Long-term push-pull cropping system shifts soil and maize-root microbiome diversity paving way to resilient farming system.

BACKGROUND: The soil biota consists of a complex assembly of microbial communities and other organisms that vary significantly across farming systems, impacting soil health and plant productivity. Despite its importance, there has been limited exploration of how different cropping systems influence soil and plant root microbiomes. In this study, we investigated soil physicochemical properties, along with soil and maize-root microbiomes, in an agroecological cereal-legume companion cropping system known as push-pull technology (PPT). This system has been used in agriculture for over two decades for insect-pest management, soil health improvement, and weed control in sub-Saharan Africa. We compared the results with those obtained from maize-monoculture (Mono) cropping system. RESULTS: The PPT cropping system changed the composition and diversity of soil and maize-root microbial communities, and led to notable improvements in soil physicochemical characteristics compared to that of the Mono cropping system. Distinct bacterial and fungal genera played a crucial role in influencing the variation in microbial diversity within these cropping systems. The relative abundance of fungal genera Trichoderma, Mortierella, and Bionectria and bacterial genera Streptomyces, RB41, and Nitrospira were more enriched in PPT. These microbial communities are associated with essential ecosystem services such as plant protection, decomposition, carbon utilization, bioinsecticides production, nitrogen fixation, nematode suppression, phytohormone production, and bioremediation. Conversely, pathogenic associated bacterial genus including Bryobacter were more enriched in Mono-root. Additionally, the Mono system exhibited a high relative abundance of fungal genera such as Gibberella, Neocosmospora, and Aspergillus, which are linked to plant diseases and food contamination. Significant differences were observed in the relative abundance of the inferred metabiome functional protein pathways including syringate degradation, L-methionine biosynthesis I, and inosine 5'-phosphate degradation. CONCLUSION: Push-pull cropping system positively influences soil and maize-root microbiomes and enhances soil physicochemical properties. This highlights its potential for agricultural and environmental sustainability. These findings contribute to our understanding of the diverse ecosystem services offered by this cropping system where it is practiced regarding the system's resilience and functional redundancy. Future research should focus on whether PPT affects the soil and maize-root microbial communities through the release of plant metabolites from the intercrop root exudates or through the alteration of the soil's nutritional status, which affects microbial enzymatic activities.

Tritrophic Interactions Mediated by Zoophytophagous Predator-Induced Host Plant Volatiles.

The zoophytophagous mirid predator Nesidiocoris tenuis and the ectoparasitoid Stenomesius japonicus are important biological control agents for several agricultural pests including the invasive leafminer, Phthorimaea absoluta, a destructive pest of Solanaceous crops especially tomato in sub-Saharan Africa. However, little is known about how feeding by N. tenuis can influence the tritrophic interactions in the tomato plant. Here, we tested the hypothesis that N. tenuis phytophagy would influence the tritrophic olfactory interactions between the host plant tomato and pest, predator, and parasitoid. In olfactometer assays, P. absoluta females and N. tenuis adults were both attracted to constitutive volatiles released by the tomato plant. Whereas females of P. absoluta avoided volatiles released by N. tenuis-infested plants, S. japonicus females and N. tenuis adults were attracted to the induced volatiles. In coupled gas chromatography-electroantennographic detection (GC-EAD) recordings of intact and N. tenuis-infested plant volatiles, antennae of P. absoluta and S. japonicus females both detected eight components, whereas N. tenuis adults detected seven components which were identified by GC-mass spectrometry (GC-MS) as terpenes and green leaf volatiles (GLVs). Dose-response olfactometer bioassays revealed that the responses of P. absoluta, N. tenuis, and S. japonicus varied with the composition and concentration of blends and individual compounds tested from N tenuis-induced volatiles. Females of P. absoluta showed no preference for an eight-component blend formulated from the individual repellents including hexanal, (Z)-3-hexenyl butanoate, and δ-elemene identified in the volatiles. On the other hand, S. japonicus females were attracted to an eight-component blend including the attractants (E)-2-hexenal, (Z)-3-hexenol, methyl salicylate, ß-phellandrene, and (E)-caryophyllene. Likewise, N. tenuis adults were attracted to a seven-component blend including the attractants ß-phellandrene, δ-elemene, and (E)-caryophyllene identified in the volatiles. Our findings suggest that there is potential for the use of terpenes and GLVs to manage the insects in the tritrophic interaction.

