Center For Tropical Agriculture Research Articles

Vietnamese cassava varieties progression across 50 years

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.

Identifying genetically redundant accessions in the world's largest cassava collection.

Crop diversity conserved in genebanks facilitates the development of superior varieties, improving yields, nutrition, adaptation to climate change and resilience against pests and diseases. Cassava (Manihot esculenta) plays a vital role in providing carbohydrates to approximately 500 million people in Africa and other continents. The International Center for Tropical Agriculture (CIAT) conserves the largest global cassava collection, housing 5,963 accessions of cultivated cassava and wild relatives within its genebank. Efficient genebank management requires identifying and eliminating genetic redundancy within collections. In this study, we optimized the identification of genetic redundancy in CIAT's cassava genebank, applying empirical distance thresholds, and using two types of molecular markers (single-nucleotide polymorphism (SNP) and SilicoDArT) on 5,302 Manihot esculenta accessions. A series of quality filters were applied to select the most informative and high-quality markers and to exclude low-quality DNA samples. The analysis identified a total of 2,518 and 2,526 (47 percent) distinct genotypes represented by 1 to 87 accessions each, using SNP or SilicoDArT markers, respectively. A total of 2,776 (SNP) and 2,785 (SilicoDArT) accessions were part of accession clusters with up to 87 accessions. Comparing passport and historical characterization data, such as pulp color and leaf characteristic, we reviewed clusters of genetically redundant accessions. This study provides valuable guidance to genebank curators in defining minimum genetic-distance thresholds to assess redundancy within collections. It aids in identifying a subset of genetically distinct accessions, prioritizing collection management activities such as cryopreservation and provides insights for follow-up studies in the field, potentially leading to removal of duplicate accessions.

Simulation and Prediction of Groundwater Dynamics in Nagarjuna Sagar Right Canal (NSRC) Command for Normal and Extreme Groundwater Recharge Conditions

Groundwater Modeling is the best tool to optimize the different combinations and to select the best combination for sustainable groundwater management. Using computer models, best solution or scenario can optimize by creating model with real conditions. In this study, computer model Visual MODFLOW was applied to Nagarjuna Sagar Right Canal Command area to simulate the groundwater dynamics. The net area irrigated under Nagarjuna Sagar Right Canal is 4.75 lakh ha. The aquifer properties of various layers and boundary conditions were fed in to the model as input for calibration and validation of the model. After calibration and validation, the model was used to predict the groundwater dynamics in the study area using different recharge scenarios. The validated groundwater model was used to predict the groundwater levels in the study area for the years 2020, 2030 and 2040 with different recharge scenarios. Global climate model was used to generate future weather data. MarkSim developed by the International Centre for Tropical Agriculture (CIAT) was used to generate the weather parameters like maximum and minimum temperatures for the years 2020, 2030 and 2040. The different recharge scenarios with average, lowest and highest recharge over the study period and projected evapotranspiration have been used and revealed that the groundwater levels increase with the increase in recharge and decreases with the decrease in recharge. The results revealed that the groundwater depleted area would decrease with the highest recharge scenario and it would increase with the lowest recharge scenario in future. The deeper groundwater table would be expected in future at Chimakurthy and Thalluru villages of Prakasam district and Karempudi and Piduguralla villages of Guntur district in the study area. This condition may be due to the excess utilization of groundwater which is less than the groundwater recharge in particular villages. The construction of rainwater harvesting structures for artificial groundwater recharge in those areas should be carried out immediately.

MODELLING IMPACT OF CROPPING PATTERN AND URBAN AREAON GROUNDWATER RESOURSES OF NAGARJUNA SAGAR RIGHTCANAL COMMAND AREA USING VISUAL MODFLOW

