Genetic Diversity in Cowpea (Vigna unguiculata (L.) Walp) under Two Growing Conditions*

This study explores the use of genetic variability for advancing the genetic improvement of Cowpea (Vigna unguiculata (L.) Walp), particularly in response to insect infestation stress. Over a period spanning 2015 to 2017, forty accessions of cowpeas were evaluated to determine their variability under both insecticide spray and no insecticide spray conditions at the Teachings and Research Farms, Federal University of Agriculture, Abeokuta. The experimental design was a randomized complete block design in three replicates. The accessions were evaluated for plant height, leaf length, leaf width, number of days of 50% flowering, number of pods per plant, pod length, number of seeds per plant, 100-seed weight, and seed yield. Data collected were subjected to principal component and single linkage cluster analyses. Principal axis I (PCA1) accounted for 39% and 35% under insecticide spray and no insecticide spray respectively to the total variation in the accessions. Plant height with a factor score of 0.38, leaf length (0.41), number of leaves (0.37), and 100-seed, weight (0.30) was related to PCAI under insecticide spray while leaf width (0.32). Pod length (0.37) and number of seeds/plant (0.38) were significant to PCA1 under no insecticide spray. Notably, accessions such as SAMPEA6, SAMPEA10, IFE-Brown, and IFE-BPE exhibited consistent performance across both conditions, while others displayed condition-specific attributes. For instance, NGB1063, NGB1152, and NGB1093 demonstrated distinct traits under insecticide spray, while NGB1146 and NGB1124 exhibited notable characteristics under no insecticide spray conditions. Therefore, identifying these forty accessions with desirable traits hold promise for future genetic improvement efforts of cowpea cultivation in Nigeria and beyond.

Agro-Morphological Variability in Eight Bambara Groundnut (Vigna subterranea (L.) Verdc.) Morphotypes from Zinder (Niger)

Bambara groundnut (Vigna subterranea (L.) Verdc.) has economic importance for the producers and the traders as cash crop since it generates substantial income for households in Niger. The objective of this study was to assess eight (8) Bambara groundnut morphotype from Université André Salifou de Zinder in Niger Republic by their morphological and agronomic characters. The experiment was conducted in a randomized complete block design with three replications during the rainy season of 2020-2021. Data were collected on the Number of leaves, Plant height (cm), Growth habit (cm), Terminal leaflet length, Terminal leaflet width, Number of nodes/stem, Number of stems/plant, Number of pods/plant, Weight of 100 pods (g), Weight of 100 seeds (g), Length of seeds (mm), Width of seeds (mm), Weight of seeds/Plot (kg). There were significant differences for all characters, except Number of leaves, Terminal leaflet length, Terminal leaflet width, Length of seeds (mm) Weight of 100 pods (g), Weight of 100 seeds (g). The morphotypes UZ-VZ-04, UZ-VZ-03, UZ-VZ-06, UZ-VZ-02 and UZ-VZ-05 have demonstrated good performance for grain weight per plot and can be useful for a breeding program.

Screen House Assessment of Cowpea [(Vigna unguiculata (L.)] Genotypes for Drought Tolerance Using Selection Indices

Cowpea [Vigna unguiculata (L.)] is one of the most important arid legumes cultivated for pulse and forage production. Drought is one of the most damageable constraints to crop production impacting negatively food security. The potential of cowpea to address food security is well established. However, not much is known about the base index selection method in breeding cowpea for drought tolerance, which is important for yields. Consequently, the present study has been conducted to: 1) evaluate the yield performance of cowpea genotypes under artificial drought and well-watered condition, 2) ranke genotype performance using selection indices, and 3) assess relationship between agronomic traits and yield. The experiment was the 2 watering conditions laid out in a Randomized Complete Block Design (RCBD) with three replications. The experiment was carried out in pots under screen house at the Department of Horticulture at KNUST. The result showed that KPR1-96-73, Simbo, CZ06-4-16, Wilibaly and Agyenkwa were high yielding in well-water condition while Ghana Shoba, Sangaraka, Nketewade, Ghana Shoni and Korobalen were high yielding genotypes in water stress condition. The average yield reduction was 60.6% and 16% for grain and fodder yield respectively. The biplot displays revealed four groups among the genotypes tested which were based on their yielding capacity and drought tolerance. In cluster B high yielding and drought tolerant genotypes were identified, high yielding and drought susceptible have been identified in cluster A, low yielding and drought tolerant in cluster D, and lastly low yielding and drought susceptible in cluster C. Genotypes in cluster B were best due to the fact that it combines high yield and tolerance to drought. They were Ghana Shoni, Nketewade, Sangaraka and Ghana Shoba. These genotypes might be suitably employed in further drought tolerance breeding programs of cowpea. Significant relationships were observed between agronomic trait and yields under drought condition.

