Agriculture Reference
In-Depth Information
C
13
. Upon development of the GS model,
canopy temperature and
δ
GEBV will be de
ned on a genotyped breeding population. The TP is a
good candidate population for general phenotyping of tolerance of
abiotic stresses. Such a genetic resource will be valuable for combining
G
E studies, GWAS, and rice breeding.
Transgenic technology could be considered as part of the solution for
rice improvement to adapt to abiotic stresses. At CIAT, in collabora-
tion with other partners in Japan, such as JIRCAS and RIKEN, we have
developed
×
470 single-copy
fertile independent events for drought tolerance from a total of 23
promoter gene combinations of
DREB
-related genes over 6 years. This
drought screening has been conducted in con
>
3,600 transgenic events and screened
>
ned screenhouses, rain-
out shelters, and natural rainfed upland
field conditions, in compliance
with biosafety regulations in Colombia. In addition to drought-related
genes, CIAT evaluates N use ef
ciency (NUE)-related genes as a collabo-
ration with other partners.
Historically, a dynamic partnership has been in place among rice
breeders and physiologists in LAC for (1) germplasm exchange as new
sources of genetic variation to be exploited by each research program,
(2) selection sites for a shuttle breeding strategy, (3) testing sites for
multienvironment trials of advanced breeding lines, and (4) capacity
building and access to new technologies. With further cooperation and
exchange among rice scientists, the future holds great promise for a more
comprehensive rice breeding strategy for conferring tolerance of the
abiotic stresses relevant to LAC and other regions.
VII. HYBRID RICE BREEDING
Hybrid rice technology refers to theuseof F
1
seeds as commercial cultivars
that are produced by crossing two elite divergent inbreds in the
eld
(Li andYuan 2000). Because of the sexual systempresent in rice, a reliable
male sterility system must be used to sterilize one parent. The other
parental line pollinates the female parent using this male sterility system
and the resulting F
1
seeds are used for commercial planting. These seeds
are uniform, produce more grain yield, increase farmers
ts, and
reduce production costs. Because of segregation, seeds harvested from
F
1
plants (F
2
seeds) will not be uniformly high yielding in the next season.
This requires that farmers purchase newF
1
seeds every year, thus offering
a way to protect research-for-development investments.
This technology was developed in Asia and spread slowly to other
countries. According toVirmani (1994), heterosis in ricewas
'
pro
rst reported
