Organization of Genes Conferring Resistance to Anthracnose in Common Bean - Translational Genomics for Crop Breeding: Biotic Stress - page 169

in the genotype TU as a single gene confer-
ring resistance against C. lindemuthianum strains
gamma and delta 2 (Fouilloux 1976). This clus-
ter is linked to the SCAR marker SAB3 in TU,
developed from the RAPD OAB3 450 , previously
described as linked to Co-5 gene in the genotype
SEL1360 (Young and Kelly 1997a; Vallejo and
Kelly 2001).
Breeding line SEL1360 was developed at
CIAT through backcrossing to the differential
cultivar G2333, shown to possess three resis-
tance loci: Co-4 , Co-5 , and Co-7 (Young et al.
1998). The RAPD marker OAB3 450 was linked to
a gene in the genotype SEL1360 conferring spe-
cific resistance to race alpha (race 17) in the F 2:3
population Black Magic (S) x SEL 1360 (R), and
linked to a gene conferring specific resistance to
race 73 in the F 2:3 population Blackhawk (S) x
SEL 1360 (R) (Young and Kelly 1997a). This
resistant gene was assumed to be the same—the
Co-5 gene derived from G2333. The lack of seg-
regation reported by Young and Kelly (1996b)
in the allelism test conducted with race 7 in the
F 2 population TU (R) x SEL1360 (R) was used
to suggest that both genotypes carried the same
resistance gene, probably included in the Co-5
cluster reported in TU. More recent studies have
shown that TU is resistant to race 3481 whereas
SEL 1360 is susceptible to it (Vallejo and Kelly
2009). Based on the presence of a differenti-
ating race, the authors proposed that the Co-5
allele in SEL 1360, MSU 7-1, and G2333 parent
be named Co-5 2 (Table 9.2). Additional confir-
mation for the location of the Co-5 locus comes
from screening of cross of MSU7-1 breeding line
with STS markers developed by McConnell et al.
(2010). In the F 2 population of MSU 7-1 crossed
with Mexico 222 and screened with race 64, the
g1233 marker located on Pv07 (McConnell et al.
2010) was shown to be linked at 1.2cM from
Co-5 gene (Sousa et al. 2012).
The resistance to race 89 in the anthracnose
differential cultivar G2333 was reported to be
controlled by two independent dominant genes
using a F 2 population derived from the cross
Ruda (S) x G2333 (R) (Alzate-Marin et al. 2001).

One of these resistance genes was dissected in a
BC 1 F 2:3 population obtained from this cross and
was linked in coupling phase to RAPD marker
OPAB3 450 , described as linked to Co-5 gene.
In the differential cultivar AB136, a mono-
genic segregation against races 73, 81, and 89
was observed in the F 2 population Michelite
(S) x AB136 (R) (Alzate-Marin et al. 1999).
Each one of these resistance specificities was
linkedtotheOPZ04 560 marker. The same authors
identified a resistance gene conferring resis-
tance against race 64 in the F 2 population Mex-
ico 222 (S) x AB136 (R), also linked to the
OPZ04 560 marker. This marker and the corre-
sponding SCAR SZ04 marker (Queiroz et al.
2004) were located on Pv07 (Freyre et al.
1998; Kelly et al. 2003; Rodrıguez-Suarez et al.
2007; Perez-Vega et al. 2010). A resistance gene
against race 89 from AB136 was also identi-
fied in the F 2 population Ruda (S) x AB136
(R) linked to RAPD marker OPAZ20 940 (Alzate-
Marin et al. 2000). SCARZ20 marker developed
from the OPAZ20 940 RAPD marker (Queiroz
et al. 2004) located on Pv07 was closely linked to
SZ04 marker (Campa et al. 2009). In agreement
with these results, two linked genes from AB136
conferring specific resistance against races 81
and 449 were mapped on Pv07 using the F 2:3
population AB136 (R) x Michelite (S), linked
to SCARZ20 and SZ04 markers (Campa et al.
2007). All these results suggests that AB136 car-
ries an anthracnose resistance cluster located on
Pv07 probably corresponding, based on its rela-
tive map position, with the Co-5 resistance clus-
ter identified in this linkage group (Campa et al.
2007, 2009).
The Co-6 gene was first described in cultivar
Catrachita, linked to RAPD marker OAK20 890 ,
as a single gene conferring specific resistance
against races 23, 64, and 73 (Young and Kelly
1996b, 1997a). Since Catrachita was derived
from the cross BAT1225 x AB136 (anthracnose-
resistant donor), it was assumed that the anthrac-
nose resistance present in AB136 was also, and
exclusively, due to the Co-6 gene described in
Catrachita (Young and Kelly 1996b, 1997a).