Agriculture Reference
In-Depth Information
the evaluation and adoption of improved germplasm throughout the
region. Impact and achievements will be presented around the follow-
ing
five main pillars:
1. Core Breeding Collection, Breeding Strategies, and Methodologies.
Planting, evaluating, and selecting breeding populations under direct-
seeding conditions in
places with high disease pressure
and high diversity of the pathogen
“
hot spots
”—
for diseases and following a
shuttle breeding scheme resulted in the development of elite lines
having plant morphological traits different from those of the original
IR8 plant type (Cuevas-Pérez et al. 1995; Berrío et al. 2012). Typically,
these elite lines developed locally in the 1980s and 1990s were taller
with fewer tillers than IR8, with heavier and translucent grains, and
better adaptation to rainfed environments and higher yield potential
than the semidwarfs (IR8, and IR22) introduced to Colombia in the
1960s. A signi
—
cant increase in panicle sterility was observed in
locally developed cultivars, which could be the result of the introgres-
sion of exotic germplasm in the core breeding collection of the rice
program or associated with problems in crop fertilization management
due to the different plant phenology exhibited by the newer cultivars.
Berrío et al. (2012) indicated that heavier 1,000 grain weight (a genetic
gain of 0.125 g year
1
) explained the higher yield potential of local
semidwarfs under irrigated (18.2%) and rainfed (14.0%) conditions
compared with that of cultivars introduced in the 1960s. The estimated
genetic gain (31.2 kg year
1
) is smaller than the 75
81 kg year
1
gain
estimated by Peng et al. (1999) at IRRI, but comparable with the genetic
gains reported by Breseghello et al. (2011) in Brazil and by Fischer and
Edmeades (2010) worldwide.
McCouch et al. (2001) and Martínez et al. (2003) summarized some
of the work done speci
-
cally at CIAT regarding the development,
evaluation, and selection of interspeci
c populations under diverse
environmental conditions. They reported on progress made in identify-
ing quantitative trait loci (QTLs) associated with yield increase in
Oryza
Ru
pogon
. Three improved rice cultivars (Bg 90-2, Oryzica 3, and
Caiapo) were crossed with
Oryza ru
pogon
. The resulting BC
2
F
1
was
evaluated on the basis of negative phenotypic selection for undesirable
agronomic traits and
300 BC
2
F
2
families were grown in replicated yield
trials at CIAT in Palmira, Colombia. Transgressive segregation was
observed for grain yield and yield components. In the cross Bg 90-2/
Oryza ru
>
pogon
, and compared with Bg 90-2, 16% of the BC
2
F
2
families
showed higher yield, while 22% had higher 1,000 grain weight, 48%
showed higher total grain yield per plant, 43% had longer panicles, and
