Axenic Culture and Induction of Callus and Sporophytes of the Appalachian Vittaria Gametophyte

Abstract

Asexually-reproducing gametophytes of the four tropical fern genera Hymenophyllum, Trichomanes, Grammitis, and Vittaria occur in the uplands of the southeastern United States (Farrar, 1967). The most common and abundant of these is the Appalachian Vittaria gametophyte, which Farrar (1978) has described in detail. Dr. A. J. Sharp of the University of Tennessee was the first to find and collect the Appalachian Vittaria gametophyte in the area of the Mountain Lake Biological Station in Virginia. Since that time, Dr. W. H. Wagner, Jr. of the University of Michigan collected it in the same area and catalogued it into a pteridophyte flora (Wagner, 1963). Other pteridologists have collected it in the area of the Highlands Biological Station in North Carolina (Wagner et al., 1970; Pittillo et al., 1975) and in Tennessee (Wofford & Evans, 1979). Other collections have located these gametophytes in several eastern states in and around the southern Appalachians (Farrar, 1978; Gastony, 1977). Appalachian Vittaria gametophytes are long-lived and produce extensive colonies in deep, protected crevices of non-calcareous rock. Although antheridia and archegonia are produced on the gametophytes, reduced, juvenile sporophytes have been found only once in the field by Farrar (1978). They were recognizable as Vittaria, but lacked sufficient characters for identification to species. Since most taxonomic characters for determining fern species are based on sporophyte morphology, the origin and affinities of these gametophytes are uncertain. They were first assigned to the genus Vittaria by Wagner and Sharp (1963) based on finding similar morphological characters between the gametophytes of the Appalachian Vittaria and those of Vittaria lineata (L.) J. E. Smith from Florida. The chromosome counts reported by Gastony (1977) have provided further evidence of their relationship. The experimental production of sporophytes might provide additional taxonomic characters for comparison with the Vittaria species. Farrar (1978) reported that Appalachian Vittaria gametophytes were difficult to maintain in axenic culture and ceased to grow on defined media. We report here successful axenic culture of the Appalachian Vittaria gametophyte and the spontaneous formation of callus and sporophytes.