Agriculture Reference
In-Depth Information
yield potential and good stability in all rice regions of Rio Grande do
Sul. It was released in 1995 and reached its highest area in 2002
2003,
with 28.8%. This genotype has decisively contributed to the develop-
ment of IRGA 422CL and Puita INTA-CL, which are tolerant of imida-
zolinone herbicides and essentially derived from IRGA 417.
Cultivars CICA 9 and Oryzica 1 are also noteworthy. CICA 9 is the
progenitor of IRGA 418, whereas Oryzica 1 contributed directly to the
development of IRGA 419, IRGA 420, and IRGA 423. Oryzica 1 also
contributed to the development of IRGA 424, IRGA 428, and IRGA 424RI.
Breeding lines CT 8008-16-31-3P-M and CT 8008-16-10-4P-M derived
from the CIAT cross CT7347/IR21015-72-3-3-3 resulted in important
cultivars developed by EPAGRI (EPAGRI 108 and EPAGRI 109). EPAGRI
108 is one of the parents of IRGA 425 and IRGA 429, both adapted to
pregerminated rice production systems, with strong stems and lodging
resistance; and line CT 8008-16-31-8P-1 is one of the parents of the
high-yielding cultivar IRGA 427. Other important breeding lines are
IRGA 411-16-1F-A (P 1356-1-3M-2-1B/BR-IRGA 409/BR-IRGA 409),
which were the parent of IRGA 423, IRGA 424 and IRGA 426, and
IRGA 1598-3-2F-1-4-1 (Tebonnet/P 1390-1-1M-2-1B), which is present
in IRGA 425 and IRGA 429.
A more recent contribution of CIAT
-
'
is germplasm is IRGA 430
(Table 5.4), resulting from the cross CT 10816-2-CA-12-M/GT 368094;
this cultivar has high yield potential, superior grain quality, and wide
adaptability in different regions of Rio Grande do Sul.
2. Progress in Yield Potential Shown by IRGA Cultivars.
BR-IRGA 409,
BR-IRGA 410, and BR-IRGA 412, medium-maturity group cultivars,
played an important role in the
first period of introduction of semidwarf
cultivars in RS. These cultivars have higher yield potential than U.S.
cultivars (10
12 t ha
1
), but show major limitations regarding suscepti-
bility to iron toxicity and blast, which reduces their yield potential in
unfavorable environments. The 1990s were marked by the release of
early-maturing cultivars (IRGA 416, IRGA 417, IRGA 418, and IRGA
421), which have lower yield potential but provide a crop management
alternative to reduce the severe red rice infestation in farmers
-
'
fields.
This trend signi
cantly reduced average grain yield, as shown by the
points below the linear regression line in Fig. 5.1.
Only after the release of IRGA 422CL in 2002, a variety essentially
derived from IRGA 417, was it possible to control red rice infestation
in farmers
fields. IRGA 422CL is tolerant of imidazolinone herbicides
and it was used as a component of the CLEARFIELD
'
Production
System. This
technology allowed signi
cant
advances
in the
