Agriculture Reference
In-Depth Information
traits lacking in elite lines is a powerful methodology in breeding and
several improved cultivars with tolerance of iron toxicity have been
released (BRS Querencia was released in 2005).
2. Molecular Breeding
Genetic Studies.
The complexity of traits controlling adaptation to
abiotic stress has led geneticists and physiologists to look for reliable
screening methods that can accelerate the breeding process. Globally, a
great effort has been made to integrate genomics, physiology, and
breeding approaches to improve tolerance of abiotic stresses in rice,
notably in breeding for adaptation to drought-prone environments (Mir
et al. 2012). Genetic mapping was conducted to identify candidate
markers for use in marker-assisted selection for traits controlling toler-
ance of abiotic stresses. Molecular breeding is an important strategy for
combining (pyramiding) traits, particularly those that are highly affected
by environment and for which scoring is lengthy, challenging (low
heritability), and costly. The diversity of mechanisms conferring toler-
ance of abiotic stresses combined with the complexity of the stresses
themselves makes it dif
cult to breed for abiotic stress tolerance in crop
plants.
CIAT, Embrapa, and numerous NARES in LAC are involved in
research projects aiming to phenotype diversity panels or segregating
populations to identify markers associated with various characters rele-
vant to crop performance and tolerance of abiotic stresses. CIAT and
Embrapa are phenotyping diversity panels for yield under drought as
well as for secondary traits relevant to drought tolerance (yield compo-
nents, canopy temperature, and
C
13
). Candidate markers are identi
ed
for further use for MAS for adaptation to drought through GWAS.
Markers signi
δ
cantly associated with traits of interest can be made avail-
able to the community of rice breeders in LAC as well as abroad to speed
up and facilitate breeding for tolerance of abiotic stresses.
Marker-Assisted Selection.
In LAC, various research centers are using
molecular breeding to enhance tolerance of abiotic stresses. Using MAS,
they seek to identify individuals carrying alleles of interest among poten-
tial parental lines, segregating progenies or transgenic events. Through
molecular breeding, gene introgression is facilitated by marker-assisted
backcrossing, and populations are improved through marker-assisted
recurrent selection by selecting and pyramidingmultiple QTLs or through
genome-wide selection in which prior knowledge of marker-trait associ-
ations is not required.
