CYTOLOGY AND LIFE HISTORY OF A BISPORIDIAL ENDOPHYLLUM

Transcription

1 CYTOLOGY AND LIFE HISTORY OF A BISPORIDIAL ENDOPHYLLUM BY M. J. THIRUMALACHAR AND M. J. NARASIMHAN Bangalore, India {Received 2 June 1949) (With I figure in the text) Germination studies of the aeciospores of a rust collected on Heliotroptum indicum L. near Sreerangapatna, Mysore, South India, indicated that the aecia are telioid and the rust was a microcyclic Fndophyllum. The rust infects leaves, tender stems and calyx lobes. On the leaves the infection patches are 5-15 mm. in diameter, often becoming larger by coalescence; on the stems they are slightly raised, and on drying turn greyish black in colour. The infected portion of the leaf dries up during summer, but the rust is not killed. Fresh sori continue to erupt along the margin of the dried infection patch, in spite of the extremely arid conditions which prevail during the summer. Microscopic examination revealed the abundance of telioid aecia on the infection patches. On the leaves they are hypophyllous, subepidermal, erumpent and pulverulent. Sections through the sori show chains of 'aeciospores' developing from the base and the presence of a well-developed peridium. The 'aecia' are not usually accompanied by pycnia, but in some cases the latter are found to occur sparsely and are globular, subepidermal (Fig. \a) and either abortive or imperfectly developed. In no instance were they seen to open out or to develop an ostiole or paraphyses. In this respect they resemble some of the species of Fndophyllum reported by Stevens & Mendiola (1931) from the Philippines. The pycnia are sometimes so deeply seated that they are invisible from the surface. Mature 'aeciospores' are angularly globoid with thin minutely punctate walls having five to eight indistinct germ pores, and they have orange-yellow contents (Fig. i d). The peridial cells are globoid, abutting on the sides, thick-walled and densely rugose. The 'aeciospores' germinate within 5-10 hr, at room temperature (20-24 C). The promycelium is stout and cylindric, and in all cases is two-celled. Sometimes the contents of the upper cell move to the apex and a septum is formed at the base cutting of an empty cell (Fig, if). A short sterigma is formed from each cell of the promycelium and bears a globular sporidium (Fig, i^). The sporidia germinate in situ, developing short germ tubes. Bifurcation of the tips of the promycelia and other abnormal features associated with excess of moisture have been observed. Germinating spores with sporidia were used for inoculating healthy Heliotropium indicum plants grown under rust-free conditions. The inoculated plants were enclosed in moist chambers for 48 hr, after which they were placed in the greenhouse for further observations. Successful infection was indicated, after 12 days, by the appearance on the leaves of small yellowish specks which expanded into yellowish patches. Aecial development was observed after 18 days.

2 ii8 M. J. THIRUMALACHAR AND M. J. NARASIMHAN Comparisons with other known species of Endophyllmn so far described indicate that the present rust is undescribed. Aecial stages of the grass rust Puccinia aristidae Tracy occur on Heliotropium. Comparisons with other aecial stages on the same host genus Fig. I. a, pycnium, x 750; b, section through young aecium showing the formation of aeciospores x 1800; c, binucleate aeciospore, x 1500; d, aeciospore showing the disposition of the germ pores, x 1500; ej, germinating tehoid aeciospores, x iooo;g, showing the formation of sporidia, x 1000; h sporidium germinating m situ, x such as Aecidium heliotropii-europaei Schroet., A. heliotropidatum Schw. and others (Sydow, H. & Sydow, P., 1924) indicate that the rust under study is distinct. The name Endophyllum heliotropii is proposed for it.

