Technological Innovations for Improving Cassava Production in Sub-Saharan Africa

Rapid analysis of hydrogen cyanide in fresh cassava roots using NIRSand machine learning algorithms: Meeting end user demand for low cyanogenic cassava

This study focuses on meeting end-users' demand for cassava (Manihot esculenta Crantz) varieties with low cyanogenic potential (hydrogen cyanide potential [HCN]) by using near-infrared spectrometry (NIRS). This technology provides a fast, accurate, and reliable way to determine sample constituents with minimal sample preparation. The study aims to evaluate the effectiveness of machine learning (ML) algorithms such as logistic regression (LR), support vector machine (SVM), and partial least squares discriminant analysis (PLS-DA) in distinguishing between low and high HCN accessions. Low HCN accessions averagely scored 1-5.9, while high HCN accessions scored 6-9 on a 1-9 categorical scale. The researchers used 1164 root samples to test different NIRS prediction models and six spectral pretreatments. The wavelengths 961, 1165, 1403-1505, 1913-1981, and 2491 nm were influential in discrimination of low and high HCN accessions. Using selected wavelengths, LR achieved 100% classification accuracy and PLS-DA achieved 99% classification accuracy. Using the full spectrum, the best model for discriminating low and high HCN accessions was the PLS-DA combined with standard normal variate with second derivative, which produced an accuracy of 99.6%. The SVM and LR had moderate classification accuracies of 75% and 74%, respectively. This study demonstrates that NIRS coupled with ML algorithms can be used to identify low and high HCN accessions, which can help cassava breeding programs to select for low HCN accessions.

Cassava pomace-based biodegradable packaging materials: a review

Starch-based biodegradable packaging materials are gaining popularity as an alternative to the adverse environmental effects caused by conventional packaging materials. Despite the fact that cassava can withstand harsh environmental conditions and convert a greater quantity of solar energy into carbohydrates, its postharvest shelf life is extremely short. The preparation of cassava starch is an important method for extending the storage life of cassava. When one ton of cassava is processed, approximately 900 kg of cassava pomace, also known as cassava bagasse and cassava pulp, are produced. Due to the high residual starch and fibre content, reinforced packaging materials made from cassava pomace predominate. In the present manuscript, many possible uses of cassava pomace in packaging materials are discussed.  Furthermore, the performance attributes of packing materials assume a crucial role in the evaluation of the quality of the respective materials. The manuscript discusses various performance characteristics of packaging materials derived from cassava pomace. The features discussed include water vapour permeability, moisture content, solubility, thickness, colour, light barrier properties, mechanical properties, FT-IR analysis, thermal stability, biodegradation, contact angle, and the presence of plasticizers. Though cassava starch film has become a favourable substitute for conventional packaging materials, commercialization is limited due to having drawbacks, and the current solutions are also catalogued in this review.

Candidate genes for field resistance to cassava brown streak disease revealed through the analysis of multiple data sources

Cassava (Manihot esculenta Crantz) is a food and industrial storage root crop with substantial potential to contribute to managing risk associated with climate change due to its inherent resilience and in providing a biodegradable option in manufacturing. In Africa, cassava production is challenged by two viral diseases, cassava brown streak disease (CBSD) and cassava mosaic disease. Here we detect quantitative trait loci (QTL) associated with CBSD in a biparental mapping population of a Tanzanian landrace, Nachinyaya and AR37-80, phenotyped in two locations over three years. The purpose was to use the information to ultimately facilitate either marker-assisted selection or adjust weightings in genomic selection to increase the efficiency of breeding. Results from this study were considered in relation to those from four other biparental populations, of similar genetic backgrounds, that were phenotyped and genotyped simultaneously. Further, we investigated the co-localization of QTL for CBSD resistance across populations and the genetic relationships of parents based on whole genome sequence information. Two QTL on chromosome 4 for resistance to CBSD foliar symptoms and one on each of chromosomes 11 and 18 for root necrosis were of interest. Of significance within the candidate genes underlying the QTL on chromosome 4 are Phenylalanine ammonia-lyase (PAL) and Cinnamoyl-CoA reductase (CCR) genes and three PEPR1-related kinases associated with the lignin pathway. In addition, a CCR gene was also underlying the root necrosis-resistant QTL on chromosome 11. Upregulation of key genes in the cassava lignification pathway from an earlier transcriptome study, including PAL and CCR, in a CBSD-resistant landrace compared to a susceptible landrace suggests a higher level of basal lignin deposition in the CBSD-resistant landrace. Earlier RNAscope® in situ hybridisation imaging experiments demonstrate that cassava brown streak virus (CBSV) is restricted to phloem vessels in CBSV-resistant varieties, and phloem unloading for replication in mesophyll cells is prevented. The results provide evidence for the involvement of the lignin pathway. In addition, five eukaryotic initiation factor (eIF) genes associated with plant virus resistance were found within the priority QTL regions.

