African Cassava Mosaic Research Articles

Using PCR and RCA Techniques to Investigate the Variants of Cassava Mosaic Virus and Their Distribution in Ghana

Cassava mosaic disease (CMD) caused by cassava begomoviruses is the major constraint to cassava production in Ghana. The disease is known to cause reduction in root yield. To ascertain the distribution of viruses causing CMD, 95 diseased cassava samples were collected in two agroecological zones of Ghana-Deciduous Forest zone and the Transitional zone. On a scale of 1-5, CMD severity was scored. Mean CMD severity score was 2.9, however there was no significant difference (p > 0.05) between the zones. Averagely, CMD score of > 2.8 in 71% of farms visited was recorded. Polymerase chain reaction (PCR) and rolling circle amplification (RCA) were employed for virus identification. PCR revealed that African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and mixed infections were prevalent in both zones. EACMV-Cameroon strain was also identified to be common within these zones. The transitional zone had the highest percentage of CMD infection. Unamplified samples from PCR were amplified using rolling circle amplification (RCA) technique. Amplification and characterisation of complete genome sequences of two isolates were carried out. The complete genome of 2780 nucleotides from samples showed a high similarity to African cassava mosaic virus-Ghana (ACMV-GH). Sequences clustered with ACMV-Ivory Coast, ACMV Nigeria-Ogo, ACMV-BF, ACMV-UG having > 96% identity. This shows the close relation that exists amongst the ACMV strains in Africa. These findings highlight the need for a continuous survey of CMD to help manage the disease in the country.

Prevalence of African Mosaic and Morphological Characterization of Cassava (Manihot esculenta Cranz) Varieties in Two Agroecological Zones of Cameroon

The objective of this work is to conduct an epidemiological study of African cassava mosaic and to characterize the diversity of local cultivars in circulation in the monomodal and bimodal rainforest zones of Cameroon. Disease-related parameters (incidence and severity index) were studied as well as morphological parameters (plant height, leaflet color, petiole color, lobe length, number of lobes, number of branches, petiole length). The results show that 96 cassava varieties were identified with 89 local varieties and 07 improved varieties. Diseased plants showed a symptom severity index of 1 to 5, which could reduce production by half in the areas considered. The leaf color was dark green, the number of branches was 3, the lobe and petiole lengths were 16.46 and 22 cm respectively, while the number of lobes was 5 the disease incidence for the two agro-ecological zones as a whole is 57.58% for a symptom severity index of 3. The epidemiological study reveals that the desease incidence of both agro-ecological zones was 57.58 % for a symptom severity index of 2 corresponding to 40 %. In the humid forest zone with monomodal spray the average incidence was 49.74% and a leaf attack rate was 29.03 % in the locality of Njombé (Cameroon's littoral region). At Ekona in southwestern Cameroon, the average incidence was 63% and leaf attack index was 1 corresponding to 20 %. In the bimodal rainforest zone (central Cameroon region), the average incidence was 60 % for a leaf attack rate was 37.11%. The expected results highlight a relatively worrying situation. Principal Component Analysis (PCA) confirms the convergence of tolerance towards the mosaic and grouped the different varieties into more or less homogeneous groups according to the morphological and epidemiological cassava descriptors. The results of the present work show that the introduction of cassava local varieties tolerant to mosaic disease in middling could be an alternative for the control of the cassava mosaic disease.

Gradual Emergence of East African cassava mosaic Cameroon virus in Cassava Farms in Côte d’Ivoire

Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are endemic threats to cassava production, causing significant yield losses. They are caused respectively by begomoviruses and ipomoviruses that are transmitted by whiteflies and infected cuttings. This study aimed to monitor and characterize viruses responsible for these diseases in order to fill existing gaps in understanding their epidemiology in Côte d’Ivoire. Field surveys were conducted in 2016, 2017, and 2020, and no CBSD symptoms were observed. However, an increase in CMD incidence was noted from 45.95% in 2016 to 51.37% in 2020, while CMD severity remained moderate over the years with a mean value of 2.29. The number of whiteflies was relatively low and decreased over the years. Molecular diagnostics carried out on cassava leaf samples allowed the detection of East African cassava mosaic Cameroon virus (EACMCMV) that occurs in single as well as in mixed infection with African cassava mosaic virus (ACMV). Single EACMCMV infection, which was detected only in three agroecological zones of eastern Côte d’Ivoire in 2016, spread throughout the country in 2017 and became more widespread in 2020 with a preponderance in central and southern zones, whereas ACMV and EACMCMV coinfection has spread to the entire zones. Phylogenetic analysis of the viral isolates showed that they are closely related to those from Burkina Faso, Ghana, and Nigeria. This changing population of cassava virus species constitutes a serious threat to cassava cultivation. Understanding the evolutionary dynamics of these viruses could help in adopting better disease management strategies to control the disease.