Groundwater models can be used for the assessment of the impact of the different cropping pattern andchange in urban area on groundwater resource and modeling is the best tool to optimize the differentcombinations or scenarios and to select the best combination or scenario for management of sustainablegroundwater resources. In this study, three-dimensional finite-difference groundwater model VisualMODFLOW 2.8.1 was used to simulate the groundwater dynamics in Nagarjuna Sagar Right CanalCommand area. The net area irrigated under Nagarjuna Sagar Right Canal is 4.75 lakh ha. Calibration andvalidation of the model has been carried out and used to predict the static groundwater storage availabilityin the study area for different cropping pattern scenarios and change in the urban area. The validatedVisual MODFLOW 2.8.1 was used to simulate the groundwater dynamics in the study area for the years2030 and 2040 with different cropping pattern scenarios and change in the urban area. Global climatemodel MarkSim, which is developed by the International Centre for Tropical Agriculture (CIAT) was usedto generate future weather data for the years 2030 and 2040. The impact of change in cropping pattern onstorage of static groundwater resource in the study area for the years 2030 and 2040 was assessed with twoscenarios of change in rice cropped area decreased by 50 per cent and 100 per cent with this cropped areacultivated equally by the ID crops. These results showed that the lesser storage of static groundwaterresources in future lesser. The change in the cropping pattern affects the net recharge of the groundwaterwhich influences the groundwater levels. Increase in paddy area increases the recharge and rise ingroundwater level has been identified. In the study area, cropping pattern could be changed from rice cropto other irrigated dry crops to prevent the increase of groundwater resources which leads the water loggingcondition in the study area. The urbanization is one of the most significant factor considering for assessmentof the response on the groundwater levels and availability of static groundwater resources. The groundwaterrecharge is very less in case of increase in urban area and generates more runoff rather than the intake ofrainfall in the ground surface as having the impervious nature. In view of increase in urban area in thestudy area, the four scenarios are proposed with the combination of 10 per cent and 20 per cent decrease inrecharge and 50 per cent and 100 per cent increase in groundwater draft and simulated the groundwater fluctuations for the years 2030 and 2040. The impact of change in the urban area on storage of availablestatic groundwater resource in the study area for the years 2030 and 2040 was assessed with four scenarioscombination of groundwater recharge and groundwater pumping. The storage of static groundwaterresources would be expected in future lesser than the present storage of static groundwater resources in allscenarios due to increase in urban area as increased in impervious nature of the ground surface. The declinein available static groundwater resources would be expected 6.38 per cent and 7.08 per cent during 2030and 2040 respectively. The rapid expansion in the urban area and their settlements is also one of the reasonsfor the depletion of groundwater resources with low recharge and high groundwater draft.

Metabolic engineering of cassava to improve carotenoids.

Cassava is a staple food used in many countries around the world, despite deficiencies in micronutrients such as provitamin A carotenoids. Unfortunately, improvement of the cassava nutritional content by use of conventional breeding is slow and difficult. Therefore, there is an urgent need to develop and standardize protocols using biotechnological tools to improve cassava. The Alliance of Biodiversity International and the International Center for Tropical Agriculture (CIAT) have worked on cassava genetic transformation over the last 30 years. Here, we describe, step by step, the procedures used for genetic transformation of cassava variety TMS60444, to improve carotenoids and other traits. This protocol includes stock setup, reagents, media preparation, materials, and equipment, for the genetic transformation of embryogenic tissues. The main expected output in publishing this protocol is to provide the basis for a reproducible and reliable method to genetically modify and/or gene edit Latin American and Asian cassava varieties.

Characterization of Colletotrichum lindemuthianum Races in Zambia and Evaluation of the CIAT Phaseolus Core Collection for Resistance to Anthracnose.

Colletotrichum lindemuthianum, the causal pathogen of common bean (Phaseolus vulgaris) anthracnose, is highly variable. Therefore, understanding its race structure and identification of new sources of resistance is necessary for the development of varieties with durable resistance. The objectives of this study were (i) to characterize isolates of C. lindemuthianum collected from three major bean-growing regions in Zambia and (ii) evaluate the International Center for Tropical Agriculture (CIAT) Phaseolus core collection for resistance to C. lindemuthianum races 37, 73, and 566 and a blend of 20 races. Isolates collected from three major bean-growing districts in Zambia, namely Mporokoso, Mpika, and Mbala, were characterized as races 37, 73, and 566, respectively. A subset of the CIAT core collection comprising 885 accessions of common bean, 13 accessions of scarlet runner bean (Phaseolus coccineus), and 11 accessions of year bean (Phaseolus dumosus) was evaluated for resistance to races 37, 73, and 566 and a blend of 20 races in a greenhouse at the University of Zambia, Lusaka, Zambia. Totals of 72, 66, 48, and 9% of P. vulgaris accessions evaluated were highly resistant to races 37, 73, and 566 and a blend of 20 races, respectively. Also, accessions of P. coccineus and P. dumosus highly resistant to races 37, 73, and 566 were identified. Only eight of the 331 P. vulgaris accessions were highly resistant to all three individual races (37, 73, and 566) and to a blend of 20 races. These eight accessions constitute a valuable breeding resource for developing varieties with durable resistance to C. lindemuthianum.

