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

Mixtures offour wheat cuttivars in Sudan - Mohamed et at.
RESULTS AND DISCUSSION
The mean performance of the treatments for grain yield is presented in Table 1. Means for the
first season were associated with significant differences (P 0.05) and means for the second
season were all similar. In the first season, Neilain performance in pure stand out yielded all
treatments, ID:IA ranked second, followed by Debeira pure stand, lA:lC mixture and
Argine pure stand. 1 D: 1 A combination out yielded its component genotypes pure stand with
101.88 yielding ability, 1.07 relative yield total and 102.77 mean relative yield (Table 2).
Although the increase in Debeira performance was more, +6.88, than the decrease in Argine
performance, -1.41 (Table 3), complementary competitive effects were indicated. A similar
trend of mixture performance was demonstrated by 1 A: 1 C with 100.66 yielding ability, 1.01
relative yield total and 100.84 mean relative yield. In this combination, Argine was more
competitive, 2.76, than Condor, -1.07. The performance of D:C genotypic mixtures,
especially in ID:IC and 3D:IC mixed stands, was modest. Debeira performance in the two
mixed stands was significantly inferior to its performance in pure stand. Debeira, though
taller, was less competitive, -17.75, with shorter Condor, 2.76, and plant height had no
competitive advantage. Other factors such as growth habit, growth rate and cycle, early
flowering and maturity may have been involved. Sage (1971) studied the behavior or
mixtures of wheat cultivars having wide phenotypic differences and found that height and
earliness in maturity were strong competitive characters. The performance of Neilain in
association with the other 3 cultivars, Debeira, Argine and Condor was unharmonious,
indicating under compensatory competition. Neilain, being taller, suppressed its component
cultivars in mixed stands. In this situation, plant height conferred high competitive ability.
Since the means of the treatments for the second season were not significantly different, our
discussion will consider the general trend of the performance of the treatments. Three
genotypic mixtures, ID:IC, 3D:IC and ID:IA out yielded all other treatments. Argine was
the leading cultivar in pure stand. Three genotypic mixtures, 1A: 1C, '1 D: 1 N ~md 1 D:3C
indicated lower performance than the performance of component genotypes in pure stand.
These included 1 A: 1 C which was second best mixed stand in first season. Of interest is the
good performance of ID: 1 C and 3D: 1 C mixed stand in this season. At this point there is no
possible explanation for this change in the performance of the two mixtures except for
genotype-environment interactions.
Based on these results ID: lA genotypic mixture only demonstrated harmonious performance
in the two seasons.
REFERENCES
De Wit, C.T. and J.P. van de Bergh. 1965. Competition between herbage plants. Neth. 1. Agric. Sci. 13: 212­
221.
Sage, G .C.M. 1971. Intervarietal competition and its possible consequences for the production of F I hybrid
wheat. 1. Agric. Sci. (Cambridge) 77: 491-498.
Schutz, W.M., Brim, c.A. and S.A. Usanis. 1968. r. Feedback system with stable equilibria in populations of
autogramous homozygous lines. Crop Sci., 8: 61-66.
Sharma, S.N. and R. Prasad. 1978. Systematic mixed versus pure stands of wheat genotypes. J. Agric. Sci.
(Cambridge) 90: 441-444.
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