The Eleventh Regional Wheat Workshop For Eastern ... - Cimmyt

Quality ofEthiopian durum wheat cultivars - Efrem et at.
pasta quality occurs. Gluten composition is the primary factor determining the quality
characteristics of durum wheat cultivars (Vazquez et al., 1996). Glutenins can be
electrophoretically divided into high (HMW) and low (LMW) molecular weight subunits. BMW
subunits are encoded by genes on the long arm ofgroup I homoeologous chromosomes (Glu-AI,
Glu-Bl, and Glu-Dl) whereas the genes encoding the LMW subunits are clustered on the short
ann (Glu-A3, Glu-B3, and Glu-D3) of the same chromosomes, tightly linked to the Gli-Bl
complex loci which encode for y-gliadin 42 and y-gliadin 45 (D'Ovidio et al. , 1992; Payne et al.,
1984; Shewry et al. , 1986; Payne, 1987).
Two LMW glutenin subunit patterns, LMW-l and LMW-2, largely explain quality differences
between some durum wheat genotypes. LMW-2 glutenin subunits confer superior quality with
respect to genotypes possessing LMW-l (Vazquez et al., 1996; D'Ovidio, 1993). Ruiz and
Carillo (1995) indicated that, in general, lines with the LMW-2 pattern had significantly greater
SDS sedimentation value and better mixograms than those with the LMW -1 patterns. The y­
gliadin components 42 and 45 are only genetic markers, without any direct involvement in dough
quality.
Assessing the relationship between durum gluten strength and glutenin properties, Carillo et al.
(1990) found that HMW subunits 6+8 and 7+8 were more commonly associated with superior
quality subunit 20 with poorer quality. Autran and Feillet (1987) reported no significant
differences between SDS means of durum genotypes with subunit 6+8 or 7+8. Genotypes with
subunit 20 however, had weaker gluten strength. Peiia et al. (1995) pointed out that subunits 6+8
and 7+8 showed significantly better durum quality than subunit 20, and, the subunit pair 6+8 was
associated with significantly higher SDS values when combined with LMW-2 than with LMW-l.
Pogna et al. (1990) indicated that gluten subunit 7+8 gave greater SDS sedimentation volume
and higher elastic recoveries than subunits 6+8 and 20, and the positive effects ofLMW-2 gluten
subunits and HMW subunit 7+8 were additive.
Yellow color pigmentation in semolina and in the finished pasta products is a desirable quality
characteristic of durum wheat. Durum contains xanthophylls (yellow pigment) and lacks
lipoxidase enzyme, which destroys the yellow pigment during processing. Joppa and Walsh
(1974) observed that durum genotypes differ in xanthophylls and lipoxidase quantity and quality.
Ethiopia is the largest producer of durum wheat in Sub-Saharan Africa and is considered to be
a center of genetic diversity for this species of wheat (Vavilov, 1951). However, very little
emphasis has been placed on improving the nutritive or processing quality of durum wheat in
Ethiopia. In this study, eleven durum wheat cultivars released in Ethiopia between 1966 and
1996 were evaluated for agronomic and nutritive and processing quality characteristics.
MATERIALS AND METHODS
Eleven durum wheat cultivars released in Ethiopia between 1966 and 1996 were included in the
study (Table 1). The materials were planted in five diverse and typical durum wheat growing
environments (Debre Zeit, Akaki, Chefe Donsa, Bichena and Alem Tena) across the country
during the 1995 and 1996 main cropping seasons. Debre Zeit and Akaki are mid-altitude
environments (1900-2300 m a.s.l.) charactelized by moderate annual rainfall (700 - 900 mrn) and
well drained black Vertisol soils. Chefe Donsa and Bichena are highland (>2300 m a.s.l.)
environments characterized with high annual rainfall (>1000 mm) and poorly drained black
Vertisol soils. Alem Tena is a lowland « 1900 m a.s.l.) site located in the Rift Valley and with
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