Centro Internacional De Agricultura Tropical Research Articles

Effect of iron-enriched bean-based diet on body weight, exercise performance and iron biomarkers in young adult BALB/c mice

Iron deficiency contributes to the global burden of disease, affecting children, premenopausal women, and population from low-income and middle-income countries. To manage the deficit of iron on diet, biofortified crops can be obtained from conventionally plant-based foods. BIO102 bean is a biofortified crop with higher iron and protein content when compared to conventional beans. Therefore, this study aimed to determine the effect of BIO102 food on body weight, exercise performance, and iron biomarkers in young adult BALB/c mice. To achieve this, 24 BALC/c mice were randomly assigned to each of the following groups (n=6 per group): Control diet (conventional diet 5010 Diet; CTRL), bean-based biofortified diet (BIO102), bean-based non-biofortified diet (NB), and corn-based diet (CD). The following parameters were assessed weekly from baseline to 8 weeks: body weight, food intake, endurance capacity, and limbs strength. Baseline blood glucose and hemoglobin measurements were made at the first, three, and eighth weeks of tail blood, and serum ferritin, hepcidin, C-reactive protein, and testosterone measurements were made at the end of 8 weeks of whole blood.During the initial week of housing (acclimatization), there were no differences among groups on neither food intake nor body weight ( p>0.05) (Figure 1). A significant difference in body weight from the second week of feeding with the natural diets was found (Figure 1). Due to signs of stress after three weeks of feeding, all the groups that took the natural diets, received 1 g of 5010Diet food as supplementation up to the end of the experiment. Both CTRL and BIO102 groups showed higher body weight gain when compared to NB and CD groups. Regarding exercise performance, no significant differences were found among groups (Figure 2). As for the iron biomarkers, no differences were determined for hemoglobin concentration and blood glucose in acclimatization (Figure 3). Interestingly, at three weeks, bean-based diet groups were significant different from CTRL group for Blood glucose concentration ( p<0.05) (Figure 3). Moreover, at 8 weeks, only CD group showed a statically significant increase in ferritin (Table 1). In summary, our results suggest that bean-based biofortified diet (BIO102) has a higher nutritional value than common crops such as conventional beans and corn, when compared with a control diet. This suggestion is because the mice feed with BIO102 diet kept body weight gain like those in CTRL group. In addition, BIO102 reduced fasting blood glucose, maintaining both endurance capacity and strength, as well as biomarkers of iron regulation. This work was funded by the following: Pontificia Universidad Javeriana Cali-Colombia, El Centro Internacional de Agricultura Tropical (CIAT) y la Fundación Banco de la República. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Classification of Megathyrsus Maximus Accessions Grown in the Colombian Dry Tropical Forest by Nutritional Assessment During Contrasting Seasons

The diversity and use of tropical forages for cattle feeding are the protagonists in livestock systems. The production and nutritional quality of forages represent a strategy of continuous research in animal feeding to help mitigate the environmental impact generated by tropical livestock. The objective of this study was to classify the nutritional behavior in contrasting seasons and the relationship with agronomic traits of a collection of 129 CIAT (Centro Internacional de Agricultura Tropical) accessions of Megathyrsus Maximus established in the Colombian dry tropics. By means of the near-infrared reflectance spectroscopy (NIRS) technique, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and in vitro dry matter digestibility (IVDMD) were determined under rainy and dry seasons as fixed effects. We measured plant height, dry matter biomass (DMB) and flowering in field. Aspects such as plant height and DMB did not show correlation with nutritional aspects, whereas flowering was correlated with the content of structural carbohydrates. Despite genotype and precipitation affecting nutritional value, there is relative nutritional steadiness in NDF, ADF, and IVDMD between seasons for some accessions. According to the cluster analysis carried out for each season, it was evidenced that from the total collection, 51.2% of the accessions during the dry season and 19.4% of the accessions during the rainy season were classified with a better nutritional profile, thus, showing a higher number of materials with better nutritional behavior in the dry season. Both the genotypic characteristics of M. maximus and environmental conditions during contrasting seasons are factors that might influence the variability of the nutritional content, productive parameters, and flowering. Additionally, fodder material classification under Hotelling's T-squared test and Nutritional Classification Index suggests accessions that might be promising for resilient nutritional quality and adequate DMB, which proves that M. maximus could become an alternative for animal feeding and sustainable livestock production during critical dry periods in tropical agroecosystems.

