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Eastern Africa is currently infested with dodders—highly invasive vines that threaten agriculture and biodiversity. We describe historical and ecological factors that have potentially shaped dodder invasion in this region. Our results reveal high levels of genetic diversity within dodder populations, which could enhance their ability to colonize new niches. Further, we identify two main population clusters in eastern and western Kenya, a pattern that is mirrored in an established invader (Cuscuta campestris) and a recent introduction (C. reflexa). Immediate control strategies are needed to limit deliberate or inadvertent seed/vine dispersal, eradicate existing populations, and monitor influx of propagules. Summary: Invasion by dodder (Cuscuta spp.), holo-parasitic plants of the Convolvulaceae family, has recently surged in Eastern Africa. Particularly, colonization by two species, Cuscuta campestris and Cuscuta reflexa that have a broad host range and rapid invasiveness, has escalated. We examined the first assessment of genetic diversity of these invasive species in Kenya to inform subsequent management practices. A comparative phylogeographic analysis, based on chloroplast and nuclear ribosomal DNA, was performed to determine genetic diversities, population structure, and isolation of C. campestris and C. reflexa in Kenya. Results reveal high genetic variation in both species within populations across localities. C. campestris had more haplotypes and higher gene diversity (P =.0001) and heterozygosity (P =.004) than C. reflexa. Both species were geographically separated, evidenced by two distinct lineages that mostly corresponded to localities east and west of Kenya. Correlation between genetic and geographic distances revealed evidence of isolation by distance (IBD). We attribute these genetic variation patterns to establishment via similar invasion routes for the studied Cuscuta spp. and suggest that Cuscuta invasion in Kenya is in the early stages of establishment. Rapid eradication is urgently needed to prevent shifts to economically important hosts, which would have devastating impacts. We recommend (i) development of targeted efforts to curb new introductions to limit the potential for genetic variability and adaptation, (ii) prevention of seed and vine dispersal from current incursions, and (iii) complete eradication of existing populations where this is feasible.

The effects of pressure (21.3, 41.3, 61.3, 81.3, and 101.3 kPa) and temperature (174–184 °C) applied during the post-frying centrifuge stage on the physico-chemical characteristics of atmospheric fried plantain chips were studied. Results showed that the surface temperature dropped very fast during the cooling process while the total oil content gradually increased. The oil uptake in the plantain chips increased by 7.7% after 9 min of post-frying cooling. Though an alteration in moisture and oil content was significantly affected (p 0.05) was observed among the samples centrifuged at different pressures. The application of vacuum pressure at 21.3 kPa together with temperature control for 5 min during the post-frying centrifuge stage was significantly effective (p

Turcicum leaf blight (TLB), is a common foliar disease of maize in Mexico that is caused by the fungal pathogen

Bananas (banana and plantains) rank sixth among staple food crops (FAO 2018), with production challenged by biotic factors, mainly fungal diseases that may cause a total loss in some orchards (Jones 2018). In April 2017, dieback symptoms (progressive blackening and necrotic aerial plant parts, leaves, fruits and peduncles) were observed on plantain (

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

Tar spot is a foliar disease of corn threatening production across the Americas. The disease was first documented in Mexico in 1904 and is now present in 15 additional countries throughout Central America, South America, and the Caribbean. Researchers and growers in Central America, South America, and the Caribbean consider tar spot to be a disease complex caused by multiple fungal pathogens. When environmental conditions are conducive for infection, these regions have experienced yield losses that can reach up to 100%. In 2015, tar spot was detected in the United States for the first time in Illinois and Indiana. Since that time tar spot has spread across the U.S. corn-growing region, and the disease has been found in Florida, Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, Pennsylvania, and Wisconsin. In 2020, tar spot was also found in southwest Ontario, Canada. Losses in the United States due to tar spot totaled an estimated 241 million bushels from 2018 to 2020. With the potential to continue to spread across the U.S. corn-growing states, much greater losses could result when environmental conditions are conducive.

Maize lethal necrosis disease (MLND) is a devastating viral disease of maize caused by double infection with Maize chlorotic mottle virus (MCMV) and any one of the Potyviridae family members. Management of MLND requires effective resistance screening and surveillance tools. In this study, we report the use of small RNA (sRNA) profiling to detect MLND causal viruses and further the development of alternative detection markers for use in routine surveillance of the disease‐causing viruses. Small RNAs (sRNAs) originating from five viruses namely MCMV, Sugarcane mosaic virus (SCMV), Maize streak virus (MSV), Maize‐associated totivirus (MATV) and Maize yellow mosaic virus (MYMV) were assembled from infected maize samples collected from MLND hot spots in Kenya. The expression of the identified viral domains was further validated using quantitative real‐time PCR. New markers for the detection of some of the MLND causal viruses were also developed from the highly expressed domains and used to detect the MLND‐causative viruses in maize and alternative hosts. These findings further demonstrate the potential of using sRNAs especially from highly expressed viral motifs in the detection of MLND causal viruses. We report the validation of new sets of primers for use in detection of the most common MLND causal viruses MCMV and SCMV in East Africa.

