Highre-solution linkage map and chromosome-scale genome assembly for cassava (Manihot esculenta Crantz) from 10 populations

Cassava (Manihot esculenta Crantz) is a major staple crop in Africa, Asia, and South America, and its starchy roots provide nourishment for 800 million people worldwide. Although native to South America, cassava was brought to Africa 400–500 years ago and is now widely cultivated across sub-Saharan Africa, but it is subject to biotic and abiotic stresses. To assist in the rapid identification of markers for pathogen resistance and crop traits, and to accelerate breeding programs, we generated a framework map for M. esculenta Crantz from reduced representation sequencing [genotyping-by-sequencing (GBS)]. The composite 2412-cM map integrates 10 biparental maps (comprising 3480 meioses) and organizes 22,403 genetic markers on 18 chromosomes, in agreement with the observed karyotype. We used the map to anchor 71.9% of the draft genome assembly and 90.7% of the predicted protein-coding genes. The chromosome-anchored genome sequence will be useful for breeding improvement by assisting in the rapid identification of markers linked to important traits, and in providing a framework for genomic selectionenhanced breeding of this important crop

Impact of host plant species and whitefly species on feeding behavior of Bemisia tabaci

Open Access JournalWhiteflies of the Bemisia tabaci species complex are economically important pests of cassava. In Africa, they cause greatest damage through vectoring viruses responsible for cassava mosaic disease and cassava brown streak disease. Several cryptic species from the B. tabaci complex colonize cassava and neighboring crops, but the feeding interactions between the different crops and B. tabaci species are unknown. The electrical penetration graph (EPG) technique makes it possible to conduct detailed feeding studies of sap-sucking insects by creating an electric circuit through the insect and the plant. The apparatus measures the voltage fluctuations while the wired-up insect feeds and produces graphs that describe feeding behavior. We utilized EPG to explore the feeding behavior of cassava-colonizing whiteflies (SSA1-SG3) on cassava, sweet potato, tomato, and cotton; and sweet potato-colonizing whiteflies (MED and IO) on cassava and sweet potato. Results show that: (1) feeding of SSA1-SG3 is not restricted to cassava. The least preferred host for SSA1-SG3 was tomato, where probing was delayed by 99 min compared to 10 min on other hosts, furthermore mean duration of phloem ingestion events was 36 min compared to 260 min on cassava. (2) Feeding of MED on cassava appeared to be non-functional, as it was characterized by short total phloem ingestion periods (5 h). (3) Wire diameter affects the feeding in a statistically and practically significant manner. Implications for whitefly control and studies of host whitefly resistance are discussed

Upscaling cassava processing machines and products in Liberia

Open Access JournalCassava is produced by more than 80% of farming households and is an important contributor to gross domestic product (GDP) in Liberia. It is therefore important to assess the status of cassava processing into food and other products. A total of one hundred and sixty (160) well-structured questionnaires were used for the collection of information from eight counties, with twenty respondents from each county. It was found out that all the counties lack adequate modern cassava processing machines, with almost all cassava processing operations being done with rudimentary equipment. Gari and wet fufu are common products in Liberian markets, with no high-quality cassava flour (HQCF) or derivatives. Consequently, user and gender friendly processing machines were installed in six established modern cassava processing centres, and new cassava products, such as fufu powder, tapioca, and HQCF with its value-added products (10% bread and pastries), were introduced. This upscaling will enhance the cassava value chain in Liberia with improvement in livelihoods, especially for vulnerable women and unemployed youth

Genome-wide analyses of cassava Pathogenesis-related (PR) gene families reveal core transcriptome responses to whitefly infestation, salicylic acid and jasmonic acid.

