UNIVERSITY OF ZIMBABWE
Department of Crop Science, Box MP167, Mt Pleasant, Harare, Zimbabwe.
Genotype x environment interaction of wheat genotypes selected
for adaptation to summer, rainfed conditions in Zimbabwe.
P. Tongoona.
Twenty wheat genotypes selected for adaptation to summer, rainfed
conditions were studied for their yield response under different
environmental conditions. The environments included four levels
of fertility, different sites (Harare and Nyanga), and two seasons
(1994-95 and 1995-96 summer seasons). Contrasting genotypic responses
to fertility, site, and seasons were detected. Genotypic reponses
generally showed an initial increase and then a decrease in yield
with an increase in fertility during the 1994-95 season at both
Nyanga and Harare. Yield levels of the entries were significantly
lower at Nyanga, being about half of those attained at Harare.
This pattern of response and yield levels was attributed to a
drought during that season and differences in actual precipitation
at each of the two sites. In the 1995-96 season, there was a general
increase in yield with increase in fertility at Nyanga, whereas
at Harare, there was a decline at the highest fertility level.
This decline was attributed to adequate rainfall received during
that season. However, why the yield response showed a peak at
Harare and none at Nyanga is unclear. Within the general trend,
a few genotypes exhibited some inconsistent responses that were
attributed to different genetic yield potentials of the entries.
Yield levels varied from a low value of about 1,000 kg/ha during
the dry season of 1994-95 to a high value of about 5,000 kg/ha
during the almost normal season of 1995-96. Significant correlations
were detected between yield and number of grains/spike (r2 = 0.621)
and between yield and number of spikelets/spike (r2 = 0.583).
These results showed that potential exists for wheat production
in some summer, rainfed environments in Zimbabwe, but seasonal
changes in rainfall would significantly impact yield performance.
Genotypes were classified according to stability of yield performance
groups.