Phragmotelium Mysorensis, a New Rust on Indian Raspberry
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PHRAGMOTELIUM MYSORENSIS, A NEW RUST ON INDIAN RASPBERRY BY M. J. THIRUMALACHAR (Department of Botany, Central College, Bangalore) Received January 13, 1942 (Communicated by Prof. T. $. Raghavan) THE genus Phragmidium founded by Link in 1824 contains several hetero- genous elements and four species that were originally placed in it, have been made the types of four new genera: Hamaspora Kornicke, Phragmotelium Sydow, Frommea Arthur and Earlea Arthur. Of these the first three genera were segregated from Phragmidium because of easily distinguishable morpho- logical characters and they are at present accepted by urediniologists. The genus Earlea erected by Arthur (1906) to provide for those species of Phrag- midium which lacked uredia in their life-cycle, is not accepted by Sydow (1915) or Dietel (1928), and Arthur himself now states that emphasis which was formerly placed upon the succession of spore-forms, should be transferred, because of a better understanding of the development of the rusts, to the vegetative states. The presence or absence of uredia which .according to Arthur, belong to the same state as telia cannot therefore be used to set off Earlea as a separate genus. Of the first three, the genus Phragmotehlum is characterised by telio- spores which have smooth walls and which germinate soon after ripening without any rest period. Their pedicels are not well developed and they do not swell in water. Aecia are further more lacking and their place is taken by aparaphysate primary uredia which form the first spore-form. As against this, the teliospores in Phragmidium are warty or verrucose, and they germinate only after a long rest period. Their pedicels are better developed and they swell when placed in water. The aecium which is the first spore- form in this genus is of the c~eoma type. Sydow (1921) transferred seven species of Phragmidium to Phragmo- teIium and three more species are mentioned by Hiratsuka (1935) who;e logical position is in the genus Phragmotelium. He does not recognise the genus Phragmotelium, which according to him is a section of Phragmidium a view with which the present author does not agree. The three species involved are ghragmidium formosanum Hirats P. Rubi-fraxinifolii Syd. (tenta- tively placed by Sydow in this genus as he had not seen the teliospores which 186 Phragmotelium mysorensis, a New Rust on Indian Raspberry 187 were later discovered by Hiratsuka), and P. Okianum Hara., and it is clear that they should be transferred to Sydow's genus as Phragmotelium formo- sanurn (Hirats) comb. nov. Phragmotelium Okianum (Hara.) comb. nov. and Phragmotelium Rubi-fraxinifolii (Syd.) comb. nov. Yet another species which is new has been recently found by the author on Rubus lasiocarpus Smith. It distinguishes itself from Phragmotelium burmanicum (Syd.) Syd., recorded on the same host, by its much larger and many septate teliospores. Indeed comparison of descriptions shows that this new species is easily the largest teliospored form for the genus. It FIG. 1 Leaf of Rubus lasiocarpus showin$ infection. X nat, si~ 188 M. J. Thirumalachar resembles Phragmotelium griseum (Diet.) Syd. But this species has telio- spores with three to four germ pores, a thicker epispore, fewer septa, slightly smaller size, and above all there are no paraphyses associated with its telia, which are characteristic of the new species. The name Phragmotelium mysorensis Thirumalachar and Mundkur is proposed for the new species. The fungus attacks only leaves (Fig. 1) causing severe blotches. The life- cycle of the rust includes all the spore-forms, viz., pycnia, aecia, uredia and telia. Uredia and telia are formed during the months of August and Septem- ber and pycnia and aecia in the months of October and November. Pycnia Pycnia are sub-cuticular (Fig. 2) and manifest themselves macroscopi- caUy as yellow specks. They are mostly formed on the midrib and the secon- dary veins (Fig. 5). The infected areas show slight swellings. The pycnial mycelia and pycnosporophores are uni-nucleate. Aecia Aecia are of the c~eoma type, covered with cylindric paraphyses, which are slightly recurved (Fig. 10). The aecial initials are formed in the hypo- dermal position by the concentration of hyph~e in the intercellular spaces (Fig. 9). The topmost cells of the hyphal knot which are uni-nucleate elongate and form a palisade layer of cells (Fig. 3). Each of these cells cuts off one or two sterile ceils which degenerate after a short period. Plasmogamy takes place between any two fertile cells, the connection being established by the dissolution of the septa (Fig. 4). In many cases the fusion of superposed cells takes place (Fig. 6). In any case the fusion cell elongates (Fig. 7), and by repeated cell divisions develops chains of aeciospore-mother-cells, which in turn form the intercalary cells and the aeciospores. Aeciospores are spherical and minutely verrucose, with three germ pores which become dis- tinct during germination (Fig. 8). The spores measure 16 x l0"6t~. Uredia Uredia are formed associated