Water use efficiency among dry bean landraces and cultivars in drought-stressed and non-stressed environments

The agricultural use of water is higher than 85% in the western USA, resulting in an increasing water deficit in the region; this situation is commonly encountered throughout the world where irrigated and irrigation-assisted production systems are operational. The objective of this study was to examine differences among dry bean (Phaseolus vulgaris L.) landraces and cultivars in terms of water use efficiency (WUE), subsequently identifying those with a high water use efficiency. Six medium-seeded (25–40 g 100 seed wt⁻¹) landraces and cultivars of pinto and red market classes were evaluated in intermittent drought-stressed (DS) and non-stressed (NS) environments at Kimberly, Idaho, USA in 2003 and 2004. Each market class comprised one each of a landrace and old and new cultivars. Mean evapotranspiration (ET) in the NS environment was 384 mm in 2003 and 432 mm in 2004; the respective ET values in the DS environment were 309 and 268 mm. Mean seed yield was higher in the DS (2678 kg ha⁻¹) and NS (3779 kg ha⁻¹) environments in 2004 than in 2003 (688 and 1800 kg ha⁻¹, respectively). Under severe drought stress in 2003, WUE in the pinto bean ranged from 1.5 for the Common Pinto landrace to 4.4 kg ha⁻¹ mm⁻¹ water for cv. Othello. The Common Red Mexican landrace had the highest WUE (3.7), followed by cvs. NW 63 (2.8) and UI 259 (1.4) in the red market class. Under favorable milder climatic conditions in 2004, the mean WUE value was 10 kg ha⁻¹ mm⁻¹ water in the DS environment and 8.7 kg ha⁻¹ mm⁻¹ water in the NS environment. We conclude that dry bean landraces and cultivars with high WUE should be used to reduce dependence on irrigation water and to develop drought-resistant cultivars to maximize yield and WUE.     

Breeding options for improving common bean for resistance against bean fly (<Emphasis Type="Italic">Ophiomyia</Emphasis> spp.): a review of research in eastern and southern Africa

Bean fly (Ophiomyia spp.) is a key pest of common bean (Phaseolus vulgaris L.) throughout eastern and southern Africa. It is known to cause total crop loss especially under drought stress and low soil fertility. This review underscores the importance of bean fly to bean production. It discusses the research achievements on genetic improvement of common bean for resistance against bean fly attack and highlights further opportunities available for rapid advance. The paper dwells on conventional breeding approaches and possibilities for utilization of marker-assisted selection. Mechanisms of common bean resistance to bean fly have been considered with a view to understand the genetic control. To maximize the effectiveness of host-plant resistance against bean fly, multiple insect resistances should be incorporated into a single bean genotype in order to ensure stability. However, this should be within the background of integrated pest management strategy.     

Nitrogen fixation by common bean (Phaseolus vulgaris L.) in pure and mixed stands in semi-arid south-east Kenya

Research was carried out in the field on the effect of intercropping common bean and maize crops in a semi-arid zone of south-east Kenya over two rainy seasons in 1997. The experimental design was a randomised complete block design with eight treatments replicated four times. Significant differences were observed in total plant dry weight by the different treatments in pure stands, 21 days after emergence with higher values under mixed cropping system in common beans. However, at 42 days after emergence, plant dry weights in uninoculated common bean pure stands with N application were significantly higher than under other treatments. Common bean yields were significantly reduced by the maize intercrop. The inoculated common bean and N application treatment recorded the largest seed dry weights and subsequently yields per hectare. These findings suggest that intercropping common beans and maize considerably suppresses the yield of the former under the semi-arid conditions of south-east Kenya. Inoculation of common bean with the commercially available Rhizobium strain 446 on the other hand was effective and improved yields. Soil analysis of the experimental plots before and after one cropping season indicated that common beans increased N slightly or maintained it at the pre-planting levels. This was unlike the pure maize plots where there was a marked decline in soil N. There was however, a marked increase in soil phosphorus in all treatment plots.     

