scholarly journals Cassava brown streak virus has a rapidly evolving genome: implications for virus speciation, variability, diagnosis and host resistance

2016 ◽  
Author(s):  
Titus Alicai ◽  
Joseph Ndunguru ◽  
Peter Sseruwagi ◽  
Fred Tairo ◽  
Geoffrey Okao-Okuja ◽  
...  
Keyword(s):  
Synonymous Substitution ◽  
Eastern Africa ◽  
Streak Virus ◽  
Yield Losses ◽  
Entire Genome ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
The Tropics ◽  
Ngs Data ◽  
Brown Streak

AbstractCassava is a major staple food for about 800 million people in the tropics and subGtropical regions of the world. Production of cassava is significantly hampered by cassava brown streak disease (CBSD), which is caused by Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). The disease is suppressing cassava yields in eastern Africa at an alarming rate. Previous studies have documented that CBSV is more devastating than UCBSV because it more readily infects both susceptible and tolerant cassava cultivars, resulting in greater yield losses. Using whole genome sequences from NGS data, we produced the first coalescentGbased species tree estimate for CBSV and UCBSV. This species framework led to the finding that CBSV has a faster rate of evolution when compared with UCBSV. Furthermore, we have discovered that in CBSV, nonsynonymous substitutions are more predominant than synonymous substitution and occur across the entire genome. All comparative analyses between CBSV and UCBSV presented here suggest that CBSV may be outsmarting the cassava immune system, thus making it more devastating and harder to control.

scholarly journals Differential Tropism in Roots and Shoots of Resistant and Susceptible Cassava (Manihot esculenta Crantz) Infected by Cassava Brown Streak Viruses

Cells ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 1221
Author(s):  
Samar Sheat ◽  
Paolo Margaria ◽  
Stephan Winter
Keyword(s):  
Virus Replication ◽  
Central Africa ◽  
Streak Virus ◽  
Virus Infections ◽  
Long Distance ◽  
Manihot Esculenta Crantz ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Long Distance Movement ◽  
Brown Streak

Cassava brown streak disease (CBSD) is a destructive disease of cassava in Eastern and Central Africa. Because there was no source of resistance in African varieties to provide complete protection against the viruses causing the disease, we searched in South American germplasm and identified cassava lines that did not become infected with the cassava brown streak viruses. These findings motivated further investigations into the mechanism of virus resistance. We used RNAscope® in situ hybridization to localize cassava brown streak virus in cassava germplasm lines that were highly resistant (DSC 167, immune) or that restricted virus infections to stems and roots only (DSC 260). We show that the resistance in those lines is not a restriction of long-distance movement but due to preventing virus unloading from the phloem into parenchyma cells for replication, thus restricting the virus to the phloem cells only. When DSC 167 and DSC 260 were compared for virus invasion, only a low CBSV signal was found in phloem tissue of DSC 167, indicating that there is no replication in this host, while the presence of intense hybridization signals in the phloem of DSC 260 provided evidence for virus replication in companion cells. In neither of the two lines studied was there evidence of virus replication outside the phloem tissues. Thus, we conclude that in resistant cassava lines, CBSV is confined to the phloem tissues only, in which virus replication can still take place or is arrested.

Expansion of the cassava brown streak disease epidemic in eastern Democratic Republic of Congo

Plant Disease ◽  
2020 ◽  
Author(s):  
Clérisse Mubasi Casinga ◽  
Rudolph R Shirima ◽  
N M Mahungu ◽  
W Tata-Hangy ◽  
Kalinga Benoit Bashizi ◽  
...  
Keyword(s):  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Smallholder Farmers ◽  
Central Africa ◽  
Virus Detection ◽  
Streak Virus ◽  
Republic Of Congo ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Brown Streak

