Agriculture Reference
In-Depth Information
diversity in the host and the privilege of accessing
field selection sites
with high disease pressure. After many years of research, tremendous
progress has been made in developing cultivar resistance to blast, as in
the case of Oryzica Llanos 5, and resistance to RHBV in Fedearroz 2000.
All this progress took place at a time when molecular tools were under
development. Nowadays, as these tools have advanced, breeders and
pathologists are under strong pressure to adopt methodologies to speed
up the development of new elite cultivars.
Several molecular markers have been identi
ed for rice blast resist-
ance genes, but their implementation in breeding programs is very
poor. Sequencing technologies would improve the quality of molecular
markers and also the implementation of MAS platforms. One big
challenge for rice researchers is the identi
cation of new resistance
genes, and new gene combinations, to sustain the development of
highly resistant cultivars for the breeding pipeline. The systematic
evaluation of pathogen populations to detect the appearance of new
variants that could break down the resistance of deployed genes and
the alternate use of effective genes to minimize the chances of being
defeated by the pathogen due to excessive exposure represent manda-
tory research activities in the future. In the case of other diseases, such
as RHBV, in which sources of resistance have already been identi
ed,
the use of molecular markers to facilitate the improvement of rice
cultivars is very near. Future studies should be directed to the identi-
fication of multiple sources of resistance to both the vector and the
virus. Special attention should be paid to emergent diseases such as
bacterial panicle blight. No sources of durable resistance have been
identi
ed so far but, even worse, the transmission mechanism and
disease cycle are poorly understood. Basic research is required to
elucidate the real potential of this disease to affect rice production
in LAC along with methodologies for germplasm evaluation. CIAT is
conducting several studies to provide insight into de
ning strategies to
manage this disease but these actions require the contribution of
institutions in other countries of the region for their validation.
A common bottleneck in breeding for resistance to diseases, both
those diseases that are important today and those that will be important
in the future, involves phenotyping methodologies. Reliable method-
ologies are available but they have been designed for a low to inter-
mediate number of genotype-treatment combinations. Institutions and
rice breeding programs should improve their infrastructure to enter
into the
“
high-throughput
”
era since this is a critical step not only for
resistance donor identi
rmation. An
overall evaluation of breeding for resistance to diseases of rice in Latin
cation but also for MAS con
