Article

Marker-assisted dissection of the oligogenic anthracnose resistance in the common bean cultivar, ‘G2333’

Federal University of Santa Catarina, Nossa Senhora do Destêrro, Santa Catarina, Brazil
Theoretical and Applied Genetics (Impact Factor: 3.51). 12/1997; 96(1):87-94. DOI: 10.1007/s001220050713

ABSTRACT  Two independently assorting dominant genes conditioning resistance to bean anthracnose were identified in an F2 population derived from the highly resistant bean differential cultivar, ‘G 2333’. One gene was allelic to the Co-4 gene in the differential cultivar ‘TO’ and was named Co-4

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, whereas the second gene was assigned the temporary name Co-7 until a complete characterization with other known resistance genes can be conducted. Two RAPD markers linked to the Co-4

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allele were identified. One RAPD, OAS13950, co-segregated with no recombinants in two segregating populations of 143 F2 individuals, whereas the second RAPD, OAL9740, mapped at 3.9 cM from the Co-4

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allele. Two 24-mer SCAR primers (SAS13), developed from the OAS13950 RAPD marker, were dominant and polymorphic, similar to the original RAPD, and supported the tight linkage between the marker(s)
and the Co-4

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allele. The markers were present in germplasm with known resistance alleles at the Co-4 locus. The presence of the markers in two other differential cultivars not previously characterized and in four navy bean
cultivars suggests the existence of a gene family for anthracnose resistance at or near the Co-4 locus. Since the Co-7 gene was present only in germplasm which also possessed the Co-4

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and Co-5 genes, the SAS13 markers were used in combination with standard inoculation techniques to identify F3 lines in which the Co-7 gene was homozygous and the Co-4

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allele was absent. A similar strategy of marker-assisted dissection is proposed to identify resistant lines in which the
Co-5 gene is absent and the Co-7 gene is present by selecting against the OAB3450 marker, which has been shown previously to be linked to the Co-5 gene. These genes cannot be distinguished using traditional screening methods since all current races of the pathogen virulent
to the Co-5 gene are avirulent to the Co-4

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and Co-7 genes. We describe the use of molecular markers tightly linked to resistance genes to facilitate the identification of an
uncharacterized resistance gene for which no discriminating race of the pathogen is known.

