Genotype x environment interaction of wheat genotypes selected for adaptation to summer, rainfed conditions in Zimbabwe
1999
Tongoona, P.
Twenty wheat (Triticum aestivum L.) 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 were detected to fertility , site and seasons. Genotypic responses genera11y showed an initial increase 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 than at Harare being about half of those attained at Harare. This pattern of response and yield levels was attributed to the drought which was experienced in that season and differences in actual precipitation at each of the two sites. During the 1995/96 season there was a general increase in yield with increase in fertility at Nyanga whilst at Harare there was a decline at the highest fertility level. This was attributed to adequate rainfall received during that season however it was not clear why the yield response showed a peak at Harare and no peak at Nyanga. Within the general trend shown, a few genotypes exhibited some inconsistent responses which was attributed to different genetic yield potentials of the entries. Yield levels varied from a low value of about 1000 kg/ha during the dry season of 1994/95 to a high value of about 5000 kg/ha during the almost normal season of 1995/96. Significant correlations were detected between yield and number of grains per spike (r = 0.621) and between yield and number of spikelets per spike (r= 0.583). These results showed that the potential for wheat production in some summer, rainfed environments in Zimbabwe exists but seasonal changes in rainfall would significantly impact on yield performance. Genotypes were classified according to stability of yield performance groups.
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