A review of agricultural aflatoxin management strategies and emerging innovations in sub-saharan Africa

Aflatoxins are highly carcinogenic secondary metabolites produced by Aspergillus flavus, A. parasiticus and A. nomius. Aflatoxin contamination of food and animal feeds is, therefore, a major food security, food safety, trade, human and domestic animal health concern. Researchers worldwide have suggested various agriculture-based strategies to manage aflatoxigenic Aspergillus species and reduce contamination to safe levels. This paper reviews various agricultural strategies that could be employed to reduce contamination of aflatoxins in food crops and animal feeds, as well as the challenges faced by these reduction strategies. Among these strategies are innovations like AflasafeTM and solar grain driers. It is hoped that this critique will stimulate refinement of the existing aflatoxin control approaches and innovations to maximize their efficacy.Keywords: aflatoxins, plant resistance, atoxigenic strains, drying instruments, aflatoxin control, food safety, mycotoxins, post-harvest losse

Transformation and Regeneration Protocol for Two Farmer Preferred Open Pollinated Tropical Maize (Zea Mays) Varieties

Article PurchasedAbstract: In vitro regeneration of open pollinated varieties (OPVs) Kakamega Striga Tolerant Population 94 (KSTP’94) and ‘Namba Nane’ alongside a tropical inbred line (CML144) was evaluated using immature zygotic embryos as explants. Four callus induction media (CIM) regimes; Murashige and Skoog (MS), Linsmaier and Skoog (LS), Chu (N6) and N6*(N6 medium fortified with 0.35 gL-1 L-proline and 0.8 mgL-1 AgNO3) were evaluated for their potential to induce callus in the three genotypes. All the media were supplemented with sucrose and five levels of 2, 4-Dichlorophenoxyacetic acid (2, 4-D) (0.5, 1.0, 1.5, 2.0 and 2.5 mgL-1). Resulting calli were matured on MS and N6 basal media supplemented with 60 g/L sucrose and similar concentration levels (0.5, 1.0, 1.5, 2.0 and 2.5 mgL-1) of 2, 4-D while the subsequent embryogenic calli were regenerated on hormone-free media. Transformability of these varieties was assessed via histochemical analysis of β-glucuronidase (GUS) reporter gene following Agrobacterium-mediated transformation. Statistical analyses were done using Statistical Analysis Software (SAS) and Graphpad Prism softwares with mean separations achieved at 95% confidence intervals. Of the 2 OPVs, KSTP’94 recorded the highest callus induction frequency (84.4%) while Namba Nane (45.6%) had the lowest. Similarly, KSTP, 94 had the highest mean of mature somatic embryos (59.7%) while Namba Nane recorded the lowest (16.4%). Assessment of regeneration frequencies from embryogenic calli revealed no significant differences among the 3 lines although CML 144 had the highest mean number of juvenile plantlets (36.7%). Analysis of transformation frequency (upon selection of calli on media with basta) showed that Namba Nane recorded the lowest transformation frequency (average 13.5%) some words missing. Transformation frequency (based on GUS positive calli) of these varieties ranged from 0.8 to 2.1%. This work therefore provides an empirical platform for potential introduction of useful genes into these varieties

Molecular Characterization of Guava Landraces in Kenya (Western and South Coast)

Guava (Psidium guajava L) is native to tropical areas of America where it exists as wild and cultivated. Guava has been used as source of food and in development of pharmaceuticals. Preliminarily molecular characterization has been used for the characterization of guava germplasm but molecular characterization of Kenyan guava has not been carried out. A study was carried out in 6 sites of Western and 3 sites of Coastal region of Kenya for genetic differences. Molecular characterization was done using the young apical leaves. DNA was extracted using modified CTAB method. DNA was amplified using 5 SSR markers and 3 markers produced scorable reproducable bands that ranged from 150-700bp. Levels of polymorphism ranged from 7-70% resulting in 7 cluster. 9 ISSR markers were screened and 4 produced scorable reproducible. The four primers generated bands ranging from 100-900bp. ISSR showed higher levels of polymorphism 51- 85% are and resulted in 3 major clusters. From the results of this study, molecular characterization can be used to give distinct differences among landraces Keywords; landraces, molecular, ISSR, SSR, Psidium guajav