Genomics,genetics and breeding of common bean in Africa: A review of tropical legume project

Common bean (Phaseolus vulgaris L.) is an important legume crop worldwide. The International Centre for Tropical Agriculture (CIAT) and its national partners in Africa aim to overcome production constraints of common bean and address the food, nutrition needs and market demands through development of multitrait bean varieties. Breeding is guided by principles of market‐driven approaches to develop client‐demanded varieties. Germplasm accessions from especially two sister species, P. coccineus and P. acutifolius, have been utilized as sources of resistance to major production constraints and interspecific lines deployed. Elucidation of plant mechanisms governing pest and disease resistance, abiotic stress tolerance and grain nutritional quality guides the selection methods used by the breeders. Molecular markers are used to select for resistance to key diseases and insect pests. Efforts have been made to utilize modern genomic tools to increase scale, efficiency, accuracy and speed of breeding. Through gender‐responsive participatory variety selection, market‐demanded varieties have been released in several African countries. These new bean varieties are a key component of sustainable food systems in the tropics.     

Variation in traits affecting nodulation of common bean under intercropping with maize and sole cropping

Common bean (Phaseolus vulgaris L.), an important food crop in Europe, America, Africa and Asia, is thought to fix only small amounts of atmospheric nitrogen. It contributes significantly to the sustainability of traditional cropping systems because of the predominance of small-scale farmers who cultivate beans in those areas. The objectives of this work were to evaluate bush bean varieties under common agronomic cropping systems and to evaluate breeding lines under low N-fertility sole cropping and intercropping systems. The purpose of the study was to characterize the genotype and cropping system's variability in symbiotic and plant characters and to identify the most suitable genotypes to establish an effective symbiosis with indigenous strains of Rhizobium. No significant differences among the bush bean varieties evaluated under typical fertilization practices were observed for N₂-fixation and plant traits except for seed nitrogen. Significant differences among the bean lines studied under low N-fertilization conditions were detected for plant growth,plant component and N₂-fixation traits. A significant interaction of bean genotype x cropping system was found for number of nodules per plant and nodule moisture on the bush bean varieties studied, and for days to emergence, days to flowering, end of flowering, shoot length, root dry weight and shoot nitrogen on the bean lines evaluated. Nodulation parameters were correlated positively with the yield components, shoot and root parts and duration of flowering, and correlated negatively with seed crude protein, pod and seed dimensions and seed dry weight. These observations indicate that it may be possible to increase both the symbiotic N₂-fixation and seed yield through plant breeding. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development of common bean (Phaseolus vulgaris L.) lines resistant to the bean pod weevil,Apion godmani Wagner,in Central America

Summary The larva of the bean pod weevil (BPW), Apion godmani Wagner (Coleoptera: Curculionidae), causes serious yield losses in common bean (Phaseolus vulgaris L.) in Mexico and Central America, by consuming the seed as it develops in the immature pod. Resistance to the BPW was identified in bean germplasm of highland Mexican origin, and these sources of resistance were incorporated into a pedigree breeding program to recover locally adapted lines resistant to Bean Common Mosaic Virus and BPW, with commercial grain for Guatemala, Honduras and El Salvador. These lines yielded as well as or better than local cultivars in the absence of the insect, and better than local cultivars when the BPW was present. Resistance appeared to be governed by several genes, and was stable across geographic areas, seasons and planting systems.     

The inheritance of bean size,pod size and number of beans per pod in cocoa (Theobroma cacao L.), with a note on bean shape

