Agriculture Reference
In-Depth Information
sources of tolerance, the identi
cation of genomic regions associated
with tolerance, and the development of populations and elite lines with
sources of tolerance.
2. Approaches to Evaluating Abiotic Stresses
Phenotyping Sites.
The choice of stress environments for phenotyping
is essential for achieving signi
cant progress in abiotic stress breeding,
and careful selection will provide the cornerstone of success. Without
an appropriate homogeneous phenotyping site, the value of data
acquired, regardless of cost and time, will be limited (Masuka et al.
2012). At CIAT headquarters in Palmira, drought and N stress evalua-
tions are being conducted with special emphasis on precise phenotyp-
ing methodologies in the greenhouse, rainout shelters, N-depletion
plots, and
fields. Automatic movable rainout shelters in the main
season are being used as an alternative to screening in the dry season
but the cost and limited space are important considerations. Field
drought phenotyping is conducted during the off (dry)-season at the
CIAT Santa Rosa experimental station belonging to FEDEARROZ
(SRES, Meta, Colombia) where timing, intensity, and duration of the
period of drought stress can be fully controlled and where soil and
climatic conditions are monitored throughout the crop cycle. The off-
season at the SRES is characterized by a dry period lasting 2 months,
from December to February. To accomplish the N-omission plots at
CIAT headquarters, phenotyping sites were normally depleted for N by
planting maize with high biomass without any fertilization for several
seasons. The N-omission plots wereusefulforscreeningalargenum-
ber of germplasm accessions against N stress. Breeding and phenotyp-
ing for tolerance of acid soils and aluminum toxicity are conducted at
the national experimental research station of the Colombian research
organization (CORPOICA station in La Libertad, Meta) in the savanna
ecosystems of the Colombian Llanos. Soils have a low pH and high
concentration of aluminum (
75%) and no treatment is applied
to correct for the soil acidity. Cold tolerance evaluations at CIAT
are conducted by FLAR under cold chamber conditions. Annually,
an average of 3000 genotypes is evaluated at germination, 6000 at the
seedling stage, and 300 at the reproductive stage. The cold-tolerant rice
nurseries are then sent to Argentina, Chile, Brazil, and Uruguay to
evaluate for other adaptive traits.
Embrapa has constructed an automated platform to evaluate water
use ef
>
ciency in a controlled environment that is capable of screening
384 plants with uniform stress. This system, named SITIS (Integrated
