Cowpea varietal influence on Striga hermonthica [(Del.) Benth] in finger millet (Eleusine coracana (L.) Gaertn) fields in Pallisa District, Eastern Uganda
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Level of Striga hermonthica infestation is beyond finger millet tolerance levels, especially for varieties grown in Uganda. Efficacy of Striga control measures have been variously investigated with limited success, either due to high costs involved or lack of compatibility of the technologies within the affected farming communities‘ socio-economic frame work. The innovation that seems to make technical and socio-economic sense to the farming communities is that of suicidal germination of Striga seeds caused by particular legume species commonly grown by the finger millet farming communities. One such legume is cowpea (Vigna unguiculata L). Understanding the relative capacity existing within different cowpea genotypes is envisioned to provide the affected farming communities with options for choice under various socio-economic circumstances. The objective of this study was therefore to reduce the impact of Striga on the finger millet productivity by using different cowpea varieties to control Striga in Eastern Uganda. A field experiment was carried out in Olok sub-county, Pallisa District in Eastern Uganda; using six farmers‘ fields as replicates. Treatments included three cowpea varieties (Ebelat, Secow3B and Secow2W) intercropped in finger millet variety, Seremi2; laid out in a randomized complete block design (RCBD). Parameters measured included the number of finger millet basal tillers, Striga emergence; finger millet flag leaf areas, plant heights, number of fingers per panicle, panicle lengths, dry weights and the weight of 1000 grain weights. Data were analysed with R Statistical Package of Version 3.3.2. Turkey‘s Honest post hoc test was used to separate means with significant treatment differences at p≤0.05. Correlations were performed among Striga and finger millet parameters. Based on Striga emergence, there was a significant (p≤0.05) cowpea varietal effect; with Seow3B being the most effective, having suppressed Striga emergence by nearly 100%. This was followed by Secow2W and Ebelat (local variety), with suppression levels of 40 and 21%, respectively. Pure finger millet stand tillered significantly more than all the finger millet-cowpea admixtures. Tillering was highest in the pure stand of finger millet, followed by, millet-Secow3B, millet-Secow2W and millet-Ebelat. Generally, cowpea intercrop treatments had no significant effect (p>0.05) on leaf area of finger millet. On the other hand, the effects were significant on finger millet plant height and panicle length, with both displaying similar response patterns, in the increasing order of Ebelat < Secow2W < Secow3B. The shortest finger millet plants were obtained in the pure stand. With regard to number of fingers per panicle, panicle dry weight and 1000 finger millet grain weight, the order of performance of the millet-cowpea admixtures was: pure finger millet stand > Ebelat > Secow2W > Secow3B. The level of Striga emergence was negatively correlated with finger millet plant height (r = - 0.854) and 1000 grain weight (r = 0.93). The mechanism of action of cowpea genotype on Striga proliferation in finger millet fields needs further investigation. It is possible that there are differences in the levels of strigolactone endowment across cowpea genotypes, and this might be genetically linked; thus setting a stage for breeders to leverage from knowledge generated from this study to expand on the scope of effective Striga control among resource poor farmers in SSA.