Tar spot complex (TSC) is a major foliar disease of maize in many Central and Latin American countries and leads to severe yield loss. To dissect the genetic architecture of TSC resistance, a genome-wide association study (GWAS) panel and a bi-parental doubled haploid population were used for GWAS and selective genotyping analysis, respectively. A total of 115 SNPs in bin 8.03 were detected by GWAS and three QTL in bins 6.05, 6.07, and 8.03 were detected by selective genotyping. The major QTL qRtsc8-1 located in bin 8.03 was detected by both analyses, it explained 14.97% of the phenotypic variance. To fine-map qRtsc8-1, the recombinant-derived progeny test was implemented. Recombinations in each generation were backcrossed, and the backcross progenies were genotyped with Kompetitive Allele Specific PCR (KASP) markers and phenotyped for TSC resistance individually. The significant tests for comparing the TSC resistance between the two classes of progenies with and without resistant alleles were used for fine-mapping. In BC5 generation, qRtsc8-1 was fine mapped in an interval of ~721 kb flanked by markers of KASP81160138 and KASP81881276. In this interval, the candidate genes GRMZM2G063511 and GRMZM2G073884 were identified, which encode an integral membrane protein-like and a leucine-rich repeat receptor-like protein kinase, respectively. Both genes are involved in maize disease resistance responses. Two production markers KASP81160138 and KASP81160155 were verified in 471 breeding lines. This study provides valuable information for cloning the resistance gene, it will also facilitate the routine implementation of marker-assisted selection in the breeding pipeline for improving TSC resistance.

Plantain (PLF) and soy flours (SF) were used to substitute wheat flour (10 and 20% w/w) in composite bread. Physico-chemical, phytochemical, and sensory properties were investigated. Partial substitution by PLF significantly increased (p < 0.05) starch, amylose, ascorbic acid, and potassium content in bread samples. In contrast, a significant improvement (p < 0.05) in protein, fat, amylopectin, and calcium content was observed with SF substitution. Composite bread with PLF and SF together lowered the hydrolysis index (HI) and glycemic index (GI) as compared with whole wheat flour. The molar phytate to minerals (iron, zinc, and calcium) ratio in all composite loaves was lower than reported critical values, except for phytate to iron. Significant differences (p < 0.05) were found in color, specific volume, and texture characteristics of loaves made from partial substitution with PLF and SF. Sensory evaluation revealed that bread with 10% PLF exhibited better scores for appearance and willingness to pay than the control. In contrast, SF negatively affected (p < 0.05) the appearance, texture, color, overall acceptance, and willingness to pay. The trade-off analysis indicated that PLF can be utilized to produce bread that meets consumers' demands, while incorporating SF as an alternative high-nutrient density bread will be beneficial for health. ispartof: Food Science & Nutrition vol:10 issue:9 pages:1-13 ispartof: location:United States status: Published online

Meloidogyne incognita causes huge yield losses in rice which is the third most important cereal crop in Kenya. The aim of this study was to identify M. incognita-resistant rice cultivars from Kenya and relate the responses to known resistance pathways with OsPR1a, OsPAL1, and OsJAMYB as marker genes in rice. Five rice cultivars BW 196, Basmati 217 (Pishori), Sindano, IR 2793-80-1 (grown in lowland irrigated fields), and NERICA 4 (grown in upland rainfed fields) were evaluated for resistance to M. incognita under greenhouse conditions in two separate trials. The number of nematode eggs, reproduction factor (RF), and the level of galling were determined. The RF was used to select resistant cultivars. There was a significant difference (P < 0.001) in the number of eggs, galling index, and RF among the cultivars. NERICA 4, BW 196, and Sindano were classified as resistant with an RF

The 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 &lt, 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.

The inherent ability of seeds (orthodox, intermediate, and recalcitrant seeds and vegetative propagules) to serve as carriers of pests and pathogens (hereafter referred to as pests) and the risk of transboundary spread along with the seed movement present a high-risk factor for international germplasm distribution activities. Quarantine and phytosanitary procedures have been established by many countries around the world to minimize seed-borne pest spread by screening export and import consignments of germplasm. The effectiveness of these time-consuming and cost-intensive procedures depends on the knowledge of pest distribution, availability of diagnostic tools for seed health testing, qualified operators, procedures for inspection, and seed phytosanitation. This review describes a unique multidisciplinary approach used by the CGIAR Germplasm Health Units (GHUs) in ensuring phytosanitary protection for the safe conservation and global movement of germplasm from the 11 CGIAR genebanks and breeding programs that acquire and distribute germplasm to and from all parts of the world for agricultural research and food security. We also present the challenges, lessons learned, and recommendations stemming from the experience of GHUs, which collaborate with the national quarantine systems to export and distribute about 100,000 germplasm samples annually to partners located in about 90 to 100 countries. Furthermore, we describe how GHUs adjust their procedures to stay in alignment with evolving phytosanitary regulations and pest risk scenarios. In conclusion, we state the benefits of globally coordinated phytosanitary networks for the prevention of the intercontinental spread of pests that are transmissible through plant propagation materials.

Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten Africa’s ecosystems, due to their rapid spread and attack on various host plant species. Most Cuscuta species cannot photosynthesize, hence rely on host plants for nourishment. After attachment through a peg-like organ called a haustorium, the parasites deprive hosts of water and nutrients leading to their death. Despite their rapid spread in Africa, dodders have attracted limited research attention, although data on their taxonomy, host range and epidemiology are critical for their management. Here, we combine taxonomy and phylogenetics to reveal presence of field dodder (Cuscuta campestris) and C. kilimanjari (both either naturalized or endemic to East Africa), and for the first time in continental Africa, presence of the giant dodder (C. reflexa) a south Asian species. These parasites have a wide host range, parasitizing species across 13 angiosperm orders. Evaluating the possibility of C. reflexa to expand this host range to tea, coffee, and mango, crops of economic importance to Africa, revealed successful parasitism, following haustorial formation and vascular bundle connections in all three crops. However, only mango mounted a successful post-attachment resistance response. Furthermore, species distribution models predicted high habitat suitability for all three Cuscuta species across major tea- and coffee-growing regions of Eastern Africa, suggesting an imminent risk to these crops. Our findings provide relevant insights into a little-understood threat to biodiversity and economic wellbeing in Eastern Africa, and providing critical information to guide development of management strategies to avert their spread.Sentence SummaryMicroscopy and habitat suitability modeling provide an early warning that dodder’s invasion in Eastern Africa poses a threat to important cash crops

Wheat (Triticum aestivum L.) crop health assumes unprecedented significance in being the second most important staple crop of the world. It is host to an array of fungal pathogens attacking the plant at different developmental stages and accrues various degrees of yield losses owing to these. Tilletia indica that causes Karnal bunt (KB) disease in wheat is one such fungal pathogen of high quarantine importance restricting the free global trade of wheat besides the loss of grain yield as well as quality. With global climate change, the disease appears to be shifting from its traditional areas of occurrence with reports of increased vulnerabilities of new areas across the continents. This KB vulnerability of new geographies is of serious concern because once established, the disease is extremely difficult to eradicate and no known instance of its complete eradication using any management strategy has been reported yet. The host resistance to KB is the most successful as well as preferred strategy for its mitigation and control. However, breeding of KB resistant wheat cultivars has proven to be not so easy, and the low success rate owes to the scarcity of resistance sources, extremely laborious and regulated field screening protocols delaying identification/validation of putative resistance sources, and complex quantitative nature of resistance with multiple genes conferring only partial resistance. Moreover, given a lack of comprehensive understanding of the KB disease epidemiology, host-pathogen interaction, and pathogen evolution. Here, in this review, we attempt to summarize the progress made and efforts underway toward a holistic understanding of the disease itself with a specific focus on the host-pathogen interaction between T. indica and wheat as key elements in the development of resistant germplasm. In this context, we emphasize the tools and techniques being utilized in development of KB resistant germplasm by illuminating upon the genetics concerning the host responses to the KB pathogen including a future course. As such, this article could act as a one stop information primer on this economically important and re-emerging old foe threatening to cause devastating impacts on food security and well-being of communities that rely on wheat.

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.

Striga spp. are obligate root hemiparasites that constrain cereal production in sub-Saharan Africa. Although purple witchweed [Striga hermonthica (Delile) Benth.] and Asiatic witchweed [Striga asiatica (L.) Kuntze] infect all cereal crops, maize (Zea mays L.) is particularly vulnerable to their infestations. A sustainable control strategy for Striga would be to breed crops with host-based resistance as part of an integrated management plan. In maize, the open-pollinated variety Kakamega Striga-tolerant population of the year 1994 (‘KSTP 94’) has been popularized as a Striga-tolerant/resistant variety. This resistance was earlier reported to result from production of low amounts of sorgomol, a less potent strigolactone. To determine whether KSTP 94 harbors postattachment resistance, we used a soil-free assay based on observation chambers called rhizotrons. We found that the size of Striga seedlings attached to ‘CML 144’ (a susceptible maize inbred line) were 2.5-fold longer than those on KSTP 94. In addition, KSTP 94 had significantly fewer Striga attachments, which corresponded to significantly lower biomass (2.6-fold) compared with CML 144. Histological analysis revealed that the low Striga growth and development while infecting KSTP 94 was due the parasite’s inability to penetrate the host’s endodermis and make effective xylem–xylem connections. We therefore conclude that in addition to preattachment resistance, KSTP 94 exhibits postattachment resistance to S. hermonthica and could therefore be a good genetic source for postattachment resistance breeding.