Host Plant-Based Artificial Diets Enhance Development, Survival and Fecundity of the Edible Long-Horned Grasshopper Ruspolia differens (Orthoptera: Tettigoniidae).

Wild swarms of the long-horned grasshoppers Ruspolia differens (Serville) which are widely harvested for consumption and sale in Africa are seasonal and unsustainable, hence the need for innovative ways of artificially producing the insects. We investigated the development, survival, and reproduction of R. differens in the laboratory on diets mixed with host plants [Digitaria gayana Kunth, Cynodon dactylon (L.) and Megathyrsus maximus Jacq (Poales: Poaceae); Ageratum conyzoides L. (Asterales: Asteraceae)] identified from guts of their wild conspecifics with a view to developing a suitable diet for artificial mass rearing of the edible insect. A standard diet comprising ground black soldier fly, Hermetia illucens L. (Diptera: Startiomyidae) larvae, soybean flour, maize flour, vitamin premix, and ground bones was tested for rearing R. differens as a control against the same ingredients incorporated with individual powders of the different host plants. Whereas R. differens developed more slowly in the diet mixed with D. gayana than in the control diet; its development was faster in the diet mixed with C. dactylon. Mortalities of R. differens in host plant-based diets were 42.5-52.5%, far lower than in the control diet with 71% mortality. The insects raised on the diet mixed with M. maximus laid approximately twice more eggs compared to R. differens fecundities from the rest of the diets. However, inclusion of host plants in the diets had no detectable influence on R. differens adult weight and longevity. These findings support inclusion of specific host plants in artificial diets used for mass rearing of R. differens to enhance its survival, development, and fecundity.

Predicting the current and future distribution of the edible long-horned grasshopper Ruspolia differens (Serville) using temperature-dependent phenology models.

The edible long-horned grasshopper Ruspolia differens (Serville) is widely distributed and consumed in sub-Saharan Africa. Efficient mass rearing of the edible grasshopper is critical to ensure their sustainable supply for food and nutritional security. Hence, we investigated the effect of temperature on development, survival and reproduction of R. differens under six constant (15, 20, 25, 30, 32 and 35 °C) and fluctuating temperatures. Using Insect Life Cycle Modeling software we fitted, linear and non-linear models to R. differens development, mortality, longevity, and fecundity. The best-fitted functions were compiled for each life stage to yield a phenology model, which was stochastically simulated to estimate the life table parameters. We used the process-based climatic phenology models, and applied establishment risk index (ERI) and generation index (GI) in a geographic information system to map the potential distribution of R. differens under current and future climates. At optimum temperatures of 30-32 °C, egg incubation period was 14-15 days and the developmental time was shortest at 52.5-58 days. Lowest nymphal mortality (3.4-13%) and the highest female fecundity was obtained at 25-30 °C. The optimum temperature for the reproduction ranged between 27 and 30 °C. Most simulated lifetable parameters were at their maximum at 28 °C. Predictive models showed that countries in the East, Central, West, Southern and the Horn of Africa were suitable for establishment of R. differens under current climate scenarios (2000). However, by 2050, climatically suitable areas for the establishment of R. differens were predicted to shrink in the West, Southern and the Horn of Africa than its current distribution. We predict up to three generations per year for R. differens in sub-Saharan Africa under current scenarios which can increase to 4 under future scenarios. The optimum rearing temperatures identified can guide optimization of mass rearing of R. differens.

Influence of inoculated gut bacteria on the development of Bactrocera dorsalis and on its susceptibility to the entomopathogenic fungus, Metarhizium anisopliae.

