Resistance to Late Blight in Potato - Translational Genomics for Crop Breeding: Biotic Stress - page 225

been observed in the potato genome. Some of
the genes underlying the resistance QTL in their
structure may be related to R genes responsible
for resistance to the same or different pathogen
and may be encoded by the same classes of genes
(Gebhardt and Valkonen 2001).
In 2002 the Global Initiative on Late Blight
(GILB) organized a survey of research and
breeding for resistance to late blight in potato,
in which 39 centers from 25 countries partici-
pated. Resistance to late blight was a high prior-
ity trait for more than 60% of the questioned
centers. The majority of responding breeding
centers (70%) indicated that the most preferred
type of resistance was the one in which both
R genes and race-non-specific resistances oper-
ate together. For 26% of respondents, exclusive
race-non-specific resistance was the most valu-
able (Zimnoch-Guzowska and Flis 2002).
Progress in identifying and cloning R genes
within the Solanum species allowed for the pro-
posal of new breeding methods for durable late
blight resistance based on genetic modification
with cisgenes in order to breed marker-free cul-
tivars with different cassettes of R genes of
Solanum origin. In this proposal management
of the resistance control, based on temporal and
spatial composition of R genes in the cassette
set, adapted to the changing pathogen potential
(Haverkort et al. 2008).

Southwest of United States to the south of Chile,
with most species found in Peru and Bolivia.
Their habitats include diverse climates and soil
conditions. There are more than 4,300 varieties
of native potatoes, mostly found in the Andes.
At the International Potato Center (CIP)
more than 7,000 accessions of native, wild, and
improved varieties are maintained in the gene
bank - the largest collection in the world. This
gene bank is supplemented by the potato col-
lections in the U.S. (NRSP-6), Germany (CGN
and GLKS), Scotland (CPC), Russia (VIR), and
Argentina (INTA). The Association of Potato
Inter-genebank Collaborators (APIC) developed
the Inter-genebank Potato Database (TPD), con-
taining in total data of 11,819 wild potato acces-
sions conserved in seven potato gene banks
(Huaman et al. 2000). The database is available
at www.potgenebank.org.
For a large number of wild potato accessions
preserved in world gene banks, the information
on resistance to diseases and pests has already
been made available (Hanneman and Bamberg
1986; Zoteyeva 1986; Darsow and Hinze 1991;
Colon 1994; Bradshaw et al. 1995; Bamberg
et al. 1996; Angeli et al. 2000; Huaman et al.
2000). In 2002, the Global Initiative on Late
Blight organized a survey on late blight resis-
tance research and breeding, in which 34 breed-
ing programs and 5 research centers partici-
pated. Cultivars, breeding lines, and wild species
were indicated as explored sources of resistance.
In total, 44 cultivars were listed as resistance
sources utilized in late blight resistance breed-
ing. The cultivar Stirling was applied as a source
by five centers; cultivars such as Jacqueline Lee,
Kuras, Lugovska, and Zarevo were used by three
centers; and Bionta, Cara, Innovator, and Torri-
don were used by two centers. In several centers
breeding lines were explored as sources of resis-
tance supplementing cultivars. The most popular
were AWN 86514-2, A90586-11, and BO718-3.
However, clones from the Neotuberosum pro-
gram of Cornell University, ABPT hybrids from
the Netherlands, and several selections from CIP,
INIFAP, VIR, IHAR, and INTA were also listed.

Sources of Resistance to P.infestans

According to the recent taxonomic and molecu-
lar studies, there are 188 known Solanum species
of wild potato along with one cultivated species
in section Petota and three species in section
Etuberosa (Spooner and Salas 2006). Part of
these species are the original ancestors of today's
potato cultivars. Spooner et al. (2005) hypothe-
sized that potato was domesticated in Peru, on
the basis of an amplified fragment length poly-
morphism (AFLP) markers study.
Wild relatives are a rich source of natu-
ral resistances to diseases, pests, and climatic
stresses. Wild Solanum species grow from the