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    • "(c) Mapping of the Rpsar-2 gene to the end of LG B8. SAS13 and Dj1kSCAR are two SCAR markers linked to the anthracnose Co-4 R gene (Adam-Blondon, 1994; Young et al., 1998). Oval symbols correspond to R genes. "
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    ABSTRACT: *In plants, the evolution of specific resistance is poorly understood. Pseudomonas syringae effectors AvrB and AvrRpm1 are recognized by phylogenetically distinct resistance (R) proteins in Arabidopsis thaliana (Brassicaceae) and soybean (Glycine max, Fabaceae). In soybean, these resistances are encoded by two tightly linked R genes, Rpg1-b and Rpg1-r. To study the evolution of these specific resistances, we investigated AvrB- and AvrRpm1-induced responses in common bean (Phaseolus vulgaris, Fabaceae). *Common bean genotypes of various geographical origins were inoculated with P. syringae strains expressing AvrB or AvrRpm1. A common bean recombinant inbred line (RIL) population was used to map R genes to AvrRpm1. *No common bean genotypes recognized AvrB. By contrast, multiple genotypes responded to AvrRpm1, and two independent R genes conferring AvrRpm1-specific resistance were mapped to the ends of linkage group B11 (Rpsar-1, for resistance to Pseudomonas syringae effector AvrRpm1 number 1) and B8 (Rpsar-2). Rpsar-1 is located in a region syntenic with the soybean Rpg1 cluster. However, mapping of specific Rpg1 homologous genes suggests that AvrRpm1 recognition evolved independently in common bean and soybean. *The conservation of the genomic position of AvrRpm1-specific genes between soybean and common bean suggests a model whereby specific clusters of R genes are predisposed to evolve recognition of the same effector molecules.
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    • "These difficulties can be avoided if the characterization of the resistance genes is carried out by direct mapping, using molecular markers. Only some of the resistance genes present in the cultivars, Cornell 49242, G2333, Mexico 222, and Widusa, have been identified using this procedure (Adam-Blondon et al. 1994; Young et al. 1998; Rodríguez- Suárez et al. 2008). Most of the Co-genes were described as single genes conferring dominant resistance (except co-8) to several anthracnose races. "
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    ABSTRACT: Resistance to nine races of the pathogenic fungus Colletotrichum lindemuthianum, causal agent of anthracnose, was evaluated in F(3) families derived from the cross between the anthracnose differential bean cultivars TU (resistant to races, 3, 6, 7, 31, 38, 39, 102, and 449) and MDRK (resistant to races, 449, and 1545). Molecular marker analyses were carried out in the F(2) individuals in order to map and characterize the anthracnose resistance genes or gene clusters present in these two differential cultivars. The results of the combined segregation indicate that at least three independent loci conferring resistance to anthracnose are present in TU. One of them, corresponding to the previously described anthracnose resistance locus Co-5, is located in linkage group B7, and is formed by a cluster of different genes conferring specific resistance to races, 3, 6, 7, 31, 38, 39, 102, and 449. Evidence of intra-cluster recombination between these specific resistance genes was found. The second locus present in TU confers specific resistance to races 31 and 102, and the third locus confers specific resistance to race 102, the location of these two loci remains unknown. The resistance to race 1545 present in MDRK is due to two independent dominant genes. The results of the combined segregation of two F(4) families showing monogenic segregation for resistance to race 1545 indicates that one of these two genes is linked to marker OF10(530), located in linkage group B1, and corresponds to the previously described anthracnose resistance locus Co-1. The second gene conferring resistance to race 1545 in MDRK is linked to marker Pv-ctt001, located in linkage group B4, and corresponds to the Co-3/Co-9 cluster. The resistance to race 449 present in MDRK is conferred by a single gene, located in linkage group B4, probably included in the same Co-3/Co-9 cluster.
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    • "duced a two gene (15:1) segregation ratio after inoculation with C. lindemuthianum race 23 (delta) that overcomes the resistance in all three differential cultivars (Gonçalves- Vidigal et al., 1997). We found a four-gene segregation ratio (255R:1S, p = 0.92) in the F 2 population from the Michelite x G 2333 cross after inoculation with race 64 but no allelism was observed in this cross, although the segregation ratio supports the presence of four independent dominant genes with one gene in Michelite and three genes (Co-4 2 , Co-5 and Co-7) in G 2333 (Young et al., 1998). The segregation ratio of 15R:1S found by us in the F 2 offspring from the Michelite x MDRK (p = 0.55), Michelite x Kaboon (p = 0.81), Michelite x Perry Marrow (p = 0.77), Michelite x AND 277 (p = 0.32) and Michelite x Widusa (p = 0.45) crosses, indicated that the gene in Michelite is independent from the genes previously characterized at the Andean Co-1 locus (Co-1, "
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    ABSTRACT: The genetic resistance of Phaseolus vulgaris L. cultivar Michelite to races 8 and 64 of Colletotrichum lindemuthianum, causal agent of bean anthracnose, was characterized. Crosses were made between Michelite and Mexico 222 cultivars and the F2 population was inoculated with race 64 in order to study the inheritance of resistance to anthracnose in Michelite. The segregation of F2 population fitted in a ratio of 3R:1S, showing the presence of a dominant gene in Michelite gene conditioning resistance to race 64. Allelism tests were conducted with F2 populations derived from crosses between Michelite and AB 136, AND 277, BAT 93, Cornell 49-242, G 2333, Kaboon, Mexico 222, Michigan Dark Red Kidney (MRDK), Ouro Negro, Perry Marrow, PI 207262, TO, TU, and Widusa. All the cultivars (except Mexico 222) were resistant to race 64. While F2 derived from the Michelite x Mexico 222 was inoculated with race 8. Additionally, allelism tests indicated that the gene present in Michelite is independent from Co-1, Co-2, Co-3, Co-4, Co-5, Co-6, Co-7, Co-9 and Co-10 genes. The monogenic inheritance observed in Michelite and the independence of this gene from those previously characterized allow the authors to propose that the anthracnose resistant gene in Michelite should be named Co-11.
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