Prediction of functional characteristics of gari (cassava flakes) using near-infrared reflectance spectrometry

Gari is a creamy, granular flour obtained from roasting fermented cassava mash. Its preparation involves several unit operations, including fermentation, which is essential in gari production. Fermentation brings about specific biochemical changes in cassava starch due to the actions of lactic acid bacteria. Consequently, it gives rise to organic acids and a significant reduction in the pH. Consumer preferences for gari are influenced by these changes and impact specific functional characteristics, which are often linked to cassava genotypes. Measurement of these functional characteristics is time-consuming and expensive. Therefore, this study aimed to develop high-throughput and less expensive prediction models for water absorption capacity, swelling power, bulk density, and dispersibility using Near-Infrared Reflectance Spectroscopy (NIRS). Gari was produced from 63 cassava genotypes using the standard method developed in the RTB foods project. The prediction model was developed by dividing the gari samples into two sets of 48 samples for calibration and 15 samples as the validation set. The gari samples were transferred into a ring cell cup and scanned on the NIRS machine within the Vis-NIR range of 400-2,498 nm wavelength, though only the NIR range of 800-2,400 nm was used to build the model. Calibration models were developed using partial least regression algorithms after spectra pre-processing. Also, the gari samples were analysed in the laboratory for their functional properties to generate reference data. Results showed an excellent coefficient of determination in calibrations (R² _Cal) of 0.99, 0.97, 0.97, and 0.89 for bulk density, swelling power, dispersibility, and water absorption capacity, respectively. Also, the performances of the prediction models were tested using an independent set of 15 gari samples. A good prediction coefficient (R² pred) and low standard error of prediction (SEP) was obtained as follows: Bulk density (0.98), Swelling power (0.93), WAC (0.68), Dispersibility (0.65), and solubility index (0.62), respectively. Therefore, NIRS prediction models in this study could provide a rapid screening tool for cassava breeding programs and food scientists to determine the food quality of cassava granular products (Gari).

Sorghum, millet and cassava as alternative dietary energy sources for sustainable quail production – A review

Diversification and expansion of the poultry industry with fast-growing and highly prolific birds such as the quail (Coturnix coturnix), could contribute significantly in achieving global food and nutrition security. However, sustainable intensification of the quail relies on the cost of dietary ingredients used during feed formulations. The use of non-conventional energy sources such as sorghum, millet, and cassava in lieu of expensive energy sources such as maize, could ensure sustainable quail businesses. Generally, alternative feedstuffs should be cost-effective and possess comparable nutritional qualities as maize. In tropical countries such as South Africa, the use of sorghum, millet, and cassava in quail diets can serve as ideal alternatives because they have relatively comparable energy values as maize. Furthermore, these alternatives are largely available and easily accessible in many farming areas of South Africa. However, the presence of antinutritional factors such as tannins, cyanides and phytic acid, among others, as well as their high fiber levels may limit their utilization in quail nutrition. Nevertheless, attempts have been made to develop improved varieties with low antinutrient compositions, for instance, low-tannin sorghum varieties are increasingly being fed to poultry birds. Furthermore, there is growing evidence that certain processing techniques such as sun-drying, soaking, boiling and fermentation, among others, can lower the concentrations of antinutrients in these alternative feedstuffs, thus increasing their feeding value. To this end, nutritional feeding trials on the positive effects of sorghum, millet and cassava in quail nutrition are inconsistent, mainly due to differences in cultivar type, harvesting site or environmental conditions, sampling, and handling methods amongst other factors. Thus, the present review aimed to discuss the potential of substituting maize with sorghum, millet, and cassava in quail diets.