Application of Integrated Computational Approaches in Prediction of Plant Virus Encoded miRNAs and Their Targeted Plant Genes.

This chapter presents a comprehensive approach to predict novel miRNAs encoded by plant viruses and identify their target plant genes, through integration of various ab initio computational approaches. The predictive process begins with the analysis of plant viral sequences using the VMir Analyzer software. VMir Viewer software is then used to extract primary hairpins from these sequences. To distinguish real miRNA precursors from pseudo miRNA precursors, MiPred web-based software is employed. Verified real pre-miRNA sequences with a minimum free energy of< -20 Kcal/mol, arefurther analyzedusingthe RNAshapes software. Validation of predictions involves comparing them with available Expressed Sequence Tags (ESTs) from the relevant plant using BlastN. Short sequences with lengths ranging from 19 to 25 nucleotides and exhibiting <5 mismatches are prioritized for miRNA prediction. The precise locations of these short sequences within pre-miRNA structures generated using RNAshapes are meticulously identified, with a focus on those situated on the 5' and 3' arms of the structures, indicating potential miRNAs. Sequences within the arms of pre-miRNA structures are used to predict target sites within the ESTs of the specific plant, facilitated by psRNA Target software, revealing genes with potential regulatory roles in the plant. To confirm the outcome of target prediction, results are individually submitted to the RNAhybrid web-based software. For practical demonstration, this approach is applied to analyze African cassava mosaic virus (ACMV) and East African cassava mosaic virus-Uganda (EACMV-UG) viruses, as well as the ESTs of Jatropha and cassava.

East African Cassava Mosaic Virus and East African Cassava Mosaic Cameroon Virus: Two Species Emerging in Togo

East African Cassava Mosaic Virus and East African Cassava Mosaic Cameroon Virus: Two Species Emerging in Togo

Haplotype-resolved genome of heterozygous African cassava cultivar TMEB117 (Manihot esculenta)

Cassava (Manihot esculenta Crantz) is a vital tropical root crop providing essential dietary energy to over 800 million people in tropical and subtropical regions. As a climate-resilient crop, its significance grows as the human population expands. However, yield improvement faces challenges from biotic and abiotic stress and limited breeding. Advanced sequencing and assembly techniques enabled the generation of a highly accurate, nearly complete, haplotype-resolved genome of the African cassava cultivar TMEB117. It is the most accurate cassava genome sequence to date with a base-level accuracy of QV > 64, N50 > 35 Mbp, and 98.9% BUSCO completeness. Over 60% of the genome comprises repetitive elements. We predicted over 45,000 gene models for both haplotypes. This achievement offers valuable insights into the heterozygosity genome organization of the cassava genome, with improved accuracy, completeness, and phased genomes. Due to its high susceptibility to African Cassava Mosaic Virus (ACMV) infections compared to other cassava varieties, TMEB117 provides an ideal reference for studying virus resistance mechanisms, including epigenetic variations and smallRNA expressions.

Genome segment ratios change during whitefly transmission of two bipartite cassava mosaic begomoviruses

Cassava mosaic disease is caused by a complex of whitefly-transmitted begomoviruses, which often occur in co-infections. These viruses have bipartite genomes consisting of DNA-A and DNA-B that are encapsidated into separate virions. Individual viruses exist in plants and whitefly vectors as populations comprising both genome segments, which can occur at different frequencies. Both segments are required for infection, and must be transmitted for virus spread to occur. Cassava plants infected with African cassava mosaic virus (ACMV) and/or East African cassava mosaic Cameroon virus (EACMCV), in which the ratios of DNA-A:DNA-B titers differed between plants, were used to examine how titers of the segments in a plant relate to their respective probabilities of acquisition by whiteflies and to the titers of each segment acquired and subsequently transmitted by whiteflies. The probabilities of acquiring each segment of ACMV did not reflect their relative titers in the source plant but they did for EACMCV. However, for both viruses, DNA-A:DNA-B ratios acquired by whiteflies differed from those in the source plant and the ratios transmitted by the whitefly did not differ from one – the ratio at which the highest probability of transmitting both segments is expected.