BACKGROUND: Symbiotic interactions between insects and bacteria have been associated with a vast variety of physiological, ecological and evolutionary consequences for the host. A wide range of bacterial communities have been found in association with the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), an important pest of cultivated fruit in most regions of the world. We evaluated the diversity of gut bacteria in B. dorsalis specimens from several populations in Kenya and investigated the roles of individual bacterial isolates in the development of axenic (germ-free) B. dorsalis fly lines and their responses to the entomopathogenic fungus, Metarhizium anisopliae. RESULTS: We sequenced 16S rRNA to evaluate microbiomes and coupled this with bacterial culturing. Bacterial isolates were mono-associated with axenic B. dorsalis embryos. The shortest embryonic development period was recorded in flies with an intact gut microbiome while the longest period was recorded in axenic fly lines. Similarly, larval development was shortest in flies with an intact gut microbiome, in addition to flies inoculated with Providencia alcalifaciens. Adult B. dorsalis flies emerging from embryos that had been mono-associated with a strain of Lactococcus lactis had decreased survival when challenged with a standard dosage of M. anisopliae ICIPE69 conidia. However, there were no differences in survival between the germ-free lines and flies with an intact microbiome. CONCLUSIONS: These findings will contribute to the selection of probiotics used in artificial diets for B. dorsalis rearing and the development of improved integrated pest management strategies based on entomopathogenic fungi.

Combining insect pathogenic fungi and a pheromone trap for sustainable management of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae).

Fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a key invasive pest of maize and other crops in Africa. Entomopathogenic fungi play an important role in regulating the immature stages of this invasive pest as opposed to synthetic pesticides that are hazardous to human, environment and biodiversity. To tackle the adult stage of the pest (the moth) and to improve on the application strategy of the fungal-based biopesticides, this study evaluated the effect of various entomopathogenic fungi isolates on S. frugiperda moths. Twenty-two isolates (16 Metarhizium anisopliae and 6 Beauveria bassiana) were screened in the laboratory to assess their pathogenicity and virulence against S. frugiperda moths. The compatibility of the most pathogenic isolates with S. frugiperda pheromone FALLTRACT lure, the horizontal transmission of the inoculum among S. frugiperda moths, and the effect on oviposition were also determined under laboratory conditions. All 22 fungal isolates screened were pathogenic to the moths, but the mortality varied significantly among the isolates (P < 0.0001) seven days post-treatment. Beauveria bassiana ICIPE 621 and M. anisopliae ICIPE 7 outperformed all the other isolates by causing 100% mortality of the moths with the lowest LT50 values of 3.6 ± 0.1 and 3.9 ± 0.0 days, respectively. Both isolates were also found compatible with FALLTRACT lure, as the lure had no effect on the conidial germination in the laboratory. Male and female moths were able to horizontally transmit conidia of both fungal isolates to untreated moths, causing high mortality of S. frugiperda in 'donor' and 'recipient' groups. In addition, the oviposition, hatchability of eggs and longevity of larvae were significantly affected on the fungal infected females. Although single moths still retained high conidial numbers 72 h post-inoculation, the number of conidia decreased with time. These results suggest that ICIPE 7 and ICIPE 621 could be used in combination with S. frugiperda pheromone in an autodissemination approach to suppress S. frugiperda population.

Isopentyl Butanoate: Aggregation Pheromone of the Brown Spiny Bug, Clavigralla tomentosicollis (Hemiptera: Coreidae), and Kairomone for the Egg Parasitoid Gryon sp. (Hymenoptera: Scelionidae).

The brown spiny bug, Clavigralla tomentosicollis Stål (Hemiptera: Coreidae) is a key pest of leguminous crops in many countries in Africa, causing significant yield losses especially in cowpea, pigeon pea and common beans. Although C. tomentosicollis uses olfaction to aggregate, little is known about the identity of the aggregation pheromone. This study aimed to identify the aggregation pheromone of C. tomentosicollis and to test its potential role in the behavior of its egg parasitoid, Gryon sp. In Y-tube olfactometer bioassays, only male volatiles strongly attracted both sexes of C. tomentosicollis. Coupled gas chromatography/electroantennographic detection (GC/EAD) and GC/mass spectrometry were used to identify antennally-active compounds from male volatiles. Antennae of both sexes detected identical components including a male-specific component, identified as isopentyl butanoate, which was also detected by antenna of the egg parasitoid. In olfactometer bioassays, both sexes of C. tomentosicollis and the egg parasitoid responded to isopentyl butanoate. These results suggest that isopentyl butanoate serves as an aggregation pheromone for both sexes of C. tomentosicollis and a useful kairomone to attract the parasitoid in the management of C. tomentosicollis.

Metarhizium anisopliae infection reduces Trypanosoma congolense reproduction in Glossina fuscipes fuscipes and its ability to acquire or transmit the parasite.