Caracterización fenotípica por resistencia a sequía terminal de germoplasma de frijol común

Terminal drought is a worldwide constraint to common bean production and its negative effects will be increased by climate change. The objective of this research was to characterize phenotypically advanced lines and commercial cultivars of common bean for their resistance to terminal drought stress. Field trials were conducted during 2012 and 2013 at Centro Internacional de Agricultura Tropical (CIAT), Palmira, Colombia. A 4x4 partially balanced lattice design with four replicates was used and, evaluated under irrigation and terminal drought. To achieve the terminal drought condition, irrigation was suspended at 22-23 days after planting. Terminal drought reduced mean grain yield by 68%. Lines SEN 56, BFS 29, NCB 226 and SER 16 showed high grain yield in both irrigated (3617-3836 kg/ ha) and terminal drought (1232-1447 kg/ha) conditions, while RCB 593 and G 40001 showed high grain yield in drought (>1270 kg/ha) and similar to checks in irrigated condition. The most resistant lines showed lower drought susceptibility index (0,88 - 1,00), earlier maturity (56 - 60 dds), superior geometric mean (1931 - 2311 kg/ha), and higher number of grains/m2, (673 - 1250). Drought resistant lines produced at least 15% and 50% more grain yield than EAP 9510-77, commercial check for Central America, in irrigated and drought condition, respectively. In addition, they were also superior to other commercial checks such as DOR 390 and Bribri.

Evidence for genotypic differences among elite lines of common bean in the ability to remobilize photosynthate to increase yield under drought

SUMMARYCommon bean (Phaseolus vulgaris L.) is the most important food legume for human consumption. Drought stress is the major abiotic stress limitation of bean yields in smallholder farming systems worldwide. The current work aimed to determine the role of enhanced photosynthate mobilization to improve adaptation to intermittent and terminal drought stress and to identify a few key adaptive traits that can be used for developing drought-resistant genotypes. Field studies were conducted over three seasons at Centro Internacional de Agricultura Tropical, Palmira, Colombia to determine genotypic differences in adaptation to intermittent (two seasons) and terminal (one season) drought stress compared with irrigated conditions. A set of 36 genotypes, including 33 common bean, two wild bean and one cowpea were evaluated using a 6 × 6 lattice design under irrigated and rainfed field conditions. Three common bean elite lines (NCB 226, SEN 56, SER 125) were identified with superior levels of adaptation to both intermittent and terminal drought stress conditions. The greater performance of these lines under drought stress was associated with their ability to remobilize photosynthate to increase grain yield based on higher values of harvest index, pod harvest index, leaf area index and canopy biomass. Two wild bean germplasm accessions (G 19902, G 24390) showed very poor adaptation to both types of drought stress. One small-seeded black line (NCB 226) was superior in combining greater values of canopy biomass with greater ability to mobilize photosynthates to grain under both types of drought stress. Two small-seeded red lines (SER 78, SER 125) seem to combine the desirable traits of enhanced mobilization of photosynthates to seed with effective use of water through canopy cooling under terminal drought stress. Pod harvest index showed significant positive association with grain yield under both types of drought stress and this trait can be used by breeders as an additional selection method to grain yield in evaluation of breeding populations for both types of drought stress.

A Tribute to Dr. Anthony C. Bellotti and His Contributions to Cassava Entomology

Anthony (Tony) Bellotti’s career as a humanitarian and entomologist followed a trajectory that took him to El Salvador with the Peace Corps (PC) in 1962, New Mexico State for a Masters, Paraguay (again with the Peace Corps), Cornell University for a Ph.D., and Colombia where he worked for the Centro Internacional de Agricultura Tropical (CIAT) from 1974 until his passing in March 2013 in Naples, Florida. Tony became a passionate advocate of cassava, and one of the world’s pre-eminent authorities on the entomology of that orphan crop that sustains millions of the world’s poorest popula tions. Tony played a crucial role in one of the most often cited and successful examples of classical biological control, the introduction of a parasitoid wasp from Paraguay to control the cassava mealybug throughout a broad area of Africa known as the Cassava Belt. His career spanned a period of time that might be referred to as a golden age of commodity programs at the international “CG Centers” organized under the Consultative Group on International Agricultural Research (CGIAR), which followed in the footsteps of Norman Borlaug and Robert McNamara, the unlikely alliance that led to the Green Revolution. Among Tony’s lesser accomplishments was his recruitment of the author to CIAT in 1986, where I worked on pests of tropi cal forages and then on cassava integrated pest management in northeastern Brazil and West Africa. Tony was a mentor and a friend whose career offers a chance to look at a unique life and his contributions to international agriculture.