Cassava begomovirus species diversity changes during plant vegetative cycles.

Cassava is a root crop important for global food security and the third biggest source of calories on the African continent. Cassava production is threatened by Cassava mosaic disease (CMD), which is caused by a complex of single-stranded DNA viruses (family: Geminiviridae, genus: Begomovirus) that are transmitted by the sweet potato whitefly (Bemisia tabaci). Understanding the dynamics of different cassava mosaic begomovirus (CMB) species through time is important for contextualizing disease trends. Cassava plants with CMD symptoms were sampled in Lake Victoria and coastal regions of Kenya before transfer to a greenhouse setting and regular propagation. The field-collected and greenhouse samples were sequenced using Illumina short-read sequencing and analyzed on the Galaxy platform. In the field-collected samples, African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV), East African cassava mosaic Kenya virus (EACMKV), and East African cassava mosaic virus-Uganda variant (EACMV-Ug) were detected in samples from the Lake Victoria region, while EACMV and East African mosaic Zanzibar virus (EACMZV) were found in the coastal region. Many of the field-collected samples had mixed infections of EACMV and another begomovirus. After 3 years of regrowth in the greenhouse, only EACMV-like viruses were detected in all samples. The results suggest that in these samples, EACMV becomes the dominant virus through vegetative propagation in a greenhouse. This differed from whitefly transmission results. Cassava plants were inoculated with ACMV and another EACMV-like virus, East African cassava mosaic Cameroon virus (EACMCV). Only ACMV was transmitted by whiteflies from these plants to recipient plants, as indicated by sequencing reads and copy number data. These results suggest that whitefly transmission and vegetative transmission lead to different outcomes for ACMV and EACMV-like viruses.

Occurrence of cassava mosaic begomoviruses in national cassava germplasm preserved in two agro‐ecological zones of Ivory Coast

AbstractCassava production in Ivory Coast is hampered by cassava mosaic disease (CMD), which is caused by several begomovirus species. To increase cassava production and conserve genetic resources, the Centre National de Recherche Agronomique (CNRA) maintains a germplasm collection of 610 cassava accessions of various origins, which is kept in open fields in Bouaké and Man. We carried out an epidemiological assessment of the collection and a molecular characterization of the viruses infecting the CNRA cassava germplasm. The field in Man was less affected by CMD (incidence 49.78%, severity 2.23, whitefly infection 2.23%), despite the abundant whitefly populations (1.34 per plant), compared to Bouaké (incidence 74.54%, severity 2.92, whitefly infection 8.04% and whitefly population of 0.34 per plant). However, the predominant mode of CMD transmission was through infected cassava cuttings at both sites. PCR analysis showed that the East African cassava mosaic Cameroon virus (EACMCMV) was always found in co‐infection with African cassava mosaic virus (ACMV), which also occurred in single infection. Co‐infections of EACMCMV and ACMV were more prevalent in Bouaké (52.64%) than Man (13.87%). Eleven complete genome sequences of cassava mosaic begomoviruses infecting the CNRA germplasm were obtained, and phylogenetic analysis showed that they are closely related to ACMV and EACMCMV isolates from Ghana, Burkina Faso and Nigeria. The results of this study will assist breeders to screen accurately for CMD resistance in progeny resulting from parental lines, enabling the strategic distribution of new clean cassava planting materials to reduce the impact of CMD.