Cassava plays a key role in assuring food security and generating income for smallholder farmers throughout central Africa, and particularly in the Democratic Republic of Congo (DRC). This status is threatened, however, by cassava brown streak disease (CBSD) which has recently expanded its incidence and range in eastern DRC. The study described here, comprises the first extensive assessment of temporal change in occurrence of CBSD and its causal viruses in DRC, based on surveys conducted during 2016 and 2018. Cassava fields were inspected in Ituri, Nord-Kivu, Sud-Kivu, Tanganyika and Haut-Katanga provinces within eastern DRC, to record foliar incidence and severity of CBSD. Leaf samples were collected for virus detection and species-level identification. New occurrences of CBSD, confirmed by virus diagnostic tests, were recorded in two provinces (Haut-Katanga and Sud-Kivu) and nine previously unaffected territories, covering an area of > 62,000 km2, and at up to 900 km from locations of previously published reports of CBSD in DRC. Overall, average CBSD incidence within fields was 13.2% in 2016 and 16.1% in 2018. In the new spread zone of Haut-Katanga, incidence increased from 1.7% to 15.9%. CBSD is now present in provinces covering 321,000 km2 which is approximately 14% of the total area of DRC. This represents a major expansion of the CBSD epidemic, which was only recorded from one province (Nord-Kivu) in 2012. Both cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) were detected in Ituri, Nord-Kivu and Sud-Kivu, but only CBSV was detected in Haut-Katanga. Considered overall, these results confirm the increasing threat that CBSD poses to cassava production in DRC and describe an important expansion in the African pandemic of CBSD.

scholarly journals Characterising Genetic Diversity in Cassava Brown Streak Virus

2018 ◽  
Author(s):  
Stephen M Crotty ◽  
Adam B Rohrlach ◽  
Joseph Ndunguru ◽  
Laura M Boykin
Keyword(s):  
Multiple Correspondence Analysis ◽  
Management Strategies ◽  
Plant Viruses ◽  
Streak Virus ◽  
New Developments ◽  
Flying Insects ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Difficult Challenge ◽  
Brown Streak

AbstractPlant viruses represent a significant threat to food security for many global populations. Cassava Brown Streak Virus (CBSV) causes immense damage to cassava crops in Eastern, Central and Southern Africa. The eradication of CBSV is a difficult challenge, as it has been shown to be fast-evolving and it is transmitted by flying insects that are ubiquitous in cassava growing regions. In this paper we demonstrate the ability of two new developments in bioinformatics that can be used to increase our understanding of CBSV and ultimately inform strategies for its combat. We reconstruct the phylogeny of 29 whole-genome virus isolates using the GHOST model. This phylogeny identifies three distinct clades among the viruses and highlights a section of the genomes that is highly influential in their divergence. We also perform Multiple Correspondence Analysis on the alignment which is consistent in recovering the three clades, and offers insight on the significance of the influence of a variety of external variables on the evolution of the viruses. Knowledge and information from this analysis will be used as a base on which to formulate sustainable Cassava Brown Streak Disease (CBSD) management strategies in Africa.

scholarly journals Widespread Occurrence and Diversity of Cassava brown streak virus (Potyviridae: Ipomovirus) in Tanzania

2011 ◽  
Vol 101 (10) ◽  
pp. 1159-1167 ◽  
Author(s):  
G. M. Rwegasira ◽  
G. Momanyi ◽  
M. E. C. Rey ◽  
G. Kahwa ◽  
J. P. Legg
Keyword(s):  
Sea Level ◽  
Sequence Divergence ◽  
Streak Virus ◽  
Widespread Occurrence ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Polymerase Chain ◽  
Information Database ◽  
Leaf Symptoms ◽  
Brown Streak

Cassava brown streak disease (CBSD) has been a problem in Tanzania since 1936. Existing literature indicated limited distribution of the disease to low altitudes, usually <100 m above sea level, but the current geographical distribution of the disease was not known. Whether a single or many strains for the virus exist in Tanzania had not been reported to date. In this study, CBSD was recorded from sea level to ≈1,800 m above sea level. In total, 2,730 cassava plants were assessed for CBSD leaf symptoms in 91 fields and root symptoms were assessed at 81 sites. A sample was taken from each site for laboratory screening for Cassava brown streak virus (CBSV). CBSD mean foliar and root incidences were 38 and 36%, respectively. Reverse-transcription polymerase chain reaction of a partial 3′-terminal coat protein (CP) region of CBSV indicated the presence of CBSV in 67 of the 91 (73%) samples. Forty-three amplicons were sequenced, and phylogenetic comparisons with nucleotide sequences from GenBank (National Center for Biotechnology Information database) suggested that one major clade of CBSV primarily exists in Tanzania. However, there was nucleotide sequence divergence of up to 19% among the 42 isolates. In all, 42 of the 43 sequences had 80 to 100% nucleotide identity with 6 previously reported CP-CBSV sequences (from Mozambique and Tanzania). In total, 13 of 42 isolates had <80% nucleotide identities with three previously reported Ugandan CBSV sequences. One isolate, FJ687177, shared <78% sequence identity with the other Tanzanian sequences but was closely related (93%) to Ugandan isolates. It is likely that isolate FJ687177 may belong to a less widely distributed recently described species (clade 2) of CBSV, named Ugandan cassava brown streak virus (UCBSV).

