Introgression Breeding for Improvement of Winter Hardiness in \u3cem\u3eLolium /Festuca\u3c/em\u3e Complex Using Androgenenesis

Intergeneric hybrids between closely related Lolium and Festuca species are used to broaden the gene pool and provide plant breeders with options to combine complementary traits to develop robust but high quality grass varieties. Androgenesis was found to be an effective procedure for selecting Lolium-Festuca genotypes comprising gene combinations rarely or never recovered by conventional backcross breeding programs. Here we describe the optimisation of androgenesis in Lolium perenne x Festuca pratensis. The male fertility and freezing tolerance of the Festulolium microspore-derived progenies were analysed and these progenies were also analysed by using genomic in situ hybridisation (GISH). The object of this study is to initiate introgression breeding for the improvement of winter hardiness in Lolium /Festuca complex

Full-gap superconductivity robust against disorder in heavy-fermion CeCu2Si2

A key aspect of unconventional pairing by the antiferromagnetic spin-fluctuation mechanism is that the superconducting energy gap must have opposite sign on different parts of the Fermi surface. Recent observations of non-nodal gap structure in the heavy-fermion superconductor CeCu$_2$Si$_2$ were then very surprising, given that this material has long been considered a prototypical example of a superconductor where the Cooper pairing is magnetically mediated. Here we present a study of the effect of controlled point defects, introduced by electron irradiation, on the temperature-dependent magnetic penetration depth $\lambda(T)$ in CeCu$_2$Si$_2$. We find that the fully-gapped state is robust against disorder, demonstrating that low-energy bound states, expected for sign-changing gap structures, are not induced by nonmagnetic impurities. This provides bulk evidence for $s_{++}$-wave superconductivity without sign reversal.Comment: 5 pages, 4 figures + Supplemental Material (1 page, 1 figure). Will appear in Phys. Rev. Let