Monogenic and epistatic resistance to bean rust infection in common bean
ABSTRACT In order to determine the relationship between resistance genes and hydrolytic enzyme induction, the interaction between two Phaseolus vulgaris cultivars (Sierra and Olathe) and two Uromyces appendiculatus races (47 and 55) were analyzed. Resistance of Sierra to race 55 was expressed as hypersensitive flecking, whereas the resistance of Olathe to race 47 was not associated with macroscopic symptoms and was classed as immunity. The Sierra/race 47 and Olathe/race 55 interactions were compatible. An analysis of a F2 population and F3 families demonstrated that a monogenic factor controlled resistance to race 47 while two genes controlled the interaction with race 55. At one locus determining resistance to race 58 resistance is dominant to susceptibility, and at the second locus hypersensitive resistance is dominant to immunity. Both alleles at the second locus are hypostatic to the susceptibility allele at the first locus. The induction of the hydrolytic enzymes β-1,3-glucanase and chitinase was monitored for the four interactions over a ten-day period. For the compatible interactions, the hydrolytic enzyme activities increased slightly over time. This pattern was also noted for the Olathe/race 55 immune-resistance interaction. In contrast, the β-1,3-glucanase and chitinase activity for the Sierra/race 55 hypersensitive-resistance interaction was significantly greater from day 2 through day 10. These results suggest the possibility that induction of hydrolytic enzyme activity may be associated with hypersensitive, but not immune resistance in the bean/bean rust interaction.
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ABSTRACT: Race-specific resistance to the bean rust pathogen (Uromyces appendiculatus) is provided by a number of loci in common bean (Phaseolus vulgaris). The Ur-3 locus controls hypersensitive resistance (HR) to 44 of the 89 races curated in the United States. To better understand resistance mediated by this locus, we developed new genetic material for analysis. We developed a population of mutagenized seed of cv. Sierra (genotype = Ur-3 ur-4 ur-6) that was screened with a bean rust race that is normally incompatible (HR response) on Ur-3 genotypes. We discovered two mutants of common bean, crg and ur3-delta3, in which uredinia formed on leaves (a compatible interaction) following infection. The F1 generation from a cross of these two mutants expressed the HR response, and the F2 generation segregated in a ratio of 9:7 (HR/uredinia formation). Therefore, the two genes are unlinked. Further genetic analysis determined that the mutation in ur3-delta3 was in the Ur-3 locus, and the mutation in crg was in a newly discovered gene given the symbol Crg (Complements resistance gene). Each mutation was inherited in a recessive manner. Unlike ur3-delta3, crg expressed reduced compatibility to bean rust races 49 and 47 that are normally fully compatible on genotypes, such as Sierra, that are homozygous recessive at the Ur-4 and Ur-6 loci. This suggests a gene mutated in crg is normally a positive compatibility factor for the bean-bean rust interaction. Polymerase chain reaction analysis of crg with primers to common bean resistance gene analogs (RGA) that contain a nucleotide-binding site sequence similar to those found in a number of plant disease resistance genes revealed that crg is missing the SB1 RGA, but not the linked SB3 and SB5 RGAs. Genetic analyses revealed that Crg cosegregates with the SB1 RGA. These results demonstrate that Crg is located near a RGA cluster in the common bean genome.Molecular Plant-Microbe Interactions 12/2000; 13(11):1237-42. DOI:10.1094/MPMI.2000.13.11.1237 · 4.46 Impact Factor
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ABSTRACT: Chitinase enzymes are induced in many plants in response to pathogen challenge and other stress stimuli. Chitinase induction in flax leaves in response to inoculation with flax rust, caused by Melampsora lini (Pers.) Lev., was investigated in a line of flax (Forge) that has four resistance genes, viz. L6, M, N and P2. Four avirulent rust strains, each of which interacts with just one of the resistance genes in Forge, as well as a strain that is virulent on Forge, were used. Thus chitinase levels associated with resistance reactions triggered by the L6, M, N or P2 genes, and by a susceptible reaction, have been compared in the same host genotype. A marked increase in chitinase activity in inoculated leaves was observed with all four resistance reactions, with the increase occurring earlier with the P2 resistance reaction compared with the L6, M, and N reactions. A moderate increase in chitinase activity was also observed in systemic (new-growth) leaves of flax plants inoculated with strains interacting with the M, N or P2 genes. Leaves inoculated with a virulent strain of rust also had increased chitinase activity but the increase was much less than that found in leaves inoculated with the avirulent strains.Australasian Plant Pathology 01/2001; 30(1):27-30. DOI:10.1071/AP00058 · 1.04 Impact Factor
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ABSTRACT: Two RAPD markers linked to gene for resistance (assayed as pustule number cm−2 leaf area) to rust [Uromyces fabae (Pers.) de Bary] in pea (Pisum sativum L.) were identified using a mapping population of 31 BC1F1 [HUVP 1 (HUVP 1 × FC 1] plants, FC 1 being the resistant parent. The analysis of genetics of rust resistance was based on the parents, F1, F2, BC1F1 and BC1F2 generations. Rust resistance in pea is of non-hypersensitive type; it appeared to be governed by a single partially dominant gene for which symbol Ruf is proposed. Further, this trait seems to be affected by some polygenes in addition to the proposed oligogene Ruf. A total of 614 decamer primers were used to survey the parental polymorphism with regard to DNA amplification by polymerase chain reaction. The primers that amplified polymorphic bands present in the resistant parent (FC 1) were used for bulked segregant analysis. Those markers that amplified consistently and differentially in the resistant and susceptible bulks were separately tested with the 31 BC1F1 individuals. Two RAPD makers, viz., SC10-82360 (primer, GCCGTGAAGT), and SCRI-711000 (primer, GTGGCGTAGT), flanking the rust resistance gene (Ruf) with a distance of 10.8 cM (0.097 rF and LOD of 5.05) and 24.5 cM (0.194 rF and a LOD of 2.72), respectively, were identified. These RAPD markers were not close enough to Ruf to allow a dependable maker-assisted selection for rust resistance. However, if the two makers flanking Ruf were used together, the effectiveness of MAS would be improved considerably.Euphytica 07/2005; 144(3):265-274. DOI:10.1007/s10681-005-6823-2 · 1.69 Impact Factor