Selection of Cowpea [(Vigna unguiculata (L.) WALP] Genotypes for Drought Tolerance Using Selection Indices

Cowpea [(Vigna unguiculata (L.)] is one of the most important arid legumes cultivated for pulse and forage production. However, in cowpea, not much is known about the base index selection method in breeding for drought tolerance. Consequently, the present study has been conducted to: 1) evaluate the yield performance of cowpea genotypes under artificial drought and well-watered condition;2) develop a base index using multiple traits for ranking genotype performance. The experiment was a 25 × 2 factorial laid out in a Randomized Complete Block Design (RCBD) with three replications. The experiment was carried out in the screen house at the Department of Horticulture at KNUST. The result showed that KPR1-96-73, Simbo, CZ06-4-16, Wilibaly and Agyenkwa were high yielding in well-water condition while Ghana Shoba, Sangaraka, NKetewade, Ghana-Shoni and Korobalen were high yielding genotypes in water stress condition. The average yield reduction was 60.6% for grain respectively. The biplot displays revealed four groups among the genotypes tested which was based on their yielding capacity and drought tolerance. In cluster B high yielding and drought tolerant genotypes were identified, high yielding and drought susceptible have been identified in cluster A, low yielding and drought tolerant in cluster D, and lastly low yielding and drought susceptible in cluster C. Genotypes in cluster B, were the best due to the fact that it combines high yield and tolerance to drought. They were Ghana Shoni, Nketewade, Sangaraka and Ghana shoba. These genotypes might be suitably employed in further drought tolerance breeding program of cowpea.

小豆(Vigna angularis)不同种植密度效应研究

为了明确种植密度对小豆产量等性状的影响,于2007年和2008年分别设置5个密度水平,在吉林省农业科学院作物育种研究所试验站进行田间试验。结果表明,在不同种植密度条件下,株高、百粒重的差异不显著,分枝数、主茎节数、单株荚数和单株产量有随着密度增大而减少的趋势。除了在最小密度10.5万株/hm2下产量有显著减少外,其他密度下的产量均没有显著差异。通径分析表明,单株产量对产量的直接贡献较大,其次是百粒重。

AFLP分析小豆种(Vigna angularis)内遗传多样性

利用 12对AFLP引物 ,对来自于世界 6个国家的 14 6份小豆 (Vignaangularis)栽培变种 (var.angularis)和野生变种 (var.nipponensis)种质的基因组DNA进行扩增 ,得到 5 80条清晰的显带 ,其中 313(5 3 93% )条呈多态性 ,平均每对AFLP引物得到 2 6 0 8条多态性带 ;平均遗传距离 0 35 ,变异幅度为 0 0 0～ 0 87。利用AFLP多态性数据进行的Jaccard’s遗传距离聚类分析绘制的聚类图 ,可将其中的 14 3份种质相互区分开 ,并将其中的 14 5份小豆资源划分成 8个明显不同组群 ,显示小豆种内存在足够的遗传多样性用于资源材料的准确鉴别与分类。 8个组群的遗传多样性表现出十分明显的地域相关性 ,以及遗传类型趋同性。通过各组群内和组群间的遗传距离比较 ,发现世界小豆主要栽培资源以及日本野生、半野生资源中蓄积的遗传多样性较匮乏 ,而储藏于中国野生小豆资源、喜马拉雅地区栽培和野生资源中的遗传多样性较丰富。

AFLP初析小豆栽培和野生变种(Vigna angularis var.angularis and var.nipponensis)间演化与地理分布关系

利用 12对AFLP引物 ,以饭豆标准品系M 0 0作对照 ,对来自中国、日本、韩国、尼泊尔、印度、不丹的 14 6份小豆栽培种 (Vignaangularisvar.angularis)和野生种 (Vignaangularisvar.nipponensis)种质的基因组DNA进行扩增 ,得到 313条多态性带。据AFLP多态性数据绘制的聚类图 ,可区分其中的 14 3份种质 ,表明小豆物种 (Vi gnaangularis)存在足够的遗传多样性 ,可用于资源材料的准确鉴别与分类。鉴于此 ,采用新开发的利用AFLP数据揭示核苷多样性的Innan’s进化树分析方法 ,进一步将 14 6份小豆资源分成 7个明显不同的地理演化群 ,即中国栽培种、日本栽培种、日本综合群 韩国栽培种、中国台湾野生种、中国野生种、尼泊尔 不丹栽培种和喜马拉雅野生种演化群。就上述地理演化群的遗传多样性、地理分布以及野生种与栽培种之间可能的演化关系进行了分析 ,初步认为栽培小豆至少应当有 4个不同类型的野生祖先和 3个不同的地理起源。

