scholarly journals Response to Cassava Brown Streak Disease Infections in Local and Improved Cassava Genotypes under Field and Greenhouse Assays in Lower Eastern Kenya

2018 ◽  
pp. 1-14
Author(s):  
I. N. Koima ◽  
C. O. Orek
Keyword(s):  
Field Experiment ◽  
Disease Incidence ◽  
Graft Infection ◽  
Rt Pcr ◽  
Local Varieties ◽  
Root Necrosis ◽  
Cassava Brown Streak Disease ◽  
Cassava Production ◽  
Greenhouse Assay ◽  
Brown Streak

Cassava brown streak disease (CBSD) is caused by two cassava brown streak viruses (CBSVs) transmitted by whiteflies (Bemisia tabaci). CBSD significantly inhibits cassava production in Kenya through losses of up to 100% in farmer-preferred but susceptible varieties. As a management strategy, the present study evaluated the effect of CBSD on two local varieties (Thika-5 & Serere) and 15 improved genotypes in lower Eastern Kenya. Between October 2016 and June 2017, the genotypes were infected with CBSVs through whitefly transmission under field experiment at SEKU research farm (1.31ºS, 37.75ºE) and chip-bud grafting at KALRO-Katumani (1.35ºS, 37.14ºS) greenhouse conditions. RCBD and CRD experimental designs were respectively applied in field and greenhouse assays. CBSD symptoms were quantified through disease incidence (DIC) and severity (DSY) every 3 months for the field experiment and weekly for greenhouse assay. At harvest, storage root necrosis (SRN) was scored and non-necrotic roots weighed as marketable root yield (MRY). Molecular diagnostics was accomplished through duplex RT-PCR. Results revealed significantly (P≤0.01) higher foliar field DIC (81- 100%) and SRN (2.3 – 5.0) recorded in Thika-5 and Serere compared to all the improved genotypes that were foliarly asymptomatic (0% DIC and mean SRN of 1.0). Concomitantly and substantially lower (P≤0.01) MRY (1.99 – 2.16 t/ha) were bulked by Thika-5 and Serere compared to 10 improved genotypes that bulked 5.81 – 9.21 t/ha MRY. Upon chip-bud graft infection, Thika-5 and Serere showed higher DIC of 81 – 90% compared to four improved genotypes with 20 - 35% DIC. Correlations between MRY, DIC and SRN were inverse and significant (P≤0.01). RT-PCR detected pre-dominantly CBSV. In conclusion, the natural whitefly-based transmission of CBSVs was ineffective compared to chip-bud grafting. The inverse correlations between CBSD symptoms and yield corroborated the deleterious impact of CBSD on cassava production. The ten improved, high yielding and asymptomatic genotypes identified in the current study could potentially be used to confer resistance against CBSD into farmer-preferred but often sensitive varieties.

scholarly journals Analysis of Interactions Between Cassava Brown Streak Disease Symptom Types Facilitates the Determination of Varietal Responses and Yield Losses

Plant Disease ◽  
2016 ◽  
Vol 100 (7) ◽  
pp. 1388-1396 ◽  
Author(s):  
I. L. Ndyetabula ◽  
S. M. Merumba ◽  
S. C. Jeremiah ◽  
S. Kasele ◽  
G. S. Mkamilo ◽  
...  
Keyword(s):  
Plant Root ◽  
Sources Of Resistance ◽  
Novel Approach ◽  
Lake Zone ◽  
Root Necrosis ◽  
Two Factors ◽  
Cassava Brown Streak Disease ◽  
Total Plant ◽  
Brown Streak

