Drought stress linked with climate change is one of the major constraints faced by common bean farmers in Africa and elsewhere. Mitigating this constraint requires the selection of resilient varieties that withstand d...Drought stress linked with climate change is one of the major constraints faced by common bean farmers in Africa and elsewhere. Mitigating this constraint requires the selection of resilient varieties that withstand drought threats to common bean production.This study assessed the drought response of 64 small red-seeded genotypes of common bean grown in a lattice design replicated twice under contrasting moisture regimes,terminal drought stress and non-stress, in Ethiopia during the dry season from November2014 to March 2015. Multiple plant traits associated with drought were assessed for their contribution to drought adaptation of the genotypes. Drought stress determined by a drought intensity index was moderate(0.3). All the assessed traits showed significantly different genotypic responses under drought stress and non-stress conditions. Eleven genotypes significantly(P ≤ 0.05) outperformed the drought check cultivar under both drought stress and non-stress conditions in seed yielding potential. Seed yield showed positive and significant correlations with chlorophyll meter reading, vertical root pulling resistance force, number of pods per plant, and seeds per pod under both soil moisture regimes, indicating their potential use in selection of genotypes yielding well under drought stress and non-stress conditions. Clustering analysis using Mahalanobis distance grouped the genotypes into four groups showing high and significant inter-cluster distance, suggesting that hybridization between drought-adapted parents from the groups will provide the maximum genetic recombination for drought tolerance in subsequent generations.展开更多
Understanding functional relations among plant traits and their modulation by growing conditions is imperative in designing selection strategies for breeding programs. This study assessed trait relationships among 196...Understanding functional relations among plant traits and their modulation by growing conditions is imperative in designing selection strategies for breeding programs. This study assessed trait relationships among 196 common bean genotypes exposed to stresses for drought and field infestation of bean fly or bean stem maggot(BSM). The study was carried out at two locations and data was analyzed with linear correlation, path coefficient and genotype × trait biplot analyses. Multiple trait data related to mechanisms of drought and bean fly tolerance were collected on 196 genotypes grown under i) water deficit at mid-pod fill, or ii) unprotected against bean fly; iii) irrigated, well watered conditions, or iv) bean fly protection with chemicals. Seed yield exhibited positive and significant correlations with leaf chlorophyll content, vertical root pulling resistance, pod harvest index, pods per plant and seeds per pod at both phenotypic and genotypic levels under stress and non-stress conditions. Genotypic correlations of traits with seed yield were greater than their respective phenotypic correlations across environments indicating the greater contribution of genotypic factors to the trait correlation. Pods per plant and seeds per pod had high positive direct effects on seed yield both under stress and non-stress whereas pods per plant had the highest indirect effect on seed yield through pod harvest index under stress.In general, our results suggest that vertical root pulling resistance and pod harvest index are important selection objectives for improving seed yield in common beans under non-stress and stress conditions, and particularly useful for drought and BSM tolerance evaluation.展开更多
This special issue is focused on grain legumes,which belong to the Fabaceae family.Legumes are the second largest family of plants in the world after the grasses and are key components of manmade and natural ecosystem...This special issue is focused on grain legumes,which belong to the Fabaceae family.Legumes are the second largest family of plants in the world after the grasses and are key components of manmade and natural ecosystems[1–3].They provide the environmental service of nitrogen fixation,so essential to soil construction and fertility maintenance,and are thus essential to agricultural systems[4,5].Different species of legumes range from huge trees to shrubs展开更多
Common bacterial blight(CBB), caused by Xanthomonas axonopodis pv. phaseoli and Xanthomonas fuscans subsp. fuscans(Xff), is a worldwide disease of common bean(Phaseolus vulgaris L.).Longyundou 5, a Chinese cultivar in...Common bacterial blight(CBB), caused by Xanthomonas axonopodis pv. phaseoli and Xanthomonas fuscans subsp. fuscans(Xff), is a worldwide disease of common bean(Phaseolus vulgaris L.).Longyundou 5, a Chinese cultivar in the Mesoamerican gene pool of common bean, displays resistance to the Xff strain XSC3-1. To identify the genetic mechanisms behind this resistance,we crossed Long 5 with a susceptible genotype to develop a mapping population of F2 plants.Plant resistance to CBB was identified at 14 and 21 days after inoculation with Xff strain XSC3-1.A major QTL at 14 and 21 days after inoculation was mapped on chromosome Pv10 with LOD scores of 6.41 and 5.35, respectively. This locus was associated with SAP6, a previouslyidentified and much-used dominant marker, but in a 4.2 cM interval between new codominant markers BMp10s174 and BMp10s244. Ten candidate genes were found between markers BMp10s174 and BMp10s244 on chromosome Pv10 and could encode defense response proteins responding to CBB pathogens. Four pairs each of epistatic QTL for CBB resistance were detected at 14 and 21 days after inoculation. Phenotypic variation explained by the epistatic QTL ranged from 7.19% to 12.15% and 7.72% to 8.80% at 14 and 21 days after inoculation, respectively. These results confirmed the importance of epistasis in CBB resistance in common bean. The adjacent markers found may be more efficient for marker assisted selection in common bean breeding for CBB resistance owing to their closer linkage to the target QTL.展开更多