Structure of genetic diversity and genome-wide association studies of bean fly (Ophiomyia spencerella) resistance in common bean

Eastern Africa is a significant region of common bean (Phaseolus vulgaris L.) production and genetic diversity. Insect pests are a major biotic constraint in subsistence crop production systems. Bean fly (Ophiomyia spencerella) is a serious pest of beans in eastern Africa highlands. Breeding efforts focus on combining adaptability traits with user preferred seed types. However, lack of information on molecular markers linked to genes modulating bean fly resistance has slowed breeding progress. The objectives were to: (i) characterize genetic diversity and uncover putative bean fly resistant genotypes within diverse seed types and market classes and (ii) identify genomic regions controlling bean fly resistance using genome-wide association analysis (GWAS). A set of 276 diverse genotypes comprising local landraces and varieties from Kenya alongside introductions from International Centre for Tropical Agriculture (CIAT), were assembled. The germplasm represented varied bean production ecologies and seed types. Genetic diversity conforming to Andean and Mesoamerican genepools was established. Out of 276 genotypes evaluated, 150 were Andean, 74 were Mesoamerican and 52 were admixed. Twenty-two genotypes were resistant to bean fly. Association mapping results for stem damage score and plant mortality identified six significant single-nucleotide polymorphisms (SNPs) on chromosomes Pv01 and Pv09. The most significant SNP marker was 12 kilobases downstream of Phvul.001G074900 gene with LOD score > 4.0 hence in linkage disequilibrium with the postulated gene. The identified candidate gene is pleiotropic and modulates both flowering time and plant responses to stress. These findings are a key step towards marker-enabled breeding in common bean for sub-Saharan Africa.

Transition From Targeted Breeding to Mainstreaming of Biofortification Traits in Crop Improvement Programs.

Biofortification breeding for three important micronutrients for human health, namely, iron (Fe), zinc (Zn), and provitamin A (PVA), has gained momentum in recent years. HarvestPlus, along with its global consortium partners, enhances Fe, Zn, and PVA in staple crops. The strategic and applied research by HarvestPlus is driven by product-based impact pathway that integrates crop breeding, nutrition research, impact assessment, advocacy, and communication to implement country-specific crop delivery plans. Targeted breeding has resulted in 393 biofortified crop varieties by the end of 2020, which have been released or are in testing in 63 countries, potentially benefitting more than 48 million people. Nevertheless, to reach more than a billion people by 2030, future breeding lines that are being distributed by Consultative Group on International Agricultural Research (CGIAR) centers and submitted by National Agricultural Research System (NARS) to varietal release committees should be biofortified. It is envisaged that the mainstreaming of biofortification traits will be driven by high-throughput micronutrient phenotyping, genomic selection coupled with speed breeding for accelerating genetic gains. It is noteworthy that targeted breeding gradually leads to mainstreaming, as the latter capitalizes on the progress made in the former. Efficacy studies have revealed the nutritional significance of Fe, Zn, and PVA biofortified varieties over non-biofortified ones. Mainstreaming will ensure the integration of biofortified traits into competitive varieties and hybrids developed by private and public sectors. The mainstreaming strategy has just been initiated in select CGIAR centers, namely, International Maize and Wheat Improvement Center (CIMMYT), International Rice Research Institute (IRRI), International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), International Institute of Tropical Agriculture (IITA), and International Center for Tropical Agriculture (CIAT). This review will present the key successes of targeted breeding and its relevance to the mainstreaming approaches to achieve scaling of biofortification to billions sustainably.

