Seed Propagation of Caladium and Dieffenbachia
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404 FLORIDA STATE HORTICULTURAL SOCIETY, 1972 attractancy of bacteria cultures to Anoetus was populations of Anoetus were the most migratory consistent with previous tests. and best stage by which to test attractancy of cultures. The hypopus is a non-feeding migratory Discussion form resistant to, and apparently formed as a re sult of environmental stress. They are transported, The soil-inhabiting, saprophytic mites Anoetus or will migrate, to areas of higher nutritional feroniarum and Rhizoglyphus robini can survive levels and lower environmental stress before com and reproduce on several fungi and bacteria com pletion of life cycle (6, 8). Since both Rhizogly monly associated with Gladiolus hortulansus. Anoe phus and Anoetus have a hypopal state in their tus is strongly attracted to bacterial cultures of life cycle, the importance of this stage relative Pseudomonas marginata and Pseudomonas mar- to their suggested vector roles demands further ginalis. Rhizoglyphus prefers Fusarium oxy- study. sporum. The fact that mites are attracted to selected Literature Cited phytopathogens may be important in elucidating 1. Bald, J. G. and R. N. Jefferson. 1952. Injury to possible disease-vector relationships of gladiolus gladioli associated with the root mite, Rhizoglyphus rhizo- in Florida. The demonstrated affinity by Anoetus phagus. Plant Dis. Reptr. 36: 435-437. 2. Englehard, A. W. 1969. Bulb mites associated with for bacterial cultures, in particular the pathogenic diseases of gladioli and other crops in Florida. Phytopath ology 59: 1025 (Abstr.). isolate P. marginata Br-1, suggest that the vector 3. Forsberg, J. L. 1959. Relationship of the bulb mite capabilities of this mite should be investigated. Rhizoglyphus echinopus to bacterial scab of gladiolus. Phy topathology 49: 539 (Abstr.). Conversely, the demonstrated affinity by Rhizo 4. 1965. The relationship of Pseu domonas marginata, Stromatinia gladioli, bulb mites, and glyphus for Fusarium cultures, and not bacterial chemical soil treatments to the occurrence and control of cultures, does not readily relate to published re scab and Stromatinia rot of gladiolus. Phytopathology 55: 1058 (Abstr.). ports implicating Rhizoglyphus mites as vectors of 5. Lelliott, R. A., Eve Billing, and A. C. Hayward. 1966. A determinative scheme for the flouorescent plant patho the causal organism of bacterial scab, P. margin genic pseudomonads. J. Appl. Bacteriol. 29: 470-489. ata. It should be pointed out that the species of 6. Poe, S. L. 1966. A study of certain factors influencing hypopial transformation in Caloglyphus boharti (Acarina: Rhizoglyphus used in these experiments is not Tyroglyphidae) M. Sc. Thesis, Northwestern State College, Natchitoches, Louisiana. the same as reported by Forsberg (3, 4) to be a 7. 1971. Microfaunal populations on vector of P. marginata. Species, or even clonal, gladiolus corms. The Florida Entomologist 54: 127-133. 8. Woodring, J. P. 1963. The nutrition and biology of variation in preferences for certain disease-causing saprophytic sarcoptiforms. In Advances in Acarology. J. A. Naegele (ed). 1: 89-111. organisms should be investigated. 9. Yoshizawa, T., I. Yamamoto, and R. Yamamoto. 1971. As noted in Experiments 3, 4, 5, hypopal Synergistic attractancy of cheese components for cheese mites, Tyrophagus putrescentiae. Botyu-Kagaku. 36: 1-7. SEED PROPAGATION OF CALADIUM AND DIEFFENBACHIA R. D. Hartman and F. W. Zettler taining pathogen-free plants as well as new hy brids. Through cross pollination, viable seed of I FAS Plant Pathology Department caladium (Caladium hortulanum Birdsey) and Gainesville dieffenbachia (Dieffenbachia picta Schott) were and obtained. Each fertilized caladium ovary con J. F. Knauss and Eleanor M. Hawkins tained < 14 seeds whereas dieffenbachia ovaries were single-seeded. Caladium fruits ripened 5-6 IF AS Agricultural Research Center, weeks after pollination and abscissed from the Apopka spadix. Dieffenbachia fruits became red upon ripening 10-12 weeks after pollination, but re Abstract. Aroids do not ordinarily set seed mained loosely attached to the spadix. Seed of under natural conditions in Florida and hence are both species germinated readily when removed commercially propagated by vegetative means. from the fruit and planted in moist peat. However, producing seed provides a means of ob- Plants of the family Araceae comprise a sub Florida Agricultural Experiment Stations Journal Series stantial proportion of the ornamentals produced No. 4615. HARTMAN ET AL.: CALADIUM AND DIFFENBACHIA FROM SEED 405 commercially in Florida. Approximately 96% of Materials and Methods the world's commercially produced caladiums are grown in Florida (7), and aroids such as aglao- The crosses were made between plants of nema, dieffenbachia, philodendron, pothos and syn- Dieffenbachia picta (Schott) 'Exotica' or Calad gonium account for nearly half of the State's ium hortulanum (Birdsey) 'Candidum.' The pa foliage industry (9). In addition, Ci*yptocoryne rental stock used in these crosses was provided spp. are aroids of considerable