Agriculture Reference
In-Depth Information
successfully implemented
field methods for evaluation and selection
of resistant materials. In general, most LAC countries base their breed-
ing or evaluation and selection for resistance on the same diseases.
Most countries in the region rely on breeding material received from
IRRI, CIAT, and FLAR, which is required to have resistance to the
main diseases in the country and be evaluated under natural disease
pressure.
2. RHBV.
This virus disease has devastated rice plantings in tropical
America for many years. The virus is transmitted by the insect vector
T. oryzicolus
, which also causes direct feeding damage on the rice plant.
Most of the research and breeding for resistance methodologies have
been developed at CIAT, although just a few countries adopted effective
greenhouse and
field methods for evaluating and selecting highly toler-
ant material. One of the main dif
”
epidemic behavior. The disease is best controlled by hybridization of
susceptible
indica
and resistant
japonica
rice genotypes and the adop-
tion of integrated disease and insect pest management (Morales and
Jennings 2010). RHBV resistance evaluations made at CIAT are based
on massive greenhouse multiplication of highly ef
culties of RHBV is its erratic
“
cyclical
cient
T. oryzicolus
-
colonies (50
80% of insect vectors) for release and infestation of spe-
cialized
field nurseries, including several thousand rice parents, breed-
ing lines, and segregating populations (Morales and Jennings 2010).
There is no immunity to RHBV and disease reaction depends on
many factors, including virus dosage and number of viruliferous vectors.
Vector colony multiplication in large screened greenhouse cages is
costly and labor-demanding, a reason for the low adoption in other
developing countries. Nevertheless, the development of rice genotypes
possessing high and stable RHBV resistance is possible, as observed in
cultivar Fedearroz 2000, a genotype that shows high resistance under
commercial production (Morales and Jennings 2010). Research is being
conducted at CIAT to understand the genetic basis of RHBV resistance
in cultivar Fedearroz 2000 and to identify molecular markers linked to
the resistance genes.
B. Perspectives
Breeding programs in LAC have a long history in developing rice
cultivars with resistance to different diseases, and they have succeeded
in providing rice cultivars that can withstand the biotic challenges
present in different countries of the region. In many cases, this success
can be attributed to key factors such as the availability of genetic
