Cowpea Isolate Research Articles

Enhanced characterization and utilization of cowpea protein isolate: Rheological and textural properties of heat-induced gels for plant-based egg omelet formulation

This study aimed to evaluate the potential of cowpea isolate (CPI) as an effective plant-based egg substitute by comparing its composition and physicochemical properties with those of commercial isolates, including mung bean, soy, and pea proteins. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis identified a distinctive vicilin-like globulin in CPI that is critical for the unique functional properties of CPI. CPI has a smaller particle size, resulting in superior gelation capacity and water retention, which are essential for egg substitute applications. Thermal analysis revealed the high stability of CPI, which is advantageous for food processing. Notably, the unique heat-induced gelation behavior of CPI, characterized by a smooth transition from solid- to liquid-like states, provided a strength not observed in its commercial counterparts. Microstructural analysis showed that the CPI gel closely resembled the egg gel, underscoring the potential of CPI to mimic the texture of eggs, particularly in omelets.

Comparison and Correlation of Corynespora cassiicola Populations from Kiwifruit and Other Hosts Based on Morphology, Phylogeny, and Pathogenicity.

Corynespora leaf spot, which is caused by Corynespora cassiicola (Berk. & M. A. Curtis) C.T. Wei (C. cassiicola), has been globally reported in many plant species. 'Hongyang' was reported as highly sensitive kiwifruit cultivar to C. cassiicola. This cultivar is an important germplasm resource in the Actinidiaceae family and is widely cultivated throughout China. Even though C. cassiicola has been identified as the pathogen associated with kiwifruits in China, the C. cassiicola population from kiwifruit has not been characterized based on morphology, phylogeny, and pathogenicity. In this study, 133 and 48 representative C. cassiicola isolates from kiwifruit and 11 other hosts, respectively, recovered from symptomatic leaves were classified into eight morphological subgroups based on host origins. Using three loci (rDNA ITS, caa5, and act1), a phylogenetic tree showed that C. cassiicola isolates in Sichuan Province were grouped into three clades. All kiwifruit isolates were genetically identical to the rubber isolates from different countries. However, most isolates from other hosts in this study were genetically identical to the cucumber, soybean, and cowpea isolates in China, Brazil, and the United States, and two strawberry isolates clustered with isolates from tomato and other hosts in China, Brazil, and the United States. Furthermore, we confirmed host shift of C. cassiicola among different plant species in this study. Although 51 isolates from kiwifruit and different hosts were pathogenic to kiwifruit, blueberry, cucumber, and soybean, virulence levels of the pathogen were diverse for four hosts. Kiwifruit isolates exhibited host specificity with regards to the original host in degree. In addition, those isolates revealed a correlation between morphology and pathogenicity. The results suggest that C. cassiicola in Sichuan Province were derived from three different phylogenetic lineages. Promotion of the susceptible 'Hongyang' cultivar led to the emergence of a regnant C. cassiicola population from kiwifruit. In conclusion, rapid development of the C. cassiicola-sensitive crop in agricultural systems led to the emergence of a regnant C. cassiicola population. In some dominant populations (e.g., the C. cassiicola population from kiwifruit in this study), host origin was found to be a key factor influencing the morphologic, genetic, and pathogenic characterization of C. cassiicola.

Antioxidant and apoptotic potential of protein isolates derived from Vigna unguiculata (L.) Walp

SummaryProjected mortalities from cancer are expected to continue escalating, with conventional chemotherapeutic regimens having extensive side effects, hence the need for therapeutics capable of terminating cancer cells selectively, through apoptosis. Therapeutic protein isolates bind specifically to target proteins inducing cell death in vitro and in vivo in various cancer cells. Therefore, this study aimed at observing the antioxidant and anticancer potential of protein isolates from five cowpea cultivars (Glenda, Embu buff, Makhatini, Veg Cowpea 2 and Veg Cowpea 3). Cytotoxicity was conducted on cancerous and non‐cancerous cell lines. Apoptosis was quantified using flow cytometry, and caspase‐3/7 activity was determined. Cytotoxicity assays revealed that Embu buff was the pre‐eminent inhibitor of cancerous cells, while also acting as a protecting mediator in a stressed non‐cancerous cell line by causing a reversal in apoptotic activity. Therefore, cowpea isolates show high potential as candidates for the therapeutic intrusion of cancer.