Identifying New Resistance to Cassava Mosaic Disease and Validating Markers for the CMD2 Locus

Cassava (Manihot esculenta Crantz) is a crucial staple crop, and provides carbohydrate energy to more than half a billion people in the tropics. Cassava mosaic disease (CMD) is the most important disease of cassava in Africa. Since Sri Lanka Cassava Mosaic Virus (SLCMV) was first reported in South East Asia in 2015, establishing sustainable solutions to CMD has become a top priority for the cassava program at the International Center for Tropical Agriculture (CIAT) and its partners. In the present study, we screened two populations for CMD resistance: VNM142, 142 clones collected from farms throughout Vietnam, and CIAT102, 102 clones resistant to CMD or mites, which were introduced from CIAT. High broad-sense heritability was observed in all the trials (>0.80). From the population VNM142, eight clones showed high CMD resistance with CMD severity scores less than 2.0. Two resistant clones had the same DNA fingerprinting with the accessions CR63 (PER262 or TAI9) and KM57 (VNM8) in the genebank, respectively. To our knowledge, this is the first report of CMD resistance in the genebank at CIAT. We also used the two populations to validate the CMD markers S12_7926132 and S14_4626854. Both markers explained 51% of the population variance in the segregating population CIAT102, but only 11% in the diverse population VNM142. Thus, we concluded that the two CMD markers could not be used to select for CMD resistance in diverse populations, but could predict the CMD resistance in segregating populations when the susceptible parents do not have resistant marker alleles and the resistance of the CMD2 donors is confirmed.

UPLC-MS based metabolomics analysis reveals metabolite compositional differences between Kenyan Commercial and NonCommercial black tea (Camellia sinensis L.) cultivars.

Camellia sinensis (L.) O. Kuntze (tea) is one of the most widely consumed beverages across the world, serving as an essential commodity crop for several developing countries. A bulk of tea’s health-promoting properties are attributed to the antioxidant properties of EGCg, its predominant polyphenol. As a result of these health benefits, tea production and consumption has expanded and promoted the development of tea industries globally. Tea cultivation is dependent on a good distribution of rainfall, and the current changes in climate pose a significant threat to its global supply chains. Through the efforts of the International Centre for Tropical Agriculture (CIAT), predictions of future climate changes in the tea growing regions of Kenya between now and 2050 have been generated. A study was conducted to develop models to identify key tea growing regions that will remain ideal for tea farming and also investigate the metabolomic differences between 243 drought susceptible NonCommercial (NComm) and 60 Commercial (Comm) cultivars. Non-targeted, high-resolution UPLC-MS was used to attain a new profound understanding of the metabolomic multiplicity between the Comm and NComm groups and to elucidate their association with tea liquor quality and drought tolerance. Several metabolites, namely argininosuccinate, caffeic acid, caffeine, catechin, citric acid, epicatechin, epigallocatechin gallate, gallic acid, gluconic acid, glucose, maltose, quercetin and theanine were found to clearly differentiate between the Comm and NComm cultivars. These detected metabolites were linked to improved tea quality and drought tolerance in the Comm cultivars.

Diagrammatic scales for the estimation of black node disease severity in common bean

ABSTRACT: The objective of this study was to design two diagrammatic scales for the evaluation of black node disease (Stagonosporopsis hortensis and Boeremia spp.) in common bean (Phaseolus vulgaris L.). The developed scales corresponded to logarithmic intervals (SADL) of seven levels and equal intervals (SADE) of nine levels. These scales were compared to the scale developed by the International Center for Tropical Agriculture (CIAT), which corresponds to a descriptive scale (NoSAD). In the scale validation the accuracy, precision, and concordance of repeatability were determined using Lin’s concordance correlation coefficient, whereas inter-rater reproducibility was determined by the overall concordance correlation coefficient (OCCC). It was observed that with the use of the proposed scales, reproducibility and repeatability were significantly improved for inexperienced raters, and reproducibility was improved in the case of experienced raters. Thus, the designed standard area diagrams with equal and logarithmic intervals are a useful tool for estimating severity under field and experimental conditions as part of the study of this patho-system.