Colletotrichum gloeosporioides is a serious postharvest pathogen of avocado fruits worldwide. Kenya lacks any registered fungicides for the management of the disease. Nevertheless, farmers commonly use commercially available fungicides such as Bayleton 25WP (Triadimefon 250 g/Kg), Milraz 76WP (Propineb 70% and Cymoxanil 6%), and Copper oxychloride 500WP for disease management. The efficacy of these fungicides against C. gloeosporioides is not known. The purpose of this study was therefore to test the inhibitory effect of these fungicides against 46 C. gloeosporioides isolates from avocado fruits collected from varieties grown at different agroecological zones in Murang’a County, a popular avocado-growing region in Kenya. Mycelial growth rate and sporulation for each isolate were measured in vitro on PDA plates amended with different concentrations of the fungicides. Plates were arranged in a completely randomized design with three replications per treatment. All fungicides were effective in vitro but there were significant differences in sensitivity among isolates. Bayleton had the highest mycelial inhibition followed by Milraz, while copper oxychloride had the lowest mycelial inhibition rates, ranging from 81% to 88%. However, copper oxychloride was more effective in inhibiting sporulation. The inhibitory effect of each fungicide was concentration-dependent, where twice the recommended concentration had the highest inhibitory effect, followed by the recommended concentration. Our results show that the fungicides used by farmers against C. gloeosporioides, the causal agent for anthracnose, are effective. We, however, recommend further field tests in different avocado-growing areas so as to validate their efficacy against various isolates and under different environments.

Plantain is a key staple food in Central and West Africa, but there is limited understanding of its market in Africa. In addition, the cooking methods for enhancing the nutritional value, consumer preference, and willingness to pay for plantain and plantain-based products are not well understood. The knowledge gaps in the market and consumer dimension of the food chain need to be known to increase plantain utilization and guide breeding efforts. This research contributes by examining the cooking methods, consumer preference, and willingness to pay for plantain and plantain-based products in Cameroon and Nigeria. A household survey sample of 454 Cameroonian consumers in four divisions of Central Region and 418 Nigerian consumers in seven government areas of Oyo State in southwest Nigeria was the basis for the analysis. The results showed some levels of similarity and difference in the consumption and cooking of boiled, roasted, and fried plantain in both countries. The trend in consumption of all plantain-based products was constant in Cameroon but increased in Nigeria. The most important factor influencing Cameroonian consumers’ choice of plantain and its products was taste, while the nutrition trait influenced Nigerian consumers. Both Cameroonian and Nigerian consumers considered packaging, location of produce, and size and quantity as the least important factors. In addition, socioeconomic characteristics were significant determinants of consumers’ choices to consume plantain and its products. Gender significantly influenced (p &lt, 0.05) taste, while nutrition was significantly driven (p &lt, 0.05) by education and annual income. Household size played a significant role (p &lt, 0.05) in consumers’ choices when the price was considered. These findings serve as a guideline to improve existing products to match the needs of consumers in each country and develop products for different consumer segments and potentially increase production.

Rice is the third most important crop in Kenya after maize and wheat. Plant parasitic nematodes (PPN) are a major rice production constraint. The objective of this study was to determine the distribution and abundance of rice PPN in Kenya and their association with environmental variables. Soil and plant samples were collected from rainfed upland and irrigated lowland rice fields in Kirogo, Thiba, Nyangati, Ombeyi, Kombura, Kakola and Mwambe Sub-locations. Twenty-two PPN genera were identified across all Sub-locations with the highest (20) number of nematode genera recorded in rainfed upland rice fields. The nematode genera Scutellonema, Hoplolaimus, Ditylenchus, Hemicycliophora, Heterodera, Paralongidorus and Tylenchus were not recorded in the irrigated lowland rice fields while Criconemella and Tylenchorhynchus were not observed in rainfed upland fields. Canonical correspondence analysis of the relationship between soil properties and nematode abundance revealed a significant (P

Striga hermonthica is a hemiparasitic weed that causes huge grain yield losses to small-scale farmers in Africa. Effective biocontrol agents against S. hermonthica can sustainably mitigate these losses. This study characterized the biocontrol potential of culturable fungal and bacterial isolates from S. hermonthica suppressive soils of western Kenya. These isolates were screened for their ability to produce antibiotic compounds and extra cellular enzymes and also their ability to cause S. hermonthica seed decay. Genomic DNA of the selected bacterial and fungal isolates was extracted and partial characterization of 16S rRNA and 18S rRNA genes performed respectively. Analysis show that antibiosis and enzymatic properties of potential biocontrol isolates correlated positively. Isolate KY041696 recorded high antibiosis, enzymatic and seed decay values. This study also revealed that bioactive bacterial isolates belonged to Bacillus, Streptomyces and Rhizobium genera. In this study, no fungal isolate caused S. hermonthica seed decay. This study therefore provides baseline information on the potential biocontrol microbes against S. hermonthica in Western Kenya that could be exploited further in the management of the weed.

