Effects of seed treatments and storage duration on Myzus persicae (Hemiptera: Aphididae) and amaranth fresh leaf yield.

The green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae), is a key insect pest of amaranth in East Africa. Pest management has been restricted to indiscriminate application of insecticides to foliage. Applying systemic insecticides to seeds has been shown to manage aphid infestations in other crop systems. We evaluated two commercially available seed treatments in East Africa, Apron Star (thiamethoxam 20 g/kg + metalaxyl-M 20 g/kg + difenoconazole 2 g/kg) and Menceron (imidacloprid 233 g/L + pencycuron 50 g/L + thiram 107 g/L) for their efficacy against M. persicae and impact on fresh leaf yield with two Amaranthus species, Amaranthus blitum (2 selections), Amaranthus hybridus (4 selections) and untreated control. Two storage periods (24 h and 3 months) with seed treatments were used. Each amaranth selection was treated individually with Apron and Monceren or untreated, and seeds were planted either 24 h or 3 months after treatment. Significant reduction in live aphids was observed with A. blitum and A. hybridus selections grown with seed treatment, at 6, 8 and 10 d after infestation (DAI) when compared with seeds grown without seed treatment. Untreated seeds of A. hybridus (selection 5) had significantly higher number of live aphids up to 243, greater percentage of damaged leaves and leaf damage score up to 84% and 64% respectively when compared with treated seeds of specific amaranth at 10 DAI. No significant difference was noted between seed treatment and storage time. Amaranth seeds treated with Monceren offered more protection against infestations of Myzus persicae than amaranth seeds treated with Apron under high tunnel experiments.

Oral acute, sub-acute toxicity and phytochemical profile of Brassica carinata A. Braun microgreens ethanolic extract in Wistar rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Currently, there is a remarkable increase in the consumption of microgreens, (young edible vegetables or herbs), as potential nutraceuticals for the management of diseases. Brassica carinata A. Braun is one of the traditional leafy vegetables cultivated in various parts of Sub- Saharan Africa. The plant is revered for its efficacy in the treatment of wounds and gastrointestinal disorders among other medicinal benefits. It is therefore crucial to characterize Brassica carinata microgreens for their phytoconstituents and ascertain their safety for use. AIM OF THE STUDY: The study evaluated the oral acute and subacute toxicity of Brassica carinata microgreens ethanol extract (BMEE) in Wistar rats and identification of its chemical composition and profile. MATERIALS AND METHODS: For acute toxicity (14 days), rats were grouped into four and received a single oral dose, the control group received distilled water, while others received 500 mg/kg, 1000 mg/kg, and 2000 mg/kg of BMEE. For the subacute toxicity (28 days), rats in four groups received daily doses of 250 mg/kg, 500 mg/kg or 1000 mg/kg and distilled water. Daily clinical observations like lethargy and mortality were conducted. Hematological, biochemical, and histopathological evaluations were performed at the end of each experiment. Phytochemical profile was determined using a UV-VIS spectrophotometer and Gas Chromatography coupled to Mass Spectrometry (GC-MS) analysis determined the potential bioactive components in the microgreens extract. RESULTS: In both acute and sub-acute toxicity studies, no mortalities, indications of abnormality, or any treatment related adverse effects were observed at doses of 2000 mg/kg, 1000 mg/kg, 500 mg/kg, and 250 mg/kg. The LD50 of BMEE was above 2000 mg/kg. No significant (p > 0.05) changes in the hematological and biochemical parameters of the treated groups compared to the control groups in both studies. Histopathological examination of the liver, kidney, lungs, and heart revealed a normal architecture of the tissues in all the treated animals. Phytochemical analyses revealed the presence of flavonoids (most abundant), phenols and alkaloids. Phytol, linoleic acid, and 9,12,15-octadecatrienoic acid, among other compounds, were identified by GC-MS analysis. CONCLUSION: The results showed that B. carinata microgreens ethanol extract is nontoxic and found to have several compounds with reported pharmacological significance suggesting safety for use.

Resistance of Amaranthus Spp. to the Green Peach Aphid (Hemiptera: Aphididae).

The green peach aphid [Myzus persicae (Sulzer)] is an important pest of amaranth grown for leaf consumption (i.e., leafy amaranth) in the tropics. Aphids reduce the amount of fresh leaf yield of amaranth and the value of leafy amaranth as aphid-infested leaves are not marketable. Our objective was to evaluate Amaranthus species selected by a breeding program in East Africa to develop cultivars for leaf consumption with resistance to M. persicae. We focused on antibiosis to determine whether varieties of Amaranthus spp. could be grown without producing an aphid population. Artificial infestations of aphids were placed on multiple selections of three species of Amaranthus: two selections of A. blitum, four selections of A. hybridus and one selection of A. hypochondriacus. Aphid populations were assessed over a 5-wk period. Evaluations of vegetative yield, leaf damage symptoms, and specific leaf area (SLA) were made of the seven selections at the end of this experiment. Aphid populations assessed 49 d after planting differed significantly (P ≤ 0.001) among the amaranth species and within selections of the same species. The selections of A. blitum had the lowest aphid populations, and A. hybridus had the highest populations. Selections of A. hybridus produced the most marketable leaves (i.e., aphid free). The fresh weight of A. blitum were the lowest of the seven selections, whereas A. hybridus had the greatest fresh leaf weight. Implications of these finding for further promotion of amaranth breeding are discussed related to pest management for leaf production.