Cassava Cultivars Research Articles

Analysis of the reducing sugar and carbohydrates total of cassava (Manihot esculenta Crantz) resistant to drought stress

Cassava (Manihot esculenta Crantz) is the third most important crop in the world and a staple food source throughout the tropics. Cassava land centers in Indonesia are controlled by Lampung Province. This situation makes Lampung a supplier of one-third of the national cassava production of the national production. However, there are still many production constraints in cassava cultivation, including drought stress. Drought stress is one of the main factors causing cassava plant death. So far, there is no drought-resistant cassava cultivar. The use of cassava seeds which are resistant to drought stress with high yields is expected to be an important alternative for drought stress control by using polyethylene glycol 6000 (PEG 6000). The purpose of this study was to analyze the reducing sugar content and the total carbohydrate content of cassava plants which were effective and resistant to drought stress. This study used a completely randomized design with one factor, namely the concentration of PEG 6000 consisting of 5 levels 0%, 10%, 20%, 30% and 40%. The results showed that the higher the concentration of PEG 6000, the total dissolved carbohydrate content and reducing sugar content in cassava plants which were resistant to drought stress increased. The highest reducing sugar content and carbohydrate content were found in the treatment of 40% PEG 6000 concentration.

Impact of improved cassava cultivars on income generation and food security of women farmers in Mkuranga district, Tanzania

PurposeThe study was conducted to investigate the impact of improved cassava cultivars on income generation and food security status of women farmers in Tanzania.Design/methodology/approachData were collected from 300 respondents (150 with improved cassava cultivars and 150 without) who were selected using purposive and random sampling techniques. Double Difference, Descriptive Statistics were the analytical tools. The Cost-of-Calorie Index was used to measure food security status of the respondents.FindingsResults show that Double Difference estimates indicated that the annual income of the women farmers with improved cassava cultivars increased by TZS 143,495.20 which was higher than that of the women farmers without improved cassava cultivars which increased by only TZS 58,500. There was a positive impact on income as a result of using the improved cassava cultivars. The Cost-of-Calorie Index showed that the food security line per adult equivalent per month was TZS 2,743.81 and TZS 2,076.69 for farmers with and without improved cassava cultivars respectively. About 66% of the women farmers with improved cassava cultivars and 33% of the women farmers without improved cassava cultivars were food secure. Policies should be formulated to encourage women farmers to adopt and sustain the use of improved cultivars of cassava.Research limitations/implicationsThe research may be limited by its scope and generalizability, as it focuses on a specific geographic area (Mkuranga District) and demographic group (women farmers).Social implicationsThe study shed light on the role of agricultural interventions in empowering women economically and enhancing their food security, potentially leading to improved social status and decision-making power within their households and communities.Originality/valueThe study contributes to the existing body of knowledge by emphasizing the benefits for women farmers when using improved cassava cultivars for income generation and food sufficiency.

Impact of Cassava Cultivars on Stylet Penetration Behavior and Settling of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae).

This study investigates the settling preferences and feeding behavior of the Bemisia tabaci whitefly on six cassava cultivars using electrical penetration graph techniques. Six distinct electrical penetration graph waveforms-non-probing, stylet pathway, phloem salivation, phloem ingestion, intracellular puncture, and xylem feeding-were identified and analyzed. Significant differences in the frequency and duration of these waveforms were observed among the cassava cultivars. The whiteflies spent the majority of their time in the non-probing phase, particularly on the Huaybong 80, Kasetsart 50, Rayong 9, and Rayong 72 cultivars. CMR-89 cultivar exhibited higher total probe durations in the phloem salivation and ingestion waveforms, suggesting a greater potential for transmission of the Sri Lankan cassava mosaic virus. The study also examined trichome density and size across the cassava cultivars, revealing that CMR-89 had the highest density and small trichomes, while Huaybong 80 had the lowest density. Trichome characteristics significantly impacted whitefly behavior: larger trichomes were negatively correlated with whitefly settling, whereas higher trichome density was positively correlated with longer settling durations. These findings indicate that trichome-based resistance mechanisms are crucial in whitefly deterrence. Overall, the results suggest that cultivars with lower trichome density and larger trichomes are more resistant to whitefly infestation and subsequent Sri Lankan cassava mosaic virus transmission. These insights are valuable for cassava breeding programs focused on enhancing pest resistance, highlighting the importance of trichome characteristics in developing more resilient cassava varieties.

