Two cell lines with 6 and 15 chromosomes were obtained from a predominantly diploid (Cchromosome line) suspension culture sf Haplopappus g r a d i s (Nutt.) Gray. Selection was found to be 'conservative' in the 4 and the 6-chromosome line, while it was 'progressive' in the 16-chromosome line. Mitotic abnormalities and chroms~ma! aberrations were most frequent in the 16-chromosome line and least frequent in the 4-chromome line. When grown in mixtures the frequency of one line i n c r d while th% other Iiae or lines were rapidly eliminated. The Cchromosome line showed the highest fitness. It was coaicluW that the 6-and/or the 16-chromosome lines were. e!irninakd from mixtures due to slower growth rates.Cytogenetic studies with plant tissue euf tures have revealed that the karyotypic composition of many cell populations changes during in vitro cu1tiviltion. The changes in the karyotype may be brought about by endoreduplication and/or a number of other mitotic irregularities (Partmen, 1963(Partmen, , 1965 Sacristan, 197 1) and nuclear fusion. The effects of these processes m y be either amplified or nullified by selection (Singh et al., 1972; Kas et al., 1970;Sacristan, 1971). A significant positive csrreIPrtisn between growth rate and chromosome number was observed in callus cultures of Picea glauca Vsss. (BeTorok, 1968) which indicates selection in favor of polypbid cells. On the other hand, strong selection for diploid cells has been demonstrated in Vicia hjmtam Grossh, suspension cultures ( Singh et al., 1972).In the present study, the kaqotypic changes in three lines of Haplopeppus gradis (Nutt . ) Gray, with different chromosome numbers, were investigated during a period s f 398 days of in vitrs culture, These lines were also grown in mixtures to investigate their relative competitive ability. MateriaL and MethodsThe H . gracilis suspension cultures used in this study were originally obtained from Dr. Tage Eriksson, Uppsala, Sweden, and have been maintained in liquid 3 5 medium (Gamborg et at., 1968) for more than four years. The majority of the cells in this culture had four chromosomes, i.e. diploid, hence it will be referred to as the 4-chromosome line.Cells from the 4-chromosome line were used to establish callus cultwes on agar, from which suspension cuitures were established. One of the cultures thus obtained had 6 chromosomes with distinct morphology. This culture will be referred to as &e 6-chromosome line.A callus culture was initiated from prstopiasts of the 4-ckomossme line (Kao et al., 1971). A suspension culture obtained from a colony of cells h r n this cdius had 16 chromosomes and will be referred to as the 16-chromssme line. h4anuscrigt received September 27, 1974. Cm. J. &net. Cytsl. 17: 109-116, 1975.Can. J. Genet. Cytol. Downloaded from www.nrcresearchpress.com by LEHIGH UNIVERSITY on 12/13/14For personal use only.

The present investigation was carried out at Anand Agricultural University, Gujarat during the year 2016 to develop a micropropagation protocol for mass multiplication of medicinally rich stevia plants. Axenic culture was established by sequential application of 200 mg/l Kanamycin, 200 mg/l Carbendazim-50% and 1000 mg/l HgCl2. Out of two different basal media, viz. Gamborg (B5) and Murashige and Skoog (MS) used, full strength MS gave highest (98%) culture establishment. Out of three different basal media, viz. Gamborg’s (B5), Linsmair and Skoog (LS), Murashige and Skoog (MS) and four different cytokinins, viz. 6-benzylaminopurine (BAP), Kinetin (Kn), Thiadiazuron (TDZ), Zeatin (Zn) tested for multiple shoot induction, full strength MS medium and 2 mg/l BAP, respectively, promoted maximum shoot formation. In the experiment to study the effect of varying strength of MS media and various plant growth regulators, viz. Indole-3-acetic acid (IAA), Indole-3-butyric acid (IBA), Naphthalene acetic acid (NAA) on in vitro rooting, ½ strength MS and 1 mg/l NAA, respectively, gave superior response. Among the 26 different combinations of potting mixtures used for primary acclimatization of in vitro rooted plants, cocopeat based substrates yielded highest survival rate (75.06%). Secondary acclimatization was carried out in the soil bags in the poly house. Thus, a reproducible and reliable micropropagation protocol for mass multiplication of Stevia rebaudiana (Bertoni) Bertoni using nodal segments has been developed.