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Induction of salt stress tolerance in cowpea [ Vigna unguiculata (L.) Walp.] by arbuscular mycorrhizal fungi Legume Res. 38 579 588 Agbicodo, E. M. Fatokun, C. A. Muranaka, S. Visser, R.G.F. van der Linden, C.G. 2009 Breeding drought tolerant cowpea

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Explants (cotyledon, cotyledonary node, second node, hypocotyl, epicotyl, and leaf) of cowpea (Vigna unguiculata) genotypes MN13 and Pinkeye Purple Hull were cultured on Murashige and Skoog basal nutrient medium. The medium was supplemented with 1 mg·L–1 benzyladenine (BA) or 1 mg·L–1 benzyladenine plus naphthalene acetic acid (BA + NAA) or 2 mg·L–1 2,4-dichlorophenoxy acetic acid (2,4-D). Cultures were maintained at 22°C for 1 month, after which they were transferred to 1 mg·L–1 BA + NAA. Cotyledons, hypocotyl, epicotyl, and leaf segments produced only calli after subculturing in BA + NAA. The second node and cotyledonary node explants cultured on the BA or BA + NAA followed by subculture on BA + NAA produced calli, shoots, and roots. The plants were then transplanted to promix but later died.

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Abstract

In the paper “Comparison of Two Methods of Hand-crossing Vigna unguiculata (L.) Walp” by K. W. Zary and J. C. Miller, Jr. [HortScience 17(2):246-248. 1982] there is an editing error in the abstract. Crossing method 1 should read “method 2” and method 2 should read “method 1.”

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Abstract

The effects of the cowpea strains of southern bean mosaic (SBMV-CS), cucumber mosaic (CMV-CS), and tobacco mosaic (TMV-CS) viruses on cowpea [Vigna unguiculata (L.) Walp] plant growth and N fixation parameters were evaluated in greenhouse and field experiments. TMV-CS infection resulted in the most severe symptoms and was associated with significant reductions in nitrogenase activity, total nodule weight, nodule number, and plant dry weight, in susceptible cultivars. Infection with CMV-CS was associated with significant reductions in nitrogenase activity, nodule number, and plant dry weight in field-grown ‘Mississippi Silver’. SBMV-CS infection was least severe and was associated with a significant reduction in nitrogenase activity and nodule weight in only 1 susceptible cultivar under field conditions.

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Cowpea (Vigna unguiculata L.) is an important grain legume, which in developing countries provides much of the protein in human diets. A plant regeneration system for cowpea was developed. Cotyledons were initiated on MS medium containing 15 to 35 mg·L-1 benzylaminopurine (BAP) for 5 to 15 days. For shoot regeneration, the explants were transferred to a medium containing 1 mg·L-1 BAP. Regeneration percentage (1% to 11%) and the number of shoots (4 to 12 shoots per explant) were significantly influenced by genotype. The duration of culturing and BAP concentration in the initiation stage significantly affected the regeneration capacity. Explants initiated on 15 mg·L-1 BAP for 5 days resulted in the highest regeneration percentage. Conversely, the highest number of shoots was obtained from explants initiated on 35 mg·L-1 BAP. This is the first report of plant regeneration of U.S. cowpea cultivars.

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Cowpea (Vigna unguiculata L.) is an important grain legume that is grown extensively in Africa, South America, India, and in the United States. This study investigated the effects of silver nitrate (AgNO3) on regeneration of cowpea cotyledon explants. Silver nitrate at 50 μm significantly increased percent regeneration in comparison to the control. The effect of duration of exposure was also determined with the ethylene inhibitor AgNO3. By exposing explants to 59 μm AgNO3 during different stages of culture, significant increases were actualized in percent regeneration and shoot number. The greatest percent regeneration was obtained when 59 μm AgNO3 was augmented to both the initiation and regeneration media or to only the regeneration media. These results indicate that the low percentage of regeneration of this genotype may be related to ethylene biosynthesis or metabolism. This study resulted in an improved regeneration system for the commercial cowpea cultivar Early Scarlet, and will be useful in developing a cowpea transformation system.

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Genotype by environment (G × E) effects in Regional Cooperative Southernpea trials for the southeastern United States were investigated to characterize the extent, pattern, and potential impact of G × E on seed yield of southernpea [Vigna unguiculata (L.) Walp] genotypes. The structure of G × E effects was investigated using the Additive Main Effect and Multiplicative Interaction (AMMI) method. AMMI analyses revealed a highly significant genotype × environment interaction, most of which was partitioned into a genotype × location component of variance. AMMI first principal component axis scores stratified environments into two groups that minimized variation within groups. Biological interpretation of groupings and visual assessment of the AMMI biplot, revealed high-yielding genotypes interacting positively with one group of environments and conversely, low-yielding genotypes interacting positively with the other group. There were some significant rank changes of genotypes as yield potential varied across environments. Some environments showed similar main effects and interaction patterns indicating that most of the G × E effects could be captured with fewer testing sites, and consequently redundancy of some testing environments over years.

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Southernpea [Vigna unguiculata (L.) Walp.] is the main source of protein in humid and subhumid tropics, but production is limited by low and erratic rainfalls. This potential calls for greater management of water deficit stress through timely irrigation and greater understanding of crop response to adverse environmental conditions. The objectives of this study were to: identify growth stages of southernpea sensitive to water deficit, estimate critical length of water deficit detrimental to southernpea during each stage, and describe physiological and morphological responses of southernpea to water deficit stress. In this study, two southernpea cultivars, `AR.91-285' and `Coronet', were used to examine the effect of water deficit stress on seed yield, number of pods per plant, number of seeds per pod, pod length, and hundred seed weight during three stages of growth. The greenhouse and field results for these parameters indicated that the vegetative stage was the least sensitive to water deficit stress, followed by podfilling and flowering stages. However, pod filling stage was found to be less sensitive than vegetative stage beyond 21 days of stress. The critical length of water deficit causing yield reduction appeared to be 7 days for flowering and pod filling stages and 14 days for vegetative stage. `Coronet' was less sensitive to water deficit stress than `AR.91-285'. Reduced plant size, change in leaf color, and wilting were plant responses during the vegetative stage. Leaf senescence, flower abscision, fewer and shorter pods, and early pod maturity were observed plant responses during the reproductive stages. We observed a general decline in stomatal conductance and net CO2 assimilation with increasing days of stress. After 7 and 14 days of water-deficit-stress vegetative growth, stomatal conductance and net CO2 assimilation returned to the levels of control.

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Abstract

The results of 2 years of field tests indicate that the level of cowpea curculio (Chalcodermus aeneus Boheman) resistance found in 2 southernpea (Vigna unguiculata) breeding lines was more effective in reducing curculio injury than the currently recommended insecticide toxaphene. No evidence was obtained that the insecticide’s effectiveness could be increased by altering the plant type.

Open Access

Cowpea [ Vigna unguiculata (L.) Walp] (2 n = 2 x = 22) is a legume of economic importance worldwide. It is widely grown in Central and West Africa with a production estimated at 5.4 million tons of dry seed ( Olufajo, 2012 ) and also grown in

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