Editing of the MeSWEET10a promoter yields bacterial blight resistance in cassava cultivar SC8.

Cassava starch is a widely used raw material for industrial production and food source for people. However, cassava bacterial blight (CBB) caused by Xanthomonas axonopodis pv. manihotis (Xam) results in severe yield losses and is the most destructive bacterial disease in all worldwide cassava-growing regions. Xam11 is a highly pathogenic subspecies from China that infects the Chinese local cassava South China No. 8 (SC8) cultivar with marked symptoms. This study showed that the transcription activator-like effector TALE20Xam11 of Xam11 strain regulates the expression of disease-susceptibility gene MeSWEET10a by binding to the EBETALE20 region of the MeSWEET10a promoter in cassava cultivar SC8. CRISPR/Cas9-generated mutations of the EBETALE20 region resulted in a significant reduction in MeSWEET10a expression after infection by Xam11, correlating with reduced disease symptoms, smaller lesion sizes and decreased bacterial proliferation compared with the wild type. Importantly, the edited plants maintained normal growth, development and yield characteristics under greenhouse conditions. The results lay a research foundation for breeding resistant cassava cultivar SC8 to bacterial blight.

Social Economic Factors Driving Cassava Adoption in Teso South, Busia County, Kenya

Cassava's significance as a food crop is underscored by its ability to thrive in poor soils, withstand drought, and tolerate marginal conditions where other crops might fail. Despite its recognized importance and the introduction of improved cultivars, cassava output in Busia County remains poor, even though it is Africa's most frequently planted staple crop. This study analysed the factors influencing adoption of improved cassava cultivars among 167 smallholder farmers in Busia County, Kenya. The objective was to determine the social and economic factors influencing the adoption of improved cassava cultivars among smallholder farmers in Teso South, Busia County. Data was collected from the sampled farmers using a multistage sampling procedure in six wards. A Binary Logit model was used to investigate the effect of the selected social and economic, factors on the adoption of improved cassava cultivars. The results revealed that the average farm size in Teso South is 2 acres (48.2%), while that set aside for cassava cultivation by households is 0.25 acres (66.4%). Gender, age, marital status and education level did not influence the farm size nor the size set aside for cassava cultivation (p>0.5). Majority 127(76.0%) of the respondents indicated that they had not adopted improved cassava cultivars on their farms (χ2 = 27.04, d.f.=1, p<0.0001). From the study, it was denoted that economic factors such as financial resources, land size and market accessibility positively and significantly influenced the adoption of improved cassava cultivars among smallholder farmers in Teso South, Busia County (β=-0.148, t=-6.886, p<0.001). Social factors such as age, gender, education and household did not influence the adoption of improved cassava cultivars among smallholder farmers in Teso South, Busia County (β=0.011, t=-0.92, p=0.926). The fitting of the model was significant (F 0.05 (3, 163) =29.303, p< 0.001). Agricultural extension programs should focus on providing targeted training and support on innovative techniques and technologies, such as the adoption of improved cassava cultivars, to enhance farmers' capacities and resilience, regardless of their educational backgrounds

Analysis of Fluorescently Labeled ISSR Markers to Reveal the Genetic Diversity of Cassava Varieties (Manihot esculenta Crantz) in the Kerala’s Tribal Area of India

The study Inter Simple Sequence Repeat (ISSR) molecular markers to genotype distinct cassava (Manihot esculenta Crantz) cultivars within tribal communities in Kerala, India. Fluorescent ISSR primers were labelled with 6-carboxyfluorescein and used for PCR amplification. The total number of bands produced was 72, of which 49 were found to be polymorphic markers; an average of 17 polymorphic bands was obtained per primer. The manuscript is a scientific validation of the traditional knowledge of tribal people regarding the diversity and wealth of cassava crops in the region, and this validation can therefore help in protecting the farmers right on a particular landrace that they cultivate. The technique used in the diversity analysis is a time-saving process as compared to conventional breeding programs for crop improvement. The data in the manuscript also supports similarity and differences of each variety to one another, which is analysed statistically with the molecular marker-based data generated. By examining genetic diversity at a high resolution, ISSR markers can provide valuable insights into the evolutionary dynamics of these cassava populations. This research contributes to the broader goal of enhancing agricultural sustainability and food security in tribal communities.

