Pyramiding of Ryd2 and Ryd3 conferring tolerance to a German isolate of Barley yellow dwarf virus-PAV (BYDV-PAV-ASL-1) leads to quantitative resistance against this isolate
Barley yellow dwarf virus (BYDV) is an economically important pathogen of barley, which may become even more important due to global warming. In barley, several loci conferring tolerance to BYDV-PAV-ASL-1 are known, e.g. Ryd2, Ryd3 and a quantitative trait locus (QTL) on chromosome 2H. The aim of the present study was to get information whether the level of tolerance against this isolate of BYDV in barley can be improved by combining these loci. Therefore, a winter and a spring barley population of doubled haploid (DH) lines were genotyped by molecular markers for the presence of the susceptibility or the resistance encoding allele at respective loci (Ryd2, Ryd3, QTL on chromosome 2H) and were tested for their level of BYDV-tolerance after inoculation with viruliferous (BYDV-PAV-ASL-1) aphids in field trials. In DH-lines carrying the combination Ryd2 and Ryd3, a significant reduction of the virus titre was detected as compared to lines carrying only one of these genes. Furthermore, spring barley DH-lines with this allele combination also showed a significantly higher relative grain yield as compared to lines carrying only Ryd2 or Ryd3. The QTL on chromosome 2H had only a small effect on the level of tolerance in those lines carrying only Ryd2, or Ryd3 or a combination of both, but the effect in comparison to lines carrying no tolerance allele was significant. Overall, these results show that the combination of Ryd2 and Ryd3 leads to quantitative resistance against BYDV-PAV instead of tolerance.
Psathyrostachys huashanica, a potential resource for resistance to Barley yellow dwarf virus-GAV
Barley/cereal yellow dwarf viruses (B/CYDVs) are recognized as serious pathogens of wheat. It is critical to find diverse sources of resistance to reduce yield losses caused by B/CYDVs. Psathyrostachys huashanica Keng, a perennial wheat-relative species, has been regarded as a potential germplasm resource because of its excellent performance on resistance to drought, salinity, wheat stripe rust and the take-all fungus. In this work, the susceptibility to BYDV-GAV of P. huashanica was evaluated following inoculation using reverse transcription-polymerase chain reaction (RT-PCR) and double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA). Additionally, an aphid-transmission test was conducted for further verification of virus infection. The results indicated that BYDV-GAV could infect P. huashanica but accumulated to much lower level in inoculated leaves of P. huashanica than in the leaves of resistant wheat line Zhong 5 and the susceptible wheat line 7182. However, no BYDV-GAV particles could be detected in new leaves of inoculated P. huashanica. In this study, we first demonstrated that P. huashanica is highly resistant to BYDV-GAV and possibly has a negative effect on the movement of the viral particles from inoculated leaves to new leaves.
Work, Status, and Income: Men in the American Occupational Structure since the Late Nineteenth Century
The historical record rarely presents researchers with precisely the evidence they desire. This is particularly true for social historians and like-minded scholars, whose subjects left precious few signs of their passing. Consequently, certain data have borne a disproportionate evidentiary load in social-historical research. The occupation a person pursued is one key piece of information on which scholars have come to depend. Our understanding of the historical social structure and where people fit into it is bound up with the interpretation of occupations. But this reliance on occupation as the primary social locator in historical research depends on some largely unexamined premises. Whether scholars group occupations or convert them into numerical status measures, they make assumptions about the nature of the occupational structure. When researchers incorporate change over time into their analyses, they suggest that the meaning of occupations remained stable for the purpose of measuring social mobility, class position, or group status-attainment. This assumption has been the subject of little discussion and even less research. For all the use to which historians have put occupation, there has been little effort to assess systematically its stability as a social or economic indicator.