Molecular characterization and infectivity of Mungbean Yellow Mosaic India virus associated with yellow mosaic disease of cowpea and mungbean

Grain legumes are an important source of dietary protein across Southeast Asia, but they suffer severe losses due to Yellow mosaic diseases (YMD), caused by members of the genus Begomovirus (family Geminiviridae). Cowpea is an annual tropical grain legume extensively cultivated in sub-Saharan Africa, Southeast Asia and South America. More than 20 viruses are reported in cowpea around the world. Despite its economic importance, little attention has been paid to the viruses infecting cowpea in India. We conducted an elaborate survey and characterization of begomoviruses infecting cowpea in the central and northeast region of India. We report complete sequences of 13 components (6 DNA-A, 6 DNA-B, and 1 complete genome) belonging to four strains of MYMIV, each of CGMV and FbSLCV. Nucleotide sequence comparison analysis showed the cowpea isolates MYMIV DNA-A [KY556679] having highest similarity (98%) with reported soybean isolate of MYMIV segment DNA-A [AY049772] and lowest similarity (77%) with lima bean isolate of horsegram yellow mosaic virus (HYMV) [AM932429] whereas cowpea isolates MYMIV DNA-B [KY556680] showed highest identity (98%) with MYMIV Brebs3 segment [JN368446] and lowest identity (94%) with MYMV LBG623 segment [KF928962]. Our survey revealed maximum incidence of MYMIV infection in cowpea in the central and northeast India. We therefore characterized the MYMIV infection in cowpea as well as its natural host, mungbean through agroinoculation of dimeric infectious clones and confirmed the pathogenicity of MYMIV. This is the first report of cowpea isolate of MYMIV infecting mungbean with YMD symptoms which is experimentally demonstrated through Koch's postulate.

Isolation and evaluation of summer legumes Rhizobia as PGPR

Rhizobia are bacteria well known for biological nitrogen fixation through symbioses. These bacteria may also perform as plant growth promoting rhizobacteria (PGPR). In this study the role of rhizobia as PGPR was studied. Rhizobia was isolated from the root nodules of various summer legumes including Glycine max (Soybaen), Vigna radiata (Mung bean), Vigna unguiculata (Cowpea), Susbenia grandiflora (Sesbania) and Cymposistetra gonoloba (Guar) grown at New Developmental Farm (NDF), the University of Agriculture Peshawar, Pakistan during summer 2011. Rhizobia were isolated from root nodules by using yeast minitol agar media, pure culture of each isolate was prepared and examined for various PGPR traits. Data revealed that 9, 83, 47 and 21% of tested strains were found to produce cyanide (HCN), siderophores, indole-acetic acid (IAA) and solubilized phosphorus respectively. Among the tested rhizoial isolates, rhizobia isolated from Vigna radiata showed highest PGPR activity fallowed by Glycine max while relatively lower PGPR activity was observed for rhizobial isolates of Cymposistetra gonoloba (Guar). All the tested isolates were gram negative. Soybaen and cowpea isolates were found to be fast growing while mung bean, susbenia and guar were slow growing in nature. This study indicates that rhizobial isolates of Vigna radiata and Glycine max have the capability to be used as PGPR.

Enhanced nicking activity of Rep in presence of pre-coat protein of Mungbean yellow mosaic India virus

Yellow mosaic disease causes severe yield loss in grain legumes in Indian subcontinent and south east Asia. The disease is caused by two virus species, Mungbean yellow mosaic India virus (MYMIV) and Mungbean yellow mosaic virus (MYMV). They have genome organization typical of Old World begomoviruses, the unique feature being the presence of an open reading frame (ORF) AV2 upstream of coat protein gene. In order to elucidate its function, ORF AV2 of blackgram isolate, Mungbean yellow mosaic India virus-[India:New Delhi:Blackgram 3:1991] MYMIV-[IN:ND:Bg3:91] and cowpea isolate, Mungbean yellow mosaic India virus-[India:New Delhi:Cowpea7:1998] MYMIV-[IN:ND:Cp7:98], respectively, were over expressed in Escherichia coli in fusion with maltose binding protein (MBP). The recombinant protein did not show efficient binding to DNA. However, both MBP-BgAV2 and MBP-CpAV2 proteins modulated nicking and ATPase activity of replication initiation protein (Rep). Even low concentration, 20 ng of MBP-BgAV2 and MBP-CpAV2 could bring 20 folds increase in nicking activity of Rep. Similarly in the presence of AV2 protein, two to three fold increase in ATPase activity was observed. It is hypothesized that AV2 protein may play a role of accessory protein modulating Rep activities.

