A New Fungal Parasite of Mosses

Abstract

Collections of the moss Leptodictyum riparium (Hedw.) Warnst. taken over several years from near Bonito Lake, New Mexico, were heavily parasitized by the fungus Stemphyllium botryosum Walr. Masses of hyphae were imbedded in the central strand of the host stem with the numerous conidia erupting only from the axil of the leaves. This is the first report of a moss parasitized by this species of fungus. Reports of moss parasitism by fungi are fairly common but in most cases the infection has not been described as specifically limited to the gametophyte, the sporophyte, or portions of these structures. A few authors have reported localized sites of hyphal growth or spore production on the moss plant: Stanley (1940) cited Eocronartium musicola solely on the gamretophyte of Campylium chrysophyllum but described no particular host response. Boros (1926) reported the genera Bryum, Buxbaumia, Gyroweissia, Tortula, and Dicranella as hosts of Cladosporium herbarum but gave no specific location of infection or host response. Seymour (1929) listed a considerable number of mosses that host parasitic fungi. Reports of localized infections on the moss sporophyte have included a new species of fungus, Pleospora pottiae, from the capsules of Pottia heimii (Boros 1926) and another new species, Sphaerulina 1 Department of Biology, Texas Technological College, Lubbock, Texas. This content downloaded from 157.55.39.59 on Mon, 17 Oct 2016 05:02:39 UTC All use subject to http://about.jstor.org/terms 244 THE BRYOLOGIST [Volume 69 muscorum, on the capsules of Mnium carolinianum (Wolf 1954). Several genera of mosses from tropical Asia were found to have the fungus Jola javansis infecting the seta and capsule (Giiumann 1922). All these articles merely touched upon the host response by mentioning a shriveled or stunted condition. Among moss collections made in 1964 from Bonito Lake near Alta, New Mexico, Leptodictyum riparium (Hedw.) Warnst. showed a large amnount of a fungus on the gametophytes. Since the locality had been visited several times previously, it was also possible to check moss collections made in 1958, 1960, and 1963. In all the collections of L. riparium some evidence of the parasitic fungus could be found. However, none of the other species of mosses in an extensive collection from this locality showed any evidence of infection with this fungus. With the help of Dr. Arthur Elliot, I identified the fungus as Stemphyllium botryosum Wallr. The perfect stage of this fungus is Pleospora herbarum. Neergaard (1945) described S. botryosum as a facultative parasite on many flowering plants 57 species have been reported as hosts for it but no mosses are included in this list. Seymour (1929) did not give Leptodictyum riparium as a host for any fungi nor was this moss discussed as a host by Nicolas (1932). The present paper is the first report of Stemphyllium botryosum (or its perfect stage) as a parasite of mosses and of Leptodictyum riparium as a host for fungi. Worthy of additional attention is the manner in which both the fungus and the moss express the host and parasite relationship. Figure 1 shows a typical stem segment of the gametophyte of L. riparium in which the hyphal strands of S. botryosum grow and from which the conidia arise. All the infected moss gametophytes are stunted. Fungal hyphae can be seen clearly following the central strand of the moss stem from node to node almost to the tip of the stem. At each node there is a denser accumulation of hyphae forming a knot or ball large enough to make the stem bulge (Fig. 2). From the nodal knot of hyphae a portion extends up the interior of the stem to the next higher node, a second portion branches out into the leaf in the costa region and a conidiophore erupts from the surface of the stem immediately above the point of leaf attachment. The conidiophores never emerge from the stem at any other place. After emergence the conidiophore may remain simple or may branch with each new branch bearing a conidium. This growth pattern is repeated at each node. The growth of the infected moss is different from that of healthy plants in several respects. Even though the plants are generally stunted, the intemodes are longer than those of a noninfected stem. Leaves where conidiophores arise are as much as one-half smaller than healthy leaves, both in length and width. The normal leaves of L. riparium are costate while those with conidiophores in the axil are ecostate. The fact that other species of mosses from the collecThis content downloaded from 157.55.39.59 on Mon, 17 Oct 2016 05:02:39 UTC All use subject to http://about.jstor.org/terms 1966] PRIOR: NEW FUNGAL PARASITE 245