Phenotypic screening and molecular characterization of cassava mosaic disease resistance in Côte d'Ivoire cassava germplasm

Cassava is the staple food crop for hundreds of millions of people in Africa. In Côte d'Ivoire, it is a main source of calories for over 26 million people. However, cassava mosaic disease (CMD), caused by cassava mosaic geminiviruses (CMGs) threaten its production. The development, adoption, and use of CMD resistant varieties remain a key CMD management strategy. Therefore, 610 accessions from the Côte d'Ivoire national cassava germplasm maintained by Centre National de Recherche Agronomique (CNRA) research stations in the cities of Man and Bouaké were characterized to assess their resistance to CMD. We found 72 accessions which were symptomless at both sites. Thirty five out of these 72 accessions were infected by African cassava mosaic virus (ACMV) without any CMD symptoms and 37 were virus free. None of the 72 symptomless accessions were infected by East African cassava mosaic Cameroon virus (EACMCMV). The remaining 538 accessions were CMD infected and displayed clear CMD symptoms. The promising 72 accessions (10 locals and 62 improved) were then tested for the presence of resistance genes, CMD1, CMD2 or CMD3. Except for 2 accessions for which no resistance gene was found, the remaining 70 accessions contained one or more resistance genes. Genotyping of the 69 symptomless accessions revealed that 56 were unique genotypes and 13 were potential duplicates. Accessions were structured in three groups with the variabilities at the individual's level. These findings reveal the existence of potential tolerant/resistant cassava accessions in CNRA's germplasm, which can contribute to CMD control and the increase of cassava production in Côte d'Ivoire.

Expression, Purification, and Characterisation of South African Cassava Mosaic Virus Cell-to-Cell Movement Protein.

South African cassava mosaic virus (SACMV) is a circular ssDNA bipartite begomovirus, whose genome comprises DNA-A (encodes six genes) and DNA-B (encodes BC1 cell-to-cell movement and BV1 nuclear shuttle proteins) components. A few secondary and tertiary structural and physicochemical characteristics of partial but not full-length begomovirus proteins have been elucidated to date. The full-length codon-optimised SACMV BC1 gene was cloned into a pET-28a (+) expression vector and transformed into expression host cells E. coli BL21 (DE3). The optimal expression of the full-length BC1-encoded movement protein (MP) was obtained via induction with 0.25 mM IPTG at an OD600 of ~0.45 at 37 °C for four hours. Denatured protein fractions (dialysed in 4 M urea), passed through an IMAC column, successfully bound to the nickel resin, and eluted using 250 mM imidazole. The protein was refolded using stepwise dialysis. The molecular weight of MP was confirmed to be 35 kDa using SDS–PAGE. The secondary structure of SACMV MP presented as predominantly β-strands. An ANS (1-anilino-8-naphthalene sulphonate)-binding assay confirmed that MP possesses hydrophobic pockets with the ability to bind ligands such as ANS (8-anilino-1-naphthalenesulphonic acid). A 2′ (3′)-N-methylanthraniloyl-ATP (mant-ATP) assay showed binding of mant-ATP to MP and indicated that, while hydrophobic pockets are present, MP also exhibits hydrophilic regions. Intrinsic tryptophan fluorescence indicated a significant conformational change in the denatured form of BC1 in the presence of ATP. In addition, a phosphatase assay showed that MP possessed ATPase activity.

African cassava mosaic virus (African cassava mosaic)

African cassava mosaic virus (African cassava mosaic)

Cassava mosaic disease (African cassava mosaic)

Cassava mosaic disease (African cassava mosaic)

East African cassava mosaic Zanzibar virus

This datasheet on East African cassava mosaic Zanzibar virus covers Identity, Distribution, Hosts/Species Affected, Vectors &amp; Intermediate Hosts, Further Information.

Proteome Mapping of South African Cassava Mosaic Virus-Infected Susceptible and Tolerant Landraces of Cassava.

The production of cassava is threatened by the geminivirus South African cassava mosaic virus (SACMV), which causes cassava mosaic disease. Cassava landrace TME3 shows tolerance to SACMV, while T200 is highly susceptible. This study aimed to identify the leaf proteome involved in anti-viral defence. Liquid chromatography mass spectrometry (LC-MS) identified 2682 (54 differentially expressed) and 2817 (206 differentially expressed) proteins in both landraces at systemic infection (32 days post infection) and symptom recovery (67 days post infection), respectively. Differences in the number of differentially expressed proteins (DEPs) between the two landraces were observed. Gene ontology analysis showed that defence-associated pathways such as the chloroplast, proteasome, and ribosome were overrepresented at 67 days post infection (dpi) in SACMV-tolerant TME3. At 67 dpi, a high percentage (56%) of over-expressed proteins were localized in the chloroplast in TME3 compared to T200 (31% under-expressed), proposing that chloroplast proteins play a role in tolerance in TME3. Ribosomal_L7Ae domain-containing protein (Manes.12G139100) was over-expressed uniquely in TME3 at 67 dpi and interacts with the ribosomal protein Sac52 (RPL10). RPL10 is a known key player in the NIK1-mediated effector triggered immunity (ETI) response to geminivirus infection, indicating a possible role for Sac52 in SACMV recovery in TME3. In conclusion, differential protein expression responses in TME3 and T200 may be key to unravel tolerance to CMD.

