15 research outputs found
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Identification of whitefly (Bemisia tabaci) proteins interacting with Tomato leaf curl Bangalore virus coat protein gene using Y2H system
Tomato leaf curl Bangalore virus (ToLCBV) (Geminiviridae) causes the economically important tomato leaf curl virus disease (ToLCVD), and is transmitted by the whitefy, Bemisia tabaci (Gennadius) (Aleyrodidae: Hemiptera). Successful transmission of the virus by the insect requires safe translocation of the virus through diferent barriers inside the vector. During the translocation, the viral coat protein will interact with many whitefy proteins, while a few of them are benefcial to virus (e.g. heat shock proteins) but some may be harmful (e.g. whitefy immune proteins). We carried out the yeast two hybrid (Y2H) assays to identify the proteins of the B.tabaci Asia 1 genetic group interacting with ToLCBV coat protein (CP). The Y2H assay initially identifed a total of 425 putative interacting whitefy proteins on a low stringent selection media, and they were reduced to 324 when the yeast colonies were grown on a high stringent media, and of which about 274 colonies produced single bands in colony PCR experiments while the remaining colonies produced multiple bands. Further, high selection pressure assays confrmed a total of 102 whitefy proteins interacting with ToLCBV CP and these included the heat shock proteins (HSPs) 70 kDa, GroEL, nucleoproteins, vitellogenins, apolipophorins, 40 s ribosomal proteins, sorbitol dehydrogenase, dipeptidyl peptidase, E3 ubiquitin, annexin, GTP cyclohydrolase, tropomyosin, salivary secreted proteins, succinate dehydrogenase, lachesins, enolase and others. The identifed proteins could be potential targets for novel whitefy control strategies such as using RNAi or insecticide target sites for developing future disease and whitefy control strategies
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PAL1 gene of the phenylpropanoid pathway increases resistance to the Cassava brown streak virus in cassava
Background: The phenylalanine ammonia lyase genes play crucial role in plant response to biotic and abiotic stresses. In this study, we characterized the role of PAL genes in increasing resistance to the Cassava brown streak virus that causes the economically important cassava brown streak disease (CBSD) on cassava in Africa. Methods: The whole transcriptomes of eight cassava varieties differing in resistance to CBSD were obtained at 1, 5 and 8 weeks after CBSV infection. Results: Analysis of RNA-Seq data identified the overexpression of PAL1, PAL2, cinnamic acid and two chalcone synthase genes in CBSD-resistant cassava varieties, which was subsequently confirmed by RT-qPCR. The exogenous application of Acibenzolar-S-Methyl induced PAL1 gene expression to enhance resistance in the susceptible var. Kalawe. In contrast, the silencing of PAL1 by RNA interference led to increased susceptibility of the resistant var. Kaleso to CBSD. Conclusions: PAL1 gene of the phenylpropanoid pathway has a major role in inducing resistance to CBSD in cassava plants and its early induction is key for CBSD resistance
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Endemism and reemergence potential of the ipomovirus Sweet potato mild mottle virus (family Potyviridae) in Eastern Africa: half a century of mystery
Viruses have the ability to frequently colonize new hosts and ecological niches because of their inherently high genetic and evolutionary plasticity. However, a virus may emerge and remain of no or less economic importance until changes in viral and/or environmental factors dictate its epidemiological status. An example is sweet potato mild mottle virus (SPMMV), which was first reported in the 1970s on sweetpotatoes in eastern Africa, has remained endemic in the region and poorly understood, yet accounting for 60-95% losses especially in mixed infections. Unlike other sweetpotato viruses which have a global incidence, SPMMV has never been confirmed outside eastern Africa. This implicates the region as its center of origin, but does not fully account for SPMMVâs exclusive geographic delimitation to eastern Africa. Despite its importance, several mysteries and research gaps surround SPMMV, which decelerate efforts for effective virus disease management in sweetpotato. The aim of this review is to articulate research gaps, propose pivotal scientific directions and stimulate knowledge generation for better management of virus diseases in sweetpotato. Vector-mediated transmission of SPMMV remains enigmatic. Here we postulate testable hypotheses to explain SPMMV transmission. Comparisons between SPMMV and cassava brown streak ipomoviruses demonstrate epidemiological âhallmarksâ for monitoring SPMMV. Evolutionary forces on SPMMV coupled with the virusâ broad host range imply a âsilent build upâ of better fit variants in a changing climate, and this could explode into a worse disease conundrum. These information gaps need urgent filling to ease future management of virus disease emergences in sweetpotato
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Adaptability and phenotypic stability of resistance to two viral diseases and yields traits in Cassava
Cassava productivity is hampered by pests and diseases including cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The main objective of this study was to identify stable superior genotypes that combine disease re-sistance and high yield. Sixteen cassava genotypes were planted in a randomized complete block design with three replications for six planting seasons (years) at five sites in Tanzania. The genotypes were assessed using the additive main effect and multiplicative interaction (AMMI) analysis, and highly significant
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Microbiome diversity and composition in Bemisia tabaci SSA1-SG1 whitefly are influenced by their hostâs life stage