Optimization of cassava (Manihot esculenta Crantz) grafting technique to enhance its adoption in cassava cultivation

Grafting techniques have been successfully adopted to improve resistance to biotic and abiotic stresses, increase yields, fruit quality and study systemic signaling in plants. This technique has not been fully explored in cassava and there is currently no standardized grafting method for this species published especially in Africa. This is the first report on cassava grafting protocol in Africa with valuable advantages including utilizing a cost-effective and environmentally friendly wooden healing chamber. In this study, we describe an optimized cleft grafting protocol for cassava utilizing a wooden healing chamber and outline the step-by-step procedure with optimum conditions to generate a high grafting success rate. Using a top wedge grafting technique with high reproducibility and success rates, we developed a straightforward and robust grafting protocol for cassava (M. esculenta) cultivars. Grafting success was recorded and this protocol produced a high grafting success of 90 % and its reproducibility makes it suitable for mass production thereby addressing the need for efficient cassava propagation. This grafting protocol requires less specialized equipment and expertise making it more accessible to farmers and researchers with limited resources to promote the use of grafting for cassava growth, yield improvement and advanced studies such as systemic long-distance signaling in plants.•Optimization of cleft grafting method obtains a high success grafting rate of cassava.•A wooden healing chamber provides a controlled environment for graft healing.•Promoting cassava grafting; a priority to produce new cultivars and explore breeding research prospects.

Cassava (Manihot esculenta) Brazilian cultivars have different chemical compositions, present prebiotic potential, and beneficial effects on the colonic microbiota of celiac individuals

The purpose of this study was to investigate the potential prebiotic properties of cassava cultivars from Northeast [Doce mel and Ourinho (OUR)] and South [Baiana, and IPR-Upira (UPI)] of Brazil in in vitro fermentation systems. The cultivars were evaluated for their chemical composition, and, then, two cultivars were selected (OUR and UPI) and subjected to in vitro gastrointestinal digestion to assess the effects on probiotics Lacticaseibacillus casei, Lactobacillus acidophilus, and Bifidobacterium animalis growth, metabolic activity, and prebiotic activity scores. Finally, the impact of cassava cultivars on the fecal microbiota of celiac individuals was evaluated using the 16S rRNA gene. Cassava cultivars have variable amounts of fiber, resistant starch, fructooligosaccharides (FOS), organic acids, phenolic compounds, and sugars, with OUR and UPI cultivars standing out. OUR and UPI cultivars contributed to the increase in the proliferation rates of L. casei (0.04–0.19), L. acidophilus (0.34–0.27), and B. animalis (0.10–0.03), resulting in more significant effects than FOS, an established prebiotic compound. Also, the positive scores of prebiotic activities with probiotic strains indicate OUR and UPI’s ability to stimulate beneficial bacteria while limiting enteric competitors selectively. In addition, OUR and UPI promoted increased relative abundance of Bifidobacteriaceae, Enterococcaceae, and Lactobacillaceae in the fecal microbiota of celiac individuals while decreased Lachnospirales, Bacteroidales, and Oscillospirales. The results show that cassava cultivars caused beneficial changes in the composition and metabolic activity of the human intestinal microbiota of celiacs. OUR and UPI cultivars from the Northeast and South of Brazil could be considered potential prebiotic ingredients for use in the formulation of functional foods and dietary supplements.

