Somatic embryogenesis in four tree legumes.

Somatic embryogenesis was achieved in four leguminous tree species, that is, Acacia catechu, Acacia arabica, Hardwickia binata, and Dalbergia sissoo using immature zygotic embryos as explants on Murashige and Skoog (MS) medium supplemented with 0.25-1.0 mg/l Kn (kinetin) and 2.0-3.0 mg/l 2,4-D (2,4-dichlorophenoxyacetic acid) or NAA (1-napthaleneacetic acid) and 3% sucrose. MS medium containing 2.0 mg/l 2,4-D and 1.0-1.5 mg/l Kn was noted to be most effective in inducing friable embryogenic callus (FEC); the number of somatic embryos per culture varied in MS medium supplemented with 1.0-2.0 mg/l 2,4-D or NAA and 0.25-1.5 mg/l kinetin. The maximum number of somatic embryos was obtained in MS medium containing 1.5-2.0 mg/l 2,4-D or NAA and 1.0-1.5 mg/l kinetin; proliferation of embryogenic calli was enhanced in cultures having 1.0-2.0 mg/l 2,4-D, 1.0-1.5 mg/l kinetin, and 400-600 mg/l L-Proline. The somatic embryos in various shapes and sizes after the first subculture on MS medium supplemented with 0.1 mg/l IAA and 0.25 mg/l BA; developed shoots and rooted in 1/2 strength MS medium supplemented with 0.1 mg/l IBA or IAA. The somatic embryo-derived plantlets were transferred to the field after being hardened in the climate-controlled hardening chamber.

Genomic relations among 31 species of Mammillaria haworth (Cactaceae) using random amplified polymorphic DNA.

Thirty-one species of Mammillaria were selected to study the molecular phylogeny using random amplified polymorphic DNA (RAPD) markers. High amount of mucilage (gelling polysaccharides) present in Mammillaria was a major obstacle in isolating good quality genomic DNA. The CTAB (cetyl trimethyl ammonium bromide) method was modified to obtain good quality genomic DNA. Twenty-two random decamer primers resulted in 621 bands, all of which were polymorphic. The similarity matrix value varied from 0.109 to 0.622 indicating wide variability among the studied species. The dendrogram obtained from the unweighted pair group method using arithmetic averages (UPGMA) analysis revealed that some of the species did not follow the conventional classification. The present work shows the usefulness of RAPD markers for genetic characterization to establish phylogenetic relations among Mammillaria species.

Assessment of genetic diversity in 31 species of mangroves and their associates through RAPD and AFLP markers.

Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers were used to assess the genetic diversity in 31 species of mangroves and mangrove associates. Four AFLP primer combinations resulted in the amplification of 840 bands with an average of 210 bands per primer combination and 11 RAPD primers yielded 319 bands with an average of 29 bands per primer. The percentage of polymorphism detected was too high indicating the high degree of genetic variability in mangrove taxa both at inter- and intra-generic levels. In the dendrogram, species belonging to a particular family/ genus, taxa inhabiting similar habitats or having similar adaptations tended to be together. There were exceptions too; as many unrelated species of mangroves form clusters. The intrafamilial classification and inter-relationships of genera in the family Rhizophoraceae could be confirmed by molecular analysis. Both the markers RAPD and AFLP were found equally informative and useful for a better understanding of the genetic variability and genome relationships among mangroves and their associated species.

Molecular characterization of five medicinally important species of Typhonium (Araceae) through random amplified polymorphic DNA (RAPD).

The interrelationship of five medicinally important species of Typhonium (Araceae) including T. venosum, which was previously placed under the genus Sauromatum, was inferred by analysis of random amplified polymorphic DNA (RAPD). DNA from pooled leaf samples was isolated and RAPD analysis was performed using 20 decamer oligonucleotide primers. Out of a total of 245 bands amplified, 12 were found to be monomorphic while 233 bands were polymorphic including 86 species-specific bands. The genetic similarities were analyzed from the dendrogram constructed by the pooled RAPD data using a similarity index. The dendrogram showed two distinct clades, one containing T. roxburghii, T. trilobatum and T. venosum and the other containing the remainder two species, i.e. T. diversifolium and T. flagelliforme. Both the clusters shared a common node approx. at 23.7% level of similarity. The maximum similarity of 31.2% was observed between T. venosum and T. trilobatum. In view of its close genetic similarity with other members of Typhonium, transfer of Sauromatum venosum to the genus Typhonium and merger of the two genera was supported.