Within the Bemisia tabaci group of cryptic whitefly species, many are damaging agricultural pests and plant-virus vectors, conferring upon this group the status of one of the worldâs top 100 most invasive and damaging âspeciesâ that affect farmersâ income and livelihoods. Studies on the microbiome of whitefly life stages are scarce, although their composition and diversity greatly influence whitefly fitness and development. We used high-throughput sequencing to understand microbiome diversity in different developmental stages of the B. tabaci sub-Saharan Africa 1 (SSA1-SG1) species of the whitefly from Uganda. Endosymbionts (Portiera, Arsenophonus, Wolbachia and Hemipteriphilus were detected but excluded from the further statistical analysis as they were not influenced by life stage using( Permutational Multivariate Analysis of Variance Using Distance Matrices, (ADONIS, p= 0.925 and Bray, p = 0.903). Our results showed significant differences in the microbiome composition in different life stages of SSA1-SG1. The diversity was significantly higher in eggs (Shannon, p = 0.024; Simpson, p = 0.047) than that in nymphs and pupae, while the number of microbial species observed by the amplicon sequence variant (ASV) was not significant (n(ASV), p = 0.094). At the phylum and genus levels, the dominant constituents in the microbiome changed significantly at different developmental stages, with Halomonas being an egg-associated genus while Bacillus and Caldalkalibacillus were common in all life stages. These findings provide the first description of differing microbiome diversity in the life stage of whiteflies, suggesting their putative role in whitefly development
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Impact of viral diseases and whiteflies on the yield and quality of cassava
Here we investigated the effect of the insect pest whitefly (Bemisia tabaci), cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) on cassava root yield and quality in two cropping seasons 2014â2015 and 2015â2016 on ten cassava
varieties in Tanzania. ANOVA (sum of squares or SS) revealed that the time of planting (42.7%) and cassava variety (29.5%) had the largest effect on whitefly population. Not surprisingly, cassava varieties also had the highest effect (SS 39.8 to 70.4%) on both diseases and yield. An increase in whitefly population led to higher disease incidences and severity in 2015â2016 compared to 2014â2015. Some CBSD-resistant and tolerant cassava varieties like Namikonga and Kiroba, respectively, harboured high whitefly populations. The CMD, CBSD and whitefly-susceptible variety, Mreteta, showed highest yield losses of up to 60%, while the resistant variety NDL 2005/1471 had approximately 1% loss. Deployment of varieties resistant to both diseases and whitefly is thus necessary to safeguard cassava production and food security of vulnerable communities in the affected African countries
The process and lessons of exchanging and managing in-vitro elite germplasm to combat CBSD and CMD in Eastern and Southern Africa
Varieties with resistance to both cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) can reverse food and income security threats affecting the rural poor in Eastern and Southern Africa. The International Institute of Tropical Agriculture is leading a partnership of five national (Malawi, Mozambique, Kenya, Tanzania and Uganda) cassava breeding programs to exchange the most elite germplasm resistant to both CMD and CBSD. This poster documents the process and the key learning lessons. Twenty to 25 stem cuttings of 31 clones comprising of 25 elite clones (5 per country), two standard checks (Kibandameno from Kenya and Albert from Tanzania), and four national checks (Kiroba and Mkombozi from Tanzania, Mbundumali from Malawi, and Tomo from Mozambique) were cleaned and indexed for cassava viruses at both the Natural Resources Institute in the United Kingdom and Kenya Plant Health Inspectorate Services, in Kenya. About 75 in-vitro plantlets per clone were sent to Genetic Technologies International Limited, a private tissue culture lab in Kenya, and micro-propagated to â„1500 plantlets. Formal procedures of material transfer between countries including agreements, import permission and phytosanitary certification were all ensured for germplasm exchange. At least 300 plantlets of each elite and standard check clones were sent to all partner countries, while the national checks were only sent to their respective countries of origin. In each country, the in-vitro plantlets were acclimatized under screen house conditions and transplanted for field multiplication as a basis for multi-site testing. Except for Tomo, a susceptible clone, all the clones were cleaned of the viruses. However, there was varied response to the cleaning process between clones, e.g. FN-19NL, NASE1 and Kibandameno responded slowly. Also, clones responded differently to micro-propagation protocols at GTIL, e.g. Pwani, Tajirika, NASE1, TME204 and Okhumelela responded slowly. Materials are currently being bulked at low disease pressure field sites in preparation for planting at 5-8 evaluation sites per country. The process of cleaning, tissue culture mass propagation, exchange and local hardening off/bulking has been successful for the majority of target varieties. Two key lessons derived from the process are that adequate preparations of infrastructure and trained personnel are required to manage the task, and that a small proportion of varieties are recalcitrant to tissue culture propagation
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Identifying putative resistance genes for barley yellow dwarf virusâPAV in wheat and barley
