ESTIMATION OF NUCLEAR RATIOS DIRECTLY FROM HETEROKARYOTIC MYCELIA IN SCHIZOPHYLLUM

MENZEL, MARGARET Y. (Florida State U., Tallahassee), and F. D. WILSON. Cytotaxonomy of twelve species of Hibiscus seetion Furcaria. Amer. Jour. Bot. 50(3): 262-271. Illus. 1963.-Metaphase-I chromosome numbers and pairing in 88 accessiens showed that H. cannabinus, H. costatus, and H. surattensis are diploid (n = 18); and H. acetosella, H. aculeatus, H. bifurcatus, H. furcellatus, H. meeusei, H. radiatus, H. rostella tus and H. sabdariffa are tetraploid (n = 36), with similar low multivalent frequencies, hence probably allotetraploids each combining 2 well-differentiated genomes. No intraspecific variation in ploidy was found. Fertile, vigorous F1 hybrids between H. furcellatus and H. bifurcatus showed complete chromosome pairing (n = 36), confirming a close relationship between the parents. Two African strains of H. diversifolius were octoploid (n = 72) with low multivalent frequency and hence probably contain 4 differentiated genomes. At least 4, perhaps 5 or 6, differentiated genome groups are represented in tropical Africa, and at least 2 in the American tropics. A SHORTAGE of j ute in world markets, which began during World War II and has become more acute as jute-producing regions consume ever larger percentages of their own output, has led to interest in jute substitutes less demanding in cultural requirements and more amenable to economical production in other parts of the world (cf. Bally, 1955a, b). Two species of the genus Hibiscus (Malvaceae), H. cannabinus L. ('kenaf') and H. sabdariffa L. ('roselle'), are among the more promising substitutes. One of the chief obstacles to cultivation of kenaf in Florida is its 1 Received for publication August 8, 1962. This report is based on research conductet1 cooperatively by the Crops Research Division and the Agricultural Engineering Research Division, Agricultural Research Service, United States Department of Agriculture, and the University of Florida Agricultural Experiment Station, Everglades Experiment Station, Belle Glade, Florida. The senior author acknowledges the courtesy of the Department of Biological Sciences, Florida State University, in making available laboratory space and other facilities for the cytological studies. Thanks are extended to the many organizations and individuals, some of whom are not mentioned in the paper, whose courtesy and cooperation made it possible to assemble the living materials and information on which this study was based. 2 Geneticists, Crops Research Division, Agricultural Research Service, United States Department of Agriculture. susceptibility to root-knot nematodes (Summers, Pate, and Wilson, 1958). Genetic resistance exists in H. acetosella Welw. ex Hiern (Pate, Summers, and Menzel, 1958) and H. sabdariffa L., and to a lesser degree in H. radiatus Cav. Hibiscus sabdariffa has not been successfully crossed with H. cannabinus. The tetraploid species H. acetosella and H. radiatus cross readily with diploid H. cannabinus (Menzel and Wilson, 1961b), but the triploid hybrids are practically sterile and the fertile, colchicine-induced H. cannabinus-acetosella allohexaploid is agronomically unsatisfactory. Hence, a survey of other relatives of H. cannabinus and H. sabdariffa was undertaken for additional sources of genetic variation. Hibiscus cannabinus and H. sabdariffa belong to section Furcaria DC. of the genus, characterized by a leathery or succulent fruiting calyx with 110 prominent nerves or ribs: each of the 5 calyx lobes has a medial nerve, and a commissural nerve passes to each sinus and then branches to form a prominent ridge along the margin of each lobe. The epicalyx bracts (bracteoles) are numerous, free or joined to the calyx only at the base, and frequently divided at the tip into an inner and an outer fork. Section Furcaria, as deThis content downloaded from 157.55.39.27 on Mon, 05 Sep 2016 03:59:52 UTC All use subject to http://about.jstor.org/terms