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Aphids (Aphis craccivora Koch) are an important vegetative stage pest of cowpea in Africa. The use of resistant cultivars is among the best management option for this pest, but the success of this strategy is influenced by the stability of the resistant genotype to the cowpea aphid biotypes present in the major cowpea growing areas in a country. This work, therefore, aimed at identifying cultivars/genotypes with stable resistance to aphid infestation across different cowpea growing ecologies in Ghana and estimating yield loss due to aphid infestation at the seedling stage. To ascertain the stability of aphid-resistant cultivars/genotypes, four cultivars/genotypes (SARC1-57-2, SARC1-91-1, IT97K-499-35, and Zaayura) and a susceptible check (Apagbaala) were tested across 18 locations in Ghana. An on-station experiment was used to quantify yield losses due to aphid attack at the seedling stage in the five cultivars/genotypes mentioned above together with 5 additional cultivars/genotypes [i.e., IT99K-573-3-2-1, IT99K-573-1-1, Padituya, Resistant BC4F3 (Zaayura//(Zaayura × SARC1-57-2)), and Susceptible BC4F3 (Zaayura//(Zaayura × SARC1-57-2))]. The results showed that SARC1-57-2 was stable in all ecologies, in terms of its resistance to aphids; it had high vigour score (3.8 ± 0.03) and low plant mortality (3.7 ± 0.22%) compared to the susceptible genotypes. The number of days to flowering and maturity were significantly higher in aphid-infested plants than in the uninfested ones. Grain yield loss was estimated to range between 3.8 and 32.8%. Except for SARC1-57-2, Resistant BC4F3, and Padituya, the remaining cultivars/genotypes sustained significant yield losses under aphid infestation. Thus, the aphid-resistance gene in SARC1-57-2 is stable against aphids. This resistance genotype can be incorporated into cowpea improvement programmes to breed for aphid-resistant cultivars. Also, the cultivation of such improved cultivars will reduce pesticide usage in cowpea production.

Abstract-This work in progress is a contribution to crop growth systems for planning and monitoring of farm activities and practices by farmers. The work outlines the initial findings related to modelling, simulation and visualization techniques for crop growth, specifically targeting the barley crop, such that the crop yield is optimized with respect to several parameters (e.g. high end user value and minimum environmental impact), thus obtaining a sustainable production. The growth process optimization is based on information, including sensor based measurements with sensor quality monitoring, from previous and the present growth season. Initially, references targeting the importance of site specific management for obtaining the objective of yield optimization under the constraint of minimizing the environmental load is pointed to. This is followed by key references on modelling, simulation and visualization of the crop growth process based on information on soil quality, field seeding, spraying/fertilization and environmental information in general. Finally, references to software tools, which could form the basis for an open source platform for a planning and monitoring system for optimal crop growth in multiple application areas are given. The contribution concludes with proposals of research questions to be pursued in the near future.