BACKGROUND:Whiteflies are a threat to cassava (Manihot esculenta), an important staple food in many tropical/subtropical regions. Understanding the molecular mechanisms regulating cassava's responses against this pest is crucial for developing control strategies. Pathogenesis-related (PR) protein families are an integral part of plant immunity. With the availability of whole genome sequences, the annotation and expression programs of the full complement of PR genes in an organism can now be achieved. An understanding of the responses of the entire complement of PR genes during biotic stress and to the defense hormones, salicylic acid (SA) and jasmonic acid (JA), is lacking. Here, we analyze the responses of cassava PR genes to whiteflies, SA, JA, and other biotic aggressors. RESULTS:The cassava genome possesses 14 of the 17 plant PR families, with a total of 447 PR genes. A cassava PR gene nomenclature is proposed. Phylogenetic relatedness of cassava PR proteins to each other and to homologs in poplar, rice and Arabidopsis identified cassava-specific PR gene family expansions. The temporal programs of PR gene expression in response to the whitefly (Aleurotrachelus socialis) in four whitefly-susceptible cassava genotypes showed that 167 of the 447 PR genes were regulated after whitefly infestation. While the timing of PR gene expression varied, over 37% of whitefly-regulated PR genes were downregulated in all four genotypes. Notably, whitefly-responsive PR genes were largely coordinately regulated by SA and JA. The analysis of cassava PR gene expression in response to five other biotic stresses revealed a strong positive correlation between whitefly and Xanthomonas axonopodis and Cassava Brown Streak Virus responses and negative correlations between whitefly and Cassava Mosaic Virus responses. Finally, certain associations between PR genes in cassava expansions and response to biotic stresses were observed among PR families. CONCLUSIONS:This study represents the first genome-wide characterization of PR genes in cassava. PR gene responses to six biotic stresses and to SA and JA are demonstrably different to other angiosperms. We propose that our approach could be applied in other species to fully understand PR gene regulation by pathogens, pests and the canonical defense hormones SA and JA

Technical Efficiency Analysis of Nigerian Cassava Farmers: A Guide for Food Security Policy

This study analyzed relationship between techn ical efficiency and socio-economic variables of cassava farmers in Nigeria. Data were collected from randomly sampled 360 cassava farmers in Nigeria using a structured questionnaire. The data were analyzed using descriptive statistics comprising mean, minimum value, maximum value and standard deviation, as well as inferential statistics, which comprised correlation and regression. The findings of the s tudy indicated that a significant relationship exists between technical efficiency and cassava output (0.542), farm income (0.612), processing cost (- 0.414), gari yield (0.608), gross margin (0.483), farming experience (0.278), education (0.699) and extension contact (0.585) of the sampled cassava farmers in Nigeria. Multiple regression result showed that variation in technical efficiency is explained by variations in annual farm income (2.718E-06), annual processing cost (- 1.542E-05), annual gross margin (9.383E-07) farming experience (3.825E-03), education (0.191) and extension contact (6.562E-02). Hence, policy that would enable cassava farmers in Nigeria increase farm income, gross margin and have access to quality education and extension services will lead to the enhancement of technical efficiency of cassava production. Furthermore, policy that would encourage experienced farmers in cassava production and ensure that cost effective improved cassava processing technology is available to the cassava farmers will enhance technical efficiency in cassava production in Nigeria. Policy that would further raise the current level of technical efficiency in cassava production in Nigeria is strongly recommended for the enhancement of the welfare of the cassava farmers in Nigeria.technical efficiency, Nigerian cassava farmers, food security policy, Crop Production/Industries, Food Security and Poverty, Productivity Analysis,

Sustainable Agricultural Bioindustry Development: Integration of Cassava Cultivation with Beef Cattle Husbandry in North Sulawesi Province

This paper reviews the potential sustainable agricultural bioindustry development based on animal feed and organic fertilizer through an integration between crops cultivation with livestock production. This bio-industrial development could be carried out successfully in Indonesia, including in the region of North Sulawesi Province. Cattle feed bioindustry could be developed from biomass of cassava plantation, such as the cassava leaves, tubers and cassava peelers. Whereas, the solid and liquid organic fertilizers bioindustry could be developed from cattle feces and urine. Agricultural bioindustry can be carried out in all areas of North Sulawesi Province, because almost in every district has beef cattle and cassava plants. The largest cassava production in North Sulawesi Province are in the regencies of Bolaang Mongondow, Sangihe Island and Talaud Island. Whereas the highest population of beef cattle are in the regencies of Bolaang Mongondow, North Bolaang Mongondow, Minahasa, North Minahasa and South Minahasa. Therefore, this type of bioindustry will be well implemented in the three regencies of Bolaang Mongondow, Minahasa and North Minahasa, as there are large cassava plants and with a high livestock population in these three areas. Although numbers of beef cattle population are also higher in some other regencies, but the production of cassava in those areas are still very small