Aluminium (Al) toxicity limits common bean productivity in acid soil regions of the tropics. To improve Al resistance of common bean, Al-sensitive
Phaseolus vulgaris
(SER16) was crossed to ...Al-resistant
P. coccineus
(G35346-3Q) to create 94 F
5:6
recombinant inbred lines (RILs) of the pedigree SER16 × (SER16 × G35346-3Q). RILs were characterized for resistance to Al in a hydroponic system with 0 and 20 μM Al in solution, and for shoot and root growth response to Al-toxic infertile acid soil in 75 cm long soil cylinder system using an oxisol of low Al- (12.5%; pH 4.6; fertilized) and high Al-saturation (77%; pH 4.1; unfertilized). G35346-3Q increased its taproot elongation rate by 3.5% between 24 and 48 h under 20 μM Al in solution, while the best RIL, Andean genotype ICA Quimbaya, and sensitive genotype VAX1 expressed reductions of 2.6, 12.5, and 69.5%, respectively. In the acid soil treatment the correlation between leaf area and total root length was highly significant under high Al saturation (
r
= 0.70***). Genotypes that were Al resistant in the hydroponic system were not necessarily tolerant to Al-toxic acid soil conditions based on shoot and root growth responses. Phenotypic evaluation using both systems allows the identification of genotypes with Al resistance combined with acid soil adaptation. Two genotypes (ALB88 and ALB91) emerged as lines with multiple traits. Results suggest that inheritance of Al resistance and acid soil tolerance in G35346-3Q is complex. Results from this work will be useful for identification of molecular markers for Al resistance in
Phaseolus
species and to improve acid soil adaptation in common bean.
Iron deficiency is a public health problem in many developing countries. Iron‐biofortified varieties of commonly consumed staple crops have the potential to contribute to the daily iron requirements ...in diets. This paper examines consumer acceptance and willingness to pay (WTP) for two iron bean varieties in Rwanda: red iron bean (RIB) and white iron bean (WIB). Using the Becker‐DeGroot‐Marschak mechanism, the paper investigates the effect of (1) nutrition information; (2) information frame; and (3) the frequency of providing the information on consumer WTP. WTP estimations take into account social interaction and nonpayment effects. Results indicate that without information about the nutritional benefits of the two iron bean varieties, consumers are willing to pay a large premium for the RIB variety, but not for the WIB variety. The nutrition information provided has a significantly positive effect on the premium for each of the iron bean varieties. Results also indicate that the effects of how the information is framed on this premium are not statistically significant. However, providing the nutrition information three times versus once significantly increases consumer demand for the WIB variety. These findings could inform the design of efficient delivery and marketing strategies for iron bean varieties in Rwanda.
La carence en fer est un problème de santé publique dans de nombreux pays en développement. Variétés fer biofortifiées de cultures de base couramment consommés ont le potentiel de contribuer aux besoins quotidiens en fer dans les régimes alimentaires. Cet article examine l'acceptation des consommateurs et la volonté de payer (CAP) pour deux variétés de haricots de fer au Rwanda: haricots rouges de fer (RIB) et de haricots de fer blanc (WIB). En utilisant le mécanisme Becker‐DeGroot‐Marschak (BDM), l′étude examine l'effet de (1) l'information nutritionnelle; (2) trame d'information et (3) la fréquence de fourniture d'informations sur le CAP des consommateurs. Estimations WTP tiennent compte de l'interaction sociale et les effets non‐paiement. Les résultats indiquent que l'absence d'informations sur les avantages nutritionnels des deux variétés de haricots fer, les consommateurs sont prêts à payer une prime pour la variété de RIB, mais pas pour la variété WIB. L'information nutritionnelle fournie a un effet significativement positif sur la prime pour chacune des variétés de haricots de fer. Les résultats indiquent également que les effets de la façon dont l'information est encadré sur cette prime ne sont pas statistiquement significatives. Cependant, en fournissant les informations nutritionnelles de trois fois par rapport à la fois augmente significativement la demande des consommateurs pour la variété WIB. Ces résultats pourraient éclairer la conception de stratégies de distribution et de marketing efficaces pour les variétés de haricots de fer au Rwanda.
We announce the genome sequence for Xanthomonas species strain Nyagatare, isolated from beans showing unusual disease symptoms in Rwanda. This strain represents the first sequenced genome belonging ...to an as-yet undescribed Xanthomonas species known as species-level clade 1. It has at least 100 kb of genomic sequence that shows little or no sequence similarity to other xanthomonads, including a unique lipopolysaccharide synthesis gene cluster. At least one genomic region appears to have been acquired from relatives of Agrobacterium or Rhizobium species. The genome encodes homologues of only three known type-three secretion system effectors: AvrBs2, XopF1 and AvrXv4. Availability of the genome sequence will facilitate development of molecular tools for detection and diagnostics for this newly discovered pathogen of beans and facilitate epidemiological investigations of a potential causal link between this pathogen and the disease outbreak.