Proline inhibits postharvest physiological deterioration of cassava by improving antioxidant capacity

Cassava (Manihot esculenta Crantz), a crucial global tuber crop, encounters significant economic losses attributed to postharvest physiological deterioration (PPD). The PPD phenomenon in cassava is closely related to the accumulation of reactive oxygen species (ROS), and amino acids play a pivotal role in regulating signaling pathways and eliminating ROS. In this study, the storage performance of eight cassava varieties were conducted. Cassava cultivar SC5 showed the best storage performance among the eight cassava varieties, but the edible cassava cultivar SC9 performed much worse. Comparative analysis of free amino acids was conducted in eight cassava varieties, revealing changes in proline, aspartic acid, histidine, glutamic acid, threonine, and serine. Exogenous supplementation of these six amino acids was performed to inhibit PPD of SC9. Proline was confirmed as the key amino acid for inhibiting PPD. Treatment with optimal exogenous proline of 5 g/L resulted in a 17.9% decrease in the deterioration rate compared to untreated cassava. Accompanied by a decrease in H2O2 content and an increase in catalase, superoxide dismutase and ascorbate peroxidase activity. Proline treatment proved to be an effective approach to alleviate cell oxidative damage, inhibit PPD in cassava, and prolong shelf life.

Morphological, anatomical, and transcriptomics analysis reveals the regulatory mechanisms of cassava plant height development

BackgroundCassava is one of three major potato crops and the sixth most important food crop globally. Improving yield remains a primary aim in cassava breeding. Notably, plant height significantly impacts the yield and quality of crops; however, the mechanisms underlying cassava plant height development are yet to be elucidated.ResultsIn this study, we investigated the mechanisms responsible for cassava plant height development using phenotypic, anatomical, and transcriptomic analyses. Phenotypic and anatomical analysis revealed that compared to the high-stem cassava cultivar, the dwarf-stem cassava cultivar exhibited a significant reduction in plant height and a notable increase in internode tissue xylem area. Meanwhile, physiological analysis demonstrated that the lignin content of dwarf cassava was significantly higher than that of high cassava. Notably, transcriptome analysis of internode tissues identified several differentially expressed genes involved in cell wall synthesis and expansion, plant hormone signal transduction, phenylpropanoid biosynthesis, and flavonoid biosynthesis between the two cassava cultivars.ConclusionsOur findings suggest that internode tissue cell division, secondary wall lignification, and hormone-related gene expression play important roles in cassava plant height development. Ultimately, this study provides new insights into the mechanisms of plant height morphogenesis in cassava and identifies candidate regulatory genes associated with plant height that can serve as valuable genetic resources for future crop dwarfing breeding.

Determination of genomic regions associated with early storage root formation and bulking in cassava.

Early cassava storage root formation and bulking is a medium of escape that farmers and processors tend to adopt in cases of abiotic and biotic stresses like drought, flood, and destruction by domestic animals. In this study, 220 cassava genotypes from the International Institute of Tropical Agriculture (IITA), National Root Crops Research Institute (NRCRI), International Center for Tropical Agriculture (CIAT), local farmers (from farmer's field), and NextGen project were evaluated in three locations (Umudike, Benue, and Ikenne). The trials were laid out using a split plot in a randomized incomplete block design (alpha lattice) with two replications in 2 years. The storage roots for each plant genotype were sampled or harvested at 3, 6, 9, and 12 month after planting (MAP). All data collected were analyzed using the R-statistical package. The result showed moderate to high heritability among the traits, and there were significant differences (p< 0.05) among the performances of the genotypes. The genome-wide association mapping using the BLINK model detected 45 single-nucleotide polymorphism (SNP) markers significantly associated with the four early storage root bulking and formation traits on Chromosomes 1, 2, 3, 4, 5, 6, 8, 9, 10, 13, 14, 17, and 18.A total of 199 putative candidate genes were found to be directly linked to early storage root bulking and formation. The functions of these candidate genes were further characterized to regulate i) phytohormone biosynthesis, ii) cellular growth and development, and iii) biosynthesis of secondary metabolites for accumulation of starch and defense. Genome-wide association study (GWAS) also revealed the presence of four pleiotropic SNPs, which control starch content, dry matter content, dry yield, and bulking and formation index. The information on the GWAS could be used to develop improved cassava cultivars by breeders. Five genotypes (W940006, NR090146, TMS982123, TMS13F1060P0014, and NR010161) were selected as the best early storage root bulking and formation genotypes across the plant age. These selected cultivars should be used as sources of early storage root bulking and formation in future breeding programs.

