Effect of environment and direction of hybridization on genetic variability in two diploid potato populations

Summary Twelve selections from each of theSolanum tuberosum Groups haploid Tuberosum and Phureja were intercrossed in a NC Design II pattern to generate reciprocal hybrids. Yield parameters, combining ability and variance components were estimated from field experiments conducted at three locations, one in Minnesota and two in Morocco. Heterosis for yield and tuber number was significant at all locations, but only in Tuberosum cytoplasm. Estimates of general combining ability (GCA) for Tuberosum parents and specific combining ability (SCA) for Tuberosum-Phureja combinations varied with location and direction of hybridization. GCA of Phreja parents, however, was consistently significant at all locations and in both cytoplasms. Genetic variance estimates revealed predominantly non-additive gene action for most traits. Environment and direction of hybridization significantly influenced estimates, of variance components, indicating that hybrid performance should be evaluated in both cytoplasms and in the target environments for effective utilization of this germplasm in future breeding efforts. Scientific Journal Series Article 14,991 of the Minnesota Agricultural Experiment Station supported in part by the U.S. Agency for International Development, contract no. 608-0160, IAV Morocco Project.     

A possible genetic source for chipping potatoes from 40 F storage

An interspecific hybrid ofS. phureja x USW1, a haploid of Katahdin, produced acceptable potato chips when processed directly from 40 F (4.5 C) storage during 3 years of testing. It was crossed with 11 interspecific hybrids. Tubers from these progenies were stored for 5 weeks at 40 F and then chipped immediately for 55 seconds in vegetable oil maintained at 375 F (190 C). Of 645 seedlings tested, chip color was acceptable in 17 and variable in 18. A group of 600 seedlings fromS. tuberosum parents treated comparably produced black-colored chips without exception.     

A new technique for measuring broadband dielectric spectra of undisturbed soil samples

A new coaxial line cell for the determination of dielectric spectra of undisturbed soil samples was developed based on a 1.625‐inch ‐ 50 Ω coaxial system. Undisturbed soil samples were collected from a soil profile of the Taunus region (Germany) and capillary saturated followed by a step‐by‐step de‐watering in a pressure plate apparatus as well as oven‐drying at 40°C. The resultant water contents of the soil samples varied from saturation to air‐dry. Permittivity measurements were performed within a frequency range from 1 MHz to 10 GHz with a vector network analyser technique. Complex effective relative permittivity or electrical conductivity was obtained by combining quasi‐analytical and numerical inversion algorithms as well as the parameterizing of measured full set S‐parameters simultaneously under consideration of a generalized fractional dielectric relaxation model (GDR). The measurement of standard materials shows that the technique provides reliable dielectric spectra up to a restricted upper frequency of 5 GHz. For the soil samples investigated, the real part of complex effective relative permittivity ?′_r,eff and the real part of complex effective electrical conductivity σ′_eff decreased with increasing matric potential or decreasing water contents. Soil texture and porosity affect the dielectric behaviour at frequencies below 1 GHz. For frequencies above 1 GHz minor texture effects were found. The presence of organic matter decreases ?′_r,eff and σ′_eff. At 1 GHz, the empirical model of Topp et al. (1980) is in close agreement with the experimentally determined real part of the effective permittivity with RMSEs ranging from 1.21 for the basal periglacial slope deposit and 1.29 for bedrock to 3.93 for the upper periglacial slope deposit (Ah). The comparison of the experimental results with a semi‐empirical dielectric mixing model shows that data, especially for the organic‐free soils, tend to be under‐estimated below 1 GHz. The main advantage of the new method compared with conventional impedance and coaxial methods is the preservation of the natural in‐situ structure and properties such as bulk density of the investigated soil samples.     

Comparison of methods for differentiation of Salmonella enterica serovar Enteritidis phage type 4 isolates

OBJECTIVE: To compare molecular typing methods for the differentiation of Salmonella enterica serovar Enteritidis phage type (PT) 4 isolates that allowed for the determination of their genetic relatedness. SAMPLE POPULATION: 27 Salmonella Enteritidis PT 4 strains isolated in the United States and Europe. PROCEDURE: Several molecular typing methods were performed to assess their ability to genetically differentiate among Salmonella Enteritidis PT 4 isolates. Results of pulse-field gel electrophoresis (PFGE), repetitive polymerase chain reaction (PCR) assay, 16S rRNA gene sequencing, random amplification of polymorphic DNA (RAPD), PCR-restriction fragment length polymorphism of 16S rRNA, and antimicrobial susceptibility were evaluated. RESULTS: Compared with results for other techniques, results for the RAPD typing method with the RAPD1 primer reveal that it was the most discriminatory fingerprinting technique, and it allowed us to cluster Salmonella Enteritidis PT 4 isolates on the basis of their genetic similarity. CONCLUSIONS AND CLINICAL RELEVANCE: This study revealed the value of RAPD with the RAPD1 primer as a tool for epidemiologic investigations of Salmonella Enteritidis PT 4. It can be used in conjunction with PFGE and phage typing to determine the genetic relatedness of Salmonella Enteritidis isolates involved in outbreaks of disease. A reliable and highly discriminatory method for epidemiologic investigations is critical to allow investigators to identify the source of infections and consequently prevent the spread of Salmonella Enteritidis PT 4.