Brachiaria hybrids: potential, forage use and seed yield

A brachiaria breeding program initiated in 1988 at CIAT (Centro Internacional de Agricultura Tropical, Cali, Colombia) combined desirable attributes found in accessions of Brachiaria brizantha and B. decumbens . Three apomictic hybrids have been released (cvv. Mulato, Mulato II and Cayman). Mulato showed agronomic potential but seed yields were low. Trials in Central America demonstrated the superiority of Mulato II, a vigorous grass with deep and branched roots, giving it excellent drought tolerance in the Brazilian Cerrado and Mexico, plus outstanding nutritional value. Following trials in Mexico and Thailand, evaluating 155 new hybrids for 7 years, cv. Cayman was released due to strong waterlogging tolerance. Research on production, quality and seed yields of brachiaria hybrids in Asia, the Americas and Africa from 2003 to 2013 is summarized in this paper.

Efficiency of Sesbania sesban and Acacia angustissima in limiting methanogenesis and increasing ruminally available nitrogen in a tropical grass-based diet depends on accession

Novel strategies to improve nutrient-poor tropical diets for ruminants should aim to increase feeding value and, simultaneously, reduce emissions of the greenhouse gas methane. Both aims were addressed in the present in vitro experiment when supplementing a low quality, tropical grass (Brachiaria humidicola; Centro Internacional de Agricultura Tropical accession number 6133) with foliage from various leguminous multi-purpose shrubs, all of them containing plant secondary metabolites in different concentrations. In detail, foliage of Acacia angustissima from the International Livestock Research Institute ( ILRI; accessions no. 459 and 15132), Sesbania sesban (ILRI 10865 and 15019), Samanea saman (ILRI 14884), and leafy crop residues of the grain legume Cajanus cajan (ILRI 16555) were supplemented at 200 g/kg dry matter. Additionally, a combination of C. cajan and S. sesban 10865 was tested. Effects on methanogenesis, ruminal nitrogen turnover and other fermentation traits were determined with the rumen simulation technique Rusitec. All supplements enhanced the fermentable nutrient supply, especially ruminally degradable crude protein, and improved the calculated microbial efficiency in nitrogen utilisation. Methanogenesis was limited by one accession of S. sesban (10865) and, less clearly, by one A. angustissima accession (459), while the other supplements remained ineffective. The first mentioned accessions proved to be far richer in several plant secondary metabolites, especially saponins and tannins. Provided in combination, C. cajan and S. sesban 10865 supported each other in their effects on nitrogen usage and total methane release. Accordingly, a combination strategy might provide, after being verified in vivo, a particularly promising option to improve low quality, tropical diets at limited environmental impact thus facilitating its adoption by stakeholders.

Dietary food intake patterns among women in rural South Haiti

We applied a Food Frequency Questionnaire (FFQ) to 153 mothers of children under five in rural South Haiti from June to late July 2007. The FFQ contained 46 items and used a 3 month reference time period. Over the previous 3 months, the majority of women reported consuming fruits (98.7%), rice (98.7%), plantains (94%), pumpkin (78.4%), corn (95.4%), mangoes (96.7%), papaya (78.9%), watermelon (52.3%), sweet potatoes (92.8%), chicken (81.0%), beef (80.4%), local bread (96.7%), salty snacks (85.0%), fish (85.0%), carrots (93.5%), raw milk (83.0%), kola (60.8%), concentrated milk (60.8%), and liver (53.6%). However, the median consumption for most nutrient dense foods was less than 2 times per week. Only corn, plantain, milk, rice, local bread and mangoes were consumed 3 or more times per week. Foods that were infrequently consumed (i.e. median less or equal 2 times a week) were: watermelon, sweet potatoes, papaya, pumpkin, carrots, liver, chicken, beef, fish, salty snacks, concentrated milk and kola. The above results suggest a need for micronutrient enhanced foods in the area to alleviate potential micronutrient deficiencies. We are currently exploring the potential contributions that orange fleshed sweet potatoes can make towards this goal. Funding provided by CIDA through the Centro Internacional de Agricultura Tropical (CIAT).

