Response of cassava cultivars to African cassava mosaic virus infection across a range of inoculum doses and plant ages

Open Access Journal; Published online: 23 Dec 2019Cassava production in Africa is constrained by cassava mosaic disease (CMD) that is caused by the Cassava mosaic virus (CMV). The aim of this study was to evaluate the responses of a range of commonly cultivated West African cassava cultivars to varying inoculum doses of African cassava mosaic virus (ACMV). We grafted 10 cultivars of cassava plants with different inoculum doses of CMV (namely two, four, or six CMD-infected buds) when the experimental plants were 8, 10, or 12 weeks old, using non-inoculated plants as controls. Three cultivars showed disease symptoms when grafted with two buds, and four cultivars showed disease symptoms when grafted with four or six buds. Most cultivars became symptomatic six weeks after inoculation, but one (‘TMS92/0326’) was symptomatic two weeks after inoculation, and two (‘Ntollo’ and ‘Excel’) were symptomatic after four weeks. Root weight tended to be lower in the six-bud than in the two-bud dose, and disease severity varied with plant age at inoculation. These results indicate that the level of CMD resistance in cassava cultivars varies with inoculum dose and timing of infection. This will allow appropriate cultivars to be deployed in each production zone of Africa in accordance with the prevalence of CMD

Variability of provitamin A carotenoids in plantain: influence of cultivar, bunch type, maturation stage, and location

Open Access Article; Published online: 01 Sept 2020In this study, the effect of ripening stage (R), cultivar (C), bunch type (T), and location (L) on the variability of provitamin A carotenoids (pVACs) in 16 plantain cultivars grown in Cameroon and Gabon was investigated. For the sixteen plantain cultivars, fruits were collected at stages 1 (unripe), 5 (ripe), and 7 (overripe) from three different bunch types (French, False Horn, and True Horn) across 13 locations in Cameroon and Gabon. For all cultivars, the highest concentration of carotenoids was found in ripe pulp (p < 0.05). For bunch type, a higher level of pVACs was observed in the French type compared with the False Horn and True Horn types at all ripening stages. In addition, the concentration of pVACs at each ripening stage varied greatly across locations. In both countries, the interaction between the four factors, particularly between R × C, R × T, R × L, R × C × L, and R × T × L, contributed significantly (p < 0.05) to the variability of pVACs in plantain. Daily consumption of 100 g of ripe plantain could meet 36.2–101.7 % of the dietary reference intakes (DRIs) for children 1–5 years old, 20.7–58.1 % for adult women, and 16.1–45.2 % for adult men. These findings can serve as a guide to reducing vitamin A deficiency (VAD) in Africa

A preliminary analysis on the effect of copper on Anopheles coluzzii insecticide resistance in vegetable farms in Benin

Open Access Journal; Published online: 14 April 2020The use of agrochemicals in vegetable production could influence the selection for insecticide resistance in malaria vectors. Unfortunately, there is a dearth of information on the potential contribution of agrochemicals to insecticide resistance in Anopheles mosquitoes breeding on vegetable farms in southern Benin. A Knowledge, Attitudes and Practices study was conducted with 75 vegetable farmers from Houeyiho and Seme to determine the main agrochemicals used in vegetable production, and the concentration and frequency of application, among other details. Mosquitoes and breeding water were sampled from the farms for analysis. Bioassays were conducted on mosquitoes, while breeding water was screened for heavy metal and pesticide residue contamination. Lambda-cyhalothrin was the main insecticide (97.5%) used by farmers, and Anopheles coluzzii was the main mosquito identified. This mosquito species was resistant (30–63% mortality rate) to λ-cyhalothrin. It was also observed that 16.7% of the examined breeding sites were contaminated with λ-cyhalothrin residues. Furthermore, copper contamination detected in mosquito breeding sites showed a positive correlation (r = 0.81; P = 0.0017) with mosquito resistance to λ-cyhalothrin. The presence of copper in λ-cyhalothrin-free breeding sites, where mosquitoes have developed resistance to λ-cyhalothrin, suggests the involvement of copper in the insecticide resistance of malaria vectors; this, however, needs further investigation