significance to Flor by Mr. Lamont Marchman of Evergreen Gardens ida's unique aquarium plant industry. Aroids are of Apopka, Inc. and Mr. Norman Hickerson of propagated commercially almost exclusively by Hickerson Flowers, Inc., of Apopka, Florida. Dief vegetative means rather than by seed. fenbachia plants were grown in a stock bed in a fiberglass house at Apopka and pollinated May- Various nematodes, bacteria and fungi infest June, 1971, whereas caladiums were grown in avoid nursery plantings in Florida and cause Gainesville either in a greenhouse or outdoors and serious economic losses. In addition, a virus of pollinated May-June, 1972. The pollination pro aroids called dasheen mosaic virus has been cedures were similar to those described by McCol shown to be widespread in Florida and elsewhere ley and Miller (8) for philodendron. All crosses (1, 3, 11). Hartman and Zettler (5) surveyed were made between 6-10 a.m. or 5-8 p.m. Caladium foliage nurseries and caladium plantings in Florida and dieffenbachia like philodendron are dicho- and provided evidence that certain mainstay dief gamous. Pollen was collected daily with a camel- fenbachia and caladium cultivars are uniformly in hair brush and transferred within 48 hours after fected with dasheen mosaic virus and hence virus- shedding to neighboring receptive blooms of differ free plants are no longer available. Such wide ent plants. Bloom receptivity was indicated 1) spread incidence of disease among aroids is abetted when the spathe began to unfurl revealing the dis by propagating these plants vegetatively. As tal portion of the spadix and 2) by the increased pointed out by Baker (2), relatively few plant stickiness of the stigmatic surfaces of the spadix. pathogens are seed-bome, and thus, seed propa Prior to pollination, the spathe was cut away from gation provides a useful means of eliminating phy- the spadix, discarded, and the pollen was gently topathogens that have proliferated in vegetative applied to the proximal ovulate portion of the material. Calla lily, for example, is an aroid that spadix with a brush. can be grown free of soft-rot bacteria, water molds and Rhizoctonia infections by planting seed rather than corms (2). Results Despite the considerable potential of seed propa Dieffenbachia fruits, although cream colored gation as a method to rid aroids of phytopathogens during most of their development, became red when and to create new horticultural varieties, most ripe approximately 10-12 weeks after pollination. Florida growers are not aware of the techniques Dieffenbachia fruits did not abscise but remained involved in producing aroid seed. A notable excep loosely attached to the spadix (Fig. 1). A spadix tion is the hybridization of philodendrons as de bore 15-30 ovaries, each containing a single round scribed by McColley and Miller (8) and by West seed 5-6 mm in diameter which was green when and Miller (10). Caladium growers once were mature. Seeds germinated within 20 days after supplied with new caladium hybrids by Mr. Frank they were removed from the fruit and planted in M. Joyner, a caladium hobbyist from Tampa, but moist peat. he has become inactive in recent years and this Unlike dieffenbachia, caladium fruits ripened work has since received no attention. Dieffenbachia 5-6 weeks after pollination and abscissed from the species were once hybridized at the turn of the spadix (Fig. 2). The exposed fruit surfaces re century, but are no longer grown from seed; thus mained green throughout their development with growers must rely upon chance somatic mutations out apparent color change at the time of abscission. for new cultivars. As indicated by McColley and The unexposed surfaces of the ovary walls were Miller (8), special techniques must be employed cream-colored at maturity. Ovulate portions of the to obtain seed of many aroids. Unfortunately the spadix contained approximately 200 seed-bearing paucity of published reports on the specific hy ovaries, each containing 1-14 oval seeds which bridization techniques for aroids deters growers were 1-1.5 mm in length and light tan in color. from using seed propagation as a useful and im As many as 1500 seeds were obtained from a portant tool. Accordingly, this study with dief single spadix. Seeds germinated readily 8-10 fenbachia and caladium was conducted. days after removal from the fruit and planting 406 FLORIDA STATE HORTICULTURAL SOCIETY, 1972 Fig. 1. Dieffenbachia spadix. A) during pollen shed. B) developing fruit 5-6 weeks after pollination. C) mature fruit 10-12 weeks after pollination. Fig. 2 Caladium spadix. A) at time of pollination. B) distal portion during pollen shed. C) proximal portion just prior to fruit abscission. D) shed fruit at abscission 5-6 weeks after pollination. HARTMAN ET AL.: CALADIUM AND DIFFENBACHIA FROM SEED 407 B Fig. 3. Dieffenbachia seedlings 12 months after germination. Note differences in foliar variegation patterns (A) and in degree of shoot proliferation (B). 408 FLORIDA STATE HORTICULTURAL SOCIETY, 1972 them in moist peat. Seed germination rate de genetic potential for deriving improved horticul creased markedly, however, when seeds were tural varieties.