Striga parasitizes transgenic hairy roots of Zea mays and provides a tool for studying plant-plant interactions

Background Striga species are noxious root hemi-parasitic weeds that debilitate cereal production in sub-Saharan Africa (SSA). Control options for Striga are limited and developing Striga resistant crop germplasm is regarded as the best and most sustainable control measure. Efforts to improve germplasm for Striga resistance by a non-Genetic Modification (GM) approach, for example by exploiting natural resistance, or by a GM approach are constrained by limited information on the biological processes underpinning host-parasite associations. Additionaly, a GM approach is stymied by lack of availability of candidate resistance genes for introduction into hosts and robust transformation methods to validate gene functions. Indeed, a majority of Striga hosts, the world’s most cultivated cereals, are recalcitrant to genetic transformation. In maize, the existing protocols for transformation and regeneration are tedious, lengthy, and highly genotype-specific with low efficiency of transformation. Results We used Agrobacterium rhizogenes strain K599 carrying a reporter gene construct, Green Fluorescent Protein (GFP), to generate transgenic composite maize plants that were challenged with the parasitic plant Striga hermonthica. Eighty five percent of maize plants produced transgenic hairy roots expressing GFP. Consistent with most hairy roots produced in other species, transformed maize roots exhibited a hairy root phenotype, the hallmark of A. rhizogenes mediated transformation. Transgenic hairy roots resulting from A. rhizogenes transformation were readily infected by S. hermonthica. There were no significant differences in the number and size of S. hermonthica individuals recovered from either transgenic or wild type roots. Conclusions This rapid, high throughput, transformation technique will advance our understanding of gene function in parasitic plant-host interactions

Efficacy of chemotherapy and thermotherapy in elimination of east African cassava mosaic virus from Tanzanian cassava landrace

Cassava mosaic disease is caused by cassava mosaic begomoviruses (CMBs) and can result in crop losses up to 100% in cassava (Manihot esculenta) in Tanzania. We investigated the efficacy of chemotherapy and thermotherapy for elimination of East African cassava mosaic virus (EACMV) of Tanzanian cassava. In vitro plantlets from EACMV‐infected plants obtained from coastal Tanzania were established in the greenhouse. Leaves were sampled from the plants and tested to confirm the presence of EACMV. Plantlets of plants positive for EACMV were initiated in Murashige and Skoog (MS) medium. On the second subculture, they were subjected into chemical treatment in the medium containing salicylic acid (0, 10, 20, 30 and 40 mg/L) and ribavirin (0, 5, 10, 15 and 20 mg/L). In the second experiment, EACMV‐infected plantlets were subjected to temperatures between 35 and 40°C with 28°C as the control. After 42 days of growth, DNA was extracted from plant leaves and PCR amplification was performed using EACMV specific primers. It was found that plant survival decreased with increasing levels of both salicylic acid and ribavirin concentrations. In general, plants treated with salicylic acid exhibited a lower plant survival % than those treated with ribavirin. However, the percentage of virus‐free plants increased with an increase in the concentration of both ribavirin and salicylic acid. The most effective concentrations were 20 mg/L of ribavirin and 30 mg/L of salicylic acid; these resulted in 85.0% and 88.9% virus‐free plantlets, respectively. With regard to thermotherapy, 35°C resulted in 79.5% virus‐free plantlets compared to 69.5% at 40°C. Based on virus elimination, ribavirin at 20 mg/L, salicylic acid 30 mg/L and thermotherapy at 35°C are recommended for production of EACMV free cassava plantlets from infected cassava landraces

Midgut bacterial diversity analysis of laboratory reared and wild Anopheles gambiae and Culex quinquefasciatus mosquitoes in Kenya

