Abstract:The reaction of winter and spring wheat to infection with barley yellow dwarf virus (BYDV-PAV) was evaluated in three-year small-plot field trials on 71 wheat varieties registered in the Czech Republic and at two locations for two years on 63 selected potential sources of resistance. Disease symptoms (VSS) were visually recorded using a 0-9 scale and the percent reduction of grain weight per spike (GWS-R) was measured on twenty plants per plot. The evaluation showed that among the registered varieties of winter and spring wheat no variety had a high resistance to BYDV (with VSS lower than 3.5). GWS-R ranged between 24% and 60%. Higher variability in VSS was detected for the registered varieties of spring wheat compared to winter wheat. Among the registered varieties of winter wheat, Saskia, Rialto, Meritto, Rexia, and Svitava, as well as the spring wheat Leguan, received the best long-term evaluations. The highest level of resistance was detected for the PSR 3628 line (a hybrid of wheat and couch-grass), but in connection with a low agronomic value. The WKL91-138 line of spring wheat and some varieties (lines) with the detected moderate level of resistance, in particular, could offer good prospects for use in breeding. The presence of the Bdv2 gene was expressed only in the reduction of virus content on the 11 th day after inoculation. Nevertheless, genotypes carrying this gene were evaluated in field trials as susceptible or very susceptible to infection with the Czech PAV isolate. Similarly, the presence of the Bdv1 gene detected with the help of WMS130 marker was no assurance of an increased level of resistance to BYDV. Hybridological analyses of crosses with the WKL91-138 line showed a polygenic nature of inheritance. Thus, the marker-assisted selection does not obviously promise success without a focus on detecting a larger number of QTLs.
The cause for the differences in germination ability of large and small confection sunflower (Helianthus annuus L.) seeds was investigated over 3 years. The source-sink relationship was manipulated to better explore the differences between seeds of various sizes and to study the role of the embryo and the pericarp (hull) in controlling germination ability. Percent germination of large seeds was significantly lower than that of small seeds when tests were performed at 15 °C. Increasing the ratio of leaf area to number of developing seeds caused an increase in mean seed mass, but resulted in a lower percentage of germination. Seed vigor, as measured by mean time to germination or to emergence of hulled seeds or by rate of root elongation, was negatively correlated with embryo mass, indicating that the low vigor of large seeds is not due to the mechanical barrier imposed by the hull. Analysis of electrolyte leakage confirmed the hypothesis that the low quality of large seeds results from a disturbance during the process of seed development.
The relation between high-molecular-weight (HMW) glutenin subunits and bread-making quality could enable selection for improved bread-making quality in early stages of breeding process. The composition of HMW glutenin subunits was investigated in F<sub>2</sub> and F<sub>7</sub> progenies derived from the cross between winter wheat varieties Sulamit and Clever. The presence of Glu-A1 (AxNull and Ax1), Glu-B1 (Bx6+By8 and Bx 17+By18) and Glu-D1 alleles (x 5+Dy10 and Dx 2+Dy12) was monitored using a PCR based assay. Segregation of alleles corresponded with the theoretically assumed 1:2:1 Mendelian ratio in F<sub>2</sub> generation, however, the values of χ<sup>2</sup>-test in F<sub>7</sub> generation indicated a strong affection of allelic frequencies by the breeding process. Significant variation was also observed in Glu-1 score frequency between F<sub>2</sub> and F<sub>7</sub> generation. These changes were probably caused by deliberate phenotypic selection for important agronomical traits. SDS and Zeleny sedimentation tests, mixographic parameter breakdown and HMW glutenin composition were analyzed in F<sub>7</sub> to reveal the effects of different combinations of HMW glutenin alleles on the bread-making quality characters. The results showed statistically significant differences in the contribution of HMW glutenin alleles. In general, the alleles Ax1, Bx17+By18 and Dx5+Dy 10 can be considered as markers of good baking quality. The data presented in this paper suggest that heterozygous constitution may also have a positive effect on bread-making quality.
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