Sustainable Transformation of Rainfed to Irrigated Agriculture Through Water Harvesting and Smart Crop Management Practices

Globally, rainfed crop yields are about 50% lower than yields obtained under irrigated conditions. The low productivity of rainfed agricultural systems is the main factor that accentuates hunger, poverty, unemployment, and illegal migration in Central America and other regions in Latin America. Because of rainfall dependence, farmers can cultivate their crops during only one growing season per year, with high vulnerability to periodic droughts and flooding. To face the challenge of a sustainable food supply in the context of increasing food demand, since the mid-2000s, FLAR (Latin American Fund for Irrigated Rice), a public-private alliance of organizations from 17 Latin American countries, CFC (Common Fund for Commodities) and CIAT (International Center for Tropical Agriculture) have been investing resources and efforts to sustainably intensify and diversify high-risk rainfed production systems through capturing runoff rainwater in reservoirs to transform those systems into highly profitable irrigated systems. This article summarizes concepts, results, and experiences from pilot farms using water harvesting in Nicaragua and Mexico, where irrigation combined with smart crop management practices allowed small-/medium-scale farmers to increase their yields of rice, maize, beans, and high-value crops by two to four times in comparison with historical yields obtained under rainfed conditions.

Screening Andean Diversity Panel Dry Bean Lines for Resistance to Bacterial Brown Spot Disease Under Field Conditions in South Africa.

Bacterial brown spot (BBS) disease caused by Pseudomonas syringae pv. syringae is an important disease of dry bean (Phaseolus vulgaris L.), with grain yield losses of 55% reported in South Africa. This study aimed to identify BBS disease-resistant genotypes from 415 Andean Diversity Panel (ADP) dry bean lines and 5 check cultivars under field conditions across three sites in South Africa: Warden and Middelburg under natural infestation and Potchefstroom under artificial inoculation. Plants at Potchefstroom were inoculated with P. syringae pv. syringae using three isolates at 21, 28, and 36 days after planting, and disease scoring was done at 7, 14, and 21 days after inoculation following a modified 1 to 9 International Centre for Tropical Agriculture (CIAT) scale. The BBS severity percentage and the area under the disease progress curve (AUDPC) were applied to quantify the reaction of bean genotypes to BBS disease. The study identified 17.2% of evaluated germplasm as resistant and 45.3% as moderately resistant. Genotypes ADP-0592, ADP-0790, ADP-0120, and ADP-0008 were selected for both resistance and high seed yield across the three environments. Genotypes ADP-0546, ADP-0630, ADP-0120, and ADP-0279 were selected for both high yield and resistance at Warden, whereas ADP-0038, ADP-0721, and ADP-0790 were selected for both traits at Middelburg, and lastly, ADP-0120 and ADP-0079 were selected for both traits at Potchefstroom. The best genotypes selected for both high yield and BBS resistance had grain yield >1.45 t ha-1 across sites and >1.85 t ha-1 at individual sites, and they out yielded the best-performing check cultivar (1.13 t ha-1) and the grand mean yield (0.87 t ha-1) across sites. The AUDPC had a strong negative correlation (r = -0.55, P < 0.001) with grain yield at Potchefstroom. Medium-seeded genotypes showed a lower AUDPC than the large-seeded genotypes, and indeterminate genotypes showed a lower AUDPC than determinate genotypes. The genotypes selected for resistance and yield can be utilized in future dry bean improvement efforts for the South African bean market.

Genetic Diversity in Common Bean (Phaseolus vulgaris L.) Germplasm to Establish a Breeding Program in the Mountainous Region of Jammu and Kashmir

Common bean (Phaseolus vulgaris L.) is native to Middle America and Andean mountains of South America. Due to its nutritious value, it is one of the most important legume crop of the world. Evaluation of genetic diversity of a crop is extremely important for the establishment of a breeding program and selection of varieties for cultivation. We evaluated the genetic diversity and phylogenetic relationship of 40 P. vulgaris ecotypes from CIAT (International Center for Tropical Agriculture) germplasm using seed protein profiles produced by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), to screen the germplasm to be used in a breeding program. A total of 21 bands scored 14 were found polymorphic. A distance matrix was generated from the similarity matrix based on polymorphic bands. The UPGMA tree was established through cluster analysis performed on the distance matrix. Six major clusters were formed on the basis of SDS_PAGE analysis with one ecotype (E13-G16832) being the most diverse. This analysis provided the basis for selection of suitable ecotypes to be used in the establishment of a breeding program.ane damage the leaves helped the tolerant genotypes to sustain under salinity stress in a better way than the susceptible genotypes.