Open Access JournalMidgut symbiotic bacteria are known to play fundamental roles in the biology of mosquitoes, however knowledge of midgut bacterial communities associated with mosquitoes is scanty due to limitation of the isolation techniques based on culturing. In this study, the composition and diversity of midgut bacteria in field collected and lab reared adult female Anopheles gambiae and Culex quinquefasciatus mosquitoes was explored using the Illumina sequencing. Deoxyribonucleic acid was isolated from the pooled midgut extracts and their 16S rRNA gene sequenced using Illumina sequencing platform. Operational taxonomic units (OTUs) were analyzed using QIIME 1.8.0; taxonomy was assigned using BLASTn against SILVA 119 and hierarchical clustering was done using R program software. Out of the total number of sequence reads obtained, 145 OTUs were realized at 3% genetic distance. The 145 OTUs spanned 12 phyla; Proteobacteria, Firmicutes, Cyanobacteria, Euryarchaeota, Gemmatimonadetes, Spirochaetae, Archeabacteria Verrucomicrobia, Chloroflexi, Bacteriodetes, Acidobacteria and Actinobacteria. Microbial community composition based on OTUs showed significant difference between field collected and lab reared mosquitoes (ᵪ2 = 45.0799, p = 3.2 × 10-5). Similarly, there was a significant difference in community composition at OTU level between Anopheles gambiae and Culex quinquefasciatus (ᵪ2 = 31.2257, p = 7.7 × 10-4). The bacterial composition and diversity appeared to be influenced by the environment and the species of the mosquitoes

Morphological and Molecular Identification of the Causal Agent of Anthracnose Disease of Avocado in Kenya

Anthracnose disease of avocado contributes to a huge loss of avocado fruits due to postharvest rot in Kenya. The causal agent of this disease has not been clear but presumed to be Colletotrichum gloeosporioides as reported in other regions where avocado is grown. The fungus mainly infects fruits causing symptoms such as small blackish spots, “pepper spots,” and black spots with raised margin which coalesce as infection progresses. Due to economic losses associated with the disease and emerging information of other species of fungi as causal agents of the disease, this study was aimed at identifying causal agent(s) of the disease. A total of 80 fungal isolates were collected from diseased avocado fruits in Murang’a County, the main avocado growing region in Kenya. Forty-six isolates were morphologically identified as Colletotrichum spp. based on their cultural characteristics, mainly whitish, greyish, and creamish colour and cottony/velvety mycelia on the top side of the culture and greyish cream with concentric zonation on the reverse side. Their spores were straight with rounded end and nonseptate. Thirty-four isolates were identified as Pestalotiopsis spp. based on their cultural characteristics: whitish grey mycelium with black fruiting structure on the upper side and greyish black one on the lower side and septate spores with 3-4 septa and 2 or 3 appendages at one end. Further molecular studies using ITS indicated Colletotrichum gloeosporioides, Colletotrichum boninense, and Pestalotiopsis microspora as the causal agents of anthracnose disease in avocado. However, with this being the first report, there is a need to conduct further studies to establish whether there is coinfection or any interaction thereof

Influence of bunch maturation and chemical precursors on acrylamide formation in starchy banana chips

The present study investigated the effect of ripening stages and chemical precursors on acrylamide formation in deep-fried chips of five plantains and one cooking banana. The highest level of acrylamide was found in the cooking banana, followed by False Horn plantain and French plantain, respectively. French plantain hybrids exhibited a significantly lower (P 0.60) with acrylamide formation in fried chips. The higher level of TP was significantly related (P < 0.05) to the lower level of acrylamide (r = −0.62). The reduced levels of carotenoid isomers, except lutein, during fruit ripening were positively correlated (P < 0.05) with acrylamide formation, especially trans-BC (r = 0.72) and 9-cis-BC(r = 0.64)

How does cultivar, maturation, and pre-treatment affect nutritional, physicochemical, and pasting properties of plantain flours?

Open Access JournalThe effect of cultivar, ripening stage, and pre-treatment method were investigated on the nutritional, physicochemical, and pasting properties of plantain flours from two plantains and two plantain hybrids. There were significant variations (p < 0.05) in chemical composition and physical properties influenced by the interaction of cultivars, ripening stages, and pre-treatment methods. The highest levels of amylose, water-holding capacity (WHC), and oil-holding capacity (OHC) were observed in unripe flours and acid-treated flour recorded the highest content of resistant starch (RS). Flour after pre-blanching contained the highest level of total phenolic (TP), carotenoid contents, and browning index (BI) value. In contrast, acid-treated flours had the lowest BI value. As ripening progressed, peak viscosity and breakdown values increased but final viscosity, setback, and pasting temperature values were reduced. Untreated flour samples showed the highest peak viscosity. Higher breakdown values were found in acid-treated samples and higher setback values in pre-blanched samples