Cassava brown streak disease (CBSD), caused by cassava brown streak viruses, is recognized as one of the most important plant disease threats to African food security. This study describes the incidence and severity of the different symptom types caused by CBSD, derived from extensive surveys in the country most severely affected by the disease: Tanzania. Total plant incidence and mean root severity of CBSD, recorded from 341 farmers’ fields, were both greater in the Coast Zone (49.5% and 3.05), than in the Lake Zone (32.7% and 2.57). Overall, the differing incidences recorded declined in the following order: total plant incidence (39.1%), plant shoot incidence (33.4%), plant root incidence (19.3%), root incidence (10.5%), and unusable root incidence (5.4%). The much lower-than-anticipated loss due to the root necrosis that is characteristic of CBSD was offset by large reductions of root number in plants expressing foliar symptoms of CBSD (15.7% in the Coast Zone and 5.5% in the Lake Zone). These data suggest that the effects of CBSD on the growth of affected plants are greater than those due to root spoilage. Based on these two factors, annual losses due to CBSD in the parts of Tanzania surveyed were estimated at >860,000 t, equivalent to more than U.S.$51 million. A novel approach to using farm-derived data on the responses of the most frequently cultivated varieties to CBSD infection allowed the grouping of the varieties into four categories, based on their relative resistance or tolerance to infection. This tool should be of value to breeders in identifying and selecting for sources of resistance or tolerance in both local and exotic germplasm, and should ultimately contribute to enhancing the management of one of Africa’s most damaging crop diseases.

scholarly journals Attempts to Identify Cassava Brown Streak Virus in Western Democratic Republic of Congo

2019 ◽  
Vol 11 (2) ◽  
pp. 31
Author(s):  
Bakelana Zeyimo ◽  
Magembe Eric ◽  
Laura Boykin ◽  
Mercy Macharia ◽  
Mahungu Nzola ◽  
...  
Keyword(s):  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Disease Incidence ◽  
Laboratory Diagnosis ◽  
Causative Organism ◽  
Streak Virus ◽  
Republic Of Congo ◽  
Cassava Brown Streak Virus ◽  
Root Necrosis ◽  
Brown Streak

Root necrosis similar to those of the cassava brown streak disease (CBSD) were observed on cassava in western provinces of the Democratic Republic of Congo (DR.Congo) in the early 2000’s. However molecular laboratory diagnosis were not able to detect any causative agent responsible for the attacks, hence, the disease related to these symptoms was named CBSD-like disease. In order to assess the distribution and the incidence of the CBSD-like disease, surveys were carried out in four western provinces, comprising, Kwango and Kwilu, Sud Ubangi, Kinshasa and Kongo Central. CBSD-like disease was observed in all surveyed provinces on the basis of root symptoms because foliar symptoms were different to those of the documented cases of CBSD in other parts of east Africa. CBSD-like disease incidence was high in Kongo Central and Sud Ubangi, exceeding an average of 50 %, but low in Kwango and Kwilu (32.8%) and in Kinshasa (19.1%). During the surveys, cassava leaf samples were collected for lab identification of the causal agent. PCR diagnosis was done on these samples using primers specific for the two known CBSVs. All samples tested negative with no amplification of DNA fragments of the correct size.  Thus, further analysis on the causative organism is needed using Next Generation Sequencing (NGS) approaches. NGS approaches will help also to identify the causative organism in other Central Africa countries (Angola, Congo-Brazzaville and Gabon) where such cassava root necrosis have been reported or are suspected.

Varietal response of cassava root yield components and root necrosis from cassava Brown streak disease to time of harvesting in Uganda

2019 ◽  
Vol 120 ◽  
pp. 58-66
Author(s):  
E. Kanju ◽  
V.N.E. Uzokwe ◽  
P. Ntawuruhunga ◽  
S. Tumwegamire ◽  
J. Yabeja ◽  
...  
Keyword(s):  
Yield Components ◽  
Root Yield ◽  
Cassava Root ◽  
Root Necrosis ◽  
Varietal Response ◽  
Cassava Brown Streak Disease ◽  
Brown Streak

scholarly journals Outlook of Cassava Brown Streak Disease Assessment: Perspectives of the Screening Methods of Breeders and Pathologists