The contribution of the CIAT genebank to the development of iron-biofortified bean varieties and well-being of farm households in Rwanda

Genebanks play an essential role in a world where agricultural biodiversity has been lost from farming habitats, malnutrition persists as global population continues to rise, and farm productivity is vulnerable to climate change. We demonstrate the importance of the genebank of the International Center for Tropical Agriculture (CIAT) to the development of seven iron-biofortified varieties of climbing bean and the impact of their adoption on farm households in Rwanda. First, we link iron-biofortified varieties of climbing beans directly to the genebank through pedigree analysis and key informant interviews with the breeders who developed them. Second, we apply various econometric models to test the impact of adoption on yield, consumption, and purchase of beans by farming households in Rwanda, building upon previous research on bush beans. We based the analysis on a dataset of nearly 1400 households, collected in 2015 by HarvestPlus. We found that the scope of the genetic diversity housed in the bean collection at CIAT was fundamental to developing successful iron-biofortified beans. We found significant positive effects of climbing varieties on yields; however, we did not find significant effects on the amounts of beans consumed by households or bean purchases. Our results suggest that it is possible to trace the journey of an accession from its introduction in the genebank to its final use by farmers and consumers. Positive effects on yield generate incentives for adoption of iron-biofortified bean varieties, potentially boosting micronutrient consumption. Further research is needed to understand the factors affecting the adoption and impacts of climbing bean varieties.

Cassava breeding and agronomy in Asia: 50 years of history and future directions.

In Asia, cassava (Manihot esculenta) is cultivated by more than 8 million farmers, driving the rural economy of many countries. The International Center for Tropical Agriculture (CIAT), in partnership with national agricultural research institutes (NARIs), instigated breeding and agronomic research in Asia, 1983. The breeding program has successfully released high-yielding cultivars resulting in an average yield increase from 13.0 t ha–1 in 1996 to 21.3 t ha–1 in 2016, with significant economic benefits. Following the success in increasing yields, cassava breeding has turned its focus to higher-value traits, such as waxy cassava, to reach new market niches. More recently, building resistance to invasive pests and diseases has become a top priority due to the emergent threat of cassava mosaic disease (CMD). The agronomic research involves driving profitability with advanced technologies focusing on better agronomic management practices thereby maintaining sustainable production systems. Remote sensing technologies are being tested for trait discovery and large-scale field evaluation of cassava. In summary, cassava breeding in Asia is driven by a combination of food and market demand with technological innovations to increase the productivity. Further, exploration in the potential of data-driven agriculture is needed to empower researchers and producers for sustainable advancement.

Adaptation and Participatory Evaluation of Shrub Forage Legumes in Highlands of Sud-Kivu, Democratic Republic of the Congo (DRC)

Livestock in the highlands of DRC faces several constraints. It strongly decreased due to high rate of mortality, looting during the wars, lack of animal feeding and livestock still reared again under traditional system. However, shrub forage legumes can contribute to mitigate one part of these constraints and play an important role to improve livestock production. The objective of this study is to use for adaptation the improved shrub forage legumes previously tested by the International Center for Tropical Agriculture (CIAT) Colombia in tropical Central Asia and Latin America whose ecological conditions are similar to those in DRC. Fifteen shrub forage legumes were randomly planted. With 3 replications, nine plantations were counted per specie or accession. The cutting period was for eight weeks. The best yield shrubs were in Mulungu L. diversifolia K782, L. diversifolia 22192 and in Nyangezi C. calothyrsus. The choice of the farmers in their participatory evaluation was generally in agreement with the agronomic trial outcomes.

A global overview of cassava genetic diversity.