BACKGROUND: Tsetse fly-borne trypanosomiasis remains a significant problem in Africa despite years of interventions and research. The need for new strategies to control and possibly eliminate trypanosomiasis cannot be over-emphasized. Entomopathogenic fungi (EPF) infect their hosts through the cuticle and proliferate within the body of the host causing death in about 3-14 days depending on the concentration. During the infection process, EPF can reduce blood feeding abilities in hematophagous arthropods such as mosquitoes, tsetse flies and ticks, which may subsequently impact the development and transmission of parasites. Here, we report on the effects of infection of tsetse fly (Glossina fuscipes fuscipes) by the EPF, Metarhizium anisopliae ICIPE 30 wild-type strain (WT) and green fluorescent protein-transformed strain (GZP-1) on the ability of the flies to harbor and transmit the parasite, Trypanosoma congolense. RESULTS: Teneral flies were fed T. congolense-infected blood for 2 h and then infected using velvet carpet fabric impregnated with conidia covered inside a cylindrical plastic tube for 12 h. Control flies were fed with T. congolense-infected blood but not exposed to the fungal treatment via the carpet fabric inside a cylindrical plastic tube. Insects were dissected at 2, 3, 5 and 7 days post-fungal exposure and the density of parasites quantified. Parasite load decreased from 8.7 × 107 at day 2 to between 8.3 × 104 and 1.3 × 105 T. congolense ml- 1 at day 3 post-fungal exposure in fungus-treated (WT and GZP-1) fly groups. When T. congolense-infected flies were exposed to either fungal strain, they did not transmit the parasite to mice whereas control treatment flies remained capable of parasite transmission. Furthermore, M. anisopliae-inoculated flies which fed on T. congolense-infected mice were not able to acquire the parasites at 4 days post-fungal exposure while parasite acquisition was observed in the control treatment during the same period. CONCLUSIONS: Infection of the vector G. f. fuscipes by the entomopathogenic fungus M. anisopliae negatively affected the multiplication of the parasite T. congolense in the fly and reduced the vectorial capacity to acquire or transmit the parasite.

Enhancing vector refractoriness to trypanosome infection: achievements, challenges and perspectives.

With the absence of effective prophylactic vaccines and drugs against African trypanosomosis, control of this group of zoonotic neglected tropical diseases depends the control of the tsetse fly vector. When applied in an area-wide insect pest management approach, the sterile insect technique (SIT) is effective in eliminating single tsetse species from isolated populations. The need to enhance the effectiveness of SIT led to the concept of investigating tsetse-trypanosome interactions by a consortium of researchers in a five-year (2013-2018) Coordinated Research Project (CRP) organized by the Joint Division of FAO/IAEA. The goal of this CRP was to elucidate tsetse-symbiome-pathogen molecular interactions to improve SIT and SIT-compatible interventions for trypanosomoses control by enhancing vector refractoriness. This would allow extension of SIT into areas with potential disease transmission. This paper highlights the CRP's major achievements and discusses the science-based perspectives for successful mitigation or eradication of African trypanosomosis.

Resolution of the Identity of 'Candidatus Liberibacter' Species From Huanglongbing-Affected Citrus in East Africa.

'Candidatus Liberibacter asiaticus', the bacterium associated with citrus Huanglongbing (HLB), was reported from Uganda and tentatively from Tanzania, posing a threat to citriculture in Africa. Two surveys of citrus expressing typical HLB symptoms were conducted in Uganda, Kenya, and Tanzania to verify reports of 'Ca. L. asiaticus' and to assess the overall threat of HLB to eastern and southern African citrus production. Samples were analyzed for the presence of 'Candidatus Liberibacter' species by real-time PCR and partial sequencing of three housekeeping genes, 16S rDNA, rplJ, and omp. 'Ca. L. africanus', the bacterium historically associated with HLB symptoms in Africa, was detected in several samples. However, samples positive in real-time PCR for 'Ca. L. asiaticus' were shown not to contain 'Ca. L. asiaticus' by sequencing. Sequences obtained from these samples were analogous to 'Ca. L. africanus subsp. clausenae', identified from an indigenous Rutaceae species in South Africa, and not to 'Ca. L. asiaticus'. Results indicate a nontarget amplification of the real-time assay and suggest that previous reports of 'Ca. L. asiaticus' from Uganda and Tanzania may be mis-identifications of 'Ca. L. africanus subsp. clausenae'. This subspecies was additionally detected in individual Diaphorina citri and Trioza erytreae specimens recovered from collection sites. This is the first report of 'Ca. L. africanus subsp. clausenae' infecting citrus and being associated with HLB symptoms in this host.

