Characterization of Intergeneric Hybrids of Saccharum using Molecular Markers

The potential use of RAPD markers in identifying genuine intergeneric hybrids of Saccharum was examined in 12 hybrids of Saccharum with Erianthus spp., Sorghum bicolor and Zea mays. In the three groups of hybrids examined, RAPD markers could precisely identify the true hybrids of Saccharum officinarum × Sorghum bicolor and Saccharum officinarum × Zea mays. Though Erianthus had a very distinct RAPD profile and as many as 107 Erianthus-specific bands were identified, a decisive profile that can identify all the hybrids could not be obtained. The strong molecular differentiation between S.officinarum and Erianthus was not adequately resolved in the RAPD profiles of their hybrid progenies which suggest that more refined molecular techniques will be required for the characterization of Saccharum–Erianthus hybrids.     

Analysis of Genetic Diversity Among Saccharum spontaneum L. From Four Geographical Regions of India, Using Molecular Markers

Saccharum spontaneum L. a wild relative of sugarcane is the most variable and diverse among the Saccharum species. This species had been successfully exploited in sugarcane improvement programmes since 1915 and most of the present day commercial varieties are derivatives of interspecific hybrids involving S. spontaneum. The S. spontaneum germplasm available today in the World collections is diverse and represent different geographical groups. In the present investigation, an attempt was made to characterize 40 S. spontaneum clones collected from 4 different geographical areas in India using 20 random, 2 ISSR and 2 telomere primers. Of the 491 bands generated by these primers 83.9% were polymorphic. The genetic diversity estimated based on these markers was found to be moderate (48.9%). The pair-wise genetic distance between the accessions ranged from 29.8 to 60.0. The accessions from Arunachal Pradesh were found to be the most diverse, while Tamil Nadu accessions showed relatively less diversity. Diversity between Tamil Nadu and Kerala collections was found to be low, while the diversity between the Orissa group and the rest was found to be high. The collections from Mayurbanj and Cuttack regions of Orissa were found to be distinct. Arunachal Pradesh accessions, being more diverse, are a potential source for exploitation in sugarcane breeding programmes.     

Carbon,iron, and aluminum responses to controlled water table fluctuations in sandy soil material

Purpose

Seasonal fluctuating water tables are common in sandy coastal plain soils, but their role in soil organic carbon dynamics is uncertain. Seasonal saturation influences biogeochemical processes that affect fate of organic matter and metals. A column study was conducted to test hypotheses that shallow water table (SWT) fluctuations reduce CO₂ loss (H1), increase leaching of dissolved organic C (DOC) and metals (Al and Fe) (H2), and result in greater net soil C storage (H3).

Materials and methods

The A- and E-horizon material of moderately well-drained sandy soils from five sites was collected for the study. Ten columns (two per site) of 90-cm height were packed to a thickness of 60 cm with E-horizon material, above which was packed 15 cm of A-horizon material from the same soil. Five columns were subjected to SWT treatments and five to deep water table (DWT) treatments. Upward CO₂ flux was measured using a NaOH (1 M) trap. Metal and DOC-C concentrations in leachates and in water sampled at the surface of columns were measured. Soil samples from the columns were collected by depth at 5–6-cm increments and tested for total and organic C, metals, and <50-μm material distribution by WT treatment.

Results and discussion

Upward flux of CO₂ was significantly less for SWT treatment. Higher DOC (for all events) and Fe concentrations (for first 18 days) were measured in SWT leachates as compared to DWT. Metal- and C concentrations were correlated (P?<?0.0001) for surface pore water samples of SWT but not for DWT. Net loss of C was significantly less under SWT condition. Results indicate significant water-table effects on magnitude and direction of C flux (solution or gaseous) and <50-μm particle distribution for sandy coastal plain soils materials.

Conclusions

Changes in water table depth can potentially alter not only net soil C storage but also the proportion of C converted to CO₂ versus DOC. Differences in the proportion would have consequences for C dynamics in ecosystems dominated by soils with fluctuating water tables such as occur extensively in the coastal plain of the SE USA and elsewhere.

     

Anticancer activity evaluation of kuanoniamines A and C isolated from the marine sponge Oceanapia sagittaria, collected from the Gulf of Thailand

The pyridoacridine alkaloids kuanoniamines A and C were isolated together with 24 α-methylcholestanol, p-hydroxybenzaldehyde, p-hydroxybenzoic acid, phenylacetic acid and 3-formylindole from the ethyl acetate extract of the marine sponge Oceanapia sagittaria (Sollas), collected from the Gulf of Thailand. Kuanoniamines A and C were evaluated for their effect on the growth of five human tumour and a non-tumour cell lines, as well as on the proliferation of human lymphocytes. Kuanoniamine A was found to be a potent growth inhibitor of all the tumour and a non-tumour cell lines while kuanoniamine C was less potent but showed high selectivity toward the estrogen dependent (ER+) breast cancer cell line. Kuanoniamine A has shown to be a more potent inhibitor of DNA synthesis than kuanoniamine C. Kuanoniamine A was also found to cause an extensive reduction of the MCF-7 cells in G2/M phase as well as an increase in the apoptotic cells.     

Demographic histories and patterns of linkage disequilibrium in Chinese and Indian rhesus macaques

To understand the demographic history of rhesus macaques (Macaca mulatta) and document the extent of linkage disequilibrium (LD) in the genome, we partially resequenced five Encyclopedia of DNA Elements regions in 9 Chinese and 38 captive-born Indian rhesus macaques. Population genetic analyses of the 1467 single-nucleotide polymorphisms discovered suggest that the two populations separated about 162,000 years ago, with the Chinese population tripling in size since then and the Indian population eventually shrinking by a factor of four. Using coalescent simulations, we confirmed that these inferred demographic events explain a much faster decay of LD in Chinese (r(2) approximately 0.15 at 10 kilobases) versus Indian (r(2) approximately 0.52 at 10 kilobases) macaque populations.     

“Bracatinga” (Mimosa scabrella Bentham), a multipurpose tree growing in Southern Brazil: chromosome number and genetic variation

Mimosa scabrella Bentham, popularly known as “bracatinga” in Brazil, is a very important multipurpose tree especially in the southern region of the country, where it occurs naturally in plant associations called “bracatingais”. The species is presently in danger of losing genetic variability as it normally occurs in regions subjected to intense urbanization, industrialization, agriculture and cattle raising. Aiming at broadening the knowledge about the species we have investigated cytogenetic characteristics and genetic diversity among natural populations. The results show that all populations are tetraploid (2n = 4× = 52) and that there is a high genetic diversity among the populations. There is still time to avoid genetic erosion of M. scabrella if the areas where the species occurs are protected.