Agriculture Reference
In-Depth Information
management and control of red rice infestation in Rio Grande do Sul,
facilitating a more ef
cient exploitation of the yield potential from
improved cultivars. This is the case of IRGA 424, a high-yielding variety
released by IRGA in 2007; it has medium maturity duration, with high
tillering capacity and cold tolerance at the vegetative stage. This cultivar
shows a high response to fertilizers (NPK) and nitrogen topdressing, thus
facilitating crop management for high productivity. It is possible to get
14 t ha
1
in favorable environments.
Two studies were conducted to assess the genetic contribution of
IRGA and EMBRAPA cultivars to yield potential. In the
rst study, Lopes
et al. (2005) estimated the evolution of grain yield from 1961 to 2004
in Rio Grande do Sul, working with traditional U.S. and semidwarf
cultivars. Results showed that the genetic gain was 102 kg ha
1
per year
(1.54%per year). In the second study, Moura Neto et al. (2011) estimated
the genetic gain due to IRGA and EMBRAPA breeding programs from
1983 to 2011, including only the advanced lines of semidwarf germ-
plasm. Based on this study, the increase in yield potential was estimated
at 2.6% and 2.2% per year for early- and medium-maturity genotypes,
respectively.
3. Breeding for Tolerance of Iron Toxicity and Adaptation to the
Pregerminated Crop Production System.
The search for rice cultivars
adapted to the pregerminated system became an important breeding
objective as red rice infestations and grain yield losses were increas-
ing, especially in the 1990s in Rio Grande do Sul. The main cultivars
planted under this system were developed by EPAGRI (EPAGRI 108,
EPAGRI 109, SCS112, andSCSBRSTioTaka, among others), but, although
they were adapted to this water seeding system and were very tolerant of
lodging, all of them were late maturing in southern Brazil. Consequently,
IRGA
s breeding program developed and released IRGA 425 (2009) and
IRGA 429 (2013), with plant lodging resistance, high-yield potential, and
excellent grain quality. Most of EPAGRI
'
s cultivars and both the IRGA
cultivars were derived from CT 8008 breeding lines from CIAT.
Iron toxicity, caused by an excess of soluble iron in
'
flooded soils, is
another constraint that limits rice production. BR-IRGA 409, BR-IRGA
412, IRGA 417, and IRGA 422CL are susceptible to iron toxicity. IRGA
developed and implemented a
field-screening methodology to evaluate
the reaction to iron toxicity of all breeding lines in a special nursery in a
field with high iron in the soil. Consequently, nowadays, only iron-
tolerant new cultivars are released. They include IRGA 416, IRGA 419,
IRGA 420, IRGA 421, IRGA 423, IRGA 424, IRGA 425, IRGA 426, IRGA
427, IRGA 428, IRGA 429, and IRGA 430.