Studies have been made on the F₁ and F₂ generations of crosses between the Amazon clones Nanay 32, Parinari 7, and Parinari 35. There is wide variation in size from pod to pod on a tree, and this is largely paralleled by variation in bean number, bean size remaining relatively constant. However in some trees bean size increases in the largest pods, bean number remaining constant. It appears that if a pod is too small for the inherent number of beans to be present at their inherent size, the number of beans which develop is reduced so that their inherent size is attained; if the pod is larger than is required for the full number of beans to attain their inherent size the beans may increase in size above the inherent value. Thus if the average bean size in a sample of pods taken from a tree indicates the inherent bean size reasonably accurately it is likely that the inherent bean number will be relatively underassessed, and conversely if the observed bean number indicates the inherent number relatively accurately it is likely that the observed bean size will overassess the inherent size. Scatter-diagrams may therefore be more informative than averages.Bean number and bean size are strongly inherited but the difficulties described above tend to obscure the pattern. In the Pa7 x Na32 F₁ progeny inherent bean sizes are low and probably relatively constant while inherent bean numbers vary widely; in consequence inherent bean numbers are well indicated by samples of pods taken from the trees, and inheritance of bean number in the F₂ progenies is very clear while inheritance of bean size is not. In contrast, in the F₁ of Pa35 x Na32, there is clear segregation in bean size while bean numbers are relatively high and constant; inheritance of bean size in the F₂ progenies is clear while the evidence of inheritance of bean number is weaker.The average pod weight of a progeny seems to be determined by the inherent bean size and the inherent bean number.Bean breadth and bean thickness tend to be negatively correlated. It is suggested that where the number of ranks of beans in a pod is high relative to the length of the pod and the inherent bean size, the beans, lacking room for expansion in thickness, tend to increase in breadth so as to attain the inherent size. Short fat pods may therefore tend to contain broad, thin, plate-like beans.     

Effect of Phosphorus Fertilizer on Soya Bean Residue Turnover in the Tropical Moist Savanna

The contributions of soya bean (Glycine max) to the maintenance of soil N, organic matter and physical properties in any cropping system is dependent on the amount of the crop residue returned after grain harvest. This amount of residue is a function of the dry matter accumulated during growth. In the topical moist savanna (MS) of West Africa where soya bean production has increased especially due to the cultivation of more hectarage of land, increase in soya bean dry matter with the resulting residue is limited by P deficiencies. In this study, the effect of P application on residue turnover by soya bean varieties of different maturity classes was evaluated across the MS. The amount of root residue in the late varieties was double that of the early and medium varieties. The effect of P application on root residue was also greater in the late varieties. Although root residue was 0.35–0.72 Mg ha^?1, this was about 17–21 % of total dry matter at harvest. Among the varieties, litter residue averaged less than 1 Mg ha^?1 in the early and medium varieties, and was 32 % higher in the late varieties. Litter residue increased by 42–46 % with P application. The total amount of soya bean residue that is a potential source of organic material in a cropping system after the export of grain is small and averaged 2.88 Mg ha^?1 . Of this, root residue constituted 18 %, litter residue 41 % and stover residue 40 %. In this study C/N ratio averaged 17.1, 34.8 and 32.2 for root, litter and stover, respectively. The amount of total residue obtained in this study shows that the benefit of the effect of soya beans on soil organic matter and physical properties derivable from a single soya bean crop is small.     

Achievements and limitations of contemporary common bean breeding using conventional and molecular approaches

Common bean (Phaseolus vulgaris L.) improvement programs have been successful using conventional breeding methods to accomplish a wide array of important objectives. Specific achievements include the extension of range of adaptation of the crop, the development of cultivars with enhanced levels of disease and pest resistance and breeding lines that possess greater tolerance to drought. The most effective breeding method depends on the expression and inheritance of the trait to be selected and the target environment. Many bean improvement programs use molecular markers to facilitate cultivar development. In fact, several recent germplasm releases have used molecular markers to introgress and or pyramid major genes and QTL for disease resistance. Related species (P. coccineus and P. acultifolius) via interspecific hybridizations remain an important albeit long-term source for resistance to economically important diseases. Slow progress has been made in the improvement of traits such as adaptation to low soil fertility and tolerance to high levels of soluble Al in the soil using conventional breeding methods. The inability to directly measure root traits and the importance of genotype × environment interaction complicate the selection of these traits. In addition, symbiotic relationships with Rhizobium and mycorrhiza need to be taken into consideration when selecting for enhanced biological N fixation and greater or more efficient acquisition of soil P. Genomic examination of complex traits such as these should help bean breeders devise more effective selection strategies. As integration of genomics in plant breeding advances, the challenge will be to develop molecular tools that also benefit breeding programs in developing countries. Transgenic breeding methods for bean improvement are not well defined, nor efficient, as beans are recalcitrant to regeneration from cell cultures. Moreover, if issues related to consumer acceptance of GMOs cannot be resolved, traits such as herbicide tolerance in transgenic bean cultivars which would help farmers reduce production costs and decrease soil erosion will remain unrealized.     