Aflatoxins are carcinogenic chemical metabolites produced by Aspergillus spp. of the section Flavi. In Kenya, Aspergillus flavus is the most prevalent and has been associated with several acute and chronic aflatoxin outbreaks in the past. In this study, we evaluated the occurrence of A. flavus in soils from two agro-ecological regions with contrasting climatic conditions, aflatoxin contamination histories and cropping systems. Aspergillus spp. were first isolated from soils before the identification and determination of their aflatoxigenicity. Further, we determined the occurrence of Pseudomonas and Bacillus spp. in soils from the two regions. These bacterial species have long been associated with biological control of several plant pathogens including Aspergillus spp. Our results show that A. flavus occurred widely and produced comparatively higher total aflatoxin levels in all (100%) study sites from the eastern to the western regions of Kenya. For the western region, A. flavus was detected in 4 locations (66.7%) that were previously under maize cultivation with the isolates showing low aflatoxigenicity. A. flavus was not isolated from soils under sugarcane cultivation. Distribution of the two bacterial species varied across the regions but we detected a weak relationship between occurrence of bacterial species and A. flavus. We discuss these findings in the context of the influence of climate, microbial profiles, cropping systems and applicability in the deployment of biological control remedies against aflatoxin contamination.

Aflatoxins are carcinogenic chemical metabolites produced by Aspergillus spp. of the section Flavi. In Kenya, Aspergillus flavus is the most prevalent and has been associated with several acute and chronic aflatoxin outbreaks in the past. In this study, we evaluated the occurrence of A. flavus in soils from two agro-ecological regions with contrasting climatic conditions, aflatoxin contamination histories and cropping systems. Aspergillus spp. were first isolated from soils before the identification and determination of their aflatoxigenicity. Further, we determined the occurrence of Pseudomonas and Bacillus spp. in soils from the two regions. These bacterial species have long been associated with biological control of several plant pathogens including Aspergillus spp. Our results show that A. flavus occurred widely and produced comparatively higher total aflatoxin levels in all (100%) study sites from the eastern to the western regions of Kenya. For the western region, A. flavus was detected in 4 locations (66.7%) that were previously under maize cultivation with the isolates showing low aflatoxigenicity. A. flavus was not isolated from soils under sugarcane cultivation. Distribution of the two bacterial species varied across the regions but we detected a weak relationship between occurrence of bacterial species and A. flavus. We discuss these findings in the context of the influence of climate, microbial profiles, cropping systems and applicability in the deployment of biological control remedies against aflatoxin contamination.

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 Aflasafe TM 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 losses

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 beColletotrichum gloeosporioidesas 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 asColletotrichumspp. 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 asPestalotiopsisspp. 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 indicatedColletotrichum gloeosporioides,Colletotrichum boninense, andPestalotiopsis microsporaas 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.

Tea polyphenols and catechins have gained prominence in determination of tea quality. Tea leaves contain large amounts of catechins and their derivatives and these have shown positive effects on human health. An experiment was carried out to determine the level of catechins and polyphenols in 20 new clones found in two distinct tea growing areas. The trial comprising twenty clones was established in two distinct sites in Kenya using randomized complete block design with three replicates and consisted of 10 popular cultivars widely cultivated in the Lake Victoria Basin and additional 10 newly improved clones. Tea leaf samples were collected across two seasons; dry and wet seasons. Tea quality parameters entailing catechins, caffeine and total polyphenols was generated for the 20 clones across the two seasons and sites. The ISO 14502-1 and ISO 14502-1:2005 procedures were used for polyphenol and catechin analyses, respectively. The ANOVA results generated indicated that the level of catechins and polyphenols in tea were significantly different (p 0.05) and varietal dependent. Generally, the assam varieties had higher levels of catechins and polyphenols than the chinary and cambod varieties, indicating why they are popularly cultivated in the East African region and whose tea quality is highly regarded. Furthermore, the results from principle component analysis (PCA) grouped the clones into three major clusters with one comprising of high quality assam varieties, a mixture of moderate quality assam, cambod and chinary varieties and low catechin content assam anthocyanin-rich variety. It is concluded that the level of catechins in tea plants are varietal dependent, although environmental stress has effects on the synthesis of flavanoids. The results demonstrated that the differences in the accumulation of catechins among the tea clones could be important for the discrimination of clonal diversity.

Cystic echinococcosis (CE) is a zoonotic disease caused by several members of the Echinococcus granulosus species complex. In East Africa, several species/strains are known to occur in livestock and humans, but host preferences, relative frequencies and spatial distribution of these taxa are poorly known. Here, we contribute livestock data for Maasailand of southern Kenya. Total CE prevalence was 25.8 % in cattle (151/587), 16.5 % in sheep (71/430) and 10.8 % in goats (21/194), which is a significant increase compared to surveys done about three decades ago. The majority of cysts occurred in the liver (56 % in cattle, 70 % in sheep and 65 % in goats). Molecular characterization by PCR-RFLP and sequencing of parts of the mitochondrial nad-1 gene was done for a subsample of 285 cysts. E. granulosus G1 was dominant in all host species (200 of 201 cysts from cattle, 68 of 69 from sheep and 11 of 15 from goats); the remaining taxa were Echinococcus canadensis G6 (one cyst from sheep, four from goats) and Echinococcus ortleppi (one cyst from cattle). Considering cyst fertility, sheep appear to be the most important hosts for E. granulosus G1, while goats were found to be suitable hosts for E. canadensis G6 (three of four cysts were fertile). For the first time, E. ortleppi was found in cattle from southern Kenya. Our data show an intense and possibly increasing level of CE transmission in southern Kenya, and the predominance of E. granulosus G1, which appears to be particularly pathogenic to humans, calls for urgent control measures.