Validity of the Latin American and Caribbean Household Food Security Scale (ELCSA) in South Haiti

We tested the validity of ELCSA in a convenience sample of 153 women with children under five in South Haiti. ELCSA was applied to the women in Creole, contained 16 items and used a reference period of 3 months. Cronbach's alpha was 0.92. Based on affirmative response prevalence, the items referring to child hunger tended to be the most severe. However, social unacceptability of procuring food was the most severe item. This question asked ‘Was there any time during the past 3 months when you had to do something that you would have preferred not to do (such as begging or sending the children to work) to be able to get food?’ There were no food secure households in the sample, 44% were food insecure (FI), 49% were very FI, and 7% were extremely FI. Criterion validity was strong. Those reporting having good/very good health ranged from 38.8% among those FI to 9.1% among those extremely FI (p=0.02). Households with children who had recently had malaria were more likely to be very/extremely FI than households where the index child had been free of malaria (82.0% vs. 37.1%, p<0.001). Additional factors associated with very/extreme FI (p<0.05) were: female‐headed household, lack of electricity at home, no land ownership, and poorer dietary quality. Results suggest that ELCSA is a valid tool for assessing household FI in rural Haiti. Funded by CIDA (7034161) through a grant to the Centro Internacional de Agricultura Tropical (CIAT).

Mapping the spatial distribution of global anthropogenic mercury atmospheric emission inventories

This paper describes the procedures employed to spatially distribute global inventories of anthropogenic emissions of mercury to the atmosphere, prepared by Pacyna, E.G., Pacyna, J.M., Steenhuisen, F., Wilson, S. [2006. Global anthropogenic mercury emission inventory for 2000. Atmospheric Environment, this issue, doi:10.1016/j.atmosenv.2006.03.041], and briefly discusses the results of this work. A new spatially distributed global emission inventory for the (nominal) year 2000, and a revised version of the 1995 inventory are presented. Emissions estimates for total mercury and major species groups are distributed within latitude/longitude-based grids with a resolution of 1×1 and 0.5×0.5°. A key component in the spatial distribution procedure is the use of population distribution as a surrogate parameter to distribute emissions from sources that cannot be accurately geographically located. In this connection, new gridded population datasets were prepared, based on the CEISIN GPW3 datasets (CIESIN, 2004. Gridded Population of the World (GPW), Version 3. Center for International Earth Science Information Network (CIESIN), Columbia University and Centro Internacional de Agricultura Tropical (CIAT). GPW3 data are available at http://beta.sedac.ciesin.columbia.edu/gpw/index.jsp). The spatially distributed emissions inventories and population datasets prepared in the course of this work are available on the Internet at www.amap.no/Resources/HgEmissions/

Breeding Cassava for Underprivileged

SUMMARY Cassava (Manihot esculenta Crantz), an important crop in the poorer rural uplands of the tropics, was an obvious target for international research attention in 1970 and the Centro Internacional de Agricultura Tropical (CIAT, headquartered in Colombia) established a cassava-breeding program. Assisted by many ancillary disciplines, the program defined its mission as breeding for low input conditions in less favorable environments to alleviate the poverty of small farmers through income generation. From its initiation, CIAT worked in a partnership with national programs. The breeding effort depended on the free exchange of germplasm, based on the understanding that CIAT would collect, evaluate, and maintain cassava germplasm and that this and any advanced materials derived from it would be freely available to any public organization. A key decision was to transfer the major applied breeding effort to Asia, while maintaining a basic breeding scheme in Colombia, with the understanding that a crop is usually more successful outside the center of crop origin and diversification than at the center. Fresh root yield of populations was improved by more than 100% and root dry matter content by more than 20%. The national program collaborators used these populations to develop many improved cultivars in many countries. The biological factors considered as critical for this successful breeding effort were: inclusion of a broad base of genetic variability obtained in the center of crop origin and diversification; evaluation of breeding materials under diverse environmental conditions; and a clear understanding of the different operational principles at different stages of breeding advancement. By 2002, Asian national programs had released more than 50 CIAT-related cassava cultivars in nine countries and farmers grew these new cultivars on more than one million ha. The economic benefits resulting from the increased productivity are well beyond one billion US$. The target population of small farmers in the poorer rural areas of the tropics captured a large proportion of these economic benefits. The understanding of crop germplasm being a common human heritage and the determination of agricultural scientists to use this for the welfare of the neediest people were the social factors for the overall success.