Common bean breeding for resistance against biotic and abiotic stresses: From classical to MAS breeding

Summary Breeding for resistance to biotic and abiotic stresses of global importance in common bean is reviewed with emphasis on development and application of marker-assisted selection (MAS). The implementation and adoption of MAS in breeding for disease resistance is advanced compared to the implementation of MAS for insect and abiotic stress resistance. Highlighted examples of breeding in common bean using molecular markers reveal the role and success of MAS in gene pyramiding, rapidly deploying resistance genes via marker-assisted backcrossing, enabling simpler detection and selection of resistance genes in absence of the pathogen, and contributing to simplified breeding of complex traits by detection and indirect selection of quantitative trait loci (QTL) with major effects. The current status of MAS in breeding for resistance to angular leaf spot, anthracnose, Bean common mosaic and Bean common mosaic necrosis viruses, Beet curly top virus, Bean golden yellow mosaic virus, common bacterial blight, halo bacterial blight, rust, root rots, and white mold is reviewed in detail. Cumulative mapping of disease resistance traits has revealed new resistance gene clusters while adding to others, and reinforces the co-location of QTL conditioning resistance with specific resistance genes and defense-related genes. Breeding for resistance to insect pests is updated for bean pod weevil (Apion), bruchid seed weevils, leafhopper, thrips, bean fly, and whitefly, including the use of arcelin proteins as selectable markers for resistance to bruchid seed weevils. Breeding for resistance to abiotic stresses concentrates on drought, low soil phosphorus, and improved symbiotic nitrogen fixation. The combination of root growth and morphology traits, phosphorus uptake mechanisms, root acid exudation, and other traits in alleviating phosphorus deficiency, and identification of numerous QTL of relatively minor effect associated with each trait, reveals the complexity to be addressed in breeding for abiotic stress resistance in common bean.     

Participatory farmers’ selection of common bean varieties (Phaseolus vulgaris L.) under different production constraints

On‐farm evaluation of 15 common bean varieties was undertaken with nine farmer groups under two fertilizer applications levels in four subcounties of Hoima and Rakai districts for two seasons to select farmers’ desired and undesired varieties. Farmers’ votes for acceptance and rejection of varieties at podding stage were converted to a preference index, and analysis of variance was conducted to examine differences in farmers’ preference indices among subcounties and combined across subcounties, seasons, management and gender. Management had no‐significant influence on the way farmers selected varieties in the subcounties. Choice of varieties varied significantly (p ≤ .001) between seasons and gender in the different subcounties. Variety Masindi Yellow Long and Farmers’ seed (Kaduli), and the introduced KATB1 were accepted by farmers due to their medium seed size, desired seed colour and potential of varietal adaptability to their farm conditions. Varieties NABE2, ROBA1 and RWR719 were deselected due to possession of traits less desired in the market. These results demonstrate the need for breeding programmes to involve diverse stakeholders in capturing the diverse traits preferences in varietal development process.     

Combining ability analysis across environments for some traits in dry bean (Phaseolus vulgaris L.) under low and high soil phosphorus conditions

Dry bean (Phaseolus vulgaris L.) is an important grain legume for small-scale farmers in eastern Africa who nonetheless, grow beans with limited phosphorus (P) fertilizer supply or none at all. Phosphorus rank second, after nitrogen (N), as the most limiting soil nutrient in bean production in East African soils. This study was conducted to determine combining ability for five polygenic traits in the red mottled, large seeded bean market class, under low and high soil P conditions and two locations. Three parents tolerant to low soil P were hybridized with five well adapted, but non-low P tolerant lines in a diallel mating scheme. The resulting 28 F₁ hybrids were evaluated in a randomized complete block design with three replications, under low and high soil P conditions at two sites. There were highly significant (P ≤ 0.001) differences among the genotypes for all the traits under all the study conditions. The GCA mean squares were highly significant (P ≤ 0.001) for these traits, indicating importance of additive effects for both study conditions and sites. The GCA × Environment and SCA × Environment were significant for all the parameters and test conditions. CAL143 had positive GCA effects that were significant; except for 100-seed weight under P stress; for all the traits and under all the study conditions. The negative GCA effects for the none P tolerant parents indicate that they impacted positively in imparting earliness.     

