Atmospheric bismuth-212: measurement and some geophysical applications

The concentrations of lead-212 and its short-lived daughter bismuth-212 in air near the ground were determined simultaneously by adaptation of the immersed-filter, delayed-coincidence technique of Assaf and Gat to measurement of the 3 x 10-(7)-second bismuth-212 and polonium-212 pair. The radioactive disequilibrium between lead-212 and bismuth-212 depends strongly on the efficiency of the ground in acting as a sink for these nuclides. This efficiency is low under dry conditions.     

The dead sea: deepening of the mixolimnion signifies the overture to overturn of the water column

Throttling of freshwater inputs into the meromictic Dead Sea weakened the long-term stability of the water column. Between 1975 and 1978 successive deepenings of the pycnocline from 70 meters to beyond 200 meters were recorded. Complete overturn finally took place during the winter of 1978-1979. This unique process was accompanied by changes in the geochemistry of several components.     

Evaluation and Bulked Segregant Analysis of Major Yield QTL qtl12.1 Introgressed into Indigenous Elite Line for Low Water Availability under Water Stress

Near isogenic lines carrying large-effect QTL (qtl12.1), which has a consistent influence on grain yield under upland drought stress conditions in a wide range of environments, were evaluated under water stress in the fields. The line which gave higher yield under drought was crossed with a local elite line, PMK3, and forwarded to F2:3 generation. Significant variation was found among the F2:3 lines for agronomic traits under water stress in the fields. Low to high broad sense heritability (H) for investigated traits was also found. Water stress indicators such as leaf rolling and leaf drying were negatively correlated with plant height, biomass and grain yield under stress. Bulked segregant analysis (BSA) was performed with the markers in the vicinity of qtl12.1, and RM27933 was found to be segregated perfectly well in individual components of drought resistant and drought susceptible bulks which were bulked based on yield under water stress among F2:3 lines. Hence, this simple and breeder friendly marker, RM27933, may be useful as a potentially valuable candidate marker for the transfer of the QTL qtl12.1 in the regional breeding program. Bioinformatic analysis of the DNA sequence of the qtl12.1 region was also done to identify and analyze positional candidate genes associated with this QTL and to ascertain the putative molecular basis of qtl12.1.     

Identification and characterization of Phoma tracheiphila mutants impaired in pathogenicity following Agrobacterium-mediated mutagenesis

Mal secco disease, caused by the pathogenic fungus Phoma tracheiphila, is a devastating disease of susceptible citrus species, especially lemon. To study the molecular interactions between the pathogen and its host, a method for identifying the genes involved in pathogenicity is needed. This work describes the transformation of P. tracheiphila phialoconidia by Agrobacterium tumefaciens, and the generation of mutated P. tracheiphila isolates exhibiting reduced virulence on rough lemon seedlings. A rapid, replicable, and reliable method for screening P. tracheiphila mutants to assess their virulence by using rough lemon seedlings was developed. Among 2263 transformants obtained, three were non-virulent and 43 displayed reduced virulence. In addition, one of the transformants, which exhibited virulence similar to that of the wild type, was used for in planta visualization of the fungus progression through the plant xylem. To our knowledge, this is the first report of A. tumefaciens-mediated transformation of P. tracheiphila, and subsequent screening of the transformants to identify non-virulent mutants.