The species Vigna unguiculata L.(Walp),commonly known as cowpea,is a multi-purpose legume that has been selected into three subspecies that are divided into grain,fodder and pod(yardlong bean)types.However,genetic bas...The species Vigna unguiculata L.(Walp),commonly known as cowpea,is a multi-purpose legume that has been selected into three subspecies that are divided into grain,fodder and pod(yardlong bean)types.However,genetic bases for distinctions are not well understood.The purpose of this study was to apply genotyping-by-sequencing(GBS)and current reference genome for V.unguiculata to distinguish three subspecies and identify signatures of divergence.The collection of 130 accessions included 128 cultivated from:1)ssp.cylindrica,fodder type;2)ssp.sesquipedalis,pod vegetable type;and 3)ssp.unguiculata,grain type.Two wilds genotypes from spp.dekindtiana and spp.pubescens,were used to anchor phylogeny.A total of 11,083 highly informative single nucleotide polymorphisms(SNPs)were discovered.Wild accessions showed distinct genetic fingerprints and were separated from cultivated subspecies.Principal component analysis showed closer relationship between ssp.unguiculata and ssp.cylindrica compared to ssp.sesquipedalis.Relative differentiation of cultivated subspecies(with Fixation Index,FST)indicated the existence of discrete signatures of selection.This work clarifies the population structure,phylogeny,and domestication of cultivated cowpeas.Furthermore,significant genetic differences between grain and pod vegetable types can provide valuable information for future breeding in three cowpea groups.展开更多
基金funding to D. Ambachew, A. Asfaw, and M. W. Blair by the Tropical Legumes project of the Generation Challenge Program (C-086-13) with support from the Bill and Melinda Gates FoundationThe Evans Allen Fund is recognized for funding Matthew W. Blair and Daniel Ambachew at Tennessee State University
文摘Drought stress linked with climate change is one of the major constraints faced by common bean farmers in Africa and elsewhere. Mitigating this constraint requires the selection of resilient varieties that withstand drought threats to common bean production.This study assessed the drought response of 64 small red-seeded genotypes of common bean grown in a lattice design replicated twice under contrasting moisture regimes,terminal drought stress and non-stress, in Ethiopia during the dry season from November2014 to March 2015. Multiple plant traits associated with drought were assessed for their contribution to drought adaptation of the genotypes. Drought stress determined by a drought intensity index was moderate(0.3). All the assessed traits showed significantly different genotypic responses under drought stress and non-stress conditions. Eleven genotypes significantly(P ≤ 0.05) outperformed the drought check cultivar under both drought stress and non-stress conditions in seed yielding potential. Seed yield showed positive and significant correlations with chlorophyll meter reading, vertical root pulling resistance force, number of pods per plant, and seeds per pod under both soil moisture regimes, indicating their potential use in selection of genotypes yielding well under drought stress and non-stress conditions. Clustering analysis using Mahalanobis distance grouped the genotypes into four groups showing high and significant inter-cluster distance, suggesting that hybridization between drought-adapted parents from the groups will provide the maximum genetic recombination for drought tolerance in subsequent generations.
基金the Alliance for Green Revolution in Africa (AGRA) PASS project for providing financial support for the field studythe South Agricultural Research Institute (SARI) for hosting this researchDrs. I.M. Rao and B. Raatz at CIAT for supplying methods to analyze the recombinant inbred lines used as well the Bill and Melinda Gates Foundation through the Generation Challenge Program (GCP), Tropical Legume I (TL-I) project, for financial support to the research
文摘Understanding functional relations among plant traits and their modulation by growing conditions is imperative in designing selection strategies for breeding programs. This study assessed trait relationships among 196 common bean genotypes exposed to stresses for drought and field infestation of bean fly or bean stem maggot(BSM). The study was carried out at two locations and data was analyzed with linear correlation, path coefficient and genotype × trait biplot analyses. Multiple trait data related to mechanisms of drought and bean fly tolerance were collected on 196 genotypes grown under i) water deficit at mid-pod fill, or ii) unprotected against bean fly; iii) irrigated, well watered conditions, or iv) bean fly protection with chemicals. Seed yield exhibited positive and significant correlations with leaf chlorophyll content, vertical root pulling resistance, pod harvest index, pods per plant and seeds per pod at both phenotypic and genotypic levels under stress and non-stress conditions. Genotypic correlations of traits with seed yield were greater than their respective phenotypic correlations across environments indicating the greater contribution of genotypic factors to the trait correlation. Pods per plant and seeds per pod had high positive direct effects on seed yield both under stress and non-stress whereas pods per plant had the highest indirect effect on seed yield through pod harvest index under stress.In general, our results suggest that vertical root pulling resistance and pod harvest index are important selection objectives for improving seed yield in common beans under non-stress and stress conditions, and particularly useful for drought and BSM tolerance evaluation.