Although numerous studies of diversity have been conducted in cassava, there is no comprehensive assessment of global genetic diversity. Here we draw on previous studies and breeders’ knowledge to select diversity sets from the International Institute of Tropical Agriculture (IITA) and the International Center for Tropical Agriculture (CIAT) genebanks and breeders’ germplasm, as well as elite germplasm and landraces from eastern, southern and central (ESC) Africa to make a global assessment of diversity in cassava, using a SNP based GoldenGate (Illumina Inc.) assay. A synthesis of results from genetic distance and ADMIXTURE analysis essentially revealed four populations (i) South American germplasm characterised by relatively higher genetic diversity with hypothetical ancestral founder genotypes from Brazil, (ii) a smaller group of African introduction germplasm which is more distantly related to all other germplasm, (iii) West Africa germplasm dominated by IITA breeding lines, containing sources of cassava mosaic disease resistance, and IITA genebank accessions from West Africa, both characterised by slightly lower diversity, and (iv) a less cohesive group of African germplasm, termed ‘Other’, with moderate levels of diversity and a majority of germplasm from ESC Africa. This study highlights opportunities for heterosis breeding, purging of duplicates in genebanks and the need for conservation of ESC Africa landraces.

Tropical and subtropical forage germplasm conservation and science on their deathbed! 1. A journey to crisis

While interest in the potential of tropical and subtropical forage (TSTF) germplasm for improved livestock production commenced earlier, it was not until the 1950s and 1960s that plant collecting and research on diversity and utilization of grasses and legumes reached significant global momentum. The subsequent engagement in pasture and forage research by the Consultative Group on International Agricultural Research (CGIAR) centres, such as the International Center for Tropical Agriculture (CIAT) and International Livestock Centre for Africa (ILCA; 1974–1995)/International Livestock Research Institute (ILRI; since 1995) from the 1970s onwards, built on the advances made by national centres in Australia, the United States of America, Kenya and elsewhere. By 1990–2000, TSTFs were recognized for contributing to a range of commercial and smallholder livestock production systems in Latin America, Australia, Southeast Asia, South Asia and Africa. However, their use, the value of further research and the need to maintain the very large and diverse collections held in international and national genebanks were challenged by this time because of perceived environmental risks, questions about whether or not past achievements could be bettered and the high costs of maintaining genebanks. Since then, the decline in investment and the quality of conservation and curation has been a relatively rapid process and reached the crisis point of today in just 20–25 years. This article traces 70 years of expansion and then decline of plant collecting, conservation, research and commercialization of TSTFs as a new commodity and examines the reasons for the sharp changes that have taken place. In a second article (this issue), the argument is made for swift and drastic action to prevent critical germplasm from being lost, to enable genebanks to play their crucial and unique role in underpinning improving production and productivity in livestock systems and to provide key germplasm tools to achieve environmental benefits.

Tropical and subtropical forage germplasm conservation and science on their deathbed! 2. Genebanks, FAO and donors must take urgent steps to overcome the crisis

Tropical and subtropical forage (TSTF) germplasm collections in the international centres of International Center for Tropical Agriculture (CIAT) and International Livestock Research Institute (ILRI), and in many national centres of developed and developing countries are under threat due to reduced financial support. Subsequent lack of skills in taxonomy, diversity assessment and adaptation would preclude them playing their crucial role in underpinning forage research for tropical and subtropical farming systems, to meet the growing global demand for livestock products together with reducing their environmental footprint. Also due to well-meant legal changes of biodiversity ownership as well as a current political culture of ‘us versus them’, germplasm collecting and sharing has become challenging. As a result, most centres have become inward-looking, have few links to other members of the global TSTF research community, including other TSTF genebanks, and are struggling to do the basics of conserving their current holdings. Undoubtedly, valuable germplasm has already been lost, and most genebanks lack the skills and knowledge to add value to research programs to develop new forages or select the best options for new environmental uses. This decline has been a relatively rapid process and reached the crisis point of today in just 20–25 years. This article proposes a four-pronged strategy based on improved efficiency, effectiveness, awareness and collaboration that should be adopted urgently. Swift and drastic action is required of international agencies, national governments, researchers and industry bodies. Much of the germplasm was collected from regions that have since undergone massive development or other changes in land use. Failure to act now will, consequently, result in further loss of genetic material forever and associated passport and descriptive information.