Progress in tetraploid wheat breeding through the use of synthetic hexaploid amphiploids

Four amphiploid lines (SHW) based on T. monococcum (Tm) and T. boeoticum (Tb) were crossed to T. durum varieties to generate 13 combinations. Field germination and winter survival of hybrid plants in F2 were assessed. Among all crosses, those with SHW8A-Tb and SHW9A-Tm showed highest field germination but with different degrees of spike fragility. The variation on seed number and weight per main spike was studied in F4–6 from SHW8ATb/ Progres and SHW5A-Tb/Severina crosses after individual selection for these traits. Ten lines with durum phenotype from the former and three genotypes with dicoccum plant shape from the latter cross were developed. SDS-PAGE indicated the presence of HMW-GS 1Ax2*+1Aynull subunits in four lines, among which 1Ax2* was inherited from T. boeoticum acc.110 through SHW8A-Tb. Most of the selected genotypes possessed γ-gliadin45, which was relating to good end-use quality. Powdery mildew testing showed that all progenies resulted from the SHW8A-Tb/Progres were susceptible to 12 races of the pathogen, while three lines derived from the SHW5A-Tb/Severina cross behaved differently: G32 expressed resistance to six, G33 to 2, and G34 to 5 races. The selected genotypes from crosses involving SHW with T. boeoticum exhibited good breeding performance compared to tetraploid wheat parents, and might be of breeding interest to further research

Exact quantization of a PT-symmetric (reversible) Li\'enard-type nonlinear oscillator

We carry out an exact quantization of a PT symmetric (reversible) Li\'{e}nard type one dimensional nonlinear oscillator both semiclassically and quantum mechanically. The associated time independent classical Hamiltonian is of non-standard type and is invariant under a combined coordinate reflection and time reversal transformation. We use von Roos symmetric ordering procedure to write down the appropriate quantum Hamiltonian. While the quantum problem cannot be tackled in coordinate space, we show how the problem can be successfully solved in momentum space by solving the underlying Schr\"{o}dinger equation therein. We obtain explicitly the eigenvalues and eigenfunctions (in momentum space) and deduce the remarkable result that the spectrum agrees exactly with that of the linear harmonic oscillator, which is also confirmed by a semiclassical modified Bohr-Sommerfeld quantization rule, while the eigenfunctions are completely different.Comment: 10 pages, 1 figure, Fast Track Communicatio

Characterization of two wheat doubled haploid populations for resistance to common bunt and its association with agronomic traits

Two segregating populations of doubled haploid (DH) wheat lines derived androgenetically from crosses ‘Svilena’ (susceptible) × A-38b-4-5-3-3 (highly resistant) and ‘Svilena’ × WWRN (moderately resistant to moderately susceptible) were characterized for resistance to common bunt. Disease incidence was evaluated after inoculation of seeds with a mixture of Tilletia foetida teliospores in two autumn sown field experiments. Two-gene model of inheritance of resistance in line A-38b-4-5-3-3 was suggested. The transgressive segregation in the latter population was indicative for a quantitative mode of inheritance. The DH lines were assessed for plant height, heading time and important yield components in a three-year field experiment without bunt infection. In both populations, transgressive segregation was observed for all agronomic characteristics. Although the disease incidence was positively correlated with most of the agronomic traits, genotypes combining bunt resistance with good yield potential were isolated from ‘Svilena’ × A-38b set of lines. These genotypes are valuable for breeding varieties designed for growing in low-input and organic farming systems. The two DH populations are suitable to be used for further studies on the genetic basis of bunt resistance