Journal of the Science of Food and AgricultureVolume 104, Issue 8 p. 4481-4484 Editorial Tropical roots, tubers and bananas: new breeding tools and methods to meet consumer preferences Dominique Dufour, Corresponding Author Dominique Dufour [email protected] French Agricultural Research Centre for International Development (CIRAD), UMR QualiSud, Univ Montpellier, Avignon Université, CIRAD, Institut Agro, IRD, Université de La Réunion, F-34398, Montpellier, France Correspondence to: D Dufour, French Agricultural Research Centre for International Development (CIRAD), Montpellier, France. E-mail: [email protected]Search for more papers by this authorHernán Ceballos, Hernán Ceballos Formerly International Center for Tropical Agriculture (CIAT), Cali, Colombia Independent consultant, Mijas, SpainSearch for more papers by this authorClair Hershey, Clair Hershey Formerly International Center for Tropical Agriculture (CIAT), Cali, Colombia Independent consultant, Flinton, PA, USASearch for more papers by this authorBruce Hamaker, Bruce Hamaker Whistler Center for Carbohydrate Research Purdue University, West Lafayette, IN, USASearch for more papers by this authorJim Lorenzen, Jim Lorenzen Bill & Melinda Gates Foundation (BMGF), Discovery/Crop R&D Global Growth & Opportunity, Seattle, WA, USASearch for more papers by this author Dominique Dufour, Corresponding Author Dominique Dufour [email protected] French Agricultural Research Centre for International Development (CIRAD), UMR QualiSud, Univ Montpellier, Avignon Université, CIRAD, Institut Agro, IRD, Université de La Réunion, F-34398, Montpellier, France Correspondence to: D Dufour, French Agricultural Research Centre for International Development (CIRAD), Montpellier, France. E-mail: [email protected]Search for more papers by this authorHernán Ceballos, Hernán Ceballos Formerly International Center for Tropical Agriculture (CIAT), Cali, Colombia Independent consultant, Mijas, SpainSearch for more papers by this authorClair Hershey, Clair Hershey Formerly International Center for Tropical Agriculture (CIAT), Cali, Colombia Independent consultant, Flinton, PA, USASearch for more papers by this authorBruce Hamaker, Bruce Hamaker Whistler Center for Carbohydrate Research Purdue University, West Lafayette, IN, USASearch for more papers by this authorJim Lorenzen, Jim Lorenzen Bill & Melinda Gates Foundation (BMGF), Discovery/Crop R&D Global Growth & Opportunity, Seattle, WA, USASearch for more papers by this author First published: 16 May 2024 https://doi.org/10.1002/jsfa.13064Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat REFERENCES 1Scott GJ, A review of root, tuber and banana crops in developing countries: past, present and future. Int J Food Sci Technol 56: 1093–1114 (2021). https://doi.org/10.1111/ijfs.14778. 10.1111/ijfs.14778 CASPubMedWeb of Science®Google Scholar 2Lebot V, Tropical Root and Tuber Crops: Cassava, Sweet Potato, Yams and Aroids (Crop Production Science in Horticulture), 2nd edn. CABI, Wallingford, Oxfordshire, UK, p. 515 (2020) https://www.cabi.org/bookshop/book/9781789243369/. Google Scholar 3Khoury CK, Achicanoy HA, Bjorkman AD, Navarro-Racines C, Guarino L, Flores-Palacios X et al., Origins of food crops connect countries worldwide. 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Plant Breed Rev 43: 243–278 (2020). https://doi.org/10.1002/9781119616801.ch7. 10.1002/9781119616801.ch7 Google Scholar 7Forsythe L, Tufan H, Bouniol A, Kleih U and Fliedel G, An interdisciplinary and participatory methodology to improve user acceptability of root, tuber and banana varieties. Int J Food Sci Technol 56: 1115–1123 (2021). https://doi.org/10.1111/ijfs.14680. 10.1111/ijfs.14680 CASPubMedWeb of Science®Google Scholar 8Béchoff A, Tomlins K, Fliedel G, Becerra Lopez-lavalle LA, Westby A, Hershey C et al., Cassava traits and end-user preference: relating traits to consumer liking, sensory perception, and genetics. Crit Rev Food Sci Nutr 58: 547–567 (2018). https://doi.org/10.1080/10408398.2016.1202888. 10.1080/10408398.2016.1202888 CASPubMedWeb of Science®Google Scholar 9 Food and Agriculture Organization of the United Nations (FAO), The State of Food and Agriculture 2010–2011: Women in Agriculture: Closing the Gender Gap for Development. FAO, Rome, Italy (2011) https://www.fao.org/3/i2050e/i2050e.pdf. 10.18356/ca0215ed-en Google Scholar 10Alamu EO, Nuwamanya E, Cornet D, Meghar K, Adesokan M, Tran T et al., Near-infrared spectroscopy applications for high-throughput phenotyping for cassava and yam: a review. Int J Food Sci Technol 56: 1491–1501 (2021). https://doi.org/10.1111/ijfs.14773. 10.1111/ijfs.14773 CASPubMedWeb of Science®Google Scholar Volume104, Issue8Special issue: Tropical roots, tubers and bananas: New breeding tools and methods to meet consumer preferences June 2024Pages 4481-4484 ReferencesRelatedInformation