KIN10-mediated HB16 protein phosphorylation and self-association improve cassava disease resistance by transcriptional activation of lignin biosynthesis genes.

Cassava bacterial blight significantly affects cassava yield worldwide, while major cassava cultivars are susceptible to this disease. Therefore, it is crucial to identify cassava disease resistance gene networks and defence molecules for the genetic improvement of cassava cultivars. In this study, we found that MeHB16 transcription factor as a differentially expressed gene in cassava cultivars with contrasting disease resistance, positively modulated disease resistance by modulating defence molecule lignin accumulation. Further investigation showed that MeHB16 physically interacted with itself via the leucine-Zippe domain (L-Zip), which was necessary for the transcriptional activation of downstream lignin biosynthesis genes. In addition, protein kinase MeKIN10 directly interacted with MeHB16 to promote its phosphorylation at Ser6, which in turn enhanced MeHB16 self-association and downstream lignin biosynthesis. In summary, this study revealed the molecular network of MeKIN10-mediated MeHB16 protein phosphorylation improved cassava bacterial blight resistance by fine-tuning lignin biosynthesis and provides candidate genes and the defence molecule for improving cassava disease resistance.

Comparative transcriptomics analysis reveals defense mechanisms of Manihot esculenta Crantz against Sri Lanka Cassava MosaicVirus

BackgroundCassava mosaic disease (CMD), caused by Sri Lankan cassava mosaic virus (SLCMV) infection, has been identified as a major pernicious disease in Manihot esculenta Crantz (cassava) plantations. It is widespread in Southeast Asia, especially in Thailand, which is one of the main cassava supplier countries. With the aim of restricting the spread of SLCMV, we explored the gene expression of a tolerant cassava cultivar vs. a susceptible cassava cultivar from the perspective of transcriptional regulation and the mechanisms underlying plant immunity and adaptation.ResultsTranscriptomic analysis of SLCMV-infected tolerant (Kasetsart 50 [KU 50]) and susceptible (Rayong 11 [R 11]) cultivars at three infection stages—that is, at 21 days post-inoculation (dpi) (early/asymptomatic), 32 dpi (middle/recovery), and 67 dpi (late infection/late recovery)—identified 55,699 expressed genes. Differentially expressed genes (DEGs) between SLCMV-infected KU 50 and R 11 cultivars at (i) 21 dpi to 32 dpi (the early to middle stage), and (ii) 32 dpi to 67 dpi (the middle stage to late stage) were then identified and validated by real-time quantitative PCR (RT-qPCR). DEGs among different infection stages represent genes that respond to and regulate the viral infection during specific stages. The transcriptomic comparison between the tolerant and susceptible cultivars highlighted the role of gene expression regulation in tolerant and susceptible phenotypes.ConclusionsThis study identified genes involved in epigenetic modification, transcription and transcription factor activities, plant defense and oxidative stress response, gene expression, hormone- and metabolite-related pathways, and translation and translational initiation activities, particularly in KU 50 which represented the tolerant cultivar in this study.

Functional Characterization of the MeSSIII-1 Gene and Its Promoter from Cassava.

Soluble starch synthases (SSs) play important roles in the synthesis of cassava starch. However, the expression characteristics of the cassava SSs genes have not been elucidated. In this study, the MeSSIII-1 gene and its promoter, from SC8 cassava cultivars, were respectively isolated by PCR amplification. MeSSIII-1 protein was localized to the chloroplasts. qRT-PCR analysis revealed that the MeSSIII-1 gene was expressed in almost all tissues tested, and the expression in mature leaves was 18.9 times more than that in tuber roots. MeSSIII-1 expression was induced by methyljasmonate (MeJA), abscisic acid (ABA), and ethylene (ET) hormones in cassava. MeSSIII-1 expression patterns were further confirmed in proMeSSIII-1 transgenic cassava. The promoter deletion analysis showed that the -264 bp to -1 bp MeSSIII-1 promoter has basal activity. The range from -1228 bp to -987 bp and -488 bp to -264 bp significantly enhance promoter activity. The regions from -987 bp to -747 bp and -747 bp to -488 bp have repressive activity. These findings will provide an important reference for research on the potential function and transcriptional regulation mechanisms of the MeSSIII-1 gene and for further in-depth exploration of the regulatory network of its internal functional elements.