Infection of crop species by parasitic plants is a major agricultural hindrance resulting in substantial crop losses worldwide. Parasitic plants establish vascular connections with the host plant via structures termed haustoria, which allow acquisition of water and nutrients, often to the detriment of the infected host. Despite the agricultural impact of parasitic plants, the molecular and developmental processes by which host/parasitic interactions are established are not well understood. Here, we examine the development and subsequent establishment of haustorial connections by the parasite dodder (Cuscuta pentagona) on tobacco (Nicotiana tabacum) plants. Formation of haustoria in dodder is accompanied by upregulation of dodder KNOTTED-like homeobox transcription factors, including SHOOT MERISTEMLESS-like (STM). We demonstrate interspecific silencing of a STM gene in dodder driven by a vascular-specific promoter in transgenic host plants and find that this silencing disrupts dodder growth. The reduced efficacy of dodder infection on STM RNA interference transgenics results from defects in haustorial connection, development, and establishment. Identification of transgene-specific small RNAs in the parasite, coupled with reduced parasite fecundity and increased growth of the infected host, demonstrates the efficacy of interspecific small RNA–mediated silencing of parasite genes. This technology has the potential to be an effective method of biological control of plant parasite infection.

The African elephant (Loxodonta africana) population in Kenya is declining at an alarming rate due to habitat destruction, human-elephant conflicts and the cur- rent escalation of poaching for ivory. This study estab- lished a standard protocol for forensic analysis of L. africana and their products such as ivory. Three multiplex PCR panels consisting of 17 Short Tandem Repeat markers were selected from 40 markers using bioinformatics tools, amplification and polymorphism. Genotyping was suc- cessful and reproducible. This method is efficient, accurate and cost effective and has potential for application in conservation of L. africana.

Biological crop pests cause serious economic losses. In Africa, the most prevalent parasites are insect pests, plant pathogenic root-knot nematodes, viruses and parasitic plants. African smallholder farmers struggle to overcome these parasitic constraints to agricultural production. Crop losses and the host range of these parasites have continued to increase in spite of the use of widely advocated control methods. A sustainable method to overcome biological pests in Africa would be to develop crop germplasm resistant to parasites. This is achievable using either genetic modification (GM) or a non-GM approach. However, there is a paucity of resistant genes available for introduction. Additionally, the biological processes underpinning host parasite resistance are not sufficiently well understood. The authors review a technology platform for using RNA-mediated interference (RNAi) as bioengineered resistance to important crop parasites in Africa. To achieve acquired resistance, a host crop is stably transformed with a transgene that encodes a hairpin RNA targeting essential parasitic genes. The RNAi sequence is chosen in such a way that it shares no homology with the host's genes, so it remains 'inactive' until parasitism. Upon parasitism, the RNAi sequence enters the parasite and post-transcriptional gene silencing (PTGS) mechanisms are activated, leading to the death of the parasite.

Mycotoxin contamination is a common problem in developing countries, particularly in cereals, and this poses a serious health risk to its consumers. Busaa is a Kenyan traditional brew whose cereal ingredients are prone to mycotoxin contamination. This study aimed at detecting the presence and subsequently quantifying aflatoxin, fumonisin and deoxynivalenol (DON), in busaa in Bomet county, Kenya. Busaa samples were collected from homesteads involved in brewing in the north eastern part of Bomet East constituency. Mycotoxins were detected in the samples using the Envirologix QuickTox kits and quantified using the QuickScan machine according to the manufacturer's instructions. Among the 61 samples tested, 93, 9.8 and 23% were contaminated with aflatoxin, fumonisin and DON, respectively, (mean: 5.2±0.2 µg/kg, range: 2.8 to 11 µg/kg; mean 1460±188 µg/kg, range 280 to 4000 µg/kg, mean 259±5.2 µg/kg, range 200 to 360 µg/kg, respectively). Although traditional brews are not directly included in the European law on mycotoxins, it is important to consider their mycotoxin levels. In this study, busaa is a mainly a maize product and also the European Union (EU) guidelines on mycotoxins in maize were used as reference. It was found out that 65.6% of busaa had aflatoxin levels above the limit set in the EU guideline (4 µg/kg). Although, the average levels of fumonisin and DON were within the set limits (fumonisins: 4000 µg/kg; DON: 1750 µg/kg), studies have shown that chronic exposure to multiple mycotoxins has detrimental health effects. Therefore, there is need for mycotoxicological quality control of traditionally produced brews for public mycotoxicological safety.Keywords: Mycotoxin, traditional brewAfrican Journal of Biotechnology Vol 13(26) 2675-2678