Vietnamese cassava varieties constitute the fundamental and pivotal element in the sustainable development programme for cassava. This article aims to encapsulate the advancements made over nearly five decades in breeding and enhancing Vietnamese cassava varieties. It delineates the suitable cassava variety structures for each period and ecological region. The selection of cassava varieties exhibiting high starch yield and disease resistance, coupled with the establishment of a suitable and efficient cassava cultivation model, exemplified by 10T for Vietnamese cassava varieties KM568, KM539, KM537, KM569, and KM94, stands as a cornerstone for sustaining cassava development over the years. Presently, we advocate for farmers to cultivate promising cassava varieties such as KM568 or KM539 (an enhanced version of the International Center for Tropical Agriculture (CIAT) cassava variety C39, refined through multiple breeding cycles from 2004 onwards), KM537, KM569, or HN1 (originally known as TMEB419), alongside popular cassava varieties: KM440, KM419, KM94, KM7, STB1, KM414, KM98-7, KM140, KM98-5, KM98-1. We have conducted Distinctness, Uniformity, and Stability (DUS) and Value for Cultivation and Use (VCU) tests, showcasing outstanding cassava varieties in large-scale farming, thereby providing compelling evidence for the prudent conservation and sustainable development of cassava. Vietnamese cassava progression (1975 to date) has traversed six stages, with five waves of restructuring cassava varieties, aligning with target orientations, farming conditions, and market demands, culminating in 16 popular cassava varieties and four promising cassava varieties KM568, KM539, KM537, and KM569.

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.

Summary This review of the literature on varietal change in sub‐Saharan Africa looks in detail at adoption of new varieties of bananas in Uganda, cassava in Nigeria, potato in Kenya, sweetpotato in Uganda and yams in Côte d’Ivoire. The review explored three hypotheses about drivers of varietal change. There was a strong confirmation for the hypothesis that insufficient priority given to consumer‐preferred traits by breeding programmes contributes to the limited uptake of modern varieties (MVs) and low varietal turnover. Lack of evidence meant the second hypothesis of insufficient attention to understanding and responding to gender differences in consumer preferences for quality and post‐harvest traits was unresolved. The evidence on the third hypothesis about the informal seed system contributing to slow uptake of MVs was mixed. In some cases, the informal system has contributed to rapid uptake of MVs, but often it appears to be a barrier with inconsistent varietal naming a major challenge.

Within communities in Osun and Imo States of Nigeria, farmer-processors grew and processed a diverse set of improved and landrace cassava varieties into the locally popular foods, gari, eba and fufu. Local and 15 main varieties were grown in a 'mother and baby trials' design in each state. Mother trials with three replications were processed by farmer-processors renown in their community for their processing skills. Baby trials were managed and processed by other farmer-processors. The objective was to identify food quality criteria to inform demand-led breeding to benefit users, especially women, given their key roles in processing. Farmer-processors evaluated the overall quality of fresh roots and derived food products through pairwise comparisons. Improved varieties had higher fresh and dry root yield. Overall, landraces ranked first for quality of gari and eba, but several improved varieties were also appreciated for good quality. Landraces in Osun had higher gari yield and a higher swelling power compared to improved varieties. Colour (browning), bulk density, swelling power, solubility and water absorption capacity were the criteria most related to food product ranking by farmer-processors. Evaluation of varieties under farmer-processors' conditions is crucial for providing guidance to breeders on critical selection criteria.