Epidemiological assessment of cassava mosaic disease in Burkina Faso.

Surveys were conducted in 2016 and 2017 across the main cassava‐growing regions of Burkina Faso to assess the status of cassava mosaic disease (CMD) and to determine the virus strains causing the disease, using field observation and phylogenetic analysis. CMD incidence varied between regions and across years but was lowest in Hauts‐Bassins (6.0%, 2016 and 5.4%, 2017) and highest in Centre‐Sud (18.5%, 2016) and in Boucle du Mouhoun (51.7%, 2017). The lowest CMD severity was found in Est region (2.0) for both years and the highest in Sud‐Ouest region (3.3, 2016) and Centre‐Sud region (2.8, 2017). The CMD infection was primarily associated with contaminated cuttings in all regions except in Hauts‐Bassins, where whitefly‐borne infection was higher than cuttings‐borne infection in 2016. PCR screening of 687 samples coupled with sequence analysis revealed the presence of African cassava mosaic‐like (ACMV‐like) viruses and East African cassava mosaic‐like (EACMV‐like) viruses as single infections at 79.5% and 1.1%, respectively. Co‐infections of ACMV‐like and EACMV‐like viruses were detected in 19.4% of the tested samples. In addition, 86.7% of the samples positive for EACMV‐like virus were found to be positive for East African cassava mosaic Cameroon virus (EACMCMV). Phylogenetic analysis revealed the segregation of cassava mosaic geminiviruses (CMGs) from Burkina Faso into three clades specific to ACMV, African cassava mosaic Burkina Faso virus (ACMBFV), and EACMCMV, confirming the presence of these viruses. The results of this study show that EACMCMV occurrence may be more prevalent in Burkina Faso than previously thought.

Acibenzolar-S-methyl induces resistance against cassava mosaic geminiviruses in Nicotiana benthamiana and their vector Bemisia tabaci in cassava (Manihot esculenta)

Cassava mosaic disease (CMD), caused by cassava mosaic geminiviruses (CMGs), is a major constraint to the cassava crop in Africa and southeastern Asia. Here, we investigated the ability of acibenzolar-S-methyl (ASM), a functional analog of salicylic acid (SA), to trigger systemic acquired resistance (SAR) against two CMGs, namely African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) in Nicotiana benthamiana. ASM treatment delayed the time to first viral symptoms appearance, reduced virus infection rate, and attenuated symptoms. Furthermore, ASM caused an enhanced recovery from symptoms of both viruses and inhibited plant death observed in N. benthamiana plants infected by EACMCV. This study further showed that ASM induced resistance to the whitefly Bemisia tabaci (Gennadius), the vector of CMGs, in cassava. Notably, we observed that ASM treatment affected adult whitefly feeding preference and oviposition in cassava under both choice and no-choice conditions. A significant reduction in whitefly adult, egg, and nymph populations was observed irrespective of ASM treatment. The results of this study show that ASM has the potential to control both CMGs and their whitefly vector which is an important first step toward managing whitefly and cassava viruses.

Population diversity of cassava mosaic begomoviruses increases over the course of serial vegetative propagation.

Cassava mosaic disease (CMD) represents a serious threat to cassava, a major root crop for more than 300 million Africans. CMD is caused by single-stranded DNA begomoviruses that evolve rapidly, making it challenging to develop durable disease resistance. In addition to the evolutionary forces of mutation, recombination and reassortment, factors such as climate, agriculture practices and the presence of DNA satellites may impact viral diversity. To gain insight into the factors that alter and shape viral diversity in planta, we used high-throughput sequencing to characterize the accumulation of nucleotide diversity after inoculation of infectious clones corresponding to African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) in the susceptible cassava landrace Kibandameno. We found that vegetative propagation had a significant effect on viral nucleotide diversity, while temperature and a satellite DNA did not have measurable impacts in our study. EACMCV diversity increased linearly with the number of vegetative propagation passages, while ACMV diversity increased for a time and then decreased in later passages. We observed a substitution bias toward C→T and G→A for mutations in the viral genomes consistent with field isolates. Non-coding regions excluding the promoter regions of genes showed the highest levels of nucleotide diversity for each genome component. Changes in the 5′ intergenic region of DNA-A resembled the sequence of the cognate DNA-B sequence. The majority of nucleotide changes in coding regions were non-synonymous, most with predicted deleterious effects on protein structure, indicative of relaxed selection pressure over six vegetative passages. Overall, these results underscore the importance of knowing how cropping practices affect viral evolution and disease progression.