利用16S-23S rDNA RFLP及16S rRNA基因序列分析方法对湖北省饭豆(Vigna umbellata L.)根瘤菌系统发育的研究

采用16S-23S rDNA间隔区段(IGS)PCR-RFLP与16S rRNA基因部分序列分析的方法对饭豆根瘤菌进行了遗传多样性及系统发育分析.由16S-23S rDNA IGS PCR-RFLP分析可知,所有菌株在52%的相似性水平上聚在一起,形成了慢生型菌群与快生型菌群这两大菌群.群Ⅰ中,在79%相似性的水平上分为ⅠA与ⅠB两个分支.群Ⅱ中,在62%相似性的水平上分为ⅡA与ⅡB两个分支,分支ⅡA在72%的相似性水平上进一步分为ⅡA1、ⅡA2和ⅡA3三簇;分支ⅡB中的饭豆根瘤菌与标准菌株USDA205T聚在一起,表现的差异并不大.由16SrRNA基因部分序列分析结果可知,供试的4个代表菌株分别位于不同的系统发育分支中.CYR4243与Sinorhizobium fredii的模式菌株USDA205T的序列相似性达到了99.87%.HCY1101与Rhizobium leguminosarum中的三叶草生物型(bv.trifolii)和豌豆生物型(bv.viceae)这两个生物型的参比菌株亲缘关系最近,序列相似性为100%.HCY5202与R.galegae亲缘关系最近,序列相似性为99.86%.CYY3302与Bradyrhizobium elkanii的参比菌株USDA86有最近的亲缘关系,序列相似性近似于100%.

饭豆(Vignaumbellata L.)根瘤菌的分离及多样性

从生长在湖北省几种不同土壤中两类饭豆 (VignaumbellataL .)的根瘤中分离、纯化并通过结瘤试验筛选出2 6株饭豆根瘤菌 ;对这些菌株和来自其它种属的 8个参比菌株的培养特性、生长速度、耐酸碱性、生长最终 pH值、耐盐性、天然抗药性、碳源和氮源的利用及部分快生型菌株质粒图谱进行了系统的比较研究 ,并通过聚类分析得到数值分类树状图谱 .结果发现 ,分离自不同类型土壤中的饭豆根瘤菌具有较大的多样性 ,在 77%的相似水平上 ,形成了三大类群 ,群Ⅰ为慢生型菌群 ,群Ⅱ与群Ⅲ为快生型菌群 ,在 80 %相似水平上各群又可进一步划分为不同亚群 ,而且亚群中部分菌株的相似性与地理来源有相关性 .图 2表 4参

Genetic diversity assessment of a set of introduced mung bean accessions(Vigna radiata L.)

Genetic resources from other countries or regions play an important role in broadening the genetic background of local breeding varieties. Here we describe observations on the adaptability of mung bean germplasm obtained from the United States Department of Agriculture and their genetic diversity assessment using SSR markers. Several accessions were shown to be mixtures,based on their phenotypes for some characters. Most accessions were able to complete their lifecycles when grown in Beijing, China, making them ideal for crossbreeding without day length control. High diversity was revealed by the SSR markers, with an average of 4.2 alleles per locus and a PIC value of 0.650 per locus. STRUCTURE analysis divided the accessions into six groups.There was no obvious trend of accessions forming groups according to their geographical origin,owing mainly to germplasm exchange and an uneven distribution of accessions. The present results indicate that this germplasm would enrich the local gene pool, and provide information for the further use of germplasm in breeding programs.