scholarly journals Re-emergence of Cassava Brown Streak Disease in Uganda

Plant Disease ◽  
2007 ◽  
Vol 91 (1) ◽  
pp. 24-29 ◽  
Author(s):  
T. Alicai ◽  
C. A. Omongo ◽  
M. N. Maruthi ◽  
R. J. Hillocks ◽  
Y. Baguma ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Identity ◽  
Cassava Mosaic Disease ◽  
Streak Virus ◽  
Sequence Comparisons ◽  
Acid Identity ◽  
Cp Gene ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Brown Streak

During November 2004, veinal chlorosis on mature cassava leaves, typical of cassava brown streak disease (CBSD), was observed at Mukono in central Uganda. Five out of 11 cultivars at the site showed CBSD symptoms (incidence range 4 to 64%). In a survey of farmers' fields, CBSD was observed in Wakiso and Mukono districts. Incidence of cassava mosaic disease was also recorded and averaged 60% for landraces (range 16.7 to 100%) and 20% for resistant varieties (range 0 to 65%). Leaf samples of plants with CBSD symptoms produced an amplicon of 222 bp using reverse transcription-polymerase chain reaction with primers that amplify a fragment of the coat protein (CP) gene of Cassava brown streak virus. Sequence comparisons based on the amplified CP gene fragment indicated that the isolates have 77 to 82.9% nucleotide and 43.9 to 56.8% amino acid identity with those from Mozambique and Tanzania. There was 95.9 to 99.5% nucleotide and 85.1 to 90.5% amino acid identity among the Ugandan isolates. These results confirm the re-emergence of CBSD in Uganda after it was first observed in the 1930s in cassava introduced from Tanzania and controlled by eradication. Prior to this report, CBSD was known to be restricted to the coastal lowlands of East Africa.

scholarly journals Cassava Brown Streak Disease and Ugandan cassava brown streak virus Reported for the First Time in Zambia

Plant Disease ◽  
2018 ◽  
Vol 102 (7) ◽  
pp. 1410-1418 ◽  
Author(s):  
Rabson M. Mulenga ◽  
Laura M. Boykin ◽  
Patrick C. Chikoti ◽  
Suwilanji Sichilima ◽  
Dickson Ng’uni ◽  
...  
Keyword(s):  
Rating Scale ◽  
Streak Virus ◽  
Sequence Variant ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Polymerase Chain ◽  
Species Specific ◽  
First Time ◽  
Virus Isolates ◽  
Brown Streak

A diagnostic survey was conducted in July 2017 in two northern districts of Zambia to investigate presence or absence of cassava brown streak disease (CBSD) and its causal viruses. In total, 29 cassava fields were surveyed and cassava leaf samples were collected from 116 plants (92 symptomatic and 24 nonsymptomatic). CBSD prevalence was approximately 79% (23 of 29) across fields. Mean CBSD incidence varied across fields but averaged 32.3% while mean disease severity was 2.3 on a 1-to-5 rating scale. Reverse-transcription polymerase chain reaction screening of all 116 samples with one generic and two species-specific primer pairs yielded DNA bands of the expected sizes from all symptomatic plants with the generic (785 bp) and Ugandan cassava brown streak virus (UCBSV)-specific (440 bp) primers. All 24 nonsymptomatic samples were negative for UCBSV and all samples tested negative with primers targeting Cassava brown streak virus. The complete genome of a representative isolate of UCBSV (WP282) was determined to be 9,050 nucleotides in length, minus the poly A tail. A comparative analysis of this isolate with global virus isolates revealed its nature as a sequence variant of UCBSV sharing 94 and 96% maximum complete polyprotein nucleotide and amino acid identities, respectively, with isolates from Malawi (MF379362) and Tanzania (FJ039520). This is the first report of CBSD and UCBSV in Zambia, thus expanding the geographical distribution of the disease and its causal virus and further reinforcing the need to strengthen national and regional phytosanitary programs in Africa.

scholarly journals PAL1 gene of the phenylpropanoid pathway increases resistance to the Cassava brown streak virus in cassava

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Siji Kavil ◽  
Gerald Otti ◽  
Sophie Bouvaine ◽  
Andrew Armitage ◽  
Midatharahally N. Maruthi
Keyword(s):  
Phenylpropanoid Pathway ◽  
Streak Virus ◽  
Rna Seq ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Chalcone Synthase Genes ◽  
Increased Susceptibility ◽  
Cassava Varieties ◽  
Brown Streak

