Epistatic Association Mapping in Homozygous Crop Cultivars

The genetic dissection of complex traits plays a crucial role in crop breeding. However, genetic analysis and crop breeding have heretofore been performed separately. In this study, we designed a new approach that integrates epistatic association analysis in crop cultivars with breeding by design. First, we proposed an epistatic association mapping (EAM) approach in homozygous crop cultivars. The phenotypic values of complex traits, along with molecular marker information, were used to perform EAM. In our EAM, all the main-effect quantitative trait loci (QTLs), environmental effects, QTL-by-environment interactions and QTL-by-QTL interactions were included in a full model and estimated by empirical Bayes approach. A series of Monte Carlo simulations was performed to confirm the reliability of the new method. Next, the information from all detected QTLs was used to mine novel alleles for each locus and to design elite cross combination. Finally, the new approach was adopted to dissect the genetic basis of seed length in 215 soybean cultivars obtained, by stratified random sampling, from 6 geographic ecotypes in China. As a result, 19 main-effect QTLs and 3 epistatic QTLs were identified, more than 10 novel alleles were mined and 3 elite parental combinations, such as Daqingdou and Zhengzhou790034, were predicted

Nearly noninvasive readout and manipulation of spin in double quantum dot using spin bias

Dynamics of two quantum dots coupled to electrodes with spin bias is investigated theoretically by means of the master equations. The two dots are coupled via exchange interaction. When the exchange interaction is much smaller than the lead-dot 2 coupling and dot 2 is under a symmetric spin bias, an initially fully polarized electron spin in dot 1 undergoes an oscillation with ignorable attenuation. Meanwhile, the direction of charge current flowing through dot 2 oscillates in the same period as that of the spin in dot 1. This allows to reverse or nearly noninvasively read out the spin in dot 1, by switching on and off the exchange interaction for a duration of half-integer or integer periods of the oscillation, respectively. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.link_to_subscribed_fulltex

Effects of electron-phonon interaction on quantum transport through single molecule transistor

The effects of the electron-phonon interaction on the nonequilibrium transport through a single molecule transistor or certain quantum dots are systematically studied, with focus on the quantum resonant tunneling, Kondo effect, and Fano effect. We find that the broken particle-hole symmetry in such system can be identified from the phonon sidebands in the spectral function at very low temperature. In the Kondo regime, two types of Kondo phonon-satellites with different asymmetric shapes are distinguished and related to the electron or hole spin-singlet, respectively. Since phonon acts as a "which way" detector, the phonon-assisted tunneling channel has no Fano interference with the reference electronic channel. © 2007 American Institute of Physics.link_to_subscribed_fulltex