2021 ◽  
Vol 12 ◽  
Author(s):  
Alfred A. Ozimati ◽  
Williams Esuma ◽  
Titus Alicai ◽  
Jean-Luc Jannink ◽  
Chiedozie Egesi ◽  
...  
Keyword(s):  
Resistance Breeding ◽  
Assessment Method ◽  
Disease Assessment ◽  
Screening Methods ◽  
Computation Method ◽  
Breeding Populations ◽  
Root Necrosis ◽  
Cassava Brown Streak Disease ◽  
The One ◽  
Brown Streak

Cassava production and productivity in Eastern, Central, and Southern Africa are ravaged by cassava brown streak disease (CBSD), causing yield losses of up to 100% when susceptible varieties are grown. Efforts to develop CBSD-resistant clones are underway. However, the methods for screening CBSD resistance currently vary between breeders and pathologists, with the limited empirical data to support their choices. In this study, we used the empirical CBSD foliar and root necrosis data from two breeding populations, termed cycle zero (C0) and cycle one (C1), to assess and compare the effectiveness of the CBSD screening methods of breeders vs. pathologists. On the one hand, the estimates of broad-sense heritability (H2) for the CBSD root necrosis assessment of breeder ranged from 0.15 to 0.87, while for the assessment method of pathologists, H2 varied from 0.00 to 0.71 in C0 clones. On the other hand, the marker-based heritability estimates (h2) for C0 ranged from 0.00 to 0.70 for the assessment method of breeders and from 0.00 to 0.63 for the assessment method of pathologists. For cycle one (C1) population, where both foliar and root necrosis data were analyzed for clones assessed at clonal evaluation trials (CETs) and advanced yield trials (AYTs), H2 varied from 0.10 to 0.59 for the assessment method of breeders, while the H2 values ranged from 0.09 to 0.35 for the CBSD computation method of pathologists. In general, higher correlations were recorded for foliar severity from the assessment method of breeders (r = 0.4, p ≤ 0.01 for CBSD3s and r = 0.37, p ≤ 0.01 for CBSD6s) in C1 clones evaluated at both clonal and advanced breeding stages than from the approach of pathologists. Ranking of top 10 C1 clones by their indexed best linear unbiased predictors (BLUPs) for CBSD foliar and root necrosis showed four overlapping clones between clonal and advanced selection stages for the method of breeders; meanwhile, only a clone featured in both clonal and advanced selection stages from the CBSD assessment method of pathologists. Overall, the CBSD assessment method of breeders was more effective than the assessment method of pathologists, and thus, it justifies its continued use in CBSD resistance breeding.

scholarly journals Optimum Time for Harvesting Cassava Tubers to Reduce Losses Due to Cassava Brown Streak Disease in Northeastern DRC

2020 ◽  
Vol 12 (5) ◽  
pp. 70
Author(s):  
Honoré Muhindo ◽  
François Wembonyama ◽  
Odette Yengele ◽  
Médard Songbo ◽  
Willy Tata-Hangy ◽  
...  
Keyword(s):  
Negative Relationship ◽  
Harvest Time ◽  
Optimum Time ◽  
Whitefly Population ◽  
Tuber Necrosis ◽  
Foliar Symptoms ◽  
Root Necrosis ◽  
Foliar Symptom ◽  
Cassava Brown Streak Disease ◽  
Brown Streak