Climate change challenges, plant science solutions

Climate change is a defining challenge of the 21st century, and this decade is a critical time for action to mitigate the worst effects on human populations and ecosystems. Plant science can play an important role in developing crops with enhanced resilience to harsh conditions (e.g. heat, drought, salt stress, flooding, disease outbreaks) and engineering efficient carbon-capturing and carbon-sequestering plants. Here, we present examples of research being conducted in these areas and discuss challenges and open questions as a call to action for the plant science community.

Organic manures and inorganic fertilizers effects on soil properties and economic analysis under cassava cultivation in the southern Cameroon

Cassava cultivation causes serious soil fertility depletion in southern Cameroon due to high mining of soil nutrients by the crop. This study aimed to evaluate the effects of Tithonia diversifolia fresh biomass (TB), poultry manure (PM) and inorganic fertilizers (IF) on soil properties, cassava yield, and the economic returns. The treatments consisted of two rates of TB (10 and 20 t ha^-1), two rates of PM (10 and 20 t ha^-1), two rates of combined TB and PM (5 and 10 t ha^-1), a single rate of inorganic fertilizers (100 N:22P:83 K kg ha^-1) and a control. The results showed that soil properties, soil quality index and cassava yield were significantly improved by the application of the organic manures. Tithonia diversifolia fresh biomass (TB) and poultry manure (PM) lowered the soil bulk density, increased soil total porosity, water holding capacity and chemical properties. TB and PM, solely or mixed, improved the aerial dry biomass (ADB) and fresh tuber yield (FTY) of cassava. The organic manures performed better than inorganic fertilizer. The highest yield (51 and 52 t ha^-1 of fresh tubers) was obtained with the mixture of TB and PM applied at 10 t ha^-1 each for the successive years. Positive and significant correlation was found between SQI and cassava yield. TB and PM combined at 10 t ha^-1 each was the most profitable and cost-effective treatment, with a good benefit:cost ratio of 3.2:1 and net return of FCFA 3.736.900 ha^-1. Thus, the use of Tithonia diversifolia fresh biomass and poultry manure is a sustainable method for cassava production in the southern Cameroon.

G-DIRT: a web server for identification and removal of duplicate germplasms based on identity-by-state analysis using single nucleotide polymorphism genotyping data

Maintaining duplicate germplasms in genebanks hampers effective conservation and utilization of genebank resources. The redundant germplasm adds to the cost of germplasm conservation by requiring a large proportion of the genebank financial resources towards conservation rather than enriching the diversity. Besides, genome-wide-association analysis using an association panel with over-represented germplasms can be biased resulting in spurious marker-trait associations. The conventional methods of germplasm duplicate removal using passport information suffer from incomplete or missing passport information and data handling errors at various stages of germplasm enrichment. This limitation is less likely in the case of genotypic data. Therefore, we developed a web-based tool, Germplasm Duplicate Identification and Removal Tool (G-DIRT), which allows germplasm duplicate identification based on identity-by-state analysis using single-nucleotide polymorphism genotyping information along with pre-processing of genotypic data. A homozygous genotypic difference threshold of 0.1% for germplasm duplicates has been determined using tetraploid wheat genotypic data with 94.97% of accuracy. Based on the genotypic difference, the tool also builds a dendrogram that can visually depict the relationship between genotypes. To overcome the constraint of high-dimensional genotypic data, an offline version of G-DIRT in the interface of R has also been developed. The G-DIRT is expected to help genebank curators, breeders and other researchers across the world in identifying germplasm duplicates from the global genebank collections by only using the easily sharable genotypic data instead of physically exchanging the seeds or propagating materials. The web server will complement the existing methods of germplasm duplicate identification based on passport or phenotypic information being freely accessible at http://webtools.nbpgr.ernet.in/gdirt/.