First Report of Tomato yellow leaf curl virus Infecting Cowpea in China

Tomato yellow leaf curl virus (TYLCV) is a devastating pathogen of tomato that causes significant yield losses in many tropical and subtropical regions (1). In China, this virus was first found in 2006 on tomato in Shanghai (2). In October 2008, chlorotic yellow leaves of cowpea (Vigna sinensis) were observed in Qingpu, Shanghai, China with 15 to 20% incidence in plants in high tunnels. Large populations of whiteflies were observed in association with the diseased cowpea. The disease agent was transmitted to cowpea (and tomato) by whiteflies, which resulted in chlorotic yellow leaves on cowpea (yellow leaf curl symptoms on tomato) that were identical to those observed in the field. On the basis of the suspected insect vector, symptomology, and severe epidemics of tomato yellow leaf curl disease (TYLCD) in Shanghai in recent years, Tomato yellow leaf curl virus was suspected as the causal agent. Total DNA was extracted from four symptomatic cowpea samples. PCR was performed with specific primers V416 (5'-CAAGGCACAAACAAGCGACG-3') and C1287 (5'-CTCAACTTCCGAATTTGGACGAC-3') to amplify a 872-bp DNA fragment of the viral coat protein (CP) gene and an amplicon of the expected size was obtained in all four samples but not from healthy leaf samples. The PCR products were sequenced and the sequences were identical among samples. Primers TYLCV-F (5'-CAGGAGGCAGCCAAGTATGAG-3') and TYLCV-R (5'-ACTAATGCCTGTTCYTTCATTCC-3') (Y = C or T/U) were designed on the basis of the sequence (Accession No. HM804856) and reported (Accession No. FM163463) CP gene to amplify the full-length viral DNA of cowpea isolate (CN:SH:Cowpea:08). The sequence was determined to be 2,781 nucleotides long (Accession No. GU434143). A comparison of the sequence with those in GenBank shows that the cowpea isolate has the highest nucleotide sequence identity (99%) with TYLCV isolate XH2 from tomato in Xinghua, Jiangsu, China (Accession No. GU111505). To our knowledge, this is the first report of TYLCV infecting cowpea in China and also the first report in the world.

Phylogenetic Analysis of Uromyces Species Infecting Grain and Forage Legumes by Sequence analysis of Nuclear Ribosomal Internal Transcribed Spacer Region

DNA sequence analysis of the nuclear ribosomal internal transcribed spacer region (ITS) was performed to determine phylogenetic relationship between 49 isolates of rusts infecting grain and forage legumes. Isolates were collected from different hosts and distinct geographic origins and represent eight species of Uromyces: U. anthyllidis, U. appendiculatus, U. ciceris-arietini, U. minor, U. pisi, U. striatus, U. viciae-fabae and U. vignae. ITS sequences revealed length polymorphisms and variation in DNA sequence that were used to characterize phylogenetic relationships by maximum parsimony, maximum likelihood and Bayesian analyses which in general agreed revealing the presence of four clearly distinct clades. Clade one included the isolates causing rust on chickpea, fenugreek and alfalfa. Clade two was composed by rust isolates of field clover and pea plants, while the third clade was formed by bean and cowpea isolates. Clade four was the largest and included all the rust isolates infecting faba bean. Within this clade, the highly supported subclusters of U. viciae-fabae collected on Lens culinaris, U. viciae-fabae collected on Vicia sativa and U. viciae-fabae collected on Lathyrus palustris suggest an ongoing process of host specialization.

First Report of Cucumber mosaic virus in Yams (Dioscorea spp.) in Ghana, Togo, and Republic of Benin in West Africa.

