A system for enhanced induction of somatic embryo‐genesis and regeneration of plants from isolated scutellar tissue of wheat has been developed. This system has been successfully used in the development of a simple and reproducible protocol for the production of self‐fertile transgenic wheat plants. The procedure is rapid resulting in the production of transgenic plantlets within 12 weeks from initiation of cultures and it avoids the need for establishing long‐term callus, cell suspension or protoplast cultures. Somatic embryos regenerated from scutella bombarded with plasmid pBARGUS were selected on L‐phosphinothricin (L‐PPT) to obtain herbicide‐resistant self‐fertile transgenic plants. Phosphinothricin acetyltransferase (PAT) activity was observed at varying levels in 50% of the plants selected on L‐PPT whereas none of the plants showed β‐glucuronidase (GUS) activity. Molecular analysis of PAT‐positive plants confirmed stable integration of both bar and gus genes in R0 and R1 progeny plants. Segregation of the PAT activity and herbicide resistance in R1 progeny plants confirmed the Mendelian inheritance of the bar gene. Additionally, isolated scutella bombarded with plasmid DNA containing a gus::nptII fusion gene driven by a rice actin promoter and its first intron were selected in the presence of geneticin to obtain fully fertile transgenic plants. Functional expression of the fusion gene was demonstrated in transgenic plants by GUS and neomycin phospho‐transferase (NPTII) enzyme assays. Southern blot analysis confirmed the integration of transgenes into the wheat genome. Histochemical GUS staining showed transmission of the fusion gene to floral organs of primary transformants and confirmed Mendelian segregation of the transgene in R1 progeny.

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The regeneration potential of shoot apical meristems of soybean, cowpea, peanut, chickpea, and bean was studied on agar-solidified MS nutrient medium supplemented with various concentrations of benzyladenine (BA) and napthaleneacetic acid (NAA) alone or in combination. Soybean plantlets could be regenerated only when 0.05–0.1 μM BA was applied in conjunction with 1 μM NAA. Cowpea meristems did not require exogenously supplied hormones for maximum (100%) plant regeneration to occur. Extremely low levels of BA (0.1–0.005 μM) in association with low levels of NAA (0.05 μM) also induced plant regeneration at very high frequency. Similarly, bean meristems differentiated into plantlets on hormone-free medium or on medium containing only the auxin, NAA. Multiple bud regeneration (15–30 buds per meristem) was induced from bean meristems at high cytokinin levels (10 μM BA). Elongated bean shoots differentiated roots on half-strength MS medium containing 1 μM indoleacetic acid (IAA). Although most combinations of BA or BA and NAA induced shoot regeneration from peanut and chickpea meristems, whole plant regeneration occurred more frequently (75%) from the former only when 0.1 μM BA was applied in combination with 10 μM NAA. Multiple axillary branching occurred from the main shoots regenerated from chickpea meristems; however, rooting occurred only when these shoots were recultured on medium containing 1 μM indolebutyric acid (IBA). Plantlets regenerated from the meristems of all these grain legumes were successfully transferred to pots and grown to maturity.

The effect of plant growth regulator concentrations and ageing of callus on the extent and nature of variation among callus culture regenerants of strawberry (Fragaria x ananassa) cv. Redcoat was examined. Plants regenerated from callus culture had reduced plant vigour, shorter petiole length and smaller leaf size, but more leaves and runners under greenhouse conditions. These responses appeared to be due to a physiological influence of plant growth regulators. No distinct phenotypic variants were observed at plant growth regulator concentrations in the range of 1-10 ~tM each of BA and 2,4-0 combination, but the highest concentration (20 txM each) of this combination produced a high frequency (10%) of dwarf type variants. The dwarf nature of these variants was maintained in the runner plants produced by the primary regenerants. The plants regenerated from 8-week-old calli did not show any distinct morphological variants. However, a significant proportion of deformed leaf shape (6-13%) and yellow leaf (21-29%) variants was obtained among plants regenerated from 16 and 24-week-old calli. The primary regenerants of the leaf shape variants were established as chimeras. The chimeric plants produced runner progeny with normal plants and plants with completely distorted leaf morphology. Both leaf shape and yellow leaf variants remained stable through runner propagation. Isozyme analysis failed to distinguish any of the variants from the standard runner plants. Flow cytometric analysis indicated the aneuploid nature of leaf shape variants but it could not distinguish dwarf and yellow leaf variants from standard runner plants.

An efficient genetic transformation protocol has been developed for strawberry cv. Redcoat using Agrobacterium tumefadens. The protocol relies on a high frequency (84%) shoot regeneration system from leaf disks. The leaf disks were inoculated with a non-oncogenic Agrobacterium tumefadens strain MP90 carrying a binary vector plasmid pBI121 which contains a chimeric nopaline synthase (NOS) promoter driven neomycin phosphotransferase (NPT II) gene and a cauliflower mosaic virus 35S (CaMV35S) promoter driven, ß-glucuronidase (GUS) marker gene. The inoculated leaf disks, pre-cultured for 10 days on non-selective shoot regeneration medium, formed light green meristematic regions on selection medium containing 50 μg/ml kanamycin. These meristematic regions developed into transformed shoots at a frequency of 6.5% on a second selection medium containing 25 μg/ml kanamycin. The selected shoots were multiplied on shoot proliferation medium in the presence of kanamycin. All such shoots were resistant to kanamycin and expressed varying levels of NPT II and GUS enzyme activity. Histochemical assays for GUS activity indicated that the 35S promoter was highly active in meristematic cells of shoot and root apices. Molecular analysis of each transgenic clone confirmed the integration of both marker genes into the strawberry genome. Leaf disks prepared from transformed plants, when put through the second selection cycle on kanamycin, formed callus and exhibited GUS activity. The rooted transformed plants were grown in a greenhouse for further characterization. The protocol may be useful for improvement of strawberry through gene manipulations.