junior Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investiga- tions, Bureau of Plant Industry, United States Department of Agriculture 4 INTRODUCTION volved the United Fruit Co.'s bringing Dr. H. W. Wollenweber over from Ger- There has been a long-felt need for many, and Dr. O. A. Reinking from a general conference of all workers on Central America. The United States the Fusarium problem in order that a workers included Dr. C. D. Sherbakoff, uniform taxonomy may be formulated of the University of Tennessee, Miss upon which future work can be based. Helen Johann and Mrs. Alice A. Bailey, The various workers have always been representing, respectively, the Offices fundamentally in reasonably close of Cereal Investigations, of Cotton, agreement regarding the principles of Truck, and Forage Crop Disease In- Fusarium classification, but there has vestigations, and of Pathological col- been a number of points which were lections of the United States Depart- not clearly understood, possibly because ment of Agriculture, in a joint study of the investigators have not been suffi- Fusarium classification. The United ciently in contact with each other. Fruit Co., through its director of agri- Variations in the methods employed in cultural research, Dr. John R. John- different laboratories have complicated ston, adopted this liberal policy in the problem of species identification. supporting the scientific work to The fact that the fungi vary according a greater extent than their purely to the environment, age, and source of economic interests required. It was culture and the failure of different agreed, on the invitation of Dr. L. R. workers to understand one another has, Jones, to hold the conference at the it is believed, largely accounted for the University of Wisconsin, in Madison. differences arising from Fusarium The purpose of the conference was studies. to give an opportunity to cooperate in Recent investigations on the banana- a personal way, to compare cultures wilt problem conducted by the United assembled from all possible sources, Fruit Co. in Central America showed and in this manner to clear up the the immediate necessity of a general somewhat tangled taxonomy of this conference on the Fusarium problem. difficult genus. All the important Because of the large number of related European cultures, those being studied Fusaria encountered in a study of the at present in the United States, and banana - wilt - producing organism on the collections made from the tropics, banana plantations, it was deemed ad- primarily from Central America, were visable to complete the fungous inves- assembled at the meeting for special tigations with a final study in Europe study and comparison. The work of or in the United States. The proposed the conference covered, in so far as studies of the United Fruit Co. were possible, the study, comparison, and discussed at the meeting of scientific identification of the specimens and societies in Cincinnati, in December, cultures of the fungi then available. 1923, and through Dr. W. A. Orton a The main studies were made on the plan for an American conference on tropical collection, since it was agreed, Fusarium was proposed. The idea in- because of the part taken by the 1 Received for publication Sept. 29, 1924; issued June, 1925. 2 Engaged in special investigations for the United Fruit Co. during the Fusarium conference at Mad- ison, Wis., in August, 1924. 3 Present at the conference in cooperation with the Offices of Cotton, Truck, and Forage Crop Disease Investigations, of Cereal Investigations, and of Pathological Collections, Bureau of Plant Industry, U. S. Department of Agriculture. 4 The writers are indebted to the Departments of Plant Pathology and of Botany of the University of Wisconsin for providing facilities with which to carry on the investigations during the period oí the con- ference. Journal of Agricultural Research, Vol. XXX, No. 9 Washington, D. C. May 1, 1925 Key No. G-469 19976—25t 4 (833) 834 Journal of Agricultural Research Vol. XXX, No. 9 United Fruit Co., that the conference others may be determined directly should facilitate, in the best way from the fungus growing under natural possible, a satisfactory definition of conditions without resorting to pure the numerous species found on banana cultures. Other Fusaria, which appear plantations. The studies made of the primarily in a microconidial stage entire collection embodied species from under natural conditions and produce all sections of the genus Fusarium, only a few sickle-shaped spores, are including important border-line strains, more difficult to identify. For these thereby making it possible to arrive the so-called normal growth must, at at a uniform taxonomy of the group. first, be