The Roles of Cassava in Marginal Semi-Arid Farming in East Nusa Tenggara—Indonesia

Risk and uncertainty in grain crop production are common in marginal semi-arid environments, such as East Nusa Tenggara province. Growing root and tuber crops in a mixed-cropping system is one of the strategies developed by smallholder farmers to substitute food grains and minimize risk. Nevertheless, root and tuber crops are not prioritized for food production systems since food crops in Indonesia are based more on grain and wetland rice production systems. This paper reviews cassava crops, which are widely cultivated by smallholder farmers. This paper contributes to understanding the roles of cassava for smallholder farmers, the diversity of the cassava germ plasm, the progress made to increase cassava productivity, and the potency of cassava crops to improve farmers’ incomes. This paper highlights that, in the low and erratic rainfall of dominant semi-arid regions, the development of cassava is pivotal to secure the harvest of food crops or food availability and income generation for marginal farmers.

Indigenous African Orphan Legumes: Potential for Food and Nutrition Security in SSA

In Sub-Saharan Africa (SSA), both crop production and the hidden hunger index (HHI, a combination of zinc, iron, and vitamin A deficiency), continue to be worse than the rest of the world. Currently, 31 out of 36 countries of SSA show the highest HHI. At the same time, several studies show climate change as a major constraint to agriculture productivity and a significant threat to SSA food security without significant action regarding adaptation. The food security of SSA is dependent on a few major crops, with many of them providing largely only an energy source in the diet. To address this, crop diversification and climate-resilient crops that have adaptation to climate change can be used and one route toward this is promoting the cultivation of African orphan (neglected or underutilized) crops. These crops, particularly legumes, have the potential to improve food and nutrition security in SSA due to their cultural linkage with the regional food habits of the communities, nutritionally rich food, untapped genetic diversity, and adaptation to harsh climate conditions and poor marginal soils. Despite the wide distribution of orphan legumes across the landscape of SSA, these important crop species are characterized by low yield and decreasing utilization due in part to a lack of improved varieties and a lack of adequate research attention. Genomic-assisted breeding (GAB) can contribute to developing improved varieties that yield more, have improved resilience, and high nutritional value. The availability of large and diverse collections of germplasm is an essential resource for crop improvement. In the Genetic Resources Center of the International Institute of Tropical Agriculture, the collections of orphan legumes, particularly the Bambara groundnut, African yambean, and Kersting's groundnut, have been characterized and evaluated for their key traits, and new collections are being undertaken to fill gaps and to widen the genetic diversity available to underpin breeding that can be further utilized with GAB tools to develop faster and cost-effective climate-resilient cultivars with a high nutrition value for SSA farmers. However, a greater investment of resources is required for applying modern breeding to orphan legume crops if their full potential is to be realized.

The future of cassava in the era of biotechnology in Southern Africa

Cassava (Manihot esculenta) is a major staple food and the world's fourth source of calories. Biotechnological contributions to enhancing this crop, its advances, and present issues must be assessed regularly. Functional genomics, genomic-assisted breeding, molecular tools, and genome editing technologies, among other biotechnological approaches, have helped improve the potential of economically important crops like cassava by addressing some of its significant constraints, such as nutrient deficiency, toxicity, poor starch quality, disease susceptibility, low yield capacity, and postharvest deterioration. However, the development, improvement, and subsequent acceptance of the improved cultivars have been challenging and have required holistic approaches to solving them. This article provides an update of trends and gaps in cassava biotechnology, reviewing the relevant strategies used to improve cassava crops and highlighting the potential risk and acceptability of improved cultivars in Southern Africa.

