Integrated control of wheat blossom midge - HGCA

Technical detail 2.Genetic Analysis of Orange Blossom Midge Resistance in WheatIntroductionAs part of the integrated project ‘The Integrated control of wheat blossom midge ‘ the John Innes Centreundertook a series of experiments to evaluate the genetic basis of variation in the responses of different UKand foreign varieties to orange blossom midge infestation. Much of this work involved the testing of precisegenetic stocks of wheat so that any tolerance/resistance observed could be attributed to specificchromosomes or genes.Materials and Methods:MaterialsFour different groups of materials were examined:1. A series of varieties that represent key current and historic germplasm used in the UK winter wheat genepool as well as lines that are parents of precise genetic stocks or mapping populations. The varietiesevaluated are shown in Figure 1.2. A set of single chromosome substitution lines where chromosomes of a donor variety, the Russian varietyBezostaya, have systematically replaced their homologous chromosome in the recipient variety Cappelle-Desprez. These were developed at the John Innes Centre using the methods described by Law and Worland(1967). Because marker analysis had shown that certain of these were not genetically correct, not all of thepossible set of 21 possible substitution lines (1A to 7D) were evaluated, and lines 4B and 5B were absent.All available lines were grown in 2001/02, 2002/03, but only substitution lines not differing significantly inflowering time but showing significant differences from the recurrent parent were grown in 2003/04, namelylines 1D, 3A and 7B, and Bezostaya was also not represented in this trial.3. A set of isogenic lines differing for alleles at the loci controlling the photoperiod response, and hence theflowering time of wheat, in the genetic background of the winter wheat cultivars Cappelle-Desprez andMercia. These consisted of lines of Cappelle-Desprez carrying an allele at the locus Ppd1 (Ppd-D1) onchromosome 2D conferring photoperiod insensitivity from the Italian variety Mara, and an allele conferring35