Yam (Dioscorea spp., family Dioscoreaceae) is one of the most important food crops cultivated in the West African yam zone comprising the forest and savannah areas of Nigeria, Ghana, Côte d'Ivoire, Republic of Benin, and Togo, which account for more than 90% of the 4.59 million ha of yam cultivation worldwide (1). A survey was conducted in 2005 to document viruses in yams in Ghana, Togo, and the Republic of Benin. Samples (1,405) from five species of yam showing mosaic, chlorosis, and stunting as well as asymptomatic plants were tested for Dioscorea bacilliform virus (DBV, genus Badnavirus), Yam mosaic virus (YMV, genus Potyvirus), and Yam mild mosaic virus (YMMV, genus Potyvirus), the three most common viruses infecting yams. In addition, samples were tested for Cucumber mosaic virus (CMV), since CMV was previously reported to infect yams in Côte d'Ivoire (2) and Nigeria (3). In protein-A sandwich-ELISA with polyclonal antibodies to a cowpea isolate of CMV, 23 of the 1,405 samples (6 of 218 samples from Togo, 13 of 628 samples from Ghana, and 4 of 559 samples from Republic of Benin) tested positive for CMV. The CMV-positive samples were from D. alata (N = 16) and D. rotundata (N = 7), whereas all samples from D. cayenensis, D. dumetorum, and D. bulbifera tested negative. CMV was detected as mixed infections with DBV, YMV, or YMMV in 21 of 23 samples. Some of these samples showed puckering, chlorosis, mottling, and crinkling, whereas some plants infected by two or more viruses were asymptomatic. Only two samples from D. rotundata had a single infection of CMV and they showed mild chlorotic symptoms in young leaves that were inconspicuous in mature leaves. In sap inoculations, the virus induced systemic mosaic in Nicotiana glutinosa. The presence of CMV in ELISA-positive yam samples was further confirmed by immunocapture-reverse transcription (IC-RT)-PCR using CMV antibodies as trapping antibody and oligonucleotide primers specific for a 485 nt corresponding to 3' end of the coat protein gene and C-terminal noncoding region of RNA-3 (4). To confirm the specificity of IC-RT-PCR, the 485-bp amplicons from an isolate from the Republic of Benin was cloned into pCR2.1 (Invitrogen, Carlsbad, CA) and three independent clones were sequenced from both orientations. Pairwise comparison of a consensus sequence (Accession No. EU274471) with corresponding sequences of other CMV isolates deposited in GenBank showed 99% identity at the nucleotide sequence level (Accession No. U22821) and revealed that the CMV isolate from yam belongs to sub-Group IA. To our knowledge, this is the first report of CMV infection in yams (D. alata and D. rotundata) in Ghana, Togo, and the Republic of Benin. Together with a previous documentation of CMV in D. alata and D. trifida in Côte d'Ivoire and Nigeria (2,3), this report adds to existing knowledge on distribution of CMV in yams with implications for yam production and germplasm distribution in the West Africa Region.

Natural Infection by Tospoviruses of Cucurbitaceous and Fabaceous Vegetable Crops in India

AbstractNatural infection of tospoviruses on three cucurbitaceous (Cucumis sativus, cucumber; Luffa acutangula, ridge gourd; Citrullus lanatus, watermelon) and three fabaceous (Vigna unguiculata, cowpea; Phaseolus vulgaris, French bean; Dolichos lablab, sem) vegetable crops in India was identified on the basis of nucleocapsid protein (NP) gene characteristics. The complete NP gene of the cowpea isolate from Kerala and the sem isolate from Tamil Nadu was 831 nucleotides long, encoding a protein of 276 amino acids. For other Tospovirus isolates from cucumber, French bean, ridge gourd and watermelon, the partial NP gene (291 nt) was sequenced. Comparative NP gene sequence analyses revealed that fabaceous isolates shared maximum identity both at the nucleotide (92–97%) and amino acid (93–97%) levels with the corresponding region of Groundnut bud necrosis virus (GBNV), whereas cucurbitaceous isolates shared maximum identity both at nucleotide (93–99%) and amino acid (95–98%) levels with the corresponding region of Watermelon bud necrosis virus (WBNV), results suggesting that the Tospovirus isolates infecting fabaceous hosts should be regarded as strain of GBNV, whereas those infecting cucurbitaceous hosts as a strain of WBNV. Nucleocapsid protein gene was conserved both in GBNV and WBNV isolates originating from different hosts and locations.