文摘This special issue is focused on grain legumes,which belong to the Fabaceae family.Legumes are the second largest family of plants in the world after the grasses and are key components of manmade and natural ecosystems[1–3].They provide the environmental service of nitrogen fixation,so essential to soil construction and fertility maintenance,and are thus essential to agricultural systems[4,5].Different species of legumes range from huge trees to shrubs
基金supported by the National Natural Science Foundation of China (31471559)the China Agriculture Research System (CARS-09)+2 种基金the National Key Technology R&D Program of China (2013BAD01B03-18a)the Evans Allen Fund of the U.S. Department of Agriculturethe Agricultural Science and Technology Innovation Program (ASTIP) of the Chinese Academy of Agricultural Sciences
文摘Common bacterial blight(CBB), caused by Xanthomonas axonopodis pv. phaseoli and Xanthomonas fuscans subsp. fuscans(Xff), is a worldwide disease of common bean(Phaseolus vulgaris L.).Longyundou 5, a Chinese cultivar in the Mesoamerican gene pool of common bean, displays resistance to the Xff strain XSC3-1. To identify the genetic mechanisms behind this resistance,we crossed Long 5 with a susceptible genotype to develop a mapping population of F2 plants.Plant resistance to CBB was identified at 14 and 21 days after inoculation with Xff strain XSC3-1.A major QTL at 14 and 21 days after inoculation was mapped on chromosome Pv10 with LOD scores of 6.41 and 5.35, respectively. This locus was associated with SAP6, a previouslyidentified and much-used dominant marker, but in a 4.2 cM interval between new codominant markers BMp10s174 and BMp10s244. Ten candidate genes were found between markers BMp10s174 and BMp10s244 on chromosome Pv10 and could encode defense response proteins responding to CBB pathogens. Four pairs each of epistatic QTL for CBB resistance were detected at 14 and 21 days after inoculation. Phenotypic variation explained by the epistatic QTL ranged from 7.19% to 12.15% and 7.72% to 8.80% at 14 and 21 days after inoculation, respectively. These results confirmed the importance of epistasis in CBB resistance in common bean. The adjacent markers found may be more efficient for marker assisted selection in common bean breeding for CBB resistance owing to their closer linkage to the target QTL.
基金The sources of funding included Evans Allen project TENX-07 to Tennessee State University from the National Institute of Food and Agriculture(NIFA)of United States Department of Agriculture(USDA)for M.S and Ph.D.student assistantship for XW,as well as research funds for MWBChina Scholarship Council(CSC)scholarship for funding of XW student establishmenta grant from Evolutionary Genomics(currently Thirsty Crops Inc.)sponsored by Bill and Melinda Gates Foundation for legume genome wide association studies.
文摘The species Vigna unguiculata L.(Walp),commonly known as cowpea,is a multi-purpose legume that has been selected into three subspecies that are divided into grain,fodder and pod(yardlong bean)types.However,genetic bases for distinctions are not well understood.The purpose of this study was to apply genotyping-by-sequencing(GBS)and current reference genome for V.unguiculata to distinguish three subspecies and identify signatures of divergence.The collection of 130 accessions included 128 cultivated from:1)ssp.cylindrica,fodder type;2)ssp.sesquipedalis,pod vegetable type;and 3)ssp.unguiculata,grain type.Two wilds genotypes from spp.dekindtiana and spp.pubescens,were used to anchor phylogeny.A total of 11,083 highly informative single nucleotide polymorphisms(SNPs)were discovered.Wild accessions showed distinct genetic fingerprints and were separated from cultivated subspecies.Principal component analysis showed closer relationship between ssp.unguiculata and ssp.cylindrica compared to ssp.sesquipedalis.Relative differentiation of cultivated subspecies(with Fixation Index,FST)indicated the existence of discrete signatures of selection.This work clarifies the population structure,phylogeny,and domestication of cultivated cowpeas.Furthermore,significant genetic differences between grain and pod vegetable types can provide valuable information for future breeding in three cowpea groups.
