Organization of Genes Conferring Resistance to Anthracnose in Common Bean - Translational Genomics for Crop Breeding: Biotic Stress - page 158

Historical Review of the Genes
Conditioning Resistances to
C.lindemuthianum

ing to gene pool. Genes Co-u , Co-12 , Co-13 , and
Co-14 represent new sources of resistance in the
Andean gene pool that lacked high levels of resis-
tance in contrast to the genes of Mesoamerican
origin. However, in limited testing to date, the
new gene Co-12 in Jalo Vermelho only condi-
tions resistance to races 9, 23, 31, 55, 65, 81, 89,
95, and 453, the Co-13 gene in Jalo Listras Pre-
tas conditions resistance to Mesoamerican races
9, 64, 65, and 73, and the Co-14 gene in Pitanga
conditions resistance to Mesoamerican races 23,
64, 65, 73, and 2047. Only the Co-12 gene con-
ditions resistance to the virulent Andean race 55,
whereas the Co-14 conditions to the highly viru-
lent race 2047 that defeats many of the resistance
genes in the differential series. Interestingly the
resistance pattern of the Co-14 gene in Pitanga is
very similar to that of reported for the Co-1 4 gene
in the Andean genotype AND 277 (Gon¸alves-
Vidigal et al. 2011). The apparent similarity of
both genes could be tested using markers tightly
linked to the Co-1 4 gene. The potential of these
new genes in providing resistance to highly viru-
lent races 3481 and 3657 from Central America
should be evaluated as these races are strongly
Mesoamerican in origin as they attack many
of the Middle American differential cultivars,
so new Andean genes could offer potential for
resistance.

In addition to the standardization of the
pathogenic variability of C. lindemuthianum
using a uniform differential host series, it became
clear that there was a need to standardize the
naming of gene symbols in the host that con-
ditioned resistance to individual races of the
pathogen. To address this issue, Kelly and Young
(1996) proposed the use of the symbol “ Co ”to
identify genes conditioning resistance to races of
C. lindemuthianum in common bean. Five orig-
inal independent genes— A , Are , Mexique 1 , 2 ,
and 3 —were renamed Co-1 to Co-5 , respectively
and a total of 20 Co-genes have since been iden-
tified and named (Table 9.2). In addition, dif-
ferent alleles conferring resistance to different
resistance profiles were described in for the loci
Co-1 , Co-3 , Co-4 , and Co-5 (see Table 9.2). A
complete description of resistance genes Co-1
to Co-10 , their mode of action, race specificity,
map location, and value to breeders was reviewed
by Kelly and Vallejo (2004). Since then, seven
additional resistance genes have been reported
(Table 9.2). The Co-11 gene, described in differ-
ential cultivar Michelite using the races 8 and 64
(Gon¸alves-Vidigal et al. 2007), is not effective
against many races but does not exhibit resis-
tance to some highly virulent Andean races such
as race 38 from Spain. The gene Co-u conferring
resistance to isolates E4 and E42b was identi-
fied in the cultivars BAT93 (Geffroy et al. 2008).
The Co-12 gene was described in cultivar Jalo
Vermelho using the races 23, 55, 89, and 453
(Gon¸alves-Vidigal et al. 2008) and the Co-13
gene was described in cultivar Jalo Listras Pre-
tras using the races 9, 64, 65, and 73 (Gon¸alves-
Vidigal et al. 2009). Finally, the presence of the
Co-14 gene has been postulated in the bean culti-
var Pitanga using race 2047 (Gon¸alves-Vidigal
et al. 2012).
Within P. vulgaris host, two major gene pools,
Andean and Middle American, exist (Gepts
1988), and resistance genes are classified accord-

Classical Genetic Analysis of
Resistance to C.lindemuthianum

Classical genetic analyses of resistance to C. lin-
demuthianum are based on the interpretation of
results obtained from F 2 segregating populations
derived from two types of crosses: R x S or R
x R (complementation or allelism tests). Results
observed in R x S crosses are used to infer the
number and mode of action of genes conferring
resistance to C. lindemuthianum . Burkholder
(1918) analyzed the resistance in a F 2 population
derived from the cross between the cvs. White
Marrow (resistant to race alpha) and Wells' Red
Kidney (susceptible to race alpha) and proba-
bly described the first analysis of resistance to