Summary“Consumers have their say: assessing preferred quality traits of roots, tubers and cooking bananas, and implications for breeding” special issue, brings together new knowledge about quality traits required for roots, tubers and bananas (RTB) varieties to successfully meet diverse user preferences and expectations, along the variety development and RTB value chains (production, processing, marketing, food preparation, consumption). Key RTB crops in sub‐Saharan Africa are cassava, yams, sweetpotatoes, potatoes and bananas/plantains. They are mainly consumed directly as boiled pieces or pounded in the form of smooth, not sticky, and stretchable dough. They are also stewed, steamed or fried. Cassava, the most widely grown RTB, is generally boiled, stewed or steamed in Eastern and Southern Africa, and in West and Central Africa is usually processed directly into derivative products, e.g. whole root fermentation through retting or heap fermentation; fermentation/dewatering of the mash. Biophysical and social knowledge presented in this issue help elaborate goals for both the processing unit operations (food scientist control) and variety traits (breeder control).

Microspore embryogenesis is the developmental plasticity of juvenile male gametophytes to switch from pollen to embryo development upon exposure to in vitro stress. It is a common method for obtaining haploid and doubled haploid plants in breeding programs for development of superior varieties via haploid-diploidization which allows fast development of homozygous lines from heterozygous parents. In cassava, obtaining haploidization through traditional methods of successive selfing is difficult because of cassava’s long reproductive cycle, high heterozygosity, and inbreeding depression. As a first step towards microspore embryogenesis, callus induction following heat treatment has not been investigated in cassava. We used two elite Ugandan cassava varieties, hereafter called “genotypes”, NASE3 and NASE14, for the study of callus induction. Heat stress of 40°C for 0, 6, 12, 18 and 24hrs and Murashige and Skoog medium supplemented with 2-9% sucrose, and 2,4-dichlorophenoxy acetic acid were used. Heating anthers of NASE3 at 40°C for 6 hrs resulted in a significantly higher percentage of callus induction on MS medium supplemented with 2% sucrose. Callus emerged from inside of the anthers with production influenced by genotype, sucrose concentration, anther density and duration in culture (P≤0.001). Limited in vitro callus differentiation was observed on auxin-and cytokinin-supplemented media. In both genotypes, embryo genic callus was obtained in liquid medium, while green callus was achieved on solid medium. This is a significant step upstream of double haploid plant production pathway in cassava: rigorous optimization of protocols downstream of callus induction are needed for regeneration of microspore-derived embryos and haploid plants.

Breeding efforts have focused on improving agronomic traits of the cassava plant however little research has been done to enhance the crop palatability. This review investigates the links between cassava traits and end-user preference in relation with sensory characteristics. The main trait is starch and its composition related to the textural properties of the food. Pectin degradation during cooking resulted in increased mealiness. Nutritional components such as carotenoids made the cassava yellow but also altered sweetness and softness; however, yellow cassava was more appreciated by consumers than traditional (white) varieties. Components formed during processing such as organic acids gave fermented cassava products an acidic taste that was appreciated but the fermented smell was not always liked. Anti-nutritional compounds such as cyanogenic glucosides were mostly related to bitter taste. Post-harvest Physiological Deterioration (PPD) affected the overall sensory characteristics and acceptability. Genes responsible for some of these traits were also investigated. Diversity in cassava food products can provide a challenge to identifying acceptance criteria. Socio-economic factors such as gender may also be critical. This review leads to questions in relation to the adaptation of cassava breeding to meet consumer needs and preference in order to maximize income, health and food security.

Cassava (Manihot esculenta Crantz) is an important source of energy in the tropics. Its starchy roots are valuable for food security as well as for different industries. Cassava is an outcrossing crop and its breeding is based on the use of heterozygous progenitors. Non-additive genetic effects are important for fresh root yield (FRY) and can be exploited through reciprocal recurrent selection. Results from three diallel studies (with 9-10 progenitors), conducted at three different environments (sub-humid, acid soils and mid-altitude valleys) in Colombia, have already been published for FRY. In this article, phenotypic analysis of dry matter yield (DMY) was also conducted. Specific combining ability effects and actual FRY and DMY data was linked to Nei’s genetic distances which were estimated through a set of 95 SNPs diagnostic of the cassava diversity. Results from regression analyses indicated inconsistent and generally weak associations between genetic distances and performance of the F1 families per se (r2 values ranging from 0.01 to 0.10) and specific combining ability effects (r2 values ranging from 0.00 to 0.28) for the two variables analyzed.