Draft genome sequence of a less-known wild Vigna: Beach pea(V. marina cv. ANBp-14-03)

Beach pea or beach cowpea(Vigna marina(Burm.)Merr.)belongs to the family Fabaceae.It is a close relative of cultivated Vigna species such as adzuki bean(V.angularis),cowpea(V.unguiculata),mung bean(V.radiata),and blackgram(V.mungo),and is distributed throughout the tropics.With its ability to tolerate salt stress,beach pea has great potential to contribute salt-tolerance genes for developing salt-tolerant cultivars in cultivated Vigna species.However,it is still underutilized in Vigna breeding programs.A draft genome sequence of beach pea was generated using a high-throughput next-generation sequencing platform,yielding 23.7 Gb of sequence from 79,929,868 filtered reads.A de novo genome assembly containing 68,731 scaffolds gave an N50 length of 10,272 bp and the assembled sequences totaled 365.6 Mb.A total of 35,448 SSRs,including 3574 compound SSRs,were identified and primer pairs for most of these SSRs were designed.Genome analysis identified 50,670 genes with mean coding sequence length 1042 bp.Phylogenetic analysis revealed highest sequence similarity with V.angularis,followed by V.radiata.Comparison with the V.angularis genome revealed 16,699 SNPs and 2253 InDels and comparison with the V.radiata genome revealed 17,538 SNPs and 2300 InDels.To our knowledge this is the first draft genome sequence of beach pea derived from an accession(ANBp-14-03)adapted locally in the Andaman and Nicobar Islands of India.The draft genome sequence may facilitate the genetic enhancement in cultivated Vigna species.

Genetic control of compound leaf development in the mungbean(Vigna radiata L.)

Many studies suggest that there are distinct regulatory processes controlling compound leaf development in different clades of legumes.Loss of function of the LEAFY(LFY)orthologs results in a reduction of leaf complexity to different degrees in inverted repeat-lacking clade(IRLC)and non-IRLC species.To further understand the role of LFY orthologs and the molecular mechanism in compound leaf development in non-IRLC plants,we studied leaf development in unifoliate leaf(un)mutant,a classical mutant of mungbean(Vigna radiata L.),which showed a complete conversion of compound leaves into simple leaves.Our analysis revealed that UN encoded the mungbean LFY ortholog(VrLFY)and played a significant role in leaf development.In situ RNA hybridization results showed that STM-like KNOXI genes were expressed in compound leaf primordia in mungbean.Furthermore,increased leaflet number in heptafoliate leaflets1(hel1)mutants was demonstrated to depend on the function of VrLFY and KNOXI genes in mungbean.Our results suggested that HEL1 is a key factor coordinating distinct processes in the control of compound leaf development in mungbean and its related non-IRLC legumes.

Genetic diversity and a population structure analysis of accessions in the Chinese cowpea [Vigna unguiculata(L.)Walp.]germplasm collection

Cowpea(Vigna imguicuiata) is an important legume crop with diverse uses. The species is presently a minor crop, and evaluation of its genetic diversity has been very limited. In this study, a total of 200 genic and 100 genomic simple sequence repeat(SSR) markers were developed from cowpea unigene and genome sequences, respectively. Among them, 27 genic and 27 genomic SSR markers were polymorphic and were used for assessment of genetic diversity and population structure in 105 selected cowpea accessions. A total of 155 alleles and 2.9 alleles per marker were identified, and the average polymorphic information content(PIC) value was 0.3615. The average PIC of genomic SSRs(0.3996) was higher than that of genic SSRs(0.3235), and most of the polymorphic genomic SSRs were composed of di-and trinucleotide repeats(51.9% and 37.0% of all loci, respectively). The low level of detected genetic diversity may be attributed to a severe genetic bottleneck that occurred during the cowpea domestication process. The accessions were classified by structure and cluster analysis into four subgroups that correlated well with their geographic origins or collection sites. The classification results were also consistent with the results from principal coordinate analysis and can be used as a guide during future germplasm collection and selection of accessions as breeding materials for cultivar improvement. The newly developed genic and genomic SSR markers described in this study will be valuable genomic resources for the assessment of genetic diversity, population structure, evaluation of germplasm accessions, construction of genetic maps, identification of genes of interest,and application of marker-assisted selection in cowpea breeding programs.

Analysis of Genetic Variation of Seed Proteins in the Genus Vigna and among Its Relatives Cultivated in China

The genetic variation of seed proteins was assayed by SDSPAGE for 24 cultivars belonging to 5 species in Vigna and 7 species in its 7 relative genera cultivated in China. There were 48 polymorphic subunit bands discriminated from electrophoretic profiles. Two dendrograms were constructed by UPGMA cluster analyses using PHYLIP3.6 respectively. Variation among genera or species was larger than that among lower taxonomic categories level. Little variation among cuhivars of yardlong bean （Vigna sesquipedalis ） and small variation of lablab （ Lablab purpureus）, pea （Pisum sativum）, or sword bean （Canavalia gladiata）, but large variation of soybean or rice bean in their origin of China were all revealed. The seed proteins profiles of traditionally regarded as typical species in Vigna such as yardlong bean, rice bean and small bean were more similar than mungbean （Vigna radiata） and black gram （Vigna mungo） were. Mungbean and black gram had distinct seed proteins pattern, they should be of two species.