Cassava biology and physiology

Cassava or manioc (Manihot esculenta Crantz), a perennial shrub of the New World, currently is the sixth world food crop for more than 500 million people in tropical and sub-tropical Africa, Asia and Latin America. It is cultivated mainly by resource-limited small farmers for its starchy roots, which are used as human food either fresh when low in cyanogens or in many processed forms and products, mostly starch, flour, and for animal feed. Because of its inherent tolerance to stressful environments, where other food crops would fail, it is often considered a food-security source against famine, requiring minimal care. Under optimal environmental conditions, it compares favorably in production of energy with most other major staple food crops due to its high yield potential. Recent research at the Centro Internacional de Agricultura Tropical (CIAT) in Colombia has demonstrated the ability of cassava to assimilate carbon at very high rates under high levels of humidity, temperature and solar radiation,which correlates with productivity across all environments whether dry or humid. When grown on very poor soils under prolonged drought for more than 6 months, the crop reduce both its leaf canopy and transpiration water loss, but its attached leaves remain photosynthetically active, though at greatly reduced rates. The main physiological mechanism underlying such a remarkable tolerance to drought was rapid stomatal closure under both atmospheric and edaphic water stress, protecting the leaf against dehydration while the plant depletes available soil water slowly during long dry periods. This drought tolerance mechanism leads to high crop water use efficiency values. Although the cassava fine root system is sparse, compared to other crops, it can penetrate below 2 m soil,thus enabling the crop to exploit deep water if available. Leaves of cassava and wild Manihot possess elevated activities of the C4 enzyme PEP carboxylase but lack the leaf Kranz anatomy typical of C4 species, pointing to the need for further research on cultivated and wild Manihot to further improve its photosynthetic potential and yield,particularly under stressful environments. Moreover, a wide range in values of Km (CO2) for the C3 photosynthetic enzyme Rubisco was found among cassava cultivars indicating the possibility of selection for higher affinity to CO2, and consequently higher leaf photosynthesis. Several plant traits that may be of value in crop breeding and improvement have been identified, such as an extensive fine root system, long leaf life, strong root sink and high leaf photosynthesis. Selection of parental materials for tolerance to drought and infertile soils under representative field conditions have resulted in developing improved cultivars that have high yields in favorable environments while producing reasonable and stable yields under stress.

In Field Damage of High and Low Cyanogenic Cassava Due to a Generalist Insect Herbivore Cyrtomenus bergi (Hemiptera: Cydnidae)

The hypothesis that cyanogenic potential in cassava roots deters polyphagous insects in the field is relevant to current efforts to reduce or eliminate the cyanogenic potential in cassava. To test this hypothesis, experiments were conducted in the field under natural selection pressure of the polyphagous root feeder Cyrtomenus bergi Froeschner (Hemiptera: Cydnidae). A number of cassava varieties (33) as well as 13 cassava siblings and their parental clone, each representing a determined level of cyanogenic potential (CNP), were scored for damage caused by C. bergi and related to CNP and nonglycosidic cyanogens, measured as hydrogen cyanide. Additionally, 161 low-CNP varieties (< 50 ppm hydrogen cyanide, fresh weight) from the cassava germplasm core collection at Centro Internacional de Agricultura Tropical (CIAT) were screened for resistance/tolerance to C. bergi. Low root damage scores were registered at all levels of CNP. Nevertheless, CNP and yield (or root size) partly explained the damage in cassava siblings (r2 = 0.82) and different cassava varieties (r2 = 0.42), but only when mean values of damage scores were used. This relation was only significant in one of two crop cycles. A logistic model describes the underlying negative relation between CNP and damage. An exponential model describes the underlying negative relation between root size and damage. Damage, caused by C. bergi feeding, released nonglycosidic cyanogens, and an exponential model fits the underlying positive relation. Fifteen low-CNP clones were selected for potential resistance/tolerance against C. bergi.