The present study aimed to determine the appropriate time to harvest cassava tuberous root which minimize the losses due to cassava brown streak disease (CBSD) in the region of Yangambi, DRC. To achieve the aim of the study, 38 cassava cultivars were evaluated in Yangambi INERA’s Research Center for CBSD in the roots at harvest time between 9 and 13 months after planting (MAP). All the 38 cultivars tested showed CBSD root necrosis symptoms. Foliar symptoms occurred on 37.6% of the evaluated cultivars while CBSD root necrosis varied significantly among cultivars (7.0% to 82.5%) depending on susceptibility and the age of plant. This indicates the differential response of the cultivars to CBSD infection. Whitefly population density decreased with age of cassava, it was of 3 whiteflies per plant (9 MAP) to 1 (10 MAP). We noticed that in older plants, whitefly population decreased from 1 at 11 MAP to none at 13 MAP. Although, some cultivars did not show CBSD symptoms up to 12 MAP, they were not necessarily less attractive to whitefly. Negative relationship (r = -0.08 and r = -0.25) has been found between whitefly number and foliar symptom severity or between whitefly and tuber necrosis severity. Beyond 12 MAP, CBSD necrosis (severity score 4) was present in the tubers of 3 cultivars (EUR/2011/0148, Yafelamonene and Ybi/2011/258). Our study shows that in order to mitigate the losses due to CBSD necrosis, the optimum harvesting time for cassava tubers in Yangambi is 9 MAP.

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 < 0.001). Disease management measures were practiced by a half of participants only. Factors found to be significantly associated with CBSD infection (p < 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.

scholarly journals Cassava Brown Streak Disease Response and Association With Agronomic Traits in Elite Nigerian Cassava Cultivars

2021 ◽  
Vol 12 ◽  
Author(s):  
Chukwuka Ugochukwu Ano ◽  
Mildred Ochwo-Ssemakula ◽  
Angele Ibanda ◽  
Alfred Ozimati ◽  
Paul Gibson ◽  
...  
Keyword(s):  
Southern Africa ◽  
Agronomic Traits ◽  
Selection Index ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Root Weight ◽  
Cassava Brown Streak Disease ◽  
Cassava Production ◽  
Eastern And Southern Africa ◽  
Brown Streak

Cassava mosaic geminiviruses (CMGs) and cassava brown streak viruses (CBSVs) cause the highest yield losses in cassava production in Africa. In particular, cassava brown streak disease (CBSD) is and continues to be a significant constraint to optimal cassava production in Eastern and Southern Africa. While CBSD has not been reported in West Africa, its recent rapid spread and damage to cassava productivity in Eastern, and Southern Africa is alarming. The aim of this study was to evaluate Nigerian cassava genotypes in order to determine their responses to CBSD, in the event that it invades Nigeria, the world’s largest cassava producer. The study gathered information on whether useful CBSD resistance alleles are present in the elite Nigerian cassava accessions. A total of 1,980 full-sib cassava seedlings from 106 families were assessed in the field at the seedling stage for a year. A subset of 569 clones were selected and assessed for another year at the clonal stage in Namulonge, central Uganda, a known hotspot for CBSD screening. Results indicated that foliar and root incidences and severities varied significantly (p ≤ 0.01, p ≤ 0.001) except for CBSD foliar incidence at 6 months (CBSD6i). Highest and lowest plot-based heritability estimates for CBSD were registered for CBSD root severity (CBSDrs) (0.71) and CBSD6i (0.5). Positive and highly significant correlations were noted between CBSD root incidence (CBSDri) and CBSDrs (r = 0.90***). Significant positive correlations were also noted between CBSD foliar severity at 3 months (CBSD3s) and CBSD foliar incidence at 6 months (CBSD6i) (r = 0.77***), CBSD3s and CBSDrs (r = 0.35***). Fresh root weight (FreshRW) negatively correlated with CBSDri and CBSDrs, respectively (r = −0.21*** and r = −0.22***). Similarly, CBSD3s correlated negatively with cassava mosaic disease severity at 3 (CMD3s) and 6 months (CMD6s), respectively (r = −0.25*** and r = −0.21***). Fifteen clones were selected using a non-weighted summation selection index for further screening. In conclusion, results revealed that the elite Nigerian accessions exhibited significant susceptibility to CBSD within 2 years of evaluation period. It is expected that this information will aid future breeding decisions for the improvement of CBSD resistance among the Nigerian cassava varieties.

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