Research Highlights of the CIMMYT Wheat Program 1999-2000

eleased in more than 30 countries under more than
40 names. The next generation of durum varieties,
released in the 1980s (e.g., Altar 84 and Aconchi 89)
trace back to breeding based on the ideotype
concept. Common features are upright leaf
characteristics derived from the Shearwater genetic
stock and significantly improved end-use quality
(yellow pigment and gluten characteristics).
Progress in Raising the
Genetic Yield Potential
To gauge historic progress due to breeding, the
relative performance of these five cultivars were
assessed in maximum yield potential trials (MYPT)
conducted at Cd. Obregon, in northwest Mexico.
Improvements in grain yield were associated with
increased biomass yield (Figure 1), though harvest
index decreased. Changes in grain yield were due
to increased grains m -2 via more grains spike -1 .
Additionally, rate of grainfill increased, cultivars
headed and matured later, and had improved test
weights.
Genetic progress in CIMMYT durum germplasm
developed during the past decade was investigated
by comparing the best performing durum
genotypes from the MYPTs. The mean of the five
hallmark checks was used for comparison to
minimize the effect of individual genotype x
environment interactions. These comparisons
retrospectively chart changes that have occurred
through genotypic improvement suggesting
strategies to affect improvement of yield per se in
the future.
For the past decade, elite germplasm exhibited
genetic advances for nearly all the agronomic
components (Figures 2 and 3) with the greatest
changes observed in grain yield, biomass, and
grains m -2 . Increases in biomass production rate
from crop emergence to physiological maturity and
from anthesis to physiological maturity were high.
Most recently, increases in both spikes m -2 (+8.9%)
and grains spike -1 (+7.2%) resulted in a dramatic
rise of +16.9% for grains m -2 . Grain biomass
production rate (+16.6%), spike weight (+4.8%),
and vegetative growth rate (+4.5%) all increased,
while the downward trend in 1000-grain weight (–
2.8%) continued. More recent genotypes are later in
heading and maturity, with a surprisingly shorter
grain-filling period.
Grain Biomass/day
Veg. Growth Rate
Grain Yield (t/ha)
70s Mexican Varieties
Yavaros 79
80s Mexican Varieties
Biomass
Harvest Index
Straw Yield 10000 8000
Spikes/m 2
Days Maturity
130
125
170 8
115
80
150
125
70
44
48
Test Weight Grain/m 2
7
15
30
300
25
14000
1000 g Weight
17
16000
35
40
400
Grains/Spike
Figure 1. Comparison of agronomic components of the
highest yielding early 1970s (Cocorit 71, Mexicali 75),
Yavaros 79, and 1980s (Altar 84, Aconchi 89) durum wheat
varieties evaluated in maximum yield potential trials at Cd.
Obregon 1991-1999.
Grain Biomass/day
Veg. Growth Rate
Grain Yield
Three Highest Yielding
70s & 80s Varieties
Biomass
Harvest Index
Straw Yield 10000
8000
Spikes/m 2
Days Maturity
130
125
190
80
170
125
120
70
46
47
Plant Height Grains/m 2
Test Weight
Grains/Spike
Figure 2. Comparison of agronomic components of the three
respective highest yielding durums compared with check
varieties (Cocorit 71, Mexicali 75, Yavaros 79, Altar 84,
Aconchi 89) evaluated in maximum yield potential trials at
Cd. Obregon 1991-1999.
9
8
17
30
350
25
15000
18
17000
35
40
450
18