Effectiveness of <Emphasis Type="Italic">Rhizobium</Emphasis> inoculation on common bean productivity as determined by inherent soil fertility status

Field experiments at Haramaya, Hirna, Fedis, and Babillae sites were conducted to evaluate the effectiveness of selected isolates of rhizobia on the common bean production using eight selected isolates of rhizobia with a control check and N fertilized (20 kg N ha^-1) treatments. The treatment was laid out in a randomized complete block design with three replications and three common bean varieties (Kufanzik, Gofta, and Dursitu).Analysis of variance revealed that inoculation, common bean varieties and their interaction significantly influenced most of the investigated yield and yield traits of common bean. Most of the tested Rhizobium isolates significantly increased the nodule number (NN) and nodule dry weight (NDW) as compared to the control check. Of the tested isolates, a higher number remarkably improved the remaining investigated traits in Hirna and Haramaya sites when compared to the Fedis and Babillae sites. In the Babillae site, N fertilization resulted in the highest NDW, total biomass yield (TBY), and grain yield (GY) of common bean. The GY increases due to inoculation of NSCBR-14 at Haramaya and Hirna sites, N fertilization at Babillae and NSCBR-31 at the Fedis site were 775.5, 609.7, 506.3, and 400.9 kg ha^-1 over the uninoculated treatments of the corresponding experimental sites, respectively. The highest NN, NDW, and plant N concentration was recorded with Dursitu while the highest GY and TBY were obtained from Kufanzik. Therefore, inherent soil fertility and the prevailed environmental factors affect the effectiveness of the inoculated isolates in enhancing common bean production in the study sites.     

Comparative analysis of diversity based on morpho-agronomic traits and microsatellite markers in common bean

Morpho-agronomic traits and microsatellite markers were used to survey genetic diversity in 115 common bean genotypes that included 70 Indian landraces, 24 released varieties and 21 exotic accessions. Twelve morpho-agronomic traits, namely, days to 50% flowering, leaflet length, leaflet width, pod length, pod width, number of pods per plant, days to maturity, seed length, seed width, number of seeds per pod, 100 seed weight and seed yield per plant were studied. Field data of two consecutive years were subjected to multivariate analysis as proposed by Mahalanobis’s D²-statistics, Tochers method of clustering and combined analysis of variance. Seventeen microsatellite markers were also used to examine genetic diversity at molecular level that showed polymorphic information content (PIC) in the range of 0.00–0.684. Dendrograms based on Euclidean distances and UPGMA analysis showed the presence of majority of released varieties into single cluster, which pointed toward their low genetic base in comparison to indigenous landraces and exotic germplasm. Significant correlation existed between morphological genetic distance and microsatellite genetic distance tested by Mantel test (r = 0.876).     

Yield–Density Relation of Glyphosate-Resistant Soya beans and their Responses to Light Enrichment in North-eastern USA

Optimum plant population densities are a key means of achieving higher seed yield in soya bean [Glycine max (L.) Merr.]. Limited information is available on yield‐density relation of glyphosate‐resistant soya beans in north‐eastern USA. The objective of this research was to determine the appropriate populations for glyphosate‐resistant soya beans, and if the yield potential of glyphosate‐resistant soya bean produced in light‐enriched conditions was affected by populations. Eight glyphosate‐resistant soya bean cultivars with three populations (300 000, 500 000 and 800 000 plants ha⁻¹) were grown under both ambient and light‐enriched conditions in 2002 and 2003. Yield of all cultivars responded to density linearly. As density increased, grain yield was increased by up to 92 % among cultivars. Light enrichment increased yield for all cultivars across the 2 years, although some cultivars were more sensitive. Harvest index either remained unchanged or declined slightly at higher density in 2002, and there was no difference among treatments in 2003. Both pod number and seed number per plant were significantly decreased with the increase of density across the 2 years, while seeds per pod declined slightly or remained unchanged. Greater seed size was obtained in higher density with varied degree depending on cultivars across the 2 years except for those cultivars with relatively larger seed. The increase in seed size by light enrichment was cultivar and density dependent, and varied between years. 800 000 plants ha⁻¹ could be a suitable practice in producing higher yield in north‐east USA for glyphosate‐resistant soya bean. Maintaining the mass of an individual seed is an important strategy in achieving high yield at high population. Establishing mechanisms responsible for the greatest yields via high population under light‐enriched conditions, may provide insights for management and phenotypic improvement.     