Assessment of genetic diversity among 16 promising cultivars of ginger using cytological and molecular markers.

Ginger (Zingiber officinale Roscoe) is an economically important plant, valued all over the world. The existing variation among 16 promising cultivars as observed through differential rhizome yield (181.9 to 477.3 g) was proved to have a genetic basis using different genetic markers such as karyotype, 4C nuclear DNA content and random amplified polymorphic DNA (RAPD). The karyotypic analysis revealed a differential distribution of A, B, C, D and E type of chromosomes among different cultivars as represented by different karyotype formulas. A significant variation of 4C DNA content was recorded in ginger at an intraspecific level with values ranging from 17.1 to 24.3 pg. RAPD analysis revealed a differential polymorphism of DNA showing a number of polymorphic bands ranging from 26 to 70 among 16 cultivars. The RAPD primers OPC02, OPA02, OPD20 and OPN06 showing strong resolving power were able to distinguish all 16 cultivars. The extent of genetic diversity among these cultivars was computed through parameters of gene diversity, sum of allele numbers per locus and Shannon's information indices. Cluster analysis, Nei's genetic similarity and genetic distances, distribution of cultivars into special distance classes and principal coordinate analysis and the analysis of molecular variance suggested a conspicuous genetic diversity among different cultivars studied. The genetic variation thus detected among promising cultivars of ginger has significance for ginger improvement programs.

Effect of a low dose of aluminum on mitotic and meiotic activity, 4C DNA content, and pollen sterility in rice, Oryza sativa L. cv. Lalat.

Aluminum toxicity in acidic soils poses a major threat to plant growth and development. The effects of a low dose of aluminum (50 microM, AlCl3) on various cytological parameters, including mitotic and meiotic chromosomal divisions, in situ nuclear DNA content, interphase nuclear volume (INV), and pollen fertility were compared in untreated (controls) and treated rice plants (Oryza sativa cv. Lalat). The results showed varied chromosomal abnormalities, including chromosome stickiness, laggards, sticky bridge, occurrence of micronuclei, as well as binucleate and multinucleated cells, as a result of aluminum treatment. Aluminum toxicity also inhibited to a small extent the growth of the rice cultivar Lalat. The mitotic and meiotic indexes, even after a prolonged period of recovery, were significantly low. The chromosomal anomalies in the meiotic cells persisted, and plants exhibited a high percentage of pollen sterility (approximately 64%). The nuclear DNA content declined markedly from 11.85 pg in the control to 6.30 pg in the treated plants. The INV also varied significantly between the untreated (controls) and the treated plants. The occurrences of different types of chromosomal aberrations, reduction in the amount of nuclear DNA, and persistence of the phytotoxic effects at the post-treatment stage suggest carcinogenic effects of aluminum on rice plants. The presence of aluminum in acidic soils might thus be extremely hazardous and might cause permanent cytotoxic disorder in rice plants.

Genomic relations among two non-mangrove and nine mangrove species of Indian Rhizophoraceae.

Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers were used to study the genomic relationship among 11 members of Indian Rhizophoraceae represented by nine true mangroves and two non-mangrove species. The AFLP and RAPD bands were scored and analyzed for genetic similarities and cluster analysis was done which separated the 11 species studied into two main groups, the true mangroves and the non-mangroves. The polymorphism observed for these markers showed a high degree of genetic diversity among the constituent taxa of the family. The phylogenetic relationship inferred from molecular marker systems supported the traditional taxonomic classification of the family Rhizophoraceae based on morphological characters at the levels of tribe, phylogeny and delimitation of genera and species, except the intra-generic classification of the genus Bruguiera and the placement of Rhizophora in the family Rhizophoraceae.