We report success of host-induced gene silencing in downregulation of aflatoxin biosynthesis in Aspergillus flavus infecting maize transformed with a hairpin construct targeting transcription factor aflR. Infestation of crops by aflatoxin-producing fungi results in economic losses as well as negative human and animal health effects. Currently, the control strategies against aflatoxin accumulation are not effective to the small holder farming systems in Africa and this has led to widespread aflatoxin exposure especially in rural populations of sub-Saharan Africa that rely on maize as a staple food crop. A recent strategy called host-induced gene silencing holds great potential for developing aflatoxin-resistant plant germplasm for the African context where farmers are unable to make further investments other than access to the germplasm. We transformed maize with a hairpin construct targeting the aflatoxin biosynthesis transcription factor aflR. The developed transgenic maize were challenged with an aflatoxigenic Aspergillus flavus strain from Eastern Kenya, a region endemic to aflatoxin outbreaks. Our results indicated that aflR was downregulated in A. flavus colonizing transgenic maize. Further, maize kernels from transgenic plants accumulated significantly lower levels of aflatoxins (14-fold) than those from wild type plants. Interestingly, we observed that our silencing cassette caused stunting and reduced kernel placement in the transgenic maize. This could have been due to “off-target” silencing of unintended genes in transformed plants by aflR siRNAs. Overall, this work indicates that host-induced gene silencing has potential in developing aflatoxin-resistant germplasm.

Guava (Psidium guajava L) is native to South America and exists as both wild and cultivated. Guava has been used as a source of food and raw materials for pharmaceuticals. The aim of this study was to determine bioactivity of methanol and water extracts from root and leaves of Kenyan guava landraces against selected pathogenic bacteria. Study samples were collected from Western and South Coast of Kenya. One hundred grams of leaf and root ground powders were used for sequential extraction using methanol and water. Extracts were evaporated and 0.2gms dissolved using the extraction solvent and tested against gram positive (Staphylococcus aureus, Bacillus subtilis) and negative bacteria (Escherichia coli). Data on inhibition zone was taken in mm and analyzed at 95% confidence interval. Extracts from Western region had significant inhibition compared to Coastal region. The two regions have different climatic conditions that result in these plants having different compounds even though they are the same species. Roots had higher inhibition compared to the leaves as they contain high levels of tannins compared to leaves. Water as an extracting solvent had higher inhibition than methanol as it is more polar and it absorbs more bioactive compounds. S. aureus was most inhibited followed by E. coli and B. subtilis respectively. There was no significant difference between the gram positive and negative bacteria. Remarkably, some methanol and water root extracts had significant inhibition against bacteria when compared to some commercial antibiotics used. Results of this study indicate that Kenyan guava roots from Western Kenya extracted with methanol and water have a potential to be used as a source of active compounds in treatment of gram positive and gram negative bacteria pathogens.

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.

Biological crop pests cause serious economic losses. In Africa, the most prevalent parasites are insect pests, plant pathogenic root-knot nematodes, viruses and parasitic plants. African smallholder farmers struggle to overcome these parasitic constraints to agricultural production. Crop losses and the host range of these parasites have continued to increase in spite of the use of widely advocated control methods. A sustainable method to overcome biological pests in Africa would be to develop crop germplasm resistant to parasites. This is achievable using either genetic modification (GM) or a non-GM approach. However, there is a paucity of resistant genes available for introduction. Additionally, the biological processes underpinning host parasite resistance are not sufficiently well understood. The authors review a technology platform for using RNA-mediated interference (RNAi) as bioengineered resistance to important crop parasites in Africa. To achieve acquired resistance, a host crop is stably transformed with a transgene that encodes a hairpin RNA targeting essential parasitic genes. The RNAi sequence is chosen in such a way that it shares no homology with the host's genes, so it remains 'inactive' until parasitism. Upon parasitism, the RNAi sequence enters the parasite and post-transcriptional gene silencing (PTGS) mechanisms are activated, leading to the death of the parasite.

Background Striga hermonthica is a hemiparasitic weed that infects cereals in Sub Sahara Africa (SSA) resulting in up to 100% grain yield loss. This significant loss in grain yields is a major contributor to food insecurity and poverty in the region. Current strategies to control the parasite are costly, unavailable and remain unpracticed by small-scale farmers, underscoring the need for more economical and sustainable control strategies. Development of resistant germplasm is the most sustainable strategy in the control of S. hermonthica, but is constrained by paucity of resistance genes for introduction into crop germplasm. RNA interference (RNAi) has potential for developing host-derived resistance against S. hermonthica by transformation of host crops with RNAi sequences targeted at critical Striga genes. The application of RNAi in management of S. hermonthica is however constrained by lack of efficient high throughput screening protocols for the candidate genes for silencing, as well as sub optimal delivery of siRNAs into the parasite. In comparison to stable transformation, viral induced gene silencing (VIGS) is a rapid and powerful tool for plant functional genomics and provides an easy and effective strategy in screening for putative candidate genes to target through RNAi. In addition, VIGS allows for a secondary amplification of the RNAi signal increasing the siRNA threshold and facilitates siRNA transport through viral movement proteins. We tested the efficiency of the Tobacco rattle virus (TRV1 and TRV2) VIGS vectors in silencing S. hermonthica phytoene desaturase (PDS) gene through agrodrench and agro-infiltration. Results We report the validation of VIGS in S. hermonthica using a silencing cassette generated from TRV with a PDS gene insert. Agro-infiltrated and agro-drenched S. hermonthica leaves showed photo-bleaching phenotypes typical for PDS silencing within 7 and 14 days post infection respectively. In both cases S. hermonthica plants recovered from photo-bleaching effects within 28 days post inoculation. The transformation efficiency of the VIGS protocol in S. hermonthica was (60 ± 2.9)%. Conclusion These results demonstrate that the TRV-VIGS system work in S. hermonthica and can be used for candidate gene validation for their role in the parasite development and parasitism, with the ultimate goal of developing resistant transgenic maize.