Preliminary Study on Geographical Distribution and Evolutionary Relationships Between Cultivated and Wild Adzuki Bean (Vigna angular is var. angularis and var. nipponensis) by AFLP Analysis

A set of representative 146 adzuki (Vigna angular is var. angularis, and var. nipponensis) germplasm from 6 Asian countries traditionally for adzuki bean production, together with an out group standard rice bean (Vigna umbellata), were analyzed by AFLP methodology using 12 informative primer pairs. 313 unambiguous polymorphic bands were created. According to the dendrogram by cluster analysis based on AFLP banding, 143 of the accessions were distinct and revealed enough genetic diversity for identification and classification of accessions within Vigna angularis. A neighbor joining tree was generated using newly developed Innan's nucleotide diversity estimate from the AFLP data. From analysis, 7 distinct evolutionary groups, named as "Chinese cultivated", "Japanese cultivated", "Japanese complex-Korean cultivated", "Chinese wild", "China Taiwan wild", "Nepal-Bhutan cultivated" and "Hymalayan wild", were detected. Nucleotide diversity with geographical distribution of each group is discussed, regarding the evolutionary relationships between wild and cultivated adzuki beans. The preliminary results indicated that cultivated adzuki bean should be domesticated from at least 4 progenitors in at least 3 geographical origins.

Sensitivity of Adzuki Bean (<i>Vigna angularis</i>) to Acifluorfen, Fomesafen, Bentazon, Imazethapyr and Halosulfuron-Methyl Applied Postemergence

New herbicide options are needed for postemergence (POST) broadleaf weed control in adzuki bean. A field study, of five experiments, was conducted over a three-year period (2014, 2015, 2016) in Ontario to evaluate the tolerance of adzuki bean to the POST application of acifluorfen (600 and 1200 g&middot;ai&middot;ha-1), fomesafen (240 and 480 g&middot;ai&middot;ha-1), bentazon (1080 and 2160 g&middot;ai&middot;ha-1), imazethapyr (100 and 200 g&middot;ai&middot;ha-1) and halosulfuron-methyl (75 and 150 g&middot;ai&middot;ha-1). Acifluorfen and fomesafen applied POST caused as much as 12% visible injury at the 1X rate and 20% visible injury at the 2X rate but had no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield. Bentazon caused as much as 23% visible injury at 1080 g&middot;ai&middot;ha-1 and 28% visible injury at 2160 g&middot;ai&middot;ha-1 but caused no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield at either rate, except at 2160 g&middot;ai&middot;ha-1 which reduced shoot dry weight 20% and height 12%. Imazethapyr caused as much as 22% visible injury at 100 g&middot;ai&middot;ha-1 and 34% visible injury at 200 g&middot;ai&middot;ha-1 but caused no adverse effect on adzuki bean population, shoot dry weight, height, maturity or yield at either rate except at 200 g&middot;ai&middot;ha-1 which delayed maturity slightly. Halosulfuron-methyl caused as much as 65% visible injury and reduced shoot dry weight, height and yield 64%, 41%, and 28%, respectively. This research concludes that acfluorfen, fomesafen, bentazon, imazethapyr and halosulfuron at the rates evaluated can cause the significant injury in adzuki bean.

A Rapid Method for Measuring Seed Protein Content in Cowpea (<i>Vigna unguiculata</i>(L.) Walp)