We present the genome sequence of the Nyagatare strain, a bacterial pathogen on beans that may be responsible for a mysterious disease emerging in Rwanda.
Biotic and abiotic stresses often occur in the same field of rural poor farmer households in tropical countries resulting in heavy losses of common bean yields. To improve resistance of common beans, ...sensitive Phaseolus vulgaris (SER16) was crossed to resistant P. coccineus (G35346-3Q) to create 94 F5:6 recombinant inbred lines (RILs) of the pedigree SER16♀ x (SER16♀ x G35346-3Q♂). The objectives of this study were to (i) identify potential parents for resistance to Al, drought and Fusarium root rot among 11 bean genotypes, (ii) to evaluate 94 F5:6 Recombinant Inbred Lines (RILs) of the cross SER 16♀ x (SER 16♀ x G35346-3Q♂) both for their resistance to Al and /or drought, (iii) to evaluate RILs for resistance to Fusarium root rot, and (iv) to identify QTL for resistance to these stresses. RILs were characterized in greenhouse for resistance to Al using a hydroponic screening employing a nutrient solution with or without 20 μM Al , to Al-toxic acid soil with high Al (HAl) and low Al (LAl) saturation, to terminal drought simulation with and without progressive soil drying, to combined stresses of Al and terminal drought in 80 cm long soil cylinder system, and to Fusarium root rot using inoculated perlite soil and sand (2:1). Two field studies were also carried on in Colombia under rainfed and irrigated conditions in Palmira, and high Al saturated acid soil in Santander of Quilichao. Our studies confirmed the superiority in Al response of Andean common beans in greenhouse trials compared to Middle American type for several root traits. Each screening method of our Al greenhouse experiments permitted an evaluation of different aspects of root traits. The two parents were virtually equal for tap root elongation rate at 24 h in the 20 μM Al treatment at about 1.4 mm h-1 while progenies ranged from less than 1-1.75 mm h-1. The correlation between leaf area and total root length was highly significant under high Al saturation (r = 0.70***) for HAl-acid soil. Two genotypes (ALB88 and ALB 91) emerged as strong multiple trait lines for the two abiotic stresses. Fusarium root rot induced root growth inhibition as high as 80.8% for the susceptible ALB 5, while resistant RILs (ALB45, ALB41, ALB126, ALB84, ALB49, ALB34, ALB88 and ALB85) didn`t show any inhibition . Seed yield under drought stress conditions was positively associated to 100-seed weight both under irrigated field (r = 0.28**) and rainfed field (r = 0.36***), and negatively associated to days to maturity (DTM) (r = - 0.36***) in field evaluation in Al-toxic acid soil in Quilichao (Colombia). QTLs for important traits including root characteristics under high Al , grain yield and yield components for drought and high Al saturation soil were identified. The use of both soil and hydroponic system, and field could contribute to evaluation of breeding materials to identify genotypes that combine Al resistance with acid soil tolerance, drought and root rot tolerance.
Bean species and genotypes show wide phenotypic variability in relation to aluminium (Al) resistance and progressive soil drying. The objective of this study was to identify and characterize sources ...of resistance to Al toxicity and progressive soil drying among six genotypes of common bean (
Phaseolus vulgaris
), four of runner bean (
P. coccineus
), and one of tepary bean (
P. acutifolius
), using hydroponic and soil cylinder screening methods. One experiment on hydroponic screening of Al resistance was carried out using a basal nutrient solution with and without 20 μM Al. Two experiments were carried out using two oxisols in 80 cm long soil cylinders with high Al (HAl) and low Al (LAl) saturation treatments. The three experiments showed an average of 36.9–53.5% inhibition of root growth with HAl compared with LAl treatments. Differences in root development and distribution were observed among genotypes and species. Two accessions of
P. coccineus
(G35346-2Q, G35464-5Q) and one Andean common bean genotype (ICA Quimbaya) were outstanding in root and shoot growth in the HAl treatments.
P. coccineus
accession (G35346-3Q) was outstanding under combined stress of Al-toxic acid soil and progressive soil drying. Accessions of
P. coccineus
may represent unique sources of Al resistance for the improvement of common bean through interspecific crosses.
We examine consumer acceptance of two iron bean varieties in Rwanda: red iron bean (RIB) and white iron bean (WIB). Using the Becker-DeGroot-Marschak mechanism, we investigate the effect of (1) ...nutrition information; (2) information frame (information emphasizing negative consequences of not having enough iron in diets versus information emphasizing benefits), and (3) the frequency of providing the information, on consumer willingness to pay (WTP) for iron bean varieties. Results indicate that in the absence of information about their nutritional benefits, consumers are willing to pay a large premium for RIB, but not for WIB, relative to the local variety. Nutrition information has a positive effect on the premium for each of the iron bean varieties. We find that the way in which the information is framed has no significant effect on this premium, whereas provision of the information three times versus once significantly increases WTP for WIB.
PDF