Thirty Years of Cassava Breeding for Productivity—Biological and Social Factors for Success

The Centro Internacional de Agricultura Tropical (CIAT, headquartered in Colombia) established a cassava (Manihot esculenta Crantz) breeding program in the beginning of the 1970s with the aim of extending the Green Revolution success to less privileged sectors of the tropical populations. The initial decade was mainly dedicated to the collection of germplasm and generation of basic breeding materials. The later decades were devoted to applied breeding in collaboration with international and national programs in Latin America, Asia, and Africa. This paper focuses on the basic breeding at CIAT/Colombia (CIAT/HQ), applied breeding at CIAT/Thailand (CIAT/Thai), and distribution and selection of improved materials with many collaborators in Asia. Fresh root yield of populations was improved by &gt;100% and root dry matter content by &gt;20%. The national program collaborators used these populations to develop many improved cultivars in many countries. The biological factors considered as critical for this successful breeding effort were as follows: inclusion of a broad base of genetic variability obtained in the center of crop origin and diversification; evaluation of breeding materials under diverse environmental conditions including high stress environments; and a clear understanding of the different operational principles at different stages of breeding advancement, as illustrated by the emphasis on harvest index in selection within populations and on biomass in population building. The understanding of crop germplasm being a common heritage and the determination of agricultural scientists to use this for the welfare of the neediest people were the social factors for the overall success.

Alert common bean

Alert is a high-yielding, semi-erect great northern common bean (Phaseolus vulgaris L.) cultivar. It was developed from a series of crosses at the Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia, on contract to the Agriculture and Agri-Food Canada (AAFC) Research Centre, Lethbridge, with cooperation from the AAFC Morden Research Station. Alert is well adapted to the eastern Canadian prairies, yielding significantly higher than the check cultivar, US1140, at 130% in the official Manitoba Dry Bean Co-operative Registration Trials. Alert is moderately resistant to white mold and resistant to races 1 and 15 of bean common mosaic virus (BCMV). It is susceptible to the alpha and alpha Brazil races of anthracnose, but resistant to the delta race. Key words: Common bean, Phaseolus vulgaris, great northern bean, cultivar description, high yield

Identifying Resistance Gene Analogs Associated With Resistances to Different Pathogens in Common Bean

ABSTRACT A polymerase chain reaction approach using degenerate primers that targeted the conserved domains of cloned plant disease resistance genes (R genes) was used to isolate a set of 15 resistance gene analogs (RGAs) from common bean (Phaseolus vulgaris). Eight different classes of RGAs were obtained from nucleotide binding site (NBS)-based primers and seven from not previously described Toll/Interleukin-1 receptor-like (TIR)-based primers. Putative amino acid sequences of RGAs were significantly similar to R genes and contained additional conserved motifs. The NBS-type RGAs were classified in two subgroups according to the expected final residue in the kinase-2 motif. Eleven RGAs were mapped at 19 loci on eight linkage groups of the common bean genetic map constructed at Centro Internacional de Agricultura Tropical. Genetic linkage was shown for eight RGAs with partial resistance to anthracnose, angular leaf spot (ALS) and Bean golden yellow mosaic virus (BGYMV). RGA1 and RGA2 were associated with resistance loci to anthracnose and BGYMV and were part of two clusters of R genes previously described. A new major cluster was detected by RGA7 and explained up to 63.9% of resistance to ALS and has a putative contribution to anthracnose resistance. These results show the usefulness of RGAs as candidate genes to detect and eventually isolate numerous R genes in common bean.

Pathogenicity and race characterization of Fusarium oxysporum f. sp. phaseoli isolates from Spain and Greece

Virulence (≡ severity of disease) and physiological specialization of nine isolates of Fusarium oxysporum f. sp. phaseoli recovered in El Barco de Avila (Castilla y León, west‐central Spain) and of two isolates from Chryssoupolis (Greece) were determined. The susceptibility/resistance response showed by a differential set of common bean cultivars (Phaseolus vulgaris) selected at the Centro Internacional de Agricultura Tropical (CIAT) delineated the isolates into two new races: races 6 and 7. The results of pathogenicity tests did not show any significant differences in virulence among the isolates. However, the reactions of several Spanish common bean cultivars indicated the presence of two groups of isolates, highly virulent and weakly virulent, among the Spanish isolates analysed. These results indicate that isolates classified in the same race are not homogeneous with respect to virulence, and suggests that race analysis using the CIAT differential cultivars is insufficient to describe the physiological specialization of F. oxysporum f. sp. phaseoli.

