Cytogenetic studies in wheat. XV. Location of rust resistance genes in VPM1 and their genetic linkage with other disease resistance genes in chromosome 2A

Inheritance studies showed that the VPM1-derived seedling resistances to stem rust, stripe rust, leaf rust, and powdery mildew were controlled by single genes; the genes for rust resistance were designated Sr38, Yr17, and Lr37, respectively, whereas the gene for resistance to powdery mildew was postulated to be Pm4b. Sr38, Yr17, and Lr37 were shown to be closely linked and distally located in the short arm of chromosome 2A. They showed very close repulsion linkage with Lr17 and were genetically independent of other genes known to be located in chromosome 2A. Previously unmapped, Yr1 appeared to be distally located in the long arm of chromosome 2A.Key words: stem rust, stripe rust, leaf rust, powdery mildew, monosomic analysis, telocentric mapping, genetic linkage.

Cytogenetical Studies in Wheat. IX. Monosomic Analyses, Telocentric Mapping and Linkage Relationships of Genes Sr21, Pm4 and Mle

Gene Sr21 for resistance to Puccinia graminis tritici in five hexaploid derivatives of the diploid Triticum monococcum was located in chromosome 2A. Since only one chromosome was involved in resistance, abnormal ratios found in some diploid wheat crosses and in one hexaploid derivative were attributed to differential transmission of gametes rather than to gene duplication in the diploid wheat sources. By using 2AS and an unknown telocentric presumed to be 2AL in telocentric mapping, Sr21 was placed 2�4�0�9 recombination units from the centromere in 2AL.

Cytogenetical Studies in Wheat VIII. Telocentric Mapping and Linkage Studies Involving Sr22 and other Genes in Chromosome 7AL

The gene Sr22 conditioning low reaction to Puecinia graminis tritid was located by telocentric mapping on chromosome 7 AL at 27 � 4 crossover units from the centromere. Sr22 was approximately 2 crossover units from en-AI (ehlorina) and 41 units from PmI for low reaction to Erysiphe graminis trifid; however, the order of Sr22 and en-AI relative to PmI was not resolved. Maximum recombination between PmI, Lr20 and SrI5, for low reactions to E. graminis tritici, P. reeondita and P. graminis tritid respectively, was estimated to be O' 3 crossover units at the 95 % probability level.

TELOCENTRIC MAPPING IN HEXAPLOID WHEAT OF GENES FOR LEAF RUST RESISTANCE AND OTHER CHARACTERS DERIVED FROM AEGILOPS SQUARROSA

Telocentrics of hexaploid wheat, Triticum aestivum spp. vulgare cv. Chinese Spring, were used to establish the chromosome arm location and crossover distance from the centromere of genes controlling characters introduced into synthetic hexaploid wheat (2n = 42 = AABBDD) from Aegilops squarrosa (2n = 14 = DD). The chromosome arm location and the crossover distance from the centromere of each gene studied are as follows: synthetic hexaploid RL 5404 — brown glumes (Rg2), 1DL, 13.3 ± 3.3%; tenacious glumes (Tg), 2Dα, 39.4 ± 4.9%; inhibitor of waxy foliage (W21), 2Dα, 52.5 ± 5.0%; adult-plant leaf rust resistance (Lr22), 2Dα, 63.6 ± 4.8%; purple coleoptile (Rc3), 7DS, 10.3 ± 2.8%; synthetic hexaploid RL 5406 — Rg2, 1DL, 1.7 ± 1.0%; Tg, 2Dα, 42.9 ± 4.6%; W21, 2Dα, 58.9 ± 4.6%; Rc3, 7DS, 9.8 ± 2.8%. A gene for seedling leaf rust resistance (Lr21) found in RL 5406 is located on chromosome 1D.