Symbiotic and genomic diversity of ‘cowpea’ bradyrhizobia from soils in Botswana and South Africa

Strain CB756 is usually an effective competitor against indigenous bradyrhizobia for nodulation of peanut in South Africa. Recently, inoculation of peanut and cowpea with CB756 in loamy sand soils of Botswana or a sandy clay loam in South Africa proved unsuccessful, achieving <2% nodule occupancy. A survey of ‘cowpea’ bradyrhizobia from five soils in Botswana and one in South Africa showed that many were effective in ability to fix N2 on peanut and cowpea. However, 15 isolates from Good Hope, Botswana were all effective on cowpea but ineffective on peanut, three failing to nodulate the latter. Selected cowpea isolates were significantly more competitive than CB756 for nodulation of cowpea in Leonard jars, but four were unsuccessful when inoculated at Roodeplaat, South Africa. When strain CB756 and two isolates were inoculated in pots containing Roodeplaat soil, at a 4:1 inoculant to soil bradyrhizobia ratio, their average nodule occupancy was 8% on cowpea compared to 40% on peanut. Significant differences in strain nodule occupancy were not detected on either cowpea or peanut. In contrast, nodule occupancy in loamy sand from Good Hope, Botswana, inoculated at a 40:1 inoculant to soil bradyrhizobia ratio, was 22.4% on cowpea and only 6.8% on peanut. In Good Hope soil, strain CB756 was the weakest competitor on cowpea but strain differences were insignificant on peanut. Whereas the Good Hope soil population was effective on cowpea, it was ineffective on peanut. DNA fingerprinting showed that isolates from Gaborone, Francistown and Roodeplaat contained several different genotypes, whereas those from Good Hope, Rasesa and Maun were more homogeneous. The dominance at Good Hope of genotypes effective on cowpea but ineffective on peanut emphasises the value of assessing the symbiotic capabilities and structures of indigenous populations.

Effect of a cowpea mild mottle virus isolate on growth and yield of bambara groundnut (&lt;i&gt;Vigna subterranea&lt;/i&gt; L.)

Effect of a cowpea mild mottle virus isolate on growth and yield of bambara groundnut (&lt;i&gt;Vigna subterranea&lt;/i&gt; L.)

Immunodiagnosis of groundnut and watermelon bud necrosis viruses using polyclonal antiserum to recombinant nucleocapsid protein of Groundnut bud necrosis virus

In vitro gene expression strategy was used for the production of polyclonal antiserum to the nucleocapsid protein (NP) of Groundnut bud necrosis virus (GBNV). The GBNV NP gene from cowpea isolate was cloned into 6x His-tagged UA cloning vector and expressed in Escherichia coli [M15] cells. The fusion protein was detected in insoluble fraction and was purified by using Ni-NTA agarose resin. The purified 6x His-fusion protein (∼32 kDa) was used for immunisation to produce a high titre polyclonal antiserum. The antiserum to the NP of GBNV at 1:4000 dilution detected successfully natural infection of GBNV and Watermelon bud necrosis virus in a wide range of cucurbitaceous, leguminous and solanaceous hosts from different locations.

Infectivity analysis of a soybean isolate of Mungbean yellow mosaic India virus by agroinoculation

Yellow mosaic disease (YMD) of legumes endemic to South Asia are caused by begomoviruses transmitted by whiteflies. Based on molecular characterization, two distinct viruses – Mungbean yellow mosaic India virus (MYMIV) and Mungbean yellow mosaic virus (MYMV) – were found previously to be the etiological agents of YMD in legumes. Here, host range studies with a soybean isolate of MYMIV (MYMIV-[Sb]) were carried out by both whitefly transmission and agroinoculation. MYMIV-[Sb] was similar to a cowpea isolate of MYMIV (MYMIV-[Cp]) in its ability to infect cowpea, thus differing from blackgram (MYMIV) and mungbean (MYMIV-[Mg]) isolates, which do not infect cowpea. Genomic analysis of DNA A and DNA B components of these MYMIV isolates show characteristic differences in complete DNA B nucleotide sequence correlating with host range differences.

First Report of Peanut stunt virus in Perennial Peanut in North Florida and Southern Georgia.

