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UsingaF 2 population derived from the cross of
TU (R) x Catrachita (R), a segregation ratio cor-
responding to two independent resistance genes
for race 64 was described, and these results were
taken as a evidence of independence between
the resistance gene present in TU ( Co-5 ) and
the one present in Catrachita ( Co-6 ) (Young and
Kelly 1996b). Independent segregation between
the OAK20 890 marker linked to Co-6 gene and
the Co-5 resistance cluster mapped in TU on
Pv07 has been observed (Campa et al. 2009).
The presence of more than one resistance gene
in AB136 has been reported (Campa et al. 2007),
so the presence of Co-5 in AB136 does not
exclude the possibility of the presence of Co-
6 resistance gene first described in Catrachita.
To date, the location on the genetic map of the
Co-6 gene described in Catrachita as linked to
the OAK20 890 marker has not been reported.
segregation for the resistance to race 65 in the
F 2 population derived from the cross PI 207262
(R) x TO (R) (Alzate-Marin et al. 2001a) sug-
gests that the gene effective against this race in
PI 207262 is located on Pv08, corresponding to
Co-4 locus. That gene was later interpreted as
a third allele Co-4 3
at the Co-4 locus (Alzate-
Marin et al. 2007).
Breeding line SEL1308 was developed at
CIAT through backcrossing with the differen-
tial cultivar G2333 known to possess the Co-
4 2 , Co-5 2 , and Co-7 genes (Young et al. 1998).
The Co-4 gene was reported to be present in
the SEL1308 line, identified at that time, as
the Co-4 2 allele based on the different resistant
patterns against in G2333 and SEL1308 geno-
types. A gene from SEL1308 conferring resis-
tance against race 1545 was linked to the SCAR
marker SAS13 in the F 2:3 population, Catrachita
(S) x SEL1308 (R). Another gene conferring
resistance against race 73 was also closely linked
to the SCAR marker SAS13 in the F 2:3 popula-
tion, Black Magic (S) x SEL1308 (R). In both
populations, no recombinants between the resis-
tant gene and the marker were detected (Young
et al. 1998). Two independent dominant genes
conferring resistance to race 73 in the donor line
G2333 were described in the F 2:3 population,
Ruda (S) x G2333 (R). One of these resistance
genes was dissected in a BC 3 F 2:3 population
and was also linked in coupling phase to RAPD
marker OPAS13 950 (Alzate-Marin et al. 2001b),
from which the SCAR SAS13 was developed.
The SAS13 marker was mapped to Pv08, in a
relative position similar to the mapped Co-4 gene
in TO (Rodrıguez-Suarez et al. 2005), confirm-
ing the presence of the Co-4 gene in the geno-
types SEL1308 and G2333. In agreement with
this result, the Co-4 resistance locus linked to the
SAS13 was physically mapped to the short arm
of bean chromosome 3, which corresponds to
Pv08, using a BAC library constructed from the
snap bean cultivar Sprite (Melotto et al. 2004).
Further support for map position of the Co-4
locus comes from the reported linkage of Mex-
ique2(Co-4) gene to the pod anthocyanin, Anp
LinkageGroupPv08
Genes conferring specific resistance to differ-
ent races of C. lindemuthianum were directly
mapped to the distal position of Pv08 from
Middle American genotypes TO, PI207262,
SEL1308 and G2333 (Figure 9.2). In differential
cultivar TO, a gene conferring specific resistance
against race 65 was mapped to Pv08 using a F 2:3
population developed from the cross Rud´a(S)x
TO (R), closely linked in coupling to OPY20 830
marker (Cardoso de Arruda et al. 2000). The
SCAR marker SY20 was developed from the
RAPD marker OPY20 830 (Queiroz et al. 2004)
and its location on Pv08 was confirmed (N. Tra-
banco, per. com.). This gene probably corre-
sponds to the Mexique 2 gene, conferring spe-
cific resistance against pathotypes gamma and
delta 2, that was first described in the differen-
tial cultivar TO (Fouilloux 1976) and was later
renamed as Co-4 gene (Kelly and Young 1996).
A single dominant gene conditioning resis-
tance to race 65 was reported in the anthracnose
differential cultivar PI 207262 investigating the
F 2 population derived from the cross Rud´a(S)
x PI 207262 (R) (Silva et al. 2007). A lack of
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