Stability of yield and Antioxidant content of selected advanced Cowpea(Vigna unguiculata [L]Walp.) mutation derived lines

Zambia has a number of cowpea germplasm which are high yielding and contain antioxidants which are useful for preventing a lot of health problems i.e. Heart attack, Hypertension, Obesity and Cancer. Unfortunately the production suitability of these germplasm in the different areas of the country is not known. Based on this, a study was conducted to evaluate the stability of cowpea yield and antioxidants (total phenolic content and condensed tannin content) in the three agro ecological zones as well as to determine the relationship between the antioxidants and the seed coat colour of the cowpeas. Multilocation field trials involving ten cowpea genotypes were conducted at three different Agro-ecological Regions. A randomized complete block design was employed with 3 replications. Cowpea grain yield and antioxidant contents of the seed were determined and a stability bases analysis tool, Additive Main effect and Multiplicative Model (AMMI) was employed for data analysis. Assessment of genotype x environment (GxE) interaction on cowpea grain yield stability indicated that GxE was not present for yield indicating that genotypes did not respond differently to varying environmental conditions. However, some genotypes had higher yields than others indicating genotype identification to specific environments. Genotypes MS1/8/1/4 and LT11/3/3/12 were adapted to high potential yielding environment and were unstable while BB4/2/4/1 and LT11/5/2/2 were adapted to low yielding environment and were stable environments. Assessment for antioxidants showed that GxE was significant (p<0.01) and higher yielding genotypes had low antioxidant contents compared to low yielding genotypes. Genotype LT PRT had higher antioxidant concentration (3.47mg/100mgCE) and stable (IPCA2 0.022) while MS PRT had lower concentrations (0.17mg/100mgCE) and unstable (IPCA1 0.630). The genotypes which had higher antioxidant concentrations had darker seed coat colour (yellowish brown and purplish brown) compared to the ones which had low antioxidant concentration (white). This study identified stable genotypes in both yield and antioxidants. However, further studies for assessing yield stability are necessary and could be achieved by including more seasons and sites to get a better understanding of GxE and yield stability of cowpea in Zambia.