Breeding cassava relies on several selection stages (single row trial-SRT; preliminary; advanced; and uniform yield trials-UYT). This study uses data from 14 years of evaluations. From more than 20,000 genotypes initially evaluated only 114 reached the last stage. The objective was to assess how the data at SRT could be used to predict the probabilities of genotypes reaching the UYT. Phenotypic data from each genotype at SRT was integrated into the selection index (SIN) used by the cassava breeding program. Average SIN from all the progenies derived from each progenitor was then obtained. Average SIN is an approximation of the breeding value of each progenitor. Data clearly suggested that some genotypes were better progenitors than others (e.g., high number of their progenies reaching the UYT), suggesting important variation in breeding values of progenitors. However, regression of average SIN of each parental genotype on the number of their respective progenies reaching UYT resulted in a negligible coefficient of determination (r (2) = 0.05). Breeding value (e.g., average SIN) at SRT was not efficient predicting which genotypes were more likely to reach the UYT stage. Number of families and progenies derived from a given progenitor were more efficient predicting the probabilities of the progeny from a given parent reaching the UYT stage. Large within-family genetic variation tends to mask the true breeding value of each progenitor. The use of partially inbred progenitors (e.g., S1 or S2 genotypes) would reduce the within-family genetic variation thus making the assessment of breeding value more accurate. Moreover, partial inbreeding of progenitors can improve the breeding value of the original (S0) parental material and sharply accelerate genetic gains. For instance, homozygous S1 genotypes for the dominant resistance to cassava mosaic disease (CMD) could be generated and selected. All gametes from these selected S1 genotypes would carry the desirable allele and 100% of their progenies would be resistant. Only half the gametes produced by the heterozygous S0 progenitor would carry the allele of interest. For other characteristics, progenies from the S1 genotypes should be, at worst, similar to those generated by the S0 progenitors.

Breeding cassava relies on a phenotypic recurrent selection that takes advantage of the vegetative propagation of this crop. Successive stages of selection (single row trial-SRT; preliminary yield trial-PYT; advanced yield trial-AYT; and uniform yield trials UYT), gradually reduce the number of genotypes as the plot size, number of replications and locations increase. An important feature of this scheme is that, because of the clonal, reproduction of cassava, the same identical genotypes are evaluated throughout these four successive stages of selection. For this study data, from 14 years (more than 30,000 data points) of evaluation in a sub-humid tropical environment was consolidated for a meta-analysis. Correlation coefficients for fresh root yield (FRY), dry matter content (DMC), harvest index (HIN), and plant type score (PTS) along the different stages of selection were estimated. DMC and PTS measured in different trials showed the highest correlation coefficients, indicating a relatively good repeatability. HIN had an intermediate repeatability, whereas FRY had the lowest value. The association between HIN and FRY was lower than expected, suggesting that HIN in early stages was not reliable as indirect selection for FRY in later stages. There was a consistent decrease in the average performance of clones grown in PYTs compared with the earlier evaluation of the same genotypes at SRTs. A feasible explanation for this trend is the impact of the environment on the physiological and nutritional status of the planting material and/or epigenetic effects. The usefulness of HIN is questioned. Measuring this variable takes considerable efforts at harvest time. DMC and FRY showed a weak positive association in SRT (r = 0.21) but a clearly negative one at UYT (r = -0.42). The change in the relationship between these variables is the result of selection. In later stages of selection, the plant is forced to maximize productivity on a dry weight basis either by maximizing FRY or DMC, but not both. Alternatively, the plant may achieve high dry root yield by simultaneously attaining "acceptable" (but not maximum) levels of FRY and DMC.

Cassava is a highly heterozygous species; hence, current methods used in classical cassava breeding cannot match the urgent need to high yielding varieties.Recently, progress was made through androgenesis and gynogenesis as pathways for raising doubled cassava haploid lines to overcome problems associated with cassava's inherent reproductive biology, but these efforts were limited (no candidate cassava plantlets were regenerated).For the first time, this study shows that pollen irradiation coupled with self-pollination and embryo rescue regenerated 62 candidate cassava plantlets.Plants of an elite cassava variety, Nase14, served as a mother plant and as the pollen donor for the irradiation.Irradiation dosages of 50 to 250 Gray studied across five pollination events and 300 or 500 Gray in one pollination event caused a reduction in pollen germination up to 67.0%.By 15 days after pollination (DAP) with irradiated pollen, up to 89.7% of the pollinated flowers had aborted.By embryo rescue time (42 DAP), significant differences were observed in number of fruits, seeds and embryos generated, with the non-irradiated pollen treatments having significantly higher numbers.Sixteen (16) heterozygous SSR markers in the parent and ploidy analysis showed that none of the regenerated plants was haploid or homozygous.However, the plantlets resulting from pollination with non-irradiated pollen had 56.2% homozygous loci, while progeny derived from irradiated treatments had frequencies of homozygous loci between 28.1 and 55.0%.This is the first time to use irradiated pollen in cassava as a pathway to generate candidate plantlets as an initial step in double haploid production.