Selection for drought resistance in early generations of common bean populations

Availability and use of high-yielding drought-resistant common bean (Phaseolus vulgaris L.) cultivars would reduce dependence on irrigation water and production costs, stabilize yield in drought-prone environments, and potentially increase profit margins for growers. Among various selection criteria, seed yield has been found to be the most effective to improve drought resistance in common bean. Our objective was to determine the effectiveness of selection for seed yield in drought-stressed (DS) and non-stressed (NS) environments in early generations of common bean populations under field conditions. One hundred thirty-four F2-derived F4 (F2:4) families from each of three double-cross populations (SX 12008, SX 12009, and SX 12010), four parents, and six checks were evaluated in replicated field trials in DS and NS environments at the Centro Internacional de Agricultura Tropical, Palmira, Colombia during the January to March growing season (1997A). The 30 highest yielding F2:5 families from each population and each environment, four parents, and two checks were again evaluated in replicated trials in their respective DS and NS environments during the June to August growing season (1997B). Three F5:7 lines from each of the four highest yielding F2:5 families from each population and each environment (a total of 72 lines), and nine parents involved in the three populations were evaluated in replicated trials in both DS and NS environments in 1998B and 1999B. Mean yieldof lines selected in the NS environment was significantly higher than the mean of parents in populations SX 12008 and SX 12010 when tested in the NS environment. In population SX 12009, lines selected in the DS environment had higher mean yield than their parents when tested in NS environment. The mean yields of lines selected in the DS and NS environments did not differ significantly when tested in the DS environment in any population. NS environment seed yields were positively correlated with DS yields, geometric mean yield (GM), percent reduction (PR) due to drought stress, and drought susceptibility index (DSI). In contrast, DS and GM yields were negatively correlated with PR and DSI, whereas the association between the latter two was positive. The 100 -seed weight was slightly reduced and mean maturity was accelerated by 2 to 4 d in DS versus NS environments. Considering the extra costs involved to test early generation selections for seed yield in DS environments, it does not appear to be advisable in common bean. Key words: Drought resistance in common bean, early generation yield test, F2-derived family selection, Phaseolus vulgaris, seed yield

A DNA-Based Procedure for In Planta Detection of Fusarium oxysporum f. sp. phaseoli

ABSTRACT We have characterized strains of Fusarium oxysporum from common bean fields in Spain that were nonpathogenic on common bean, as well as F. oxysporum strains (F. oxysporum f. sp. phaseoli) pathogenic to common bean by random amplified polymorphic DNA (RAPD) analysis. We identified a RAPD marker (RAPD 4.12) specific for the highly virulent pathogenic strains of the seven races of F. oxysporum f. sp. phaseoli. Sequence analysis of RAPD 4.12 allowed the design of oligonucleotides that amplify a 609-bp sequence characterized amplified region (SCAR) marker (SCAR-B310A280). Under controlled environmental and greenhouse conditions, detection of the pathogen by polymerase chain reaction was 100% successful in root samples of infected but still symptomless plants and in stem samples of plants with disease severity of >/=4 in the Centro Internacional de Agricultura Tropical (CIAT; Cali, Colombia) scale. The diagnostic procedure can be completed in 5 h and allows the detection of all known races of the pathogen in plant samples at early stages of the disease with no visible symptoms.

AC Black Diamond common bean

AC Black Diamond is a high-yielding, large-seeded, shiny black dry bean (Phaseolus vulgaris L.) cultivar. It was developed from a series of crosses at the Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia, on contract to the Agriculture and Agri-Food Canada (AAFC) Research Centre, Lethbridge, with cooperation from the AAFC Research Station Morden. AC Black Diamond is well adapted to the Canadian prairies, yielding significantly more than the check cultivar, UI 906, at 122% in narrow-rows an d 106% in wide-rows. AC Black Diamond is moderately susceptible to white mold and resistant to bean common mosaic virus (BCMV). Key words: Common bean, Phaseolus vulgaris, shiny large-seeded black bean, cultivar description, high yield