Abstract 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.

scholarly journals Farmer and Field Survey in Cassava-Growing Districts of Rwanda Reveals Key Factors Associated With Cassava Brown Streak Disease Incidence and Cassava Productivity

2021 ◽  
Vol 5 ◽  
Author(s):  
Chantal Nyirakanani ◽  
Jean Pierre Bizimana ◽  
Yves Kwibuka ◽  
Athanase Nduwumuremyi ◽  
Vincent de Paul Bigirimana ◽  
...  
Keyword(s):  
Yield Potential ◽  
Viral Diseases ◽  
Streak Virus ◽  
Factors Associated ◽  
Cassava Brown Streak Virus ◽  
Cassava Brown Streak Disease ◽  
Cassava Production ◽  
Seed System ◽  
The Impact ◽  
Brown Streak

Cassava (Manihot esculenta Crantz) is a vital crop in Rwanda where it ranks as the third most consumed staple. However, cassava productivity remains below its yield potential due to several constraints, including important viral diseases, such as cassava brown streak disease (CBSD). Because various factors can be addressed to mitigate the impact of viral diseases, it is essential to identify routes of virus contamination in the cassava agrosystems from the seed system to farmer's practices and knowledge. The present study aimed at (1) assessing the current cassava seed system and farmers' practices and their knowledge of the biotic constraints to cassava production, (2) determining the status of CBSD as well as critical factors associated with its spread through the seed system channels, and (3) determining factors that influence cassava productivity in Rwanda. A cross-sectional study was carried out from May to September 2019 in 13 districts of Rwanda. A total of 130 farmers and cassava fields were visited, and the incidence and severity of CBSD were evaluated. CBSD was detected in all cassava-producing districts. The highest field incidence of CBSD was recorded in the Nyanza district (62%; 95% CI = 56–67%) followed by the Bugesera district (60%; 95% CI = 54–65%), which recorded the highest severity score of 3.0 ± 0.6. RT-PCR revealed the presence of CBSD at the rate of 35.3%. Ugandan cassava brown streak virus was predominant (21.5%) although cassava brown streak virus was 4% and mixed infection was 10%. An informal cassava seed system was dominant among individual farmers, whereas most cooperatives used quality seeds. Cassava production was found to be significantly influenced by the use of fertilizer, size of the land, farming system, cassava viral disease, and type of cassava varieties grown (p &lt; 0.001). Disease management measures were practiced by a half of participants only. Factors found to be significantly associated with CBSD infection (p &lt; 0.05) were the source of cuttings, proximity to borders, age of cassava, and knowledge of CBSD transmission and management.

scholarly journals Screening for Resistance in Farmer-Preferred Cassava Cultivars from Ghana to a Mixed Infection of CBSV and UCBSV

Plants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 1026
Author(s):  
Wilfred Elegba ◽  
Wilhelm Gruissem ◽  
Hervé Vanderschuren
Keyword(s):  
Mixed Infection ◽  
Effective Control ◽  
Streak Virus ◽  
Storage Roots ◽  
Cassava Brown Streak Virus ◽  
Screening For Resistance ◽  
Cassava Brown Streak Disease ◽  
Cassava Production ◽  
Control And Management ◽  
Brown Streak

Cassava brown streak disease (CBSD) caused by the Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) is a threat to cassava production in Africa. The potential spread of CBSD into West Africa is a cause for concern, therefore screening for resistance in farmer-preferred genotypes is crucial for effective control and management. We multiplied a selection of eleven cassava cultivars grown by farmers in Ghana to test their response to a mixed infection of CBSV (TAZ-DES-01) and UCBSV (TAZ-DES-02) isolates using a stringent top-cleft graft inoculation method. Virus titers were quantified in the inoculated scions and cuttings propagated from the inoculated scions to assess virus accumulation and recovery. All cultivars were susceptible to the mixed infection although their response and symptom development varied. In the propagated infected scions, CBSV accumulated at higher titers in leaves of eight of the eleven cultivars. Visual scoring of storage roots from six-month-old virus-inoculated plants revealed the absence of CBSD-associated necrosis symptoms and detectable titers of CBSVs in the cultivar, IFAD. Although all eleven cultivars supported the replication of CBSV and UCBSV in their leaves, the absence of virus replication and CBSD-associated symptoms in the roots of some cultivars could be used as criteria to rapidly advance durable CBSD tolerance using breeding and genetic engineering approaches.

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