Impact of Seasonal Variation and Processing Methods on the Cassava-Derived Dietary Cyanide Poisoning, Nutritional Status, and Konzo Appearance in South-Kivu, Eastern D.R. Congo

This study aimed at evaluating the impact of seasons on the nutritional status and on dietary cassava-related cyanide exposure in Burhinyi and Idjwi, two areas in the eastern Democratic Republic of the Congo, witnessing similarly high cassava-derived cyanide poisoning but differently affected by konzo and malnutrition. Cyanide content in cassava roots and flour, and urinary thiocyanate levels (uSCN) of 54 subjects (40 from Burhinyi and 14 from Idjwi, aged 28.7 (12.1) years, 63% women) were measured during the rainy season (RS) and dry season (DS), using picrate paper kits A and D1. Local processing methods proved to be efficient in removing cyanogenic compounds in fresh cassava roots during the RS. However, the cyanide content in flour samples significantly increased during DS, with ~50% of samples containing unsafe levels (>10 ppm) of cyanide content. Strikingly, the uSCN (µmol/L), from being comparably high in RS (~172.0), slightly decreased during DS in Burhinyi (~103.2; p = 0,3547), but not in Idjwi (~172; p = 0,1113). Furthermore, serum proteins and albumin levels significantly decreased during the DS, witnessing a worsening of nutritional status, in Burhinyi but not in Idjwi. The consumption of bitter cassava roots (OR = 5.43, p = 0.0144) and skipping heap fermentation (OR = 16.67, p = 0.0021) were independently associated with very high uSCN levels during the DS. Thus, restoring the traditional processing methods, and complying with them in either season should ensure the safe consumption of cassava.

The Sensory Profiles of Flatbreads Made from Sorghum, Cassava, and Cowpea Flour Used as Wheat Flour Alternatives

Sorghum, cowpea, and cassava are underutilised gluten-free sources of flour that have the potential to be used in bread products in sub-Saharan Africa. Excessive wheat imports affect the economies of countries in sub-Saharan Africa, driving the search for wheat flour alternatives. To extend the use of sorghum, cowpea, and cassava flours toward bread production, it is vital that the sensory properties of these flours are better understood. A trained sensory panel evaluated and described the sensory properties of flatbread models prepared from red non-tannin sorghum, fractions (whole and dehulled) of two cowpea varieties, cassava starch, and designated flour composites. The composites were prepared using cassava starch and sorghum flour at 0%, 35%, and 70%, respectively, with 30% cowpea flour. The addition of sorghum intensified sorghum aroma in flatbread, while cowpea flours contributed a beany flavour. Flatbreads from cassava-cowpea composites had a chewier and rubberier mouthfeel, an intense fermented aroma and flavour, and a sour aftertaste compared to single flours, but were most similar to the wheat flatbread, with a residual beany flavour. Information from this study can guide food product developers toward developing new bread products from sorghum, cassava, and cowpea composite flours, thereby moving Africa towards a more sustainable food system. Further research on the effects of the sensory characteristics on consumer liking of the flatbreads is needed.

Fifty years of a public cassava breeding program: evolution of breeding objectives, methods, and decision-making processes

This paper reviews and analyzes key features from cassava breeding at the International Center for Tropical Agriculture (CIAT) over 50 years and draws lessons for public breeding efforts broadly. The breeding team, jointly with national program partners and the private processing sector, defined breeding objectives and guiding business plans. These have evolved through the decades and currently focus on four global product profiles. The recurrent selection method also evolved and included innovations such as estimation of phenotypic breeding values, increasing the number of locations in the first stage of agronomic evaluations, gradual reduction of the duration of breeding cycles (including rapid cycling for high-heritability traits), the development of protocols for the induction of flowering, and the introduction of genome-wide predictions. The impact of cassava breeding depends significantly on the type of target markets. When roots are used for large processing facilities for starch, animal feeding or ethanol production (such as in SE Asia), the adoption of improved varieties is nearly universal and productivity at the regional scale increases significantly. When markets and relevant infrastructure are weak or considerable proportion of the production goes for local artisanal processing and on-farm consumption, the impact has been lower. The potential of novel breeding tools needs to be properly assessed for the most effective allocation of resources. Finally, a brief summary of challenges and opportunities for the future of cassava breeding is presented. The paper describes multiple ways that public and private sector breeding programs can learn from each other to optimize success.