Plant volatiles influence the African weaver ant-cashew tree mutualism.

Plant volatiles influence virtually all forms of ant-plant symbioses. However, little is known about their role in the mutualistic relationship between the African weaver ant and the cashew tree. In this study, we tested the hypothesis that cashew tree volatiles from plant parts most vulnerable to herbivory viz. inflorescence, leaves, and fruits, are attractive to weaver ants. Using behavioral assays, we show that these volatiles attract weaver ants but without significant difference in preference for any of the odors. These same plant parts are associated with extra floral nectaries (EFNs') and therefore we evaluated the possibility that the ants associate the volatiles with food rewards. We found that perception of the odors was followed by a searching response that led the ants to non-volatile sugar rewards. More importantly, we observed that weaver ants spent significantly more time around the odor when it was paired to a reward. Chemical analysis of volatiles showed that the plant parts shared similarities in chemical composition, dominated by monoterpenes and sesquiterpenes. Additionally, we evaluated the attractiveness of a synthetic blend of three ocimene isomers ((E)-ß-ocimene, (Z)-ß-ocimene and allo-ocimene) identified in cashew leaf odor and shown to constitute a candidate kairomone for the cashew pest Pseudotheraptus wayi. We found that the attractiveness of the blend was dose dependent, and the response of the ants was not significantly different to that established with the crude volatiles from plant tissues. These results present new and interesting possibilities for improving weaver ant performance in cashew pest management.

Evaluating the mitochondrial genomic diversity, global distribution and niche overlap of two invasive Phthorimaea species.

This study sought to evaluate the genetic diversity of two invasive Phthorimaea species (Phthorimaea operculella Zeller and Phthorimaea absoluta Meyrick), and identify potential niche overlap of both species. The complete mitogenomes of P. operculella and P. absoluta were sequenced and compared. Furthermore, the diversity within the family Gelechiidae was assessed. Subsequently, two species distribution models (MaxEnt and BIOCLIM) were used to identify niche overlaps of both species globally. The complete mitogenomes of both species were similar in size and structure, with a pairwise identity of 92.3%. The models showed a niche overlap of both species and revealed areas of marginal to high suitability for both pests in countries where they have not been reported. Therefore, these results present a compelling case for a deeper genetic and ecological investigation of the Gelechiidae family for taxonomic harmonization, an early warning for surveillance, stricter phytosanitary considerations and preventive management against the spread of the pests.

Zoophytophagous predator sex pheromone and visual cues of opposing reflectance spectra lure predator and invasive prey.

INTRODUCTION: In sub-Saharan Africa, the invasive South American leafminer Phthorimaea absoluta is the most damaging tomato pest. Females of the pest can reproduce both sexually and through parthenogenesis and lay their eggs on all tomato plant parts. The mirid predator Nesidiocoris tenuis, a biological control agent for the pest, is also a tomato pest when prey population is low. To date, however, no study has developed an eco-friendly solution that targets both the predator and its host in a tomato farming system. OBJECTIVE: To develop a bio-based management system for both pest and predator based on the combined use of sexual communication in the predator and visual cues. METHODS: We collected volatiles from both sexes of the Kenyan population of the predator N. tenuis and identified candidate sex pheromone components by coupled gas chromatography-mass spectrometry (GC-MS). We used electrophysiological assays to identify antennally-active odorants in the volatiles, followed by field trials with different pheromone-baited colored traps to validate the responses of both predator and prey. Thereafter, we compared the reflectance spectra of the colored traps with those of different tomato plant tissues. RESULTS: Our results reveal an interplay between different sensory cues which in the predator-prey interaction may favor the predator. Antennae of both sexes of predator and prey detect the predator sex pheromone identified as 1-octanol and hexyl hexanoate. Unexpectedly, our field experiments led to the discovery of a lure for P. absoluta females, which were lured distinctly into a pheromone-baited trap whose reflectance spectrum mimicked that of ripe tomato fruit (long wavelength), an egg-laying site for females. Contrastingly, N. tenuis males were lured into baited white trap (short wavelength) when the predator is actively searching for prey. CONCLUSION: Our results demonstrate the novel use of a predator sex pheromone and different visual cues to assess complex trophic interactions on tomatoes.

