Somatic Embryogenesis and Plant Regeneration from Protoplasts of Cowpea (Vigna sinensis)

Immature cotyledons of cowpea (Vigna sinensis Endlo) were used for protoplast isolation. Enzyme solution for protoplast isolation contained 40% cellulase Onozuka R-10,0.30% Macerozyme R-10 and 2% hemicellulase. The purified protoplasts were cultured in Bs,MS or KM8p liquid medium in dark (25℃) at a density of 1 × 105–5 × 105/ml. The protoplasts started cell division in 3–5 days . Sustained cell divisions resulted ill formation of cell clusters and small calli,with cell division frequency reaching 23%–28% in MS medium . Calli of 2 mm in size were transferred onto MSB (MS salts+B5 vitamins) medium with 2 mg/L 2,4-D, 0. 5mg /L BA forfurther growth. Embryogenic calli appeared on this medium. After passage to fresh medium with the same composition, the embryogenic calli were transferred into MSB liquid medium to establish suspension culture. When the suspended calli were transferred back onto MSB agar medium with 0. 1 mg /L IAA, 0.5mg/L KT, 5% mannitol (cultured in light,2000 lx,12h/d), a lot of adventitious roots formed in 7–10 days, and then somatic embryos formed from the protoplast derived calli. But only a few embryoids developed further into the cotyledonary stage ,and the others died at globular, heart-shaped, or torpeto stage . Finally, some cotyledonary embryoids germinated and developed into plantlets or shoots with leaves.     

Growth and yield responses of cowpea and maize to inoculation withGlomus mosseae in sterilized soil under field conditions

Summary The effects of inoculation of cowpea and maize withGlomus mosseae and sowing into field soil fumigated with formalin are reported. Root infection was significantly, though temporarily, decreased and grain yield increased, by sterilization. Inoculation increased root infection, shoot yields, P contents and grain yield. IITA Journal Series Paper No. 205.     

Maternal inheritance of plant variegation in cowpea, Vigna unguiculata (L.) Walp.

A chimeric plant was observed in the F₂ generation of a cross between a mutant cultivar, Ife BPC, and a germplasm line, TVu 2, in cowpea, Vigna unguiculata (L.) Walp. The chimeric plant had four lateral branches, one of which was intensely variegated, while the others were mostly green with few white sectors. F₃ progeny from the intensely variegated branch of this plant were all variegated, while seed derived from the mostly green branches produced only green progeny. In subsequent generations, the descendants of the variegated branch bred true for the variegated trait, while those of the mostly green branches were also true-breeding for green colour. No pure-green or pure-white shoots were observed in any of the variegated plants examined in this study. Consequently, no pure-green or pure-white seedlings were produced from seeds harvested from the variegated plants. The results of reciprocal crosses between variegated and normal green plants indicate that variegation is inherited in a strictly uniparental maternal fashion. This is the first report of a cytoplasmically inherited mutation affecting foliage colour in cowpea. Received: 10 March 2000 / Accepted: 16 May 2000     

Growth response of major USA cowpea cultivars: II. Effect of salinity on leaf gas exchange

In an effort to elucidate the physiological processes involved in cowpea differential growth response of four major USA cowpea cultivars (CB5, CB27, 8517 and 7964) to increasing salinity, we investigated the effect of salinity on leaf gas exchange of net photosynthetic rate per unit leaf mass (Pnm) and per unit leaf area (Pna), and stomatal conductance (gs) of the four cowpea cultivars. The experiment was set up as a standard split-plot design in which cowpea plants were grown in greenhouse sand tanks irrigated with nutrient solutions. Seven salinities ranging from 2.6 to 20.5 dS m⁻¹ were constructed based on Colorado River water salt composition with NaCl, CaCl₂ and MgSO₄ as the salinization salts. Light-saturated Pnm, Pna and gs of fully expanded trifoliage were examined at the vegetative growth and flowering stages, and the data were analyzed using a split-plot analysis of variance (ANOVA) model. We found a highly significant (P ≤ 0.0001) reduction of Pnm, Pna and gs due to salinity. The responses of Pnm, Pna and gs to salinity could be further described by a general model of log(y) = a₁ + a₂x + a₃x², where y represents either Pnm, Pna, or gs; a₁, a₂ and a₃, empirical constants; x, salinity. We found that Pnm was more sensitive to salinity than Pna. Additionally, we found that increasing stomatal closure with increasing salinity might limit Pnm or Pna. While we did not find any significant difference (P > 0.05) of Pnm and Pna among the four cultivars, we did find a significant difference (P ≤ 0.05) in gs. No significant salt × cultivar interaction effect (P > 0.05) was found with Pnm, Pna and gs indicating that the four cowpea cultivars have the same response pattern of their leaf gas exchange to salinity.     