with telia. They are yellow and are surrounded by cylindric incurved paraphyses (Fig. 17). Urediospores are also yellow, echinulate (Fig. 14), with a single indistinct germ pore. The spores are stipitate, binucleate and measure 16 x 1 lit. When germinated on slides by the method suggested by the writer (1940) the germ tube with two nuclei can be observed (Fig. 15). Formation of appresorium at the tip of the germ tube is also of common occurrence. Phragmotelium mysorensis, a New Rust on Indian Raspberry 189 Fins. 2-9 Fig. 2. Camera lucida drawing of a pycnium, x 1800. Fig. 3. Fertile cells of the ~cium. x 1800. Figs. 4 and 6. Fusion of fertile cells, x 1800. Fig. 5. Showing the development of pycnia and a~cia on the midrib of the leaf. x400. Fig. 7. Development of a~ciospores-mother- cells, x1800. Fig. 8. iEeiospore germination showing three germ tubes, x560. Fig. 9, Section through an recial initial, x900, 190 M.J. Thirumalachar FiGs. 10-17 Fig. 10. /Ecium showing chains of spores and cylindric paraphyses, xg00. Fig. 11. Mature teliospore, x900. Fig. 12. Section through a mature telium, x400. Fig. 13. Ger- minating teliospore, x400. Fig. 14. Urediospore showing echinulate exospore, x1260. Fig. 15. Showing urediospore germination, x560. Fig. 16. Urd-nucleatesporidium. x900. Fig. 17. Section throu~,h a ~r showing stipitate spores and paraphyses, x400, Phragmotelium mysorensis, a New Rust on Indian Raspberry 191 Te~ Telia are hypophyllous, chestnut-brown in colour and are minutely distributed on the leaf surface. They are associated with paraphyses (Fig. 12). The teliospores are stipitate, and mature spores are five to six-septate. Telial initials are hypodermal from which cylindrical hypha~ with two conspicuous nuclei are differentiated. Each of these divides into a stalk cell and a spore initial. The latter by a series of conjugate mitosis and periclinal wall formation forms five to six-septate teliospores. Seven septate teliospores are also developed in rare cases. Mature teliospores are yellowish-brown, stipitate, smooth-walled with' two germ pores in each cell. The cells of the teliospores are superposed, and are slightly constricted along the septa. Teliospores germinate soon after they are mature (Fig. 13). In sections through the telia with spores of different maturity promycelia with basidiospores were observed in all the mature spores. It is evident that the teliospores are not resting spores. Following germination and formation basidiospores the promycelium breaks down, and the empty spore coat shrivels up and turns black in colour. Material collected for spore germination studies from old infected leaves had spores without cell contents. Teliospore germination indicated that the promycelium emerges through the germ pore and at one time more than one cell of the teliospore germinates simultaneously. The yeUowish-brown contents of the teliospores migrate into the promycelium. A four-celled promycelium is formed giving rise to basidiospores. The basidiopores are thin-walled, spherical and uni- nucleate (Fig. 16). They measure 11 x 10"Stz. Leaves of Rubus lasioearpus with freshly erupted telia were taken and suspended over young plants raised from cutting under rust-free conditions. The leaves of host plant were kept moist by spraying them with water. The plants were enclosed under bell-jars. After twenty days small discolourised spots were observed indicating the first sign of infection. Eight days after the pycnia were observed appearing macroscopically as orange yellow specks. Further development could not be followed owing to the death of the host plant. Description of the Rust PhragmoteRum mysorensis Thirumalachar and Mundkur, Spec. nov. Pycnia epiphyllous, sub-cuticular, without paraphyses. Aecia of the caeoma type, covered with long cylindric paraphyses; aeciospores yellow, oval or spherical, minutely verrucose, with three germ pores, measuring 16• 10.67. Uredia hypophyllous, associated with telia, minute, sparsely 192 M.J. Thirumalachar distributed, surrounded by incurved cylindric paraphyses; urediospores yellow, spherical, echinulate measuring I6 x l I/x, with an indistinct germ pore. Telia erumpent, chest-nut brown, sparsely distributed on the leaf surface, provided with paraphyses; teliospores stipitate, five to seven septate 5 celled spore measuring 64.5 to 73.5 x 23-2/z, 6-celled spore 77.4-85 x 23-2/x, and 7-celled spore 82-88 x 23-4/x, yellowish-brown smooth thin- walled, with two indistinct germ pores in each cell; pedicel hyaline, not swelling in water measuring 40 to 48g, spores germinating in situ immediately. Basidiospores thin-walled, spherical, measuring 11 • 10.5/z. Hab. on leaves of Rubus lasiocarpus Smith. leg., Thirumalachar, Nandi Hills, Mysore State, 16-2-1941. Type deposited in Herb. Crypt. Ind. Orient. of the Imperial Agricultural Research Institute, New Delhi. PhragmoteIium mysorensis Thirumalachar et Mundkur Spec. nov. Pycnia epiphylla, sub-cutioularia, aparaphysata, Aecia ca~moidea, paraphysibus, longis, cylindricis tecta; aeciospora: flavid~e, ovat~e vel spherical, tenuiter echinulata~, tribus germinatioins sporis instructae, magni- tudinis 16x 10.6/~.