Organization of Genes Conferring Resistance to Anthracnose in Common Bean - Translational Genomics for Crop Breeding: Biotic Stress - page 172

Widusa. However, based on the current knowl-
edge about the anthracnose resistance present in
the cultivars used in these allelism tests, the inde-
pendence between the gene present in Miche-
lite and some of the Co-genes described should
be reconsidered. For instance, the independence
between the resistance gene present in Miche-
lite and Co-9 was tested in the cross Michelite
x BAT93 (R x R) against race 64. In BAT93,
the presence of the Co-9 gene was described
(Geffroy et al. 1999) and recently, other inde-
pendent anthracnose resistance locus, named as
Co-u and located in Pv02, was reported in this
cultivar (Geffroy et al. 2008). The 15R:1S seg-
regation ratio found in the F 2 population Miche-
lite x BAT93 suggests that one dominant gene
confers resistance to race 64 in BAT93, but
it is unknown if these resistance gene corre-
sponds to Co-9 or to Co-u locus, so the possi-
bility that Co-11 correspond with Co-u should
not be discarded. The existence of the Co-11
gene as a new anthracnose resistance gene should
be confirmed, given the existence of more than
one resistance gene in bean genotypes MDRK,
Kaboon, Widusa, TU, and AB136 (Campa et al.
2007, 2009, 2011; Rodrıguez-Suarez et al. 2008)
used to test independence with the Co-1 , Co-1 2 ,
Co-1 5 , Co-5 , and Co-6 genes.

GeneCo-14

The presence of the Co-14 gene has been pos-
tulated in the bean cultivar Pitanga, landrace
cultivar from Brazil, following inoculation of
segregating populations with races, 23, 64, 65,
and 2047 (Gon¸alves-Vidigal et al. 2012). Inde-
pendence from previously reported Co-genes is
based segregation in 14 F 2 populations inocu-
lated with various races listed above. The fact
that some of the differentials are now known to
carry more than a single gene on different LGs,
independence will need to be tested using family-
derived populations challenged against a number
of differentiating races capable of detecting all
known genes in the differentials. Since the resis-
tance 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 should be tested using markers tightly
linkedtothe Co-1 4 gene before the independence
of the Co -14 gene can be fully accepted by the
bean community.

Genomic Organization of Resistance
to Anthracnose

Genes with different function are involved in the
response to C. lindemuthianum (Borges et al.
2012; Oblessuc et al. 2012). Many plant disease
resistance genes (R genes) encode proteins that
are part of the plant-pathogen interaction. R
proteins can have two functions: they work as
sensors detecting pathogens or they activate the
reaction to pathogens (Chisholm et al. 2006).
The most characterized R genes encode proteins
containing a leucine-rich repeat motif (LRR).
The vast majority of genes cloned so far can
be classified in three families considering the
conserved motif in R gene products: NBS-
LRR (Nucleotide-Binding Site- LRR), eLRR
(extracytoplasmic LRR), and LRR-Kinase
(McDowell and Woffenden 2003). The NBS-
LRR family has also been classified in two types
based on the N-terminal domain of the R protein:

GeneCo-12

The Co-12 gene was described in the landrace
Jalo Vermelho as a gene independent from the
previously described Co-1 , Co-2 , Co-3 , Co-4 ,
Co-5 , Co-6 , Co-7 , Co-9 , Co-10 , Co-11 , and Co-
13 loci (Gon¸alves-Vidigal et al. 2008). The
resistance in Jalo Vermelho against races 23, 55,
89, and 453 is controlled by one dominant gene
in each case, as is deduced from the 3R:1S seg-
regation ratios obtained in F 2 populations in R x
S crosses, being Jalo Vermelho the resistant par-
ent. Additional analysis should be carried out to
verify that the same locus is involved in the resis-
tance reaction to the races 23, 55, 89, and 453
and its independence from previously described
resistance genes.