Plant Genome III Conference Plant Genome III Conference
The utility of transformation as a breeding tool is highly dependent on the expression of the introduced trait and the phenotype of the transgenic plant. 'Golden Promise' barley plants (TI generation) containing coat protein (cp) sequences of the PAV stereotype of the barley yellow dwarf virus (SYDV- PAV) driven by the CaMV-35S promoter (Wan and Lemaux, 1994, Plant Physiol., vol 104) were assayed for field resistance to barley yellow dwarf (BYD) and for agronomic performance. This was the initial screen for resistance. Replicated testing was conducted at four locations of 44 lines representing 15 independent transformation events. Plots consisted of paired rows of 10 plants, with one row inoculated with BYDV-PAV. Controls included: untransformed 'Golden Promise'; 'Golden Promise' transformed with a selectable marker but not the cp gone; and 'Atlas 681 and 'Atlas 571, which contain the Yd2 and yd2 alleles, respectively. The Yd2 allele confers resistance to BYDV-PAV. The tissue culture and transformation process generated obvious somaclonal variation within and among transformation events. Plant height, vigor, and seed yield were reduced in most of the transformed lines. The reaction of transformed lines to BYDV infection was varied, but BYD symptoms were generally severe and indistinguishable from the control. Individual plants with low levels of putative resistance were observed. The low vigor of the transformed plants may have hampered the expression and identification of resistance. Thus, introgression of the SYDV-PAV cp gene into non-transformed cultivars will be necessary to properly evaluate it as a practical source of BYD resistance.