Principles of Plant Genetics and Breeding

Figure 5 A foundation seed field of “Saber” rice.
Figure 6 DNA markers on chromosome 2 that are associated
with the Pi-b blast resistance gene are present in “Saber” and its
parent, “TeQing” (Fjellstrom et al. 2004).
BREEDING RICE 505
of 2). Its reaction to eight races of blast shows excellent
resistance, however it appears to be segregating for
resistance to race IB49 (rating of 2 and 4).
1999
In an effort to further clarify the level of resistance to
the IB49 race of blast, F 13 seed from the 265 bulk harvested
1998 Headrow 1 plants is evaluated for reaction
to race IB49 during the 1999 spring greenhouse
planting. Of some 300 seedlings that are screened,
37% are highly resistant (rating of 1–2), 61% are moderately
resistant (rating of 3–4), and 2% are susceptible
(rating of 5–6). This suggests that further selection in
RU9601378 may allow for improvement in resistance
to this pathotype.
During the summer, RU9603178 is evaluated in the
same manner as before in the 1999 URRN and Texas
statewide trials using the bulked harvested F 13 seed
from the 265 rows in Headrow 1. Agronomic and
milling quality results from this trial are consistent with
the previous year. Its reaction to eight of the blast races
shows excellent resistance, however it is rated as susceptible
(rating of 4) to IB49.
Headrow 2 is planted in the summer using 596 F 13
panicle rows derived from the 30 row selections from
1998. The information collected for the objective
description of the variety in 1998 is verified in the
Headrow 2 field. Each of the 596 rows is harvested
separately for verification of reaction to blast race IB49
during the fall greenhouse planting. Over 99% of the
families are rated as highly resistant (rating of 1–2) and
the remaining families are rated as moderately resistant
(rating of 3). This indicates that the 30 families that
had been selected in the 1998 Headrow 1, and which
constitute Headrow 2, are highly resistant to this
pathotype.
2000
Approximately 20 F 14 families that had been rated as
resistant (i.e., 1) and 20 families that had been rated as
moderately resistant (i.e., 3) to IB49 in the fall 1999
greenhouse planting are re-evaluated in the spring
2000 greenhouse planting. All plants in the 40 families
are confirmed to be resistant or moderately resistant and no susceptible plants are identified. This verifies the resistant/moderate
resistant rating to IB49 infection of Headrow 2 of RU9603178 and indicates that resistance is not due to escapes nor is there heterogeneity
for susceptibility. However, as a precaution, families rated as 3 are eliminated and only families that had an IB49 rating
of 1 are provided to the foundation seed program. The objective description of the variety is provided to the state inspector to
evaluate the foundation seed field (Figure 5).
Families that had a resistance rating of 2 to IB49 are bulked and used for further field testing during 2000. The same battery of
field trials, disease screenings, and quality tests are conducted as before. DNA markers are developed that are associated with the
Pi-b blast-resistance gene that is found in “TeQing” and explains the multirace resistance to blast that is observed in RU9603178
(Figure 6) (Fjellstrom et al. 2004).
By the end of the 2000 field season, RU9603178 has been evaluated at over 40 environments and it is decided to proceed with
public release of the variety. The name “Saber” is selected in honor of the Texas A&M University Corps of Cadets. The complete
set of data collected over the previous five field seasons is summarized to justify to the state seed board the release of “Saber”. In
February 2001, the seed board accepts “Saber” into the state seed certification program, which allows the foundation seed that
was produced in 2000 to be sold as certified (F 15 ) seed for the 2001 planting season.