In spring 2001, symptoms similar to aphid-vectored peanut stunt disease caused by Peanut stunt virus (PSV) were observed on perennial peanut (Arachis glabrata) cv. Floragraze in Jackson and Gulf counties, FL and Lowndes County, GA. Symptoms observed in commercial hay fields and at the North Florida Research and Education Center in Marianna and Quincy included malformed leaves, plant chlorosis, leaf mottling, and stunted plants, which resulted in reduced foliage yield. Leaf symptoms were visible throughout the growing season. Stunting was more common in spring and early summer. No symptoms were seen on rhizomes. Diagnosis of PSV (genus Cucumovirus) from symptomatic leaves and rhizome materials of 12 plants was confirmed by a direct antigen-coated enzyme-linked immunosorbent assay (DAC-ELISA). ELISA tests were repeated three times. Antibodies specific to the Clemson isolate, serotype E, were obtained from Clemson University, Clemson, SC. DAC-ELISA (1) values of 0.1 A405 above the healthy control for perennial peanut were considered positive for foliage and rhizome material tested. ELISA values ranged from 0.4 to 2.1. The mean ELISA value of the positive controls was 2.65. Symptomatic plants were also tested with ELISA using available antibodies from Agdia Inc., Elkart, IN, for Tomato spotted wilt virus, from ATCC for Peanut stripe virus, and from Clemson University (Cowpea isolate) for Cucumber mosaic virus, but all results were negative. To our knowledge, this is the first report of PSV on perennial peanut in Florida and southern Georgia. At this time, it is not known what role perennial peanut may play as a reservoir of the virus in the vicinity of peanut fields. Little is known about the potential for forage production loss and stand longevity. Next season, molecular detection techniques and epidemiological studies on peanut and perennial peanut will be conducted to ascertain the incidence and possible impact of PSV in Georgia and Florida. Reference: (1) A. G. Gillaspie, Jr. et al. Plant Dis. 79:388, 1995.

Influence of altered solvent environment on the functionality of pigeonpea (Cajanus cajan) and cowpea (Vigna unguiculata) protein isolates

Functional properties of pigeonpea and cowpea isolates were determined as a function of pH and NaCl concentrations. At low pH, nitrogen solubility decreased with increasing NaCl concentration whereas, at high pH, it increased. Addition of NaCl to the solvent medium resulted in a marginal improvement and a significant improvement, in the emulsifying activity and emulsion stability of pigeonpea isolate, respectively. The above treatment decreased these properties for the cowpea isolate. Varying both the pH and NaCl concentrations resulted in significant improvements in the emulsifying properties of the isolates relative to the control treatment. NaCl concentrations higher than 0.1 M significantly (P<0.05) increased the expansion of pigeon and cowpea protein–stabilized foams but reduced foam stability, and adjusting pH from 2 to 8 improved foam expansion but decreased foam stability. Varying both the pH and salt concentration had similar effects on the foaming properties of the isolates. The least gelation concentration (LGC) of the isolates decreased with increasing salt concentration. Adjusting the pH to values away from the apparent isoelectric point, elicited similar responses in LGC. In 0.5 M NaCl solution, adjusting the pH to 2, 6 and 8 resulted in significant reductions in LGC relative to the distilled water protein suspensions.

Infection process and identity of the hemibiotrophic anthracnose fungus ( Colletotrichum destructivum) from cowpea ( Vigna unguiculata)

The infection process of a hemibiotrophic Colletotrichum species causing anthracnose disease in cowpea (Vigna unguiculata) was studied by light and electron microscopy. During the biotrophic phase, the fungus produced unusual, large, multilobed, multiseptate infection vesicles with elongated neck regions, which remained confined within the initially-infected epidermal cell. Biotrophy lasted for the first 72 h of the host-pathogen interaction. The necrotrophic phase was characterized by the rapid development of invasive secondary hyphae which radiated from the multilobed vesicles into the surrounding tissues, producing water-soaked lesions on the surface of infected organs. Eventually, acervuli erupted in abundance on the surface of colonized tissues 120 h after inoculation. Each acervulus possessed, characteristically, one septate melanized seta. Multilobed vesicles were successfully isolated from homogenates of infected leaves by isopycnic centrifugation and were shown to lack cross-reactivity to monoclonal antibodies raised against infection structures of C. lindemuthianum. Analysis of the nucleotide sequences of the amplified D2 and ITS-2 regions of rDNA revealed very close similarities (97–99%) between the cowpea isolate and three isolates of C. destructivum obtained from lucerne (Medicago sativa). The results presented here, in addition to other morphological and growth attributes, suggest that the hemibiotrophic cowpea anthracnose pathogen must be considered as a form of C. destructivum.