3 Cytology and life history of a bisporidial Endophyllum 119 Endophyllum heliotropii Thirum. & Narasimhan, n.sp. Pycnia subepidermal, not well developed. Aecia telioid, hypophyllous, developed on slightly hypertrophied spots, golden-yellow, cupulate, erumpent and pulverulent, peridiate. Pseudoperidia firm, reflexed; peridial cells angularly globoid to polygonal, densely rugose, wall 1-5-2^ thick, measuring ^ U-'^ll^- Aeciospores developed in chains, angularly globoid, golden-yellow, thin-walled, minutely punctate, x I2-I5-5;LI, with five to eight indistinct germ pores. Spores germinate at maturity by a two-celled promycelium bearing globular sporidia. Habitat: on the leaves, stems and infiorescence of Heliotropium indicum L., Sreerangapatna, Mysore, leg. H. C. Govindu and B. A. Razi (type), 28 December Type material deposited in the Herb. Crypt. Ind. Orient. New Delhi, in Herb. C.M.I., Kew, England, in the Arthur Herbarium, Purdue University, Lafayette, Indiana, and in the Mycological Herbarium, U.S.D.A., Behsville Maryland. Pycnia subepidermalia, haud evoluta. Aecia telioidea, evoluta in maculis tenuiter hypertrophiatis, lutea, cupulata, erumpentia atque pulverulentia, peridiata. Pseudoperidia firma, refiexa, cellulae peridiales angulariter globoideae ad polygonales, dense rugosae, parietibus 1-5-2/^. crassis magn ^ I3~i7/^- Aeciosporae catenulatae, angulariter globoideae, luteae, tenuibus parietibus praeditae, minute punctatae, magn x12-i5-5/x; inmaturitataegerminantesper 2-cellulatumpromyceliumglobularibus, sporidiis ornatum. Hab. In foliis atque caulibus et inflorescentia Heliotropii indici L. CYTOLOGY A cytological study of the rust seemed desirable, since the aeciospores on germination developed a two-celled promycelium. As Jackson (1935) has pointed out, the presence of a two-celled promycelium in rusts is correlated, in every case which has been investigated, with some variation in nuclear sequence. The material for cytological study was fixed in Allen's modified Bouin's fluid and the microtome sections were stained with Heidenhain's iron-alum haematoxylin or Newton's iodine-gentian violet. The germinated spores were stained by the method suggested by one of the writers (Thirumalachar, 1940). Observations indicated that the mycelium in the host is intercellular and binucleate. The aecial initials are subepidermal in origin and the cells composing them are binucleate. The basal cells abstrict aeciospores in succession (Fig. ib). Sterile intercalary cells have been observed in very few cases. The aeciospores are binucleate even in the mature state and the nuclei do not fuse (Fig. ic). In a germinating aeciospore the promycelium is formed as a tubular cylindric structure. The two nuclei move into the promycelium and show no further divisions (Fig. le). Instead, the two nuclei are separated by the formation of a septum. The upper cell of the promycelium first forms a sterigma bearing a globular sporidium, followed by similar development in the lower cell (Fig. i^). The nucleus after migrating into the sporidium undergoes a division resulting in a binucleate condition. This is clearly seen in the germinating sporidium. The nuclear division in the sporidium probably initiates the dicaryophase, since the mycelia in the host resulting from sporidial infection are binucleate. The type of nuclear cycle outlined for Endophyllum heliotropii has many points in common with Herpobasidium filicinum (Rostr.) Lind. (Thelephoraceae), investigated by Jackson (1935), who compared it with the known types of variation in the nuclear

4 120 M. J. THIRUMALACHAR AND M. J. NARASIMHAN cycle met with in microcyclic rusts. The basidium in H. filicinum is two-celled, formed by a single division of the fusion nucleus. No evidence for a second division of the nucleus was found by Jackson, and since there was a binucleate condition in the host, he assumed that the first division of the sporidial nucleus on germination may initiate the dicaryophase. Jackson further compared it with Puccinia arenariae (Schum,) Wint,, where the promycelium is two-celled bearing sporidia. However, in Herpobasidium filicinum, if Jackson's assumption of the nuclear cycle is correct, the second division is delayed till the sporidia germinate. The Fndophyllum under study shows the same type of initiation ofthe dicaryophase and a two-celled promycelium as in Herpobasidium filicinum, with this difference, that the two nuclei in the telioid aeciospore do not fuse, but remain separate. In this respect it resembles Fndophyllum euphorbiae-sylvaticae (DC.) Wint. which, however, forms a four-celled promycelium bearing four uninucleate sporidia. Further, the mycelium within the host is uninucleate in contrast to the binucleate condition in Herpobasidium filicinum and Fndophyllum heliotropii. The writers wish to acknowledge their thanks to Dr G. R. Bisby, Commonwealth Mycological Institute, Kevv^, England, for going through the manuscript. Rev. Dr Father H. Santapau, Professor at St Xavier's College, Bombay, kindly translated the diagnosis of the new species into Latin. REFERENCES JACKSON, H. S. (1935). The nuclear cycle in Herpobasidiumfilicinum with a discussion of the significance of homothallism in Basidiomycetes. Mycologia, 27, STEVENS, F. L. & MENDIOLA, V. B. (1931). Aecioid short cycle rusts of the Philippine Islands. Philipp. Agric. 20, SYDOW, H. & SYDOW, P. (1924). Monographia Uredinearum, 4, 671. Leipzig. THIRUMALACHAH, M. J. (1940). A method for germinating and staining teleutospores. J. Indian Bot. Soc.

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