produced. It is, therefore, It is believed that the main points of necessary to make a careful study from difference have been agreed upon and pure culture in order accurately to that the present paper will present a identify these organisms. Generally, clearer understanding of the Fusarium macroconidia are regarded as the problem from the standpoint of the normal spore type. In certain groups, identification of species. however, the microconidia may have Material of each species studied and definite characters, such as a pearlike identified at the conference will be shape or a formation in chains, which deposited in the pathological collec- aid in the determination of the section tions herbarium of the Bureau of (Sporotrichiella, Arthrosporiella) and, Plant Industry, United States Depart- in exceptional cases, may even lead to ment of Agriculture, for permanent the identification of species (F. poae preservation. The cultures will be (Peck) Wr., F. moniliforme Sheld., F. prepared in the manner most satis- decemcellulare Brick.). factory for the preservation of her- Other normal reproductive stages, barium material. Pure cultures of such as chlamydospores, by their each of the species studied and iden- presence or absence indicate the border tified will also be placed in the bureau. of certain groups (Elegans, Lateritium). These cultures will have substantially Sclerotia may be characteristic for the status of type specimens. groups (Lateritium) and even for a number of species {F. sclerotium Wr.). CRITERIA OF THE NORM Color of the conidia and color of the aerial mycelium and stroma are further Only a résumé of the criteria of the reliable characters for taxonomy. norm will be here considered, since a Minor characters such as mycelium, complete discussion of the subject has hyphae with specialized cells, coremia- appeared in former publications (5, 9).b like aggregations of hyphae, and aro- The normal condition of Fusaria from matic odors may also be of some the standpoint of determination may importance for differentiation. In op- be present in nature, but generally it position to the norm there are abnormal must be produced by growing the features which might be valuable to fungi under pure culture conditions. mention in the diagnosis. Not so A few Fusaria such as F. dimerum much stress, however, is placed on Penz., F. scirpi Lamb, et Fautr., F. degenerated conditions in the life culmorum (W. G. Sm.) Sacc, and some cycle of Fusaria. 5 Reference is made by number (italic) to "Literature cited," p. 843. May 1, 1925 Taxonomic Studies of Fusarium 835 -Stages in the life cycle of Fusaria: A-F, H and S, microconidia. I-R, T-X, macroconidia. Y, Swellings of hyphae. Z, Ai-Di, Chlamydospores. Ei-Fi, Conidial propagation from conidia. Gi, Sclerotium. Hi, Sporodochium. Ii, Sclerotiain clusters on an erumpent base. Ki, Columns formed by conidia borne in chains. Li,-Ni, Pionnotes covering either the medium directly (Li), or a mycelial sheet (Mi), or numerous associated sporodochia (Ni) formed on the substratum. Examples: Fusarium poae (Peck) Wr. (A, J), F. orthoceras App. et Wr. (B, E, K, Ai, Bi), F. moniliforme Sheld. (C, F, G, GO, F. chenopodinum (Thüm.) Sacc. (D, M, N, Z), F. argillaceum (Fr.) Sacc. (H, I, Ci, DO, F. subcarneum Crouan (L), F. flavum (Fr.) Wr. (O), F. dimerum Penz. (P), F. salicis Fuck. (Q), F. sarcochroum (Desm.) Sacc. (R, S), F. vitícola Thüm. (T), F. solani (Mart. pr. p.) App. et Wr. (U), F. vasinfectum Atk. (V, normal, W, swollen, X, dried spore), F. tricinctum (Cda.) Sacc. with swellings of hyphae (y), F. macroxysporum Lindf. with pionnotal propagation of macroconidia (Ei) and development of microconidia (Fi). 836 Journal of Agricultural Research Vol. XXX, No. 9 For a proper understanding of the tions except Ventricosum terms (8) used for normal forms of re- and some species of Ele- productive stages and mycelium of gans and Eupionnotes Fusaria the characters considered of (#) in columns represent- primary importance are enumerated ing a chainlike develop- below. ment, as in F. stilboides I. NORMAL REPRODUCTIVE STAGES Wr. (fig. 1, KO. c. Shape: Fusoid-lanceolate, 1. Microconidia: 0-(0-3)-septate7 globose-pearshaped as in F. slightly curved, mostly poae (Peck) Wr. (fig. 1A); el- apedicellate, F. argilla- lipsoidal as in F. orthoceras ceum (Fr.) Sacc. (fig. 1, App. et Wr. (fig. 1, B); ovoid- I); slightly sickle-shaped, fusoid as in F. moniliforme apedicellate, F. betae Sheld. (fig. 1, C); comma- (Desm.) Sacc. (fig. 1, K) ; shaped as in F. chenopodinum sickle-shaped, pedicellate, most of the species; (Thüm.) Sacc. (fig. 1, D). strongly dorsiventral, F. They may be found scattered scirpi Lamb, et Fautr. (fig. 1, A-D), in false heads and F. chenopodinum (fig. 1, E), or in chains (fig.