Cowpea (Vigna unguiculata (L.) Walp), a legume crop that is grown in the worldwide, provides beneficial proteins for human consumption and animal feeding. In comparison, Rapid N analyzer as traditional method, has been widely used to measure protein content through the percentage of total nitrogen in the seed’s grounded powder. Near-Infrared Reflectance (NIR) has commonly been used to measure protein content in soybean seeds using whole grain without the need of seed grinding, which makes it possible to obtain fast results at a lower cost-per-analysis than the traditional combustion method. The specific objective of this study is to test a rapid method for measuring cowpea seed protein content by the NIR analyzer comparing to the traditional rapid N analyzer. A total of 240 cowpea genotypes were used in this study, including six seed coat colors, black, blackeye, browneye, cream, pinkeye, and red with 40 cowpea genotypes. The results showed that a linear relationship exists between the NIR analyzer and the Rapid N analyzer in the six different color groups. The correlation efficiency (r) between the seed protein contents from NIR and Rapid N was higher for pinkeye seed (r = 0.867), blackeye (0.771), cream (0.729), browneye (0.700), and red (0.623), respectively, but lower for black seeds, indicating that the NIR analyzer can be used to measure protein content for cowpea seeds with the five types of seed coat except black. Overview, the cowpea seed protein content measured from the NIR analyzer showed a little higher seed protein content. A series of regression models with different seed coat color have been built to adjust to protein content of colorful cowpea seeds from the NIR analyzer. But, it is not recommended to use for black color seeds due to a very low correlation efficiency (r) value with 0.184.

Arsenic Induced Changes in Growth and Physiological Responses in <i>Vigna radiata</i>Seedling: Effect of Curcumin Interaction

Arsenic is a great hazard to the environment since it is a major source of soil and water contami-nation leading to phytotoxicity. Arsenic caused reduction in seed germination and growth of plants including mung bean (Vigna radiata) causing loss of crop productivity. This investigation evaluates effect of arsenic toxicity in mung bean with an attempt to ameliorate it by the applica-tion of curcumin. Arsenic induced reduction in fresh, dry mass, length of root and shoot and pig-ment content. The result of the present study suggests that curcumin at lower concentration ameliorates arsenic induced toxicity in Vigna radiata.

Evaluation of Total Seed Protein Content in Eleven Arkansas Cowpea (Vigna unguiculata (L.) Walp.) Lines

Cowpea is cultivated on more than 11 million hectares with a worldwide production of 5.4 million tons of dried seeds. Cowpea is an affordable source of protein, which is used as an alternative to soybean for people who are allergic to soybean protein. The aim of this research was to assess the variability of the total seed protein content in cowpea. Eleven Arkansas breeding lines were used in this study. Field experiment design was a randomized complete block design (RCBD) with 2 blocks, and conducted in three different locations within Arkansas State (Fayetteville, Alma, and Hope) in 2015. A standard chemical protocol was performed involving an analysis of the total nitrogen by combustion using an Elementar Rapid N III instrument to estimate the protein content. The average protein content was 25.4%, and ranged from 23.7% to 27.4% with a standard deviation of 1.9%. The significant effects of genotype, environment (location), and genotype by environment were observed for the total seed protein content in cowpea. The broad sense heritability (H2) for cowpea seed protein was estimated to be 57.8% based on the eleven cowpea genotypes studied. The cowpea lines, “Early Scarlet” and 09-204 had the highest seed protein content with 27.4% and 26.9% dried seed weight, respectively. This study provides valuable information on cowpea protein content for breeders to select and utilize those breeding lines with high seed protein content to develop new high protein cowpea cultivars.

土壤中Cd^2＋胁迫对gfp基因标记的饭豆(Vigna umbellate L．)根瘤菌生物毒性的研究

利用绿色荧光蛋白基因(gfp)标记研究了土壤中Cd2+胁迫对饭豆(Vigna umbellate L.)根瘤菌JMC1402G腐生存活的影响,同时也探讨了Cd2+胁迫对其共生固氮能力的影响。结果表明,YMA培养基平板培养时,Cd2+对JMC1402G的LC50为8.15μg·mL-1。不管土壤灭菌与否,当土壤中Cd2+添加量为3mg·kg-1时,向土壤接种的37d内对JMC1402G的腐生存活无影响,当Cd2+添加量为20mg·kg-1时,土壤中JMC1402G的数量明显低于对照,随着Cd2+添加量的进一步增大,土壤中JMC1402G的数量迅速落于104cfu·g-1以下。饭豆盆栽试验结果表明,Cd2+添加量在0￣20mg·kg-1范围内对JMC1402G共生固氮能力的影响不大,当土壤中Cd2+添加量达到50mg·kg-1时,对JMC1402G产生较明显的生理毒性,当Cd2+添加量达到100mg·kg-1,饭豆根瘤菌-饭豆体系失去结瘤能力。JMC1402G质粒快检结果表明,JMC1402G在Cd2+添加量为0、3、20、50、100mg·kg-1的土壤中营腐生生活37d,未出现质粒丢失情况。