Rapid plant regeneration and analysis of genetic fidelity of in vitro derived plants of Chlorophytum arundinaceum Baker--an endangered medicinal herb.

An efficient in vitro multiplication system via multiple shoot bud induction and regeneration has been developed in Chlorophytum arundinaceum using shoot crown explants. Optimum regeneration frequency (87%) and desirable organogenetic response in the form of de novo organized multiple shoot buds without an intervening callus phase was obtained on Murashige and Skoog's (MS) minimal organics medium containing 3% sucrose (w/v) supplemented with 4 x 10(-6) M Kn and 2 x 10(-6) MIBA. Axenic secondary explants with multiple shoot buds on subculturing elicited best response with 1 x 10(-5) M Kinetin (Kn) and 5 x 10(-6) M indole-3-butyric acid (IBA) giving rise to an average of 18.74 shoots per culture with mean shoot length of 7.6 cm +/- 1.73. Varying molar ratios of either Kn/IBA or Kn/NAA revealed statistically significant differences in the regeneration frequencies among the phytohormone treatments. It was observed that the shoot bud differentiation and regeneration was influenced by the molar ratios of cytokinins/auxin rather than their relative concentrations. Healthy regenerated shoots were rooted in half strength MS basal medium containing 3% sucrose (w/v) supplemented with 5 x 10(-6) M IBA. Following simple hardening procedures, rooted plantlets, were transferred to soil-sand (1:1; v/v) with more than 90% success. Genetic fidelity was assessed using random amplified polymorphic DNA (RAPD), karyotype analysis and meiotic behaviour of in vitro and in vivo plants. Five arbitrary decamers displayed same banding profile within all the micropropagated plants and in vivo explant donor. The cytological and molecular analysis complemented and compared well and showed no genomic alterations in the plants regenerated through shoot bud differentiation. High multiplication frequency, molecular, cytological and phenotypic stability ensures the efficacy of the protocol developed for the production and conservation of this important endangered medicinal herb.

Cytomixis impairs meiosis and influences reproductive success in Chlorophytum comosum (Thunb) Jacq. - an additional strategy and possible implications.

Spontaneous intercellular chromatin migration/cytomixis was observed to occur in the pollen mother cells (PMCs) of the Chlorophytum comosum for the first time. The migration through cytomictic channels was more pronounced in meiosis-I and very rare in meiosis-II. The process was associated with erratic meiosis, which was characterized by defects in chromosome organization and segregation. Cytomixis was more intense in the month of April than in July and consequently the frequency of meiotic irregularities was much more pronounced during the month of April. As a consequence of abnormal meiosis, fertility was drastically reduced resulting in meager seed efficiency of 17% only. Recombination system also does not guarantee the release of sufficient variability. We view the phenomenon of cytomixis as genetically controlled mechanism involving meiotic genes and operating through signal transduction pathway triggered by the environmental stimuli. The evolutionary significance and tenable hypothesis in the backdrop of existing literature is also proposed.