Cassava yield loss in farmer fields was mainly caused by low soil fertility and suboptimal management practices in two provinces of the Democratic Republic of Congo

A better understanding of the factors that contribute to low cassava yields in farmers’ fields is required to guide the formulation of cassava intensification programs. Using a boundary line approach, we analysed the contribution of soil fertility, pest and disease infestation and farmers’ cultivation practices to the cassava yield gap in Kongo Central (KC) and Tshopo (TSH) provinces of the Democratic Republic of Congo. Data were obtained by monitoring 42 and 37 farmer-managed cassava fields during two cropping cycles in KC and one cropping cycle in TSH, respectively. Each field was visited three times over the cassava growing period for the observations. Logistic model was fitted against the observed maximum cassava root yields and used to calculate the achievable yield per field and for individual factor. At field level, the factor that led to the lowest achievable yield (Y_up(i)1) was considered as the dominant yield constraint. Cassava yield loss per field was expressed as the increase in the maximal root yield observed per province (Y_att- attainable yield) compared to Y_up(i)1. Y_att was 21 and 24 t ha⁻¹ in TSH and KC, respectively. With the cassava varieties that farmers are growing in the study areas, pests and diseases played a sparse role in the yield losses. Cassava mosaic was the only visible disease we observed and it was the dominant yield constraint in 3% and 12% of the fields in KC and TSH, respectively. The frequent yield constraints were suboptimal field management and low soil fertility. Cultivation practices and soil parameters led to Y_up(i)1 in 47% and 50% of the fields in KC, and in 47% and 41% of those in TSH, respectively. Individual soil parameters were the yield constraint in few fields, suggesting that large-scale programs in terms of lime application or recommendation of the blanket fertilisers would result in sparse efficacy. In KC, yield losses caused by low soil fertility averaged 6.2 t ha⁻¹ and were higher than those caused by suboptimal field management (5.5 t ha⁻¹); almost nil for cassava mosaic disease (CMD). In TSH, yield losses caused by low soil fertility (4.5 t ha⁻¹) were lower than those caused by suboptimal field management (6.5 t ha⁻¹) and CMD (6.1 t ha⁻¹). Irrespective of the constraint type, yield loss per field was up to 48% and 64% of the Y_att in KC and TSH, respectively. Scenario analysis indicated that the yield losses would remain at about two third of these levels while the dominant constraint was only overcome. We concluded that integrated and site-specific management practices are needed to close the cassava yield gap and maximize the efficacy of cassava intensification programs.     

Spatial variability of salt-affected soils in the middle Ebro Valley (Spain) and implications in plant breeding for increased productivity

Barley breeding programs have empirically selected for improving grain yield and quality. The objective of this study was to quantify genetic gains in yield in 2-rowed malting barley cultivars released from 1944to 1998 in Argentina, identifying the major physiological traits responsible for them. For this purpose, a field experiment was conducted in absence of biotic and abiotic stressful factors and with lodging being prevented mechanically. Until the 1970's,potential yield was maintained nearly constant at 5.25 mg ha^-1 and since then it increased at a rate of 41 kg ha^-1 year^-1. That bi-linear trend was closely related to the trend of averaged yields obtained by farmers. The contribution made by breeding yield potential to the total yield gains achieved by farmers was estimated in c. One third. Neither time to heading nor time to maturity were systematically modified by breeding. However, the partitioning of the developmental time was modified: time to achieve both maximum number of floret primordia and length of the jointing –heading period were increased with the year of release of the cultivars. The main component associated with yield was the number of grains per m², due to variations in number of spikes per m².Total and vegetative biomass at maturity increased with the year of release of the cultivars, at a rate of 45 and 19 kg ha^-1 year^-1, while both harvest index and stem height remained virtually unmodified. Differences in biomass at heading among cultivars were related to the improvement on the abilities to capture more radiation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Maturity Class and P Effects on Soya Bean Grain Yield in the Moist Savanna of West Africa