Barley yellow dwarf viruses (BYDVs) are one of the most widespread and economically important plant viruses affecting many cereal crops. Growing resistant varieties remains the most promising approach to reduce the impact of BYDVs. A Recent RNA sequencing analysis has revealed potential genes that respond to BYDV infection in resistant barley genotypes. Together with a comprehensive review of the current knowledge on disease resistance in plants, we selected nine putative barley and wheat genes to investigate their involvement in resistance to BYDVâPAV infection. The target classes of genes were (i) nucleotide binding site (NBS) leucineârich repeat (LRR), (ii) coiledâcoil nucleotideâbinding leucineârich repeat (CCâNBâLRR), (iii) LRR receptorâlike kinase (RLK), (iv) casein kinase, (v) protein kinase, (vi) protein phosphatase subunits and the transcription factors (TF) (vii) MYB TF, (viii) GRAS (gibberellic acidâinsensitive (GAI), repressor of GAI (RGA) and scarecrow (SCR)), and (ix) the MADSâbox TF family. Expression of genes was analysed for six genotypes with different levels of resistance. As in previous reports, the highest BYDVâPAV titre was found in the susceptible genotypes Graciosa in barley and Semper and SGS 27â02 in wheat, which contrast with the resistant genotypes PRSâ3628 and Wysor of wheat and barley, respectively. Statistically significant changes in wheat show upâregulation of NBSâLRR, CCâNBSâLRR and RLK in the susceptible genotypes and downâregulation in the resistant genotypes in response to BYDVâPAV. Similar upâregulation of NBSâLRR, CCâNBSâLRR, RLK and MYB TF in response to BYDVâPAV was also observed in the susceptible barley genotypes. However, no significant changes in the expression of these genes were generally observed in the resistant barley genotypes, except for the downâregulation of RLK. Casein kinase and Protein phosphatase were upâregulated early, 10 days after inoculation (dai) in the susceptible wheat genotypes, while the latter was downâregulated at 30 dai in resistant genotypes. Protein kinase was downâregulated both earlier (10 dai) and later (30 dai) in the susceptible wheat genotypes, but only in the later dai in the resistant genotypes. In contrast, GRAS TF and MYB TF were upâregulated in the susceptible wheat genotypes while no significant differences in MADS TF expression was observed. Protein kinase, Casein kinase (30 dai), MYB TF and GRAS TF (10 dai) were all upâregulated in the susceptible barley genotypes. However, no significant differences were found between the resistant and susceptible barley genotypes for the Protein phosphatase and MADS FT genes. Overall, our results showed a clear differentiation of gene expression patterns in both resistant and susceptible genotypes of wheat and barley. Therefore, further research on RLK, NBSâLRR, CCâNBSâLRR, GRAS TF and MYB TF can lead to BYDVâPAV resistance in cereals
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Effect of aphid biology and morphology on plant virus transmission
Aphids severely affect crop production by transmitting many plant viruses. Viruses are obligate intracellular pathogens mostly depend on vectors for their transmission and survival. Majority of economically important plant viruses are transmitted by aphids. They transmit viruses either persistently (circulative or non-circulative) or non-persistently. Plant virus transmission by insects is a process evolved over time and strongly influenced by insect morphological features and biology. Over the past century, large body of research has provided detailed knowledge of the molecular process underlying virus- vector interactions. In this review, we discuss how aphid biology and morphology can affect plant virus transmission
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Microbiome diversity and reproductive incompatibility induced by the prevalent endosymbiont Arsenophonus in two species of African cassava Bemisia tabaci whiteflies
A minimum of thirteen diverse whitefly species belonging to the Bemisia tabaci (B. tabaci) species complex are known to infest cassava crops in sub-Saharan Africa (SSA), designated as SSA1-13. Of these, the SSA1 and SSA2 are the predominant species colonising cassava crops in East Africa. The SSA species of B. tabaci harbour diverse bacterial endosymbionts, many of which are known to manipulate insect reproduction. One such symbiont, Arsenophonus is known to drive its spread by inducing reproductive incompatibility in its insect host and are abundant in SSA species of B. tabaci. However, whether Arsenophonus affects the reproduction of SSA species is unknown. In this study, we investigated both the reproductive compatibility between Arsenophonus infected and uninfected whiteflies by inter/intra-specific crossing experiments involving the sub-group 3 haplotypes of the SSA1 (SSA1-SG3), SSA2 species, and their microbial diversity. The number of eggs, nymphs, progenies produced, hatching rate, survival rate were recorded for each cross. In intra-specific crossing trials, both male and female progenies were produced and thus demonstrated no reproductive incompatibility. However, the total number of eggs laid, nymphs hatched, and the emerged females were low in the intraspecies crosses of SSA1-SG3A+, indicating the negative effect of Arsenophonus on whitefly fitness. In contrast, the inter-species crosses between the SSA1-SG3 and SSA2 produced no female progeny and thus demonstrated reproductive incompatibility. The relative frequency of other bacteria colonising the whiteflies was also investigated using Illumina sequencing of 16S rDNA and diversity indices were recorded. Overall, SSA1-SG3 and SSA2 harboured high microbial diversity with more than 137 bacteria discovered. These results described for the first time the microbiome diversity and the reproductive behaviours of intra/inter species of Arsenophonus in whitefly reproduction which is crucial for understanding the invasion abilities of cassava whiteflies