In vitro mutagenesis in Rosa hybrida using oryzalin as a mutagen and screening of mutants by randomly amplified polymorphic DNA (RAPD) marker

Apical and axillary meristems of Rosa hybrida Cv. First red were pretreated with various concentrations (0, 5.0, 10.0, 15.0, 20.0, 25.0 and 30.0 μM) of oryzalin (C12H18N4O6) to induce variation in vitro. The present results indicate that fifty percent survivability (LD50) was obtained in 20 μm oryzalin. Both the treated and untreated meristems were cultured in Murashige and Skoog (MS) basal medium supplemented with 0.5 mg/l benzylaminopurine (BAP), 0.01 mg/l indole acetic acid (IAA), 25 mg/l adenine sulphate (Ads) and 20 μm oryzalin. The elongated shoots were rooted in the half strength MS basal medium supplemented with 0.25 mg/l indole-3-butyric acid (IBA) and about 60% rooted plants survived in the green house. A total of 28 mutants were obtained and evaluated by randomly amplified polymorphic DNA (RAPD) markers using control as untreated meristems. Out of the twenty-eight mutants, eight mutants, which deviate from the DNA banding pattern when compared with the control plants, were obtained. This result showed the efficiency of oryzalin to induce in vitro variability in hybrid rose and detect variation through molecular markers. This investigation will give a better understanding on the rose breeding program.Key words: Hybrid rose, in vitro, oryzalin, mutation

An assessment of genetic fidelity of in vitro grown plantlets of rose (Rosa hybrida) through molecular markers

A simple and routine method for the analysis of somaclonal variation among tissue culture derived rose plants is a prerequisite for precise monitoring of quality control during rapid mass micropropagation. Random  amplified polymorphic DNA (RAPD) and inter simple sequence repeats (ISSR) molecular marker techniques were employed to validate the genetic fidelity in three varieties of Rosa hybrida [Culture varieties (cvs) First  Red, Cri Cri and Pusa Gaurav] multiplied in vitro by axillary multiplication for up to 26 subcultures. Twelve  RAPD and seventeen ISSR primers generated a total of 119, 104 and 114 amplicons in cvs First Red, Cri Cri  and Pusa Gaurav, respectively. A homogeneous amplification profile was observed between the explant source and all the micropropagated plantlets. The result indicated the clonal fidelity of the tissue culture raised R.  hybrida plantlets and corroborated the assumption that axillary multiplication is the safest mode for  multiplication of true to type plants without any somaclonal variation.Key words: Rosa hybrida, in vitro, genetic fidelity, molecular markers

Fast X-Ray Fluorescence Microtomography of Hydrated Biological Samples

Metals and metalloids play a key role in plant and other biological systems as some of them are essential to living organisms and all can be toxic at high concentrations. It is therefore important to understand how they are accumulated, complexed and transported within plants. In situ imaging of metal distribution at physiological relevant concentrations in highly hydrated biological systems is technically challenging. In the case of roots, this is mainly due to the possibility of artifacts arising during sample preparation such as cross sectioning. Synchrotron x-ray fluorescence microtomography has been used to obtain virtual cross sections of elemental distributions. However, traditionally this technique requires long data acquisition times. This has prohibited its application to highly hydrated biological samples which suffer both radiation damage and dehydration during extended analysis. However, recent advances in fast detectors coupled with powerful data acquisition approaches and suitable sample preparation methods can circumvent this problem. We demonstrate the heightened potential of this technique by imaging the distribution of nickel and zinc in hydrated plant roots. Although 3D tomography was still impeded by radiation damage, we successfully collected 2D tomograms of hydrated plant roots exposed to environmentally relevant metal concentrations for short periods of time. To our knowledge, this is the first published example of the possibilities offered by a new generation of fast fluorescence detectors to investigate metal and metalloid distribution in radiation-sensitive, biological samples

HIV infection of non-dividing cells: a divisive problem

Understanding how lentiviruses can infect terminally differentiated, non-dividing cells has proven a very complex and controversial problem. It is, however, a problem worth investigating, for it is central to HIV-1 transmission and AIDS pathogenesis. Here I shall attempt to summarise what is our current understanding for HIV-1 infection of non-dividing cells. In some cases I shall also attempt to make sense of controversies in the field and advance one or two modest proposals