Effect of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates of Phoma bakeriana

Summary The effects of culture media, temperature and light on radial growth and pycnidium production of cowpea isolates (PB1, PB2, PB3) of Phoma bakeriana were investigated in vitro. There was no isolate effect on growth and pycnidium production but some evidence of a medium effect. Exceptionally high growth rate on two media corresponded with high pycnidium production; while low growth rates on other media were generally associated with high sporulation. There was a large temperature effect and an isolate effect on growth with a significant temperature by isolate interaction. Temperatures of 5°C, 10°C and 35°C inhibited pycnidium formation completely while the range 15–30°C had no effect on sporulation. Maximum growth and pycnidium production occurred at 25°C. Near-ultraviolet radiation seemed to have caused higher pycnidium counts than the other light sources.

Formae speciales differentiation of Phytophthora vignae isolates from cowpea and adzuki bean.

The pathogenicity of 17 isolates of Phytophthora vignae Purss from adzuki beans and 4 isolates from cowpeas was compared. Isolates from adzuki beans were virulent to adzuki beans, but not to cowpeas, while isolates from cowpeas were virulent to cowpeas, but not to adzuki beans. The soluble proteins and isoenzymes patterns of these isolates, compared by zone electrophoresis, showed no qualitative differences between adzuki bean and cowpea isolates. Although the pathogens of both adzuki beans and cowpeas have bean treated as P. vignae, two formae specials are proposed for these two fungi on the basis of their specific pathogenicity: P. vignae f. sp. adzukicola Tsuchiya, Yanagawa et Ogoshi for the former and P. vignae f. sp. vignae Tsuchiya, Yanagawa et Ogoshi for the latter. Furthermore, from differences in pathogenicity to six cultivars of adzuki bean, three races (1, 2 and 3) were recognized within f. sp. adzukicola.

Identification of Promiscuous Nodulating Soybean Efficient in N2 Fixation1

Many developing countries lack the facilities to produce and distribute high quality rhizobia inoculants for farmers who are interested in planting soybeans [Glycine max (L.) Merr.]. If soybean varieties were available that could nodulate effectively with the ubiquitous, cowpea‐type rhizobia, farmers could successfully grow soybeans without inoculation or fertilizer N. When 400 diverse soybean lines were tested at five sites in Nigeria for the ability to nodulate with indigenous rhizobia, only 10 were highly promiscuous, that is, capable of forming an effective symbiosis at all sites. Some entries were rated as compatible with indigenous rhizobia at one or two sites but failed to nodulate profusely at the other locations. Twenty‐two isolates from nodules collected from profusely nodulated soybean plants and three other isolates prepared from cowpea nodules, were used to inoculate the 10 most compatible selections from the previous trial and two U.S. varieties, ‘Bossier’ and TGm 294. ‘Malayan’, a local Nigerian cultivar, formed an effective symbiosis with 21 of 22 soybean isolates; nodule and shoot weights in each case being greater than or equal to inoculation with Nitragin multistrain inoculant. Other accessions that displayed high degrees of promiscuity were M‐381, TGm 120, TGm 119, Indo 180, and Indo 243. Whereas, Bossier formed an effective symbiosis with only one of the isolates, and TGm 294 was compatible with only 2 of the 22 rhizobia isolates. The promiscuously nodulating soybeans identified in the screening trial were also compatible with at least two of the three cowpea isolates, but Bossier and TGm 294 were compatible with none of them. When the scion of Bossier on ‘Jupiter’ (both of which have high yield potential) was grafted onto the root stocks of ‘Orba’ or Malayan (Promiscuous nodulators) enough N was fixed to meet the requirements of high yielding genotypes. These results indicate that by genetically incorporating promiscuity into varieties with high yield potential one would not necessarily reduce yield potential.