Mitogenomic profiling and gut microbial analysis of the newly identified polystyrene-consuming lesser mealworm in Kenya.

Plastic waste has recently become a major global environmental concern and one of the biggest challenges has been seeking for alternative management options. Several studies have revealed the potential of several coleopteran species to degrade plastics, and this is the first research paper on plastic-degradation potential by lesser mealworms from Africa. This study evaluated the whole mitogenomic profile of the lesser mealworm to further identify the insect. The ability of the mealworm to consume Polystyrene (PS) was also evaluated alongside its associated gut microbiota diversity. Our results showed a complete circular mitochondrial genome which clustered closely to the Alphitobius genus but also suggested that our insect might be a new subspecies which require further identification. During the PS feeding trials, overall survival rates of the larvae decreased when fed a sole PS diet while PS intake was observed to increase over a 30-day period. The predominant bacteria observed in larvae fed PS diets were Kluyvera, Lactococcus, Klebsiella, Enterobacter, and Enterococcus, while Stenotrophomonas dominated the control diet. These findings demonstrated that the newly identified lesser mealworm can survive on a PS diet and has a consortium of important bacteria strongly associated with PS degradation. This work provides a better understanding of bioremediation applications, paving the way for further research into the metabolic pathways of plastic-degrading microbes and bringing hope to solving plastic waste pollution while providing high-value insect protein towards a circular economy.

Interactions between Bacillus thuringiensis and selected plant extracts for sustainable management of Phthorimaea absoluta.

Phthorimaea absoluta is a global constraint to tomato production and can cause up to 100% yield loss. Farmers heavily rely on synthetic pesticides to manage this pest. However, these pesticides are detrimental to human, animal, and environmental health. Therefore, exploring eco-friendly, sustainable Integrated Pest Management approaches, including biopesticides as potential alternatives, is of paramount importance. In this context, the present study (i) evaluated the efficacy of 10 Bacillus thuringiensis isolates, neem, garlic, and fenugreek; (ii) assessed the interactions between the most potent plant extracts and B. thuringiensis isolates, and (iii) evaluated the gut microbial diversity due to the treatments for the development of novel formulations against P. absoluta. Neem recorded the highest mortality of 93.79 ± 3.12% with an LT50 value of 1.21 ± 0.24 days, Bt HD263 induced 91.3 ± 3.68% mortality with LT50 of 2.63 ± 0.11 days, compared to both Bt 43 and fenugreek that caused < 50% mortality. Larval mortality was further enhanced to 99 ± 1.04% when Bt HD263 and neem were combined. Furthermore, the microbiome analyses showed that Klebsiella, Escherichia and Enterobacter had the highest abundance in all treatments with Klebsiella being the most abundant. In addition, a shift in the abundance of the bacterial genera due to the treatments was observed. Our findings showed that neem, garlic, and Bt HD263 could effectively control P. absoluta and be integrated into IPM programs after validation by field efficacy trials.

Biostimulant and antagonistic potential of endophytic fungi against fusarium wilt pathogen of tomato Fusarium oxysporum f. sp. lycopersici.

Endophytic fungal-based biopesticides are sustainable and ecologically-friendly biocontrol agents of several pests and diseases. However, their potential in managing tomato fusarium wilt disease (FWD) remains unexploited. This study therefore evaluated effectiveness of nine fungal isolates against tomato fusarium wilt pathogen, Fusarium oxysporum f. sp. lycopersici (FOL) in vitro using dual culture and co-culture assays. The efficacy of three potent endophytes that inhibited the pathogen in vitro was assessed against FWD incidence, severity, and ability to enhance growth and yield of tomatoes in planta. The ability of endophytically-colonized tomato (Solanum lycopersicum L.) plants to systemically defend themselves upon exposure to FOL were also assessed through defence genes expression using qPCR. In vitro assays showed that endophytes inhibited and suppressed FOL mycelial growth better than entomopathogenic fungi (EPF). Endophytes Trichoderma asperellum M2RT4, Hypocrea lixii F3ST1, Trichoderma harzianum KF2R41, and Trichoderma atroviride ICIPE 710 had the highest (68.84-99.61%) suppression and FOL radial growth inhibition rates compared to EPF which exhibited lowest (27.05-40.63%) inhibition rates. Endophytes T. asperellum M2RT4, H. lixii F3ST1 and T. harzianum KF2R41 colonized all tomato plant parts. During the in planta experiment, endophytically-colonized and FOL-infected tomato plants showed significant reduction of FWD incidence and severity compared to non-inoculated plants. In addition, these endophytes contributed to improved growth promotion parameters and yield. Moreover, there was significantly higher expression of tomato defence genes in T. asperellum M2RT4 colonized than in un-inoculated tomato plants. These findings demonstrated that H. lixii F3ST1 and T. asperellum M2RT4 are effective biocontrol agents against FWD and could sustainably mitigate tomato yield losses associated with fusarium wilt.

