In vitro propagation of cashewnut

The Agrobacterium rhizogenes oncogenes rolB and ORF13 increase formation of generative shoots and induce dwarfism in Arabidopsis thaliana (L.) Heynh

Plant transformation with the wild type Ri plasmid T-DNA of Agrobacterium rhizogenes is a promising method for breeding of compact plants and has been the subject of numerous studies. However, knowledge concerning the isolated functions of single genes and ORFs from the plasmid is limited. The rolB and ORF13 oncogenes of A. rhizogenes show considerable promise in plant breeding, but have not been comprehensively studied. Detailed information regarding the morphological impact of specific genes of the Ri plasmid will allow for optimized targeted breeding of plants transformed with the wild type Ri plasmid T-DNA. rolB and ORF13 were recombined into the genome of Arabidopsis thaliana using Gateway^® cloning and the effect on plant growth was assessed biometrically throughout the plants' life cycle. rolB-lines exhibited dwarfing, early necrosis of rosette leaves, altered leaf and flower morphology, and developed an increased number of inflorescences per rosette area compared to the wild type. ORF13-lines were extremely dwarfed, attaining only ca. 1% of the rosette area of the wild type, leaf and flower size was reduced, and the shape modified. The study documents that the traits inferred by the rolB oncogene yield plants with increased formation of generative shoots, but also result in some degree of premature senescence of vegetative organs. The extreme dwarfism seen in ORF13-lines indicate that this oncogene may be more important in the dwarfing response of plants transformed with the wild type Ri plasmid T-DNA than previously assumed and that transformation with this oncogene induces a very compact phenotype.

Micropropagation of seedless lemon (Citrus limon L. cv. Kaghzi Kalan) and assessment of genetic fidelity of micropropagated plants using RAPD markers

A micropropagation protocol was developed for multiplication of seedless lemon (Citrus limon L. cv. Kaghzi Kalan) using nodal explants. The maximum shoot regeneration was observed on low level of BAP (0.1 mg l(-1)) or kinetin (0.5 mg l(-1)). BA was recorded to be better than kinetin in terms of number of days taken to bud break. The maximum number of shoots per explant was observed on 0.1 mg l(-1) BA and 0.5 mg l(-1) kinetin. Shoot proliferation decreased with increasing concentration of BA alone, but in case of a combination of BA and NAA (0.1 mg l(-1) each), it increased with increasing concentration of BA up to 10.0 mg l(-1). None of the treatments including BA or kinetin alone or BA in combination with NAA produced significantly more shoots for commercial exploitation. In the case of a combination of BA + kinetin + IBA, the maximum (5.5 shoots per explants) proliferation was observed on MS medium containing 1.0 mg l(-1) BA + 0.5 mg l(-1) kinetin + 0.5 mg l(-1) IBA or 0.25 mg l(-1) BA + 1.0 mg l(-1) kinetin + 1.0 mg l(-1) IBA. Regenerated shoots showed root induction on MS basal medium or on MS medium containing 1.0 mg l(-1) IBA. It is concluded that a five-fold increase (1.0 mg l(-1) BA + 0.5 mg l(-1) kinetin + 0.5 mg l(-1) IBA) in axillary shoot proliferation, while seven-fold increase (0.25 mg/l mg l(-1) BA + 1.0 mg l(-1) kinetin + 1.0 mg l(-1) IBA) during the second cycle of multiplication could be obtained using the two plant growth regulator combinations. PCR amplification with 14 different random primers confirmed no somaclonal variant up to two cycles of shoot multiplication.