Genetically engineered virus-resistant plants in developing countries: current status and future prospects.

Plant viruses cause severe crop losses worldwide. Conventional control strategies, such as cultural methods and biocide applications against arthropod, nematode, and plasmodiophorid vectors, have limited success at mitigating the impact of plant viruses. Planting resistant cultivars is the most effective and economical way to control plant virus diseases.

Molecular cloning and structural analysis of the gene encoding Bacillus cereus exochitinase Chi36.

The chi36 gene encoding exochitinase Chi36 was cloned from a Bacillus cereus 6E1 subgenomic library. The chi36 open reading frame is 1080 bp long encoding a Chi36 precursor protein of 360 amino acids, consisting of a 27 amino acid N-terminal signal peptide and a 333 amino acid sequence found in the mature Chi36 protein of 36.346 kDa.

Molecular characterization of whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) populations infesting cassava.

Bemisia tabaci (Gennadius) populations, collected from cassava and other plants in major cassava-cultivation areas of Sub-saharan Africa and from elsewhere around the world, were studied to determine their biotype status and genetic variation. Random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) markers were used to examine the genetic structure of the populations. The dendogram obtained using the neighbour joining method (NJ) split the cassava-associated populations from the non-cassava types with a 100% bootstrap probability.

Variants of East African cassava mosaic virus and Its Distribution in Double Infections with African cassava mosaic virus in Nigeria.

In a survey for cassava mosaic begomoviruses conducted in 1997 and 1998 in Nigeria, East African cassava mosaic virus (EACMV) was detected by the polymerase chain reaction together with African cassava mosaic virus (ACMV) in 27 out of 290 cassava leaf samples of infected plants from 254 farmers' fields in five agroecological zones. One plant was infected with EACMV only. Five variant isolates of EACMV were observed based on their reactions to primers that could detect Cameroonian and East African strains of EACMV.

Purification and characterization of a Bacillus cereus exochitinase.

Five extracellular chitinases of Bacillus cereus 6E1 were detected by a novel in-gel chitinase assay using carboxymethyl-chitin-remazol brilliant violet 5R (CM-chitin-RBV) as a substrate. The major chitinase activity was associated with a 36-kDa (Chi36) gel band. Chi36 was purified by a one-step, native gel purification procedure derived from the new in-gel chitinase assay.

First Report of East African Cassava Mosaic Begomovirus in Ghana.

Virus species causing cassava mosaic disease have been categorized into three classes based on their reaction with monoclonal antibodies (MAbs) and their distribution (2). These viruses have different, scarcely overlapping distribution: African cassava mosaic begomovirus (ACMV) occurs in Africa west of the Rift Valley and in South Africa; East African cassava mosaic (EACMV) occurs in Africa east of the Rift Valley and in Madagascar; and Indian cassava mosaic virus (ICMV) occurs in India and Sri Lanka (2). During 1998, surveys were conducted in farmers' fields in Ghana to assess the incidence and reaction of local cassava cultivars to cassava mosaic disease.

Detection of episomal banana streak badnavirus by IC-PCR.

A polymerase chain reaction (PCR) based strategy to detect episomal banana streak badnavirus (BSV) in banana and plantain plants that carry integrated BSV sequences was developed. Antisera used in immuno-capture polymerase chain reaction (IC-PCR) are capable of binding a large number of BSV serotypes. The primers used for PCR are capable of annealing to and amplifying across the aspartic protease-reverse transcriptase domain boundaries of both episomal and integrated BSV sequences and result in similar or identical sequence size fragments from either template.

First Report of East African Cassava Mosaic Begomovirus in Nigeria.

Cassava (Manihot esculenta Crantz) is an important food crop in sub-Saharan Africa. One of the major production constraints is cassava mosaic disease caused by African cassava mosaic (ACMV) and East African cassava mosaic (EACMV) begomoviruses. ACMV is widespread in its distribution, occurring throughout West and Central Africa and in some eastern and southern African countries.

A New Virus on Maize in Nigeria: Maize Mild Mottle Virus.

Maize (Zea mays) and itch grass (Rottboellia cochinchinensis) plants exhibiting a mild mosaic or mottle were collected from a farmer's field near Mokwa, Nigeria, in 1993. Icosahedral virions (approximately 28 to 30 nm) were purified from symptomatic tissue by differential centrifugation in 0.1 M phosphate buffer, pH 7.

Properties of a virus causing mosaic and leaf curl disease of Celosia argentea L. in Nigeria.

A sap transmissible virus, causing mosaic and leaf curl disease of Celosia argentea, was isolated at vegetable farms in Amuwo Odofin, Tejuoso, and Abule Ado, Lagos, Nigeria. The virus had a restricted host range confined to a few species of the Amaranthaceae, Chenopodiaceae and Solanaceae families. It failed to infect several other species of the Aizoaceae, Brassicaceae, Cucurbitaceae, Fabaceae, Lamiaceae, Malvaceae, Poaceae and Tiliaceae families.

Effect of Temperature on Symptom Expression and Reliability of Banana Streak Badnavirus Detection in Naturally Infected Plantain and Banana (Musa spp.).

The effect of temperature on symptom expression and detection of banana streak badnavirus (BSV) by immunosorbent electronmicroscopy (ISEM) and enzyme-linked immunosorbent assay of 12 in vitro-propagated plantain hybrids (genome AAB × AA), 3 ABB cooking banana, and 3 AAB plantain landraces was studied. Experiments were done for 2 years under two temperature regimes, 28 to 35°C in a screenhouse and 22°C in a temperature-controlled room. Most BSV-infected plants of plantain hybrids expressed symptoms under both conditions.

Cowpea embryo rescue. 1. Influence of culture media composition on plant recovery from isolated immature embryos.

Factors responsible for successful rescue of immature embryos of cowpea [Vigna unguiculata (L.) Walp.] and V.

Identification of okra mosaic virus from Indigofera spicata in Nigeria.

Okra mosaic virus (OMV, tymovirus group) was isolated from Indigofera spicata plants growing at the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria. Its identity was established on the basis of particle morphology, analysis of viral coat protein and nucleic acid and serology. In reciprocal agar gel diffusion tests, the virus isolate from I.

Evidence that cowpea aphid-borne mosaic and blackeye cowpea mosaic viruses are two different potyviruses.

The immunoreactivity of a panel of polyclonal antibodies and monoclonal antibodies (MAbs) raised against African isolates of potyviruses from cowpea and African yam bean was examined in ELISAs. A serological study including reference isolates followed by further characterization in differential hosts resulted in separation of the potyviruses into two distinct serogroups, one containing blackeye cowpea mosaic virus (BlCMV) and the other containing cowpea aphid-borne mosaic virus (CAMV). Using biotin-labelled MAbs, the BlCMV isolates were further subdivided into two serotypes and the CAMV isolates into five serotypes.

Origin and phylogeny of Guinea yams as revealed by RFLP analysis of chloroplast DNA and nuclear ribosomal DNA.

The origin and phylogeny of the Guinea yams, consisting of the white yam (Dioscorea rotundata Poir.) and the yellow yam (D. cayenensis Lamk.