Maize edible-legumes intercropping systems for enhancing agrobiodiversity and belowground ecosystem services.

Intensification of staple crops through conventional agricultural practices with chemical synthetic inputs has yielded positive outcomes in food security but with negative environmental impacts. Ecological intensification using cropping systems such as maize edible-legume intercropping (MLI) systems has the potential to enhance soil health, agrobiodiversity and significantly influence crop productivity. However, mechanisms underlying enhancement of biological soil health have not been well studied. This study investigated the shifts in rhizospheric soil and maize-root microbiomes and associated soil physico-chemical parameters in MLI systems of smallholder farms in comparison to maize-monoculture cropping systems (MMC). Maize-root and rhizospheric soil samples were collected from twenty-five farms each conditioned by MLI and MMC systems in eastern Kenya. Soil characteristics were assessed using Black oxidation and Walkley methods. High-throughput amplicon sequencing was employed to analyze fungal and bacterial communities, predicting their functional roles and diversity. The different MLI systems significantly impacted soil and maize-root microbial communities, resulting in distinct microbe sets. Specific fungal and bacterial genera and species were mainly influenced and enriched in the MLI systems (e.g., Bionectria solani, Sarocladium zeae, Fusarium algeriense, and Acremonium persicinum for fungi, and Bradyrhizobium elkanii, Enterobacter roggenkampii, Pantoea dispersa and Mitsuaria chitosanitabida for bacteria), which contribute to nutrient solubilization, decomposition, carbon utilization, plant protection, bio-insecticides/fertilizer production, and nitrogen fixation. Conversely, the MMC systems enriched phytopathogenic microbial species like Sphingomonas leidyi and Alternaria argroxiphii. Each MLI system exhibited a unique composition of fungal and bacterial communities that shape belowground biodiversity, notably affecting soil attributes, plant well-being, disease control, and agroecological services. Indeed, soil physico-chemical properties, including pH, nitrogen, organic carbon, phosphorus, and potassium were enriched in MLI compared to MMC cropping systems. Thus, diversification of agroecosystems with MLI systems enhances soil properties and shifts rhizosphere and maize-root microbiome in favor of ecologically important microbial communities.

Effect of cooking methods on nutritional value and microbial safety of edible rhinoceros beetle grubs (Oryctes sp.).

Although edible rhinoceros beetle (Oryctes sp.) larvae are popularly consumed in many countries worldwide, they are prepared using different methods such as boiling, roasting, toasting, and deep-frying, whose effect on nutritional value and microbial safety is scarcely known. Here we investigated the effect of these methods on the nutritional value and microbial safety of Oryctes sp. larvae. Our hypothesis was that cooking the grubs using the four methods had no effect on their nutritional content and microbial loads and diversity. The grubs were analyzed for proximate composition, and fatty and amino acid profiles using standard chemical procedures; and microbial safety using standard culturing procedures. Deep-frying reduced protein and carbohydrate content, but elevated fat content. Boiling lowered ash content, but increased fibre and carbohydrate composition. Roasting and toasting increased protein and ash contents, respectively. Forty fatty acids were detected in the larvae, of which levels of only five were not significantly affected by cooking method, while the levels of the others were differentially affected by the different cooking methods. Amino acid profiles and levels were largely comparable across treatments, but lysine and arginine were higher in all cooked grubs than raw form. All the cooking methods eliminated Enterobacteriaceae, Shigella sp. and Campylobacter sp. from the grubs. Except boiling, all methods reduced total viable count to safe levels. Salmonella sp. were only eliminated by toasting and roasting; while boiling promoted growth of yeast and moulds. Staphylococcus aureus levels exceeded safety limits in all the cooking methods. These findings offer guidance on the type of method to use in preparing the grubs for desired nutritional and safety outcomes.

