Agriculture Reference
In-Depth Information
To select for ideal root systems for drought-challenged environments,
CIAT has focused on pyramiding major root QTLs into LAC cultivars.
The physiological and phenotypic effect of these pyramided QTL lines
is being evaluated under drought to understand the interactions among
QTLs and tolerance mechanisms under stress. The most effective com-
binations of traits will then be bred into important cultivars using
MAS, and relevant germplasm made available to breeders of NARES
partners for use in their programs. CIAT has extensive experience with
introgressions and pyramiding of QTLs in relevant rice lines. Field
validation of
Dro1
(deeper rooting) introgressed lines of IR64 demon-
strated a positive relationship between root architecture and yield
performance under drought stress. This validation is useful for testing
the
ed under
controlled conditions. Progress will generate prebreeding materials for
various abiotic stress tolerances, including nutrient stress.
CIAT and FLAR, in collaboration with NARCH-Japan, began a survey
of allelic variation in a rice nursery with contrasting tolerance of low
temperatures. Parental candidates combining a cold-tolerant pheno-
type and genotype were identi
field application of promising root traits that are identi
ed. The introgression of loci for cold
tolerance into sensitive
indica
cultivars was pursued via MABC and
several populations were developed. Phenotyping and genotyping
have been completed and the results are being validated (FLAR 2013).
In the context of population improvement, MARS consists of improv-
ing the population mean value for a few traits through successive cycles
of recombination in which genotypes are selected via MAS. In MARS
breeding, markers used for the selection process are those showing
signi
cant association with the trait of interest. CIAT has started an
RS breeding program for tolerance of drought and, through the use of a
breeder SNP chip, will proceed to MARS to enrich the population for
traits related to tolerance. The advantage of applying MARS in popula-
tion improvement is reviewed in Section III.
The
Pup1
QTL controlling tolerance of low P conditions (Chin et al.
2011) was sought and found among some parental lines that constituted
the RS population CNA9. Through MARS, this QTL will be
fixed in the
population to improve the mean for this characteristic.
Genomic selection is the latest method of MAS and it considers
markers on the whole genome rather than only those signi
cantly asso-
ciated with the traits of interest, as in the case of MARS (see Section III).
A training population of 355 individuals, designed to develop a GS
model, was genotyped with a large number of SNP markers, phenotyped
for yield under optimum conditions, and submitted to water-limited
conditions to score each individual for yield under drought, as well as