Field trials were replicated at four sites in the moist savanna ecological zone of West Africa to study the effect of maturity class and phosphorus (P) rate on grain yield and total protein yield (TPY) of some new soya bean varieties. Grain yield and TPY averaged 1.43 Mg ha^?1 and 587 kg ha^?1, respectively. Without P application grain yield and TPY were not significantly different among the varieties. In addition, at zero P treatment, grain yield and TPY were not significantly different among three sites where available P was 6.2 mg kg^?1 or less. P application depressed grain yield and TPY at a site where the available soil P was high (16.2 mg kg^?1). With P application grain yield and TPY were in the range of 1.2–2.28 Mg ha^?1 and 505–948 kg ha^?1, respectively, for the varieties compared with 0.99–1.12 Mg ha^?1 and 454–462 kg ha^?1 when P was not applied. The response of grain yield to 30 kg P ha^?1 was substantial at Gidan Waya (113 %), Kasuwan Magani (63 %) and Fashola (60 %), three sites where available soil P was low. The application of 30 kg P ha^?1 increased grain yield by 21 % in early, 26 % in medium and 58–70 % in the late varieties. Significant variety by P rate interaction effects were observed on grain yield and TPY but not on grain protein concentration (GPC). TPY showed greater response to P in the late varieties than in the early or medium. While seed size correlated significantly and positively with GPC, P application had no significant effect on GPC.     

Development and validation of a robust KASP marker for zt2 locus in faba bean (Vicia faba)

Faba bean has the potential to become a key food and feed protein crop in many areas of the world. The presence of tannins in its seed coat has limited the deployment of this crop as feed and food. The expression of either of the two recessive genes, zt1 and zt2, causes a great reduction of tannins from the seed coat and results in a white flower phenotype. Molecular markers linked to these loci are fundamental tools for speeding up the breeding of low-tannin varieties. The main aim of this study was to develop and validate a robust molecular marker linked to the zt2 locus. We used 176 recombinant inbred lines of the Disco/2 × ILB 938/2 cross at F₆ and genotyped those using 257 SNP (single nucleotide polymorphism) markers. An SNP marker associated with zt2 locus was found on faba bean chromosome 3 and was used to develop a high-throughput low-cost KASP (kompetitive allele-specific PCR) marker. The KASP marker can successfully discriminate low-tannin faba beans carrying zt2 from those carrying zt1 and wild-type alleles.     

Effect of water deficit on morphoagronomic traits of black common bean genotypes (Phaseolus vulgaris L.) with contrasting drought tolerance

Brazil is the world's largest producer of common beans (Phaseolus vulgaris L.). Drought stress harms the morphological and agronomic traits of beans. This study evaluates the reaction to water deficit in five genotypes of black beans. The experiment was conducted in the IDR-IAPAR-EMATER in Londrina-PR, Brazil. A split-plot design was used, with three replications. The genotypes were included in the subplots and the treatments with or without water deficit in the plots. Water deficit was induced on the pre-flowering stage and maintained for 20 days in the plots submitted to drought stress. For the growth analysis, plants were collected at 35, 54 and 70 days after emergence. At the stage of physiological ripeness, several morphological and yield traits were evaluated. The genotypes IPR Uirapuru and BRS Esplendor can be considered tolerant and used as a tolerant source to water deficit in common bean germplasm banks. The line LP 08-90 has morphological and agronomic adaptations efficient to overcome water deficit's effects, presenting a higher grain yield in both crop conditions, which indicates the success of black beans breeding to deal with water deficit.