Arnold M. Opiyo

Impact of direct-electric-current on growth and bioactive compounds of African nightshade (Solanum scabrum Mill.) plants

Production of indigenous African leafy vegetables such as African nightshade ( Solanum scabrum Mill.), whose high nutritional and medicinal value is well documented is still limited due to insufficient preharvest techniques. Electric current is known to improve quality in food crops. Therefore, in the present study, the effects of direct-electric-current (DC) on growth and characteristic bioactive and health promoting compounds were evaluated in different morphological sections, i.e., leaves and stems of African nightshade cv. Olevolosi. Six weeks old plants were exposed to different DC applied with a voltage of 8 and 16 V, 10 h/day for 12 days. Non-treated plants served as control. Plant growth, primary and secondary plant compounds were evaluated. Applying DC increased leaf fresh (11.5-14.4%) and dry (12.1-24.2%) weight as well as marketable leaves (29.1-55.3%). Biosynthesis of chlorophylls and carotenoids was enhanced by increased DC. Furthermore, dietary fibre fractions such as hemicellulose was promoted (23.3-45.3%) by DC applications, while cellulose and lignin remained unaffected. Minerals accumulated with increasing DC. Alteration of cell membrane permeability due to DC may enhance physiological processes leading to the improved growth and acceleration of bioactive compounds in African nightshade leaves.

Net cover color influence nutritive quality of African nightshade and spiderplant

ABSTRACT Indigenous leafy vegetables play a major role in strategies to attain food and nutritional security for African households. However, the potential of these vegetables in meeting the nutritional requirements have not been adequately exploited. This study assessed effects of shadenets on nutritive value of African indigenous leafy vegetables. The vegetables African nightshade (Solanum scabrum Mill.) and spiderplant (Cleome gynandra L.) and net covers colored white, gray, blue, and yellow, with unnetted plants as a control were used. From the 7th week after sowing (spiderplant) and transplanting (African nightshade) and at 2-week intervals nutritive quality variables were determined. Compared to open field, white net produced higher leaf β-carotene at 13 weeks after planting by 6% and 17% for African nightshade and spiderplant, respectively. Use of blue net cover reduced leaf vitamin C content by 94.5% and 79% in African nightshade and spiderplant, respectively, compared to open field at 15 weeks after planting. Higher leaf calcium was consistently recorded for plants grown under yellow net cover for African nightshade and white nets for spiderplant; but was reduced under blue net for both species on most sampling dates. Leaf iron content was maximized under yellow net cover for both crops. Use of net covers reduced leaf crude fiber content compared to open field; high leaf phenolic content was obtained in crops grown under white net for both vegetables. The crop responses were attributed to spectral quality, light intensity, and environmental changes to which the crops were subjected. The different colored agronet covers differentially influenced crop leaf nutritive quality.

Loss of African Indigenous Leafy Vegetables along the Supply Chain

ABSTRACT Due to high perishability, African indigenous leafy vegetables (AIVs) tend to suffer heavy postharvest loss. There is a lack of information regarding management of loss of these vegetables. This study sought to identify, and assess, types and causes of AIV loss in the supply chain. The study was done across the AIV producing location of Nakuru, Kisii, and Kakamega, in Kenya, involving 45 AIV farmers from each location. Parameters studied were socio-demographic profiles, harvesting, transportation, and marketing in relation to postharvest loss. The AIV production is primarily by women who were mainly smallholder farmers. Major problems identified were inappropriate harvesting and handling techniques, inadequate postharvest treatment and preservation methods, poor roads, lack of cold storage facilities, unhygienic market conditions, and lack of implementation by regulatory bodies on AIV handling, quality, and safety standards. Values were affected by location and supply chain stage. Yellowing, wilting, presence of foreign bodies, mechanical damage, and insect pest and disease damage were major postharvest problems along the supply chain. On average, farmers experienced loss between 10 and 50% with some experiencing >50%; this varied with location and supply stage. Short AIV shelf-life (1–2 d) is a major concern. Postharvest loss is unique for specific locations and supply chain stage, and attributed to AIV production, harvesting, handling, distribution, and marketing dynamics.

Effect of Coloured Agro-Net Covers on Insect Pest Control and Yield of Tomato (Solanum lycopersicon Mill)

Tomato ( Solanum lycopersicon Mill) is one of the most important vegetable crops consumed throughout the world; and is rich in important vitamins, minerals and antioxidants. Production of the crop in open fields is however constrained by several biotic and abiotic stresses that lead to low tomato yields and quality. This study aimed at determining the effects of coloured agro-net covers on microclimate, pest infestation and yield of tomato cultivar ‘‘Rio Grande’’. The study consisted of two trials conducted using a randomized complete block design (RCBD) with five replications and six treatments. Tomato plants were grown under blue, yellow, grey, white or multi-coloured net covers with a no net cover as the control. Data were collected on microclimate (temperature, soil moisture, relative humidity and photosynthetically active radiation), pest counts and crop yield variables. Net covering modified the tomato crop microclimate with highest temperatures and soil moisture and, relative humidity levels recorded under white (21.03 o C), blue (30.03%) and multi-coloured net covers (76.26%), respectively compared to the no net control treatment (16.32 o C, 14.82% and 64.90%). Photosynthetically active radiation (PAR) was lowest under the blue agro-net cover (416.09 µmol m -2 s -1 ) and highest under control treatment (985.00 µmol m -2 s -1 ). Tomato plants grown under coloured-colour nets (yellow and blue) had lower population of silverleaf whitefly, thrips and aphids while mite population was lower under neutral-colour net covers (white, grey and multi-coloured). The neutral-colour net covers (24938.87, 19525.16 and 21541.93 kg/ha) resulted in higher yields compared to coloured-colour net covers (16804.62 and 14551.05 kg/ha). Results of the study indicate that use of agro-net covers especially the neutral-colour net cover can improve microclimate, protect tomato against insect pests and can be considered a viable strategy for tomato production by smallholder growers.