Cassava mosaic virus in Africa: Functional analysis of virus coat proteins based on evolutionary processes and protein structure

African cassava mosaic virus (ACMV) has been identified as a typical example of a pathogenic microorganism that constitutes a global menace to cassava's profitable production, especially in Africa, where the highest economic yield loss of 34 million tons usually is recorded annually. Functional analysis of virus coat proteins based on evolutionary processes and structure of ACMV isolates from fifteen African countries was conducted with Indian cassava mosaic virus and East African cassava mosaic Malawi virus as checks. The study revealed that ACMV coat proteins (CPs) belong to the nuclear export factor BR1 family in the Gemini-coat protein superfamily. Moreover, the phylogenetic analysis performed shows a very strong affinity amongst the African isolates within their geographical regions without evidence of evolutionary divergence amongst all the isolates. Multiple sequence alignment of the genes revealed a highly conserved domain and three motifs. Thirteen of the isolates from Africa share similar physicochemical properties and possess DNA-binding property. A three-dimensional homology model structure was built for ACMV CPs with Ramachandran plot values between 99 and 100%. The gene annotation analysis predicted most of the coat proteins associated with the virion and virus capsid, undertaking mainly organic compound and nucleic acids binding molecular functions and shuttling as the dominant biological process. Therefore, this study established that ACMV isolates have common ancestral descent. These findings form a strong basis that could be harnessed by applying molecular techniques for effective detection and management of ACMV isolates, causing substantial cassava losses recorded annually across several continents of the globe.

Growth Performance of Eleven Improved Cassava Varieties and their susceptibility to Some Insect Pests and Diseases in Humid Tropics, Rivers State,

Study on the agronomic evaluation and disease resistance of eleven improved cassava varieties was carried out in Rivers State University Teaching and Research Farm in a Randomized Complete Block Design (RCBD). The eleven varieties assessed are TMS 30572, TMS 98/0510, TMS 98/0581, TMS 98/0505, TMS 92/0326, TME 419, TMS 01/1371, TMS 01/1368, TMS 07/0593, TMS 95/0289 and TMS 96/1632 were evaluated for plant height, leaf number, number of branches, number of flowers, insect infestation and disease incidence. The plant height of the cassava varieties revealed that eight varieties (TMS 01/1371, TMS 01/1368, TMS 30572, TME 419, TMS 98/0505, TMS 96/1632, TMS 98/0510 and TMS 07/0593) are tall varieties while TMS 98/0581, TMS 92/0326 and TMS 95/0289 are short varieties. The highest leaf number was recorded in TMS 01/1371 but the tall varieties like TMS 01/1368, TMS 96/1632 and TME 419 had low leaf number. TMS 98/0581, TMS 92/0326 and TMS 95/0289 were shown to have scanty leaves. TMS 01/1371 was significantly higher (P<0.05) than other varieties in plant height, leaf number and branches. Four varieties flowered namely TMS 07/0593, TMS 01/1371, TMS 30572 and TMS 98/0505. TMS 30572 and TMS 92/0326 were highly susceptible to both African Cassava Mosaic and Xanthomona sp. (Bacterial blight diseases) while TMS 95/0289, TMS 01/1368 and TMS 98/0505 were less susceptible to African Cassava Mosaic virus disease alone. Insect infestations (White fly: Bemisia sp. and Mealybugs: Phenacoccus sp.) on the tested varieties were significantly minimal though five cultivars (TMS 98/0505, TMS 96/1632, TMS 98/0510, TMS 98/0581 and TMS 95/0289) were completely resistant. Therefore, there is urgent need to withdraw the varieties that are susceptible, and use more of the varieties that are disease resistant for high crop yield, breeding and higher productivity.