Research Highlights of the CIMMYT Wheat Program 1999-2000

of improved seed and new technologies to farmers.
This problem would be reduced with hybrid
triticale. In hybrids maximum levels of heterosis are
expressed in the F1 hybrid, so in order to achieve
maximum yields, pedigreed seed would have to be
purchased every year.
Chemical hybridizing agent (CHA)
hybrids
Early research at CIMMYT on triticale hybrids
aimed at evaluating heterosis for agronomic traits
in hexaploid triticale hybrids produced using a
chemical hybridizing agent. Thirty-one hybrids
from 3 male and 15 female elite hexaploid spring
triticales were produced by CHA. All triticales used
were complete R-genome types, except one 2D(2R)
chromosome substituted type, which was used as a
male parent. Male parents were selected based on
performance under high production conditions.
Female parents were selected based on
performance in different agro-ecological zones and
for their contrasting yield component expression.
Yield trials including CHA hybrids and parents
were conducted under high production conditions
in Cd. Obregon during the 1995-96 and 1996-97
growing cycles to evaluate grain yield and
agronomic traits.
A combined analysis of 1995-96 and 1996-97 data
revealed, on average, 9.5% mid-parent and 5.2%
high parent heterosis for grain yield. Maximum
heterosis values greater than 20% were observed
for grain yield in high-parent (22.9%), mid-parent
(24.9%), and low parent (28.9%) comparisons.
Mid-parent heterosis for agronomic components
were observed in: biomass (9.1%), straw yield
(9.0%), 1000 grain weight (11.4%), culm weight
(12.0%), and spike weight (12.4%). This differential
contribution of yield components to grain yield
heterosis could be exploited in designing hybrids.
Several hybrids revealed superior biomass
performance and would be preferred for forage
utilization, e.g. whole crop silage production.
Cytoplasmic male sterility (CMS)
hybrids
Several alien cytoplasms, such as Triticum timopheevi
Zhuk., Aegilops sharonensis, Aegilops juvenalis,
Aegilops heldreichi and Aegilops ovata cytoplasm,
cause male sterility in wheat and triticale. Triticum
timopheevi Zhuk. cytoplasm has been used in
different countries to produce commercial bread
wheat hybrids. In wheat, fertility restoration genes
from Triticum timopheevi Zhuk. have been
introduced and are employed along with modifier
genes for fertility restoration. In contrast to wheat,
most triticales carry fertility restoration genes on
the R genome.
In 1994, CIMMYT started a small applied research
project on hexaploid spring CMS triticale hybrids
based on T. timopheevi Zhuk. cytoplasm. In the first
phase, elite CIMMYT spring triticales were crossed
onto a CMS source to identify non-restoring lines
(potential females in CMS hybrids) and lines
carrying restorer genes (potential males). Out of 25
genotypes that exhibited complete or partial
sterility in the F1 hybrid generation (CMS source x
tester line), 18 lines were retained as potential CMS
recipients and subsequently backcrossed. After four
backcrosses, 300 test hybrids were produced during
the 1997 El Batan crop cycle from 15 CMS lines and
27 male lines. The restoration capacity of the elite
triticales used as males had been determined in the
F1 hybrid generation. Two hundred CMS hybrids
and their parents were tested under high
production conditions at Cd. Obregon during the
1997-98 growing cycle to evaluate grain yield.
Analysis of 1997-98 data revealed, on average, 9.1%
mid-parent and 3.3% high parent heterosis for grain
yield. Heterosis values for grain yield in mid-parent
comparisons were: 29 hybrids: 1-5%, 34 hybrids: 6-
10%, 41 hybrids: 11-15%, 31 hybrids: 16-20%, 17
hybrids: 21-30%, and 3 hybrids: more than 30%
with a maximum of 48%. Heterosis values for grain
yield for high-parent comparisons were: 42 hybrids:
1-5%, 35 hybrids: 6-10%, 28 hybrids: 11-15%, 11
hybrids: 16-20%, 1 hybrid: 21-30%, and 3 hybrids:
more than 30% with a maximum of 44%.
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