Pheromonal variation and mating between two mitotypes of fall armyworm (Spodoptera frugiperda) in Africa.

In the Americas, the fall armyworm (Spodoptera frugiperda) exists in two genetically distinct strains, the corn (C) and rice (R) strains. Despite their names, these strains are not associated with host plant preferences but have been shown to vary in pheromone composition and male responses. Recently, S. frugiperda was detected in Africa as an invasive species, but knowledge about variation in strain types, pheromone composition and inter-strain mating of populations of the pest in the continent has not been fully examined. Therefore, this study aimed to investigate variations, if any in the pheromone composition of female moths, male moth responses, and mating between C and R mitotypes of S. frugiperda populations in Kenya, as well as their geographic distribution. Strains (mitotypes) of S. frugiperda were identified using mitochondrial DNA (mtDNA) markers, and their pheromonal composition determined by coupled gas chromatography-mass spectrometric (GC-MS) analysis. Male moth responses to these compounds were evaluated using GC-electroantennographic detection (EAD), electroantennogram (EAG), and wind tunnel assays. Oviposition assays were used to determine whether R and C mitotype moths could mate and produce eggs. The results showed that both the R and C mitotypes were present, and there were no statistically significant differences in their distribution across all sampled locations. Five pheromone compounds including (Z)-7-dodecenyl acetate (Z7-12:OAc), (Z)-7-tetradecenyl acetate (Z7-14:OAc), (Z)-9-tetradecenyl acetate (Z9-14:OAc), (Z)-11-tetradecenyl acetate (Z11-14:OAc) and (Z)-11-hexadecenyl acetate (Z11-16:OAc), were detected in the pheromone glands of female moths of both mitotypes, with Z9-14:OAc being the most abundant. The relative percentage composition of Z9-14:OAc was similar in both mitotypes. However, the R mitotype had a 2.7 times higher relative percentage composition of Z7-12:OAc compared to the C mitotype moth, while the C mitotype moth had a 2.4 times higher relative percentage composition of Z11-16:OAc than the R mitotype moth. Male moths of both mitotypes exhibited similar responses to the pheromone compounds, showing the strongest responses to Z9-14:OAc and Z7-12:OAc in electrophysiological and behavioural assays. There was mating between R and C mitotypes with egg production comparable to mating within the same mitotype. Our results revealed that differences between the two S. frugiperda mitotypes are characterized by female moth pheromone composition rather than male moth responses to the pheromones, and that this does not prevent hybridisation between the mitotypes, which may have implications for their management.

Biochemistry and transcriptomic analyses of Phthorimaea absoluta (Lepidoptera: Gelechiidae) response to insecticides.

Phthorimaea absoluta is an invasive solanaceous plant pest with highly devastating effects on tomato plant. Heavy reliance on insecticide use to tackle the pest has been linked to insecticide resistance selection in P. absoluta populations. To underline insights on P. absoluta insecticide resistance mechanisms to diamides and avermectins, we evaluated the transcriptomic profile of parental (field-collected) and F8 (lab-reared) populations. Furthermore, to screen for the presence of organophosphate and pyrethroid resistance, we assessed the gene expression levels of acetylcholinesterase (ace1) and para-type voltage-gated sodium channel (VGSG) genes in the F1 to F8 lab-reared progeny of diamide and avermectin exposed P. absoluta field-collected populations. The VGSG gene showed up-regulation in 12.5% and down-regulation in 87.5% of the screened populations, while ace1 gene showed up-regulation in 37.5% and down-regulation in 62.5% of the screened populations. Gene ontology of the differentially expressed genes from both parental and eighth generations of diamide-sprayed P. absoluta populations revealed three genes involved in the metabolic detoxification of diamides in P. absoluta. Therefore, our study showed that the detoxification enzymes found could be responsible for P. absoluta diamide-based resistance, while behavioural resistance, which is stimulus-dependent, could be attributed to P. absoluta avermectin resistance.