Abstract Food losses can occur during production, postharvest, and processing stages in the supply chain. With the onset of worldwide food shortages, interest in reducing postharvest losses in cassava has been increasing. In this research, the main goal was to evaluate biochemical changes and identify the metabolites involved in the deterioration of cassava roots. We found that high levels of ascorbic acid (AsA), polyphenol oxidase (PPO), dry matter, and proteins are correlated with overall lower rates of deterioration. On the other hand, soluble sugars such as glucose and fructose, as well as organic acids, mainly, succinic acid, seem to be upregulated during storage and may play a role in the deterioration of cassava roots. Cultivar Branco (BRA) was most resilient to postharvest physiological deterioration (PPD), while Oriental (ORI) was the most susceptible. Our findings suggest that PPO, AsA, and proteins may play a distinct role in PPD delay.

Waxy cassava starch (WS) from a spontaneous mutation offer enough advantages to encourage the development of commercial varieties. However, breeding work is limited because only one source of WS was available. This article reports the discovery of five new sources of WS which were compared with commercial (CC) and high amylose (HA) cassava starches (19.9 and 30.2% amylose, respectively). Waxy starch gels were considerably clearer and had higher solubility and swelling power than those from CC. Pasting temperature and peak viscosity in WS were higher (68.5 degrees C and 1149 cP) than in CC (64.2 degrees C and 993 cP). No retrogradation or syneresis could be detected in refrigerated gels or after freeze/thaw cycles in any WS gel. Average lambda(max) for WS, CC and HA were 540.2, 591.3 nm, and 607.0 nm, respectively. Amylopectins from WS displayed (M) over bar (w) between 271 x 10(6) and 551 x 10(6) g mol(-1), (R) over bar (G) ranged between 229 and 298 nm and nu(G) values ranged between 0.38 and 0.40 (between the sphere and the random coil). The apparent density distributions in all WS suggested close densities and branching structure. The corrected average number of glucosyl units in a linear chain averaged 21.2 in WS and 23.1 in CC. Amylopectins from WS showed a slightly more branched structure (average 4.8%) than in CC (average 4.3%), but lower than in HA (7.0%). WS exhibited larger average granule size (15.9 mu m) compared with CC (14.3 mu m). New sources of WS will contribute the breeding efforts to develop successful commercial varieties. (C) 2015 Elsevier Ltd. All rights reserved.

Consolidates relevant molecular and phenotypic information on cassava to demonstrate relevance of heterosis, and alternatives to exploit it by integrating different tools. Ideas are useful to other asexually reproduced crops. Asexually propagated crops offer the advantage that all genetic effects can be exploited in farmers' production fields. However, non-additive effects complicate selection because, while influencing the performance of the materials under evaluation, they cannot be transmitted efficiently to the following cycle of selection. Cassava can be used as a model crop for asexually propagated crops because of its diploid nature and the absence of (known) incompatibility effects. New technologies such as genomic selection (GS), use of inbred progenitors based on doubled haploids and induction of flowering can be employed for accelerating genetic gains in cassava. Available information suggests that heterosis, non-additive genetic effects and within-family variation are relatively large for complex traits such as fresh root yield, moderate for dry matter or starch content in the roots, and low for defensive traits (pest and disease resistance) and plant architecture. The present article considers the potential impact of different technologies for maximizing gains for key traits in cassava, and highlights the advantages of integrating them. Exploiting heterosis would be optimized through the implementation of reciprocal recurrent selection. The advantages of using inbred progenitors would allow shifting the current cassava phenotypic recurrent selection method into line improvement, which in turn would allow designing outstanding hybrids rather than finding them by trial and error.

Food losses can occur during production, postharvest, and processing stages in the supply chain. With the onset of worldwide food shortages, interest in reducing postharvest losses in cassava has been increasing. In this research, the main goal was to evaluate biochemical changes and identify the metabolites involved in the deterioration of cassava roots. We found that high levels of ascorbic acid (AsA), polyphenol oxidase (PPO), dry matter, and proteins are correlated with overall lower rates of deterioration. On the other hand, soluble sugars such as glucose and fructose, as well as organic acids, mainly, succinic acid, seem to be upregulated during storage and may play a role in the deterioration of cassava roots. Cultivar Branco (BRA) was most resilient to postharvest physiological deterioration (PPD), while Oriental (ORI) was the most susceptible. Our findings suggest that PPO, AsA, and proteins may play a distinct role in PPD delay.