Molecular Genetic Diversity of Manioc (Manihot esculenta Crantz) Using Simple Sequence Repeated Markers (SSR) in the Kara Region of Togo

Cassava (Manihot esculenta Crantz), a plant of the future, is one of the main crops with high genetic potential. Therefore, the knowledge of its genetic variability would be of great importance for its effective use in genetic improvement programs. The objective of this work was to characterize the genetic diversity of cassava cultivars present in the Kara region of Togo. Thus, a total of 91 cassava leaf samples collected in the 7 prefectures of the Kara region were analyzed using 7 pairs of SSR microsatellite primers. Fifty-three alleles were detected with an average of 7.57 alleles per locus. The polymorphic information content ranged from 0.63 to 0.83 with an average of 0.74, indicating a high level of marker polymorphism. Molecular analysis of variance revealed that the majority of variability occurred within individuals and accounted for 99 % of the total variation between individuals. Weak genetic differentiation (Fst=0.011) was also observed between populations. The genetic structuring model based on the Neighbour-Joining algorithm method divided the individuals into 6 groups independently of local names. These results indicate the presence of high genetic resource variability in the studied populations. Therefore, it would be important to implement management strategies to better conserve cassava genetic resources and to facilitate the identification of successful cultivars.

Molecular Genetic Diversity of Cassava (Manihot esculenta CRANTZ) in the Maritime Region of Togo using Simple Sequence Repeat (SSR) Markers

Cassava is a plant cultivated for its calorie-rich leaves and tuberous roots. Unfortunately, genetic improvement of cassava is limited by the lack of information on its genetic variability. The objective of the present work was to study the genetic and molecular diversity of cassava cultivars using microsatellite markers (SSR) in the Maritime region of Togo. A total of 95 cassava individuals from 7 cultivars were evaluated using 7 SSRs. The average polymorphic information content was 0.74 and the average number of alleles per locus was 7. The average observed heterozygosity was lower than the expected average heterozygosity for the 7 cultivars, showing positive fixation indices and presence of inbreeding. Molecular analysis of variance revealed greater molecular variation within cultivars (94%). The dendrogram constructed using the Neighbor Joining method resulted in 3 groups. The high genetic diversity observed could be due to the exchange of cuttings by growers. This diversity would be valuable for efficient germplasm management and for effective use of the material in breeding.

Assessment of Yellow and White Fleshed Cassava Tuberous Root Cultivars Reveals Different Responses to Post-harvest Physiological Deterioration

Identification of post-harvest physiological deterioration (PPD) tolerance in cassava is crucial, as PPD significantly hampers the cassava tuberous root industry by shortening storage periods post-harvest and diminishing product quality. Characteristics linked to PPD tolerance encompass high carotenoid levels and low dry matter content (DMC). This study aimed to evaluate the PPD responses of six yellow fleshed and ten white-fleshed cassava tuberous roots and determine the source of PPD tolerance. PPD and DMC assessments were conducted using standard methods at three storage periods: 2, 5, and 10 days after harvest (DAH). The k-means clustering analysis revealed six clusters, each corresponding to distinct PPD symptom patterns and tolerance statuses. Cluster 1, comprising three yellow-fleshed and three white-fleshed cassava cultivars, demonstrated PPD tolerance with minimal symptoms up to 5 DAH. Clusters 2 and 3 exhibited a moderate PPD response with elevated symptoms at 5 DAH, comprising three yellow-fleshed and three white-fleshed cassava cultivars. Clusters 4 to 6 displayed a sensitive response to PPD, showcasing a significant increase in symptoms at 5 and 10 DAH, with four white-fleshed cassava cultivars identified within this cluster. These findings underscored the presence of PPD tolerance in both yellow-fleshed and white-fleshed cassava tuberous roots. The correlation between PPD and DMC was significant only at 2 DAH, displaying a moderate positive correlation. Consequently, this study identified three cultivars, “Carvita-25”, “Manggu”, and ““Ubi Kuning””, with high DMC and low PPD incidence at 5 DAH, suggesting their suitability for further breeding programs.