Aflatoxins are a major problem in Eastern Province of Kenya and Aspergillus flavus has been associated with frequent outbreaks of aflatoxicoses in this region. This study evaluated the efficacy of 15 selected medicinal plants from Eastern Kenya against A. flavus. Different concentrations of 1000mg/ml, 750mg/ml and 400mg/ml using Agar Well Diffusion Method were used. Plants found to have inhibition zones of more than 10mm at 400mg/ml had their bark further assayed for antifungal activity. Both the leaf and bark extracts that were found to be effective were assayed for minimum inhibition concentrations (MIC) and minimum fungicidal concentrations (MFC) using Sabouraund Dextrose broth (SDB) micro-dilution method. The methanolic leaf and bark extracts of the fifteen plants assayed displayed concentration depended antifungal activities that was comparable to that of the reference drug Miconazole at 10mg/ml. Leaf extracts showed better antifungal activity than the bark extracts. For instance, Boscia coriacea (mean 17.40mm) had the highest zone of inhibition followed by Zanthoxylem chalybeum (mean 17.20mm). For the bark extracts, Croton megalocarpus (mean 15.0mm) recorded significantly high antifungal activity while Tithonia diversfolia (mean 13.0mm) had the lowest at 400mg/ml. Senna siamea had the lowest MIC and MFC of 6.25mg/ml and 12.5mg/ml respectively. The preliminary phytochemical analysis of the 15 effective medicinal plants revealed the presence of bioactive compounds that included tannins, saponins, flavonoids, terpenoids, cardiac glycosides and alkaloids. The results obtained from the study could be used as a viable management strategy against A. flavus and aflatoxins in the region so as to ensure low mycotoxin exposure as well as low environmental pollution.

Background Once a transgenic plant is developed, the selectable marker gene (SMG) becomes unnecessary in the plant. In fact, the continued presence of the SMG in the transgenic plant may cause unexpected pleiotropic effects as well as environmental or biosafety issues. Several methods for removal of SMGs that have been reported remain inaccessible due to protection by patents, while development of new ones is expensive and cost prohibitive. Here, we describe the development of a new vector for producing marker-free plants by simply adapting an ordinary binary vector to the double right border (DRB) vector design using conventional cloning procedures. Findings We developed the DRB vector pMarkfree5.0 by placing the bar gene (representing genes of interest) between two copies of T-DNA right border sequences. The β-glucuronidase (gus) and nptII genes (representing the selectable marker gene) were cloned next followed by one copy of the left border sequence. When tested in a model species (tobacco), this vector system enabled the generation of 55.6% kanamycin-resistant plants by Agrobacterium-mediated transformation. The frequency of cotransformation of the nptII and bar transgenes using the vector was 66.7%. Using the leaf bleach and Basta assays, we confirmed that the nptII and bar transgenes were coexpressed and segregated independently in the transgenic plants. This enable separation of the transgenes in plants cotransformed using pMarkfree5.0. Conclusions The results suggest that the DRB system developed here is a practical and effective approach for separation of gene(s) of interest from a SMG and production of SMG-free plants. Therefore this system could be instrumental in production of “clean” plants containing genes of agronomic importance.

The Pseudomonas syringae pathogen is genetically diverse, presumably due to the adaptation of individual pathovars to suit the environments of their respective host plants. Given the immense damage and yield loss due to BBC disease that is caused by Psg, this study sought to determine the diversity associated to virulence of the PSG isolates on coffee in Kenya. Twelve strains of Psg pathogen were collected from different coffee growing regions in Kenya and characterized using both phenotypic and molecular tools using inoculation via host-pathogen interaction and genomic sequencing. The sequencing was done using 16S ribosomal RNA primers 8 F and 1492 R and sequences were then retrieved for alignment and phylogenetic analysis using MEGA 6 via clustalW. The results correlating the 16S rRNA diversity found in the strains with their virulence by inoculation in 4 different coffee genotypes revealed possible existence of different races of Psg. The study provides new knowledge on the nature of virulence of BBC pathogen and a platform towards breeding for durable resistance in Kenya.