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    Volume 3 Number 8 August 2017

    Resistance to Callosobruchus maculatus Developed Via Gamma Radiation in Cowpea

    Pages: 65-71
    Authors: Langa Tembo ; Lawrent Pungulani ; Philemon H. Sohati ; Juliet C. Mataa ; Kalaluka Munyinda
    Among the biotic stresses that affect cowpea (Vigna unguiculata L) productivity, infestation by cowpea bruchid beetles (Callosobruchus maculatus) is a major problem, causing yield losses of up to 100 %. To alleviate this problem, use of resistant varieties is a feasible approach for small-scale farmers. In Zambia, there are no reported sources of resistance to C. maculatus. The objectives of this study were: i) to evaluate certain cowpea mutants, generated at the University of Zambia, for resistance to C. maculatus; ii) to cluster the tested genotypes based on height, number of pods per plant, 100-seed weight, yield ha-1, number of eggs laid and adult emergence; and iii) to evaluate the candidate mutants for protein content. Experiments were conducted at three locations in 2014/15. The mutants, LT 11-5-2-2, BB 7-9-7-5 and BB-14-16-22, were found to be resistant to C. maculatus across locations and they out-performed their respective parents (p< 0.05) in the degree of resistance to C. maculatus. Cluster analysis, using selected agronomic parameters, showed that the selected resistant mutants (cluster B) were more similar to each other (95 %) than to Namuseba and Msandile (included as susceptible genotypes), which clustered at a similarity level of 78 % (cluster A). The mutants, LT 11-5-2-2, BB 7-9-7-5 and BB-14-16-22, showed resistance to C. maculatus, but their protein content was similar to their parents, indicating that this crucial trait had been maintained in the mutants.

    Yield Gap as Occurring in Lowland Rice Cropping under Guinea Savanna Ecology: Spatial and Temporal Diagnosis for Fixing Research Priority

    Pages: 51-64
    Authors: Konan K. Firmin ; Koné Brahima ; Nangah K. Yves ; N’gazoua K. René ; Traoré M. Joachim ; Zadi Florent ; Yao Guy Fernand ; Kouadio K. Hippolyte ; Yao-kouamé Albaert
    Two lowlands under continuous rice-rice cropping in the centre of Côte d’Ivoire were surveyed in 2013 and 2014 considering 31 rice fields (farmers) for each location. Soil samples (93) were taken in 0 – 20 cm depth systematically (50 m along × 20 m across) extending the hydromorphic zone (HZ), the fringe valley (FV) and the valley bottom (VB) along the upper stream (US), median (MS) and downstream (DS) positions respectively. Highest yields of 6.09 – 6.16 tha-1 were observed in DS and MS while limited chances of 24% to 30.17% were characterizing the yield over 5 tha-1 (yield class I) in dry season against 18% - 46.31% in wet season. Weeding and irrigation were the most significant agricultural practices for yield improvement during wet and dry seasons respectively meanwhile, soil content of silt and humification rate (K2) were reversibly accounting for 65.85% contributions of the yield class I in addition to Ca and Mg effects. Of course, the recommended NPK fertilizer (150 and 200 kgha-1) should contained Mg in basal application (transplanting) when, 75 and 150 kgha-1 of urea were required at the tillering stage in dry and wet seasons respectively. However, applying NPK fertilizer at heading stage could further increase the yield during the wet season. Definitively, the yield gap was defined as absolute and relative for well understanding and research priority was identified as relevant matters for dry season and hydromorphic zone during further study.