豇豆胰蛋白酶抑制剂(CpTI)基因转化欧美杨的研究

本研究建立了欧美107杨的高频再生体系,用改良的根癌农杆菌介导法将豇豆胰蛋白酶抑制剂(CpTI)基因导入107杨中。经过严格的卡那霉素(Km)筛选,得到了Km抗性(Kmr)植株。对部分Kmr植株进行PCR及PCR-Southern杂交鉴定,证实CpTI基因已整合进杨树基因组中。转基因植株的饲虫实验表明,其中部分株系的叶片可在一定程度上抑制扁刺蛾幼虫的生长。     

Fungicidal activity of some plant extracts against rhizoctonia

The leaf extracts of Piper guinensis, Ocimum sanctum, O. gratissimum and Cymbopogon citratus were effective in reducing the radial growth of Rhizoctonia solani in vitro and in checking the spread of the disease caused by the pathogen in the field. P. guinensis was the best in checking the spread of the pathogen both in vitro and in vivo. This was followed by C. citratus, O. sanctum and O. gratissimum. Citrus limon reduced the radial growth of the pathogen in vitro but failed to check the spread of the disease effectively in the field. Alcohol extracts were more effective than water extracts.     

Integrated Pearl Millet Management in the Sahel: Effects of Legume Rotation and Fallow Management on Productivity and Striga Hermonthica Infestation

Increasing population density and food needs in the Sahel are major drivers behind the conversion of land under natural vegetation to arable land. Intensification of agriculture is a necessity for farmers to produce enough food. As manure is scarce and fertilizers expensive, this study looks into the potential role of cowpea (Vigna unguiculata L.) and short duration fallow in maintaining soil fertility and productivity and in reducing the major weed problem Striga hermonthica (Del.) Benth. The research was carried out ‘on-farm’ in a traditional millet (Pennisetum glaucum (L.) R.Br.) growing area in the Malian Sahel, near Bankass. The four year experiment combined 0, 2, 5, and 7 years of preceding fallow with (i) 4 years of millet, (ii) 1 year of cowpea + 3 years of millet, and (iii) 1 year of cowpea + 3 years of millet/cowpea inter-cropping. Total millet production (4 years) was 1440 kg ha⁻¹ for all systems with 2, 5 or 7 years of preceding fallow against 1180 kg ha⁻¹ for systems without fallow. Cowpea grain production showed no significant differences between fallow treatments. Over 4 years, all cropping systems produced similar total amounts of millet grain, implying that the millet ‘lost’ during the year with a pure cowpea crop in treatments (ii) and (iii) was compensated within three years, while the cowpea grain production was an additional benefit. Such compensation was however not observed for increasing number of preceding fallow years, showing that there is no additional production benefit in 5–7 years of fallow as compared to 2 years.The soil organic carbon content decreased more slowly in treatments with a cowpea pure crop in 1998 than in the millet pure crop, while overall higher contents were observed after preceding fallow also after four years of cropping. Striga hermonthica infestation decreased linearly with duration of preceding fallow, but also after seven years of fallow and one year of cowpea the hemi-parasitic weed still re-appeared. Overall the intensification through a cowpea pure crop and cowpea intercrop in these millet-based systems improved production and a number of other characteristics of the system, making it more viable.Treatments used in the experiments reported here are indicated by the following abbreviations, for further details see text below.     

Alarming increase in the incidence of Cucumber mosaic virus in cowpea (Vigna unguiculata (L.) Walp.) in northern Nigeria

Cowpea plays a key nutritional role in the diet of the Nigerian people. Viral diseases are a major limitation to cowpea production worldwide, and thus, constant viral surveillance is crucial for monitoring and management purposes. In this study, cowpea leaf samples from fields in three northern Nigeria states, Kano, Kaduna and Niger, were tested to determine the status of six common viruses previously reported in these cowpea-producing states following the release of virus-resistant varieties. Cowpea aphid-borne mosaic virus (CABMV), Blackeye cowpea mosaic virus (BICMV), Cowpea mottle virus, Southern bean mosaic virus and Cucumber mosaic virus (CMV) were detected. Cowpea yellow mosaic virus, which was previously reported in all three states, was not detected in any of the samples tested, while CMV that was previously regarded as unimportant to cowpea production in Nigeria had the highest incidence in all three states, and the overall highest incidence of 58.8%, while CABMV had the lowest incidence (7.5%). CMV was also present in seven of the ten mixed infection combinations detected. Dual infection of CMV and BICMV, which often results in cowpea stunt, the most devastating cowpea disease in the USA, was the most frequently detected mixed infection (28.1%) and was detected in all three states. This observed elevation in CMV infection in cowpea must be closely monitored and swiftly managed to avert possible devastating crop yield losses.