Elevated viral small RNA profiling in cassava cultivars suppress the occurrence of Cassava brown streak disease (CBSD)

Cassava brown streak disease (CBSD), caused by cassava brown streak virus (CBSV) and; Ugandan cassava brown streak virus (UCBSV) causes the most destructive cassava disease in Tanzania. Thus, breeders urgently need CBSD-resistant cultivars to combat the impact of this disease, safeguard cassava production, improve the yields and secure food supply for communities reliant on this staple crop. In this study, we used four cassava cultivars; Albert, KBH 2002/135, KBH 2006/026 and Kiroba to explore how viral small interfering RNA (vsiRNAs), an antiviral silencing mechanism, confers CBSD resistance. Cassava plants were inoculated by grafting method using the single infection of CBSV, UCBSV and mixed infection of these viruses (co-infection). Total RNA was extracted from leaves of each cultivar followed by deep sequencing. The result showed that high level of vsiRNAs was produced in inoculated plants, with the most prominent class being 21 and 22 nucleotides. Kiroba produced the highest level of vsiRNA in both CBSV and UCBSV, whereas KBH 2006/026 produced high level of vsiRNA only with UCBSV infections. In contrast to UCBSV, inoculation with CBSV stimulated severe symptoms but relatively low levels of vsiRNA. Co-infection treatment showed a more complex interaction between the host and virus, with variations in the severity and amount of vsiRNA produced. We conclude that resistance to CBSD varies depending on the type of cultivar and virus species, and the occurrence of CBSD is suppressed in plants with elevated vsiRNA. Therefore, a good understanding on the resistance status of parental materials for breeding is recommended to breeders as a basis for improving cassava production.

Cultivares de mandioca de mesa eficientes e responsivas ao uso do fósforo

ABSTRACT Table cassava cultivars efficient in the use of phosphorus (P) and responsive to phosphate fertilization represent a crop option for regions with low availability of the nutrient and for crops using technological packages, such as investment in fertilization. The objective of the study was to classify table cassava cultivars regarding efficiency and responsiveness to P application in two agricultural crops. For this, four table cassava cultivars (Água Morna, BRS Gema de Ovo, Recife and Venâncio) were evaluated under conditions of low P availability (and without phosphate fertilization) and high availability (and fertilized with 240 kg ha-1 of P2O5). The Água Morna cultivar proved to be efficient and responsive in the two harvests evaluated. Only the Venâncio cultivar was classified as non-efficient. There was variation in the response of the Recife cultivar between the crops evaluated.

Evaluation of Cassava Peeling Machine using Dimensional Analysis Technique

Cassava processing for various products requires an efficient peeling process. However, peeling – the first step in its processing – has been considered laborious and time-consuming; hence, the need for full mechanization. Several mechanical peeling approaches have been exploited by researchers toward achieving ideal peeling. In this study, an innovative abrasive cassava peeling machine, combining chemical and mechanical peeling methods, was used for the experiment using TMS 30572 and TME 419 cassava cultivars. The physical and technological characteristics of the motion of the roots within the peeling compartment were subjected to analysis. Model equations based on dimensional analysis were adopted to predict the functionalities between cassava and the peeler variables. The following cassava roots properties were established: distal diameter (TME 419: 15.20-26.50 mm; TME 30572: 10.20-35.10 mm), peel thickness (TME 419: 1.60-4 mm; TME 30572: 1.80-4 mm) and moisture content (TME 419: 59.20-61.18%; TME 30572: 58.40-60.40%). The machine’s peeling efficiency (μ), mechanical damage (λ), peel retention (P) and throughput capacity (η) were 62.02-86.45%, 1.26-2.90%, 8.26-11.63%, 900-1,210.5 kg/h, respectively, for both cultivars. A linear relationship was found between the machine speed, velocity of conveyance and peeling time. The study revealed that the machine resulted in the careful removal of the cassava peels achieving good peeling efficiency at a speed of 1,600 rpm &lt; Nt &lt; 2,600 rpm depending on the variety. It is recommended for peeling operations in cassava processing factories.