Oluyemisi A. Akinyemiju

Primary Somatic Embryos from Axillary Meristems and Immature Leaf Lobes of Selected African Cassava Varieties

The study evaluated high-value African cassava varieties for primary somatic embryogenesis usingaxillarymeristems (AM) and immature leaf lobes (LL) on picloram based medium. The study was conducted at the Central Biotech Lab, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria between 2006 and 2009. Completely randomized design with four replicates was used for the study. Using LL explants, there were significan t (P=.05) differences in percent responding leaf lobes, percent explant with pre -embryogenic structure, PSEF and PSEE among cassava varieties. The PSEF of the only three varieties that produced mature somatic embryo were 93.6, 88.5 and 85.7% for TME 12, Ki

Response of soil mites to hexazinone application in Nigeria

Abstract Soil samples were taken periodically from plots treated with hexazinone (1.0 kg a.i./ha) and untreated control plots at different depths of the Obafemi Awolowo University Teaching and Research Farm before hexazinone application and for a period of 112 days after application (DAA). Soil samples were also taken at the 0–7.5 cm layer in an adjacent undisturbed forest plot. Mites were extracted from the soil samples and compared for differences and similarities in densities. In the control plots, the 0–7.5 cm soil layer supported the highest percentages of soil mites on all sampling occasions while in the hexazinone plots the 7.5–15.0 cm soil layer supported the highest percentages of soil mites between 84 and 112 days after application. During the first 56 days, mite densities decreased in the forest and increased in the untreated control plots. Between 56 and 112 days after application, mite densities increased in the forest, did not change in the control plots and decreased in the hexazinone plots. Almost all dominant mite groups were significantly less abundant in the hexazinone plots than the untreated control plots in the 0–7.5 and 7.5–15.0 cm soil layers. At the 15.0–22.5 cm soil layer, the density of Annectacarus sp. was unusually very high in the hexazinone plots.

Influence of Type and Age of Primary Somatic Embryo on Secondary and Cyclic Somatic Embryogenesis of Cassava ( Manihot esculenta Crantz)

This study investigated the influence of age of the cotyledons, cut from primary somatic embryos (PSE) developed from shoot meristems (SM) or immature leaf lobes (LL), on secondary somatic (SSE) and cyclic (CSE) embryogenesis of two cassava cultivars at th e Central Biotech Laboratory, International Institute of Tropical Agriculture (IITA), Ibadan, between 2006 and 2010. A completely randomized design with three replicates was used for the study. Only PSE at the age of 4 weeks recorded significant (P<0.05) d ifferences in SSE frequency and efficiency between the SM and LL sources. CSE production was highest using 0 to 4 weeks old SSE cotyledons, and significant (P<0.05) differences were only recorded between the SM and LL sources when the age of the SSE cotyle dons was older than 6 weeks. The CSE frequencies from the SM source were significantly greater than that from the LL source when 8 and 10 week -old SSE cotyledons were used. The OriginalResearch Article

In vitro Propagation of Solanecio biafrae and Determination of Genetic Stability of Plantlets Using RAPD and ISSR Markers

Abstract An efficient and reproducible micropropagation protocol of Solanecio biafrae (Oliv. & Hiern) C. Jeffrey has been developed from nodal stem segments. Shoot development was obtained on Murashige and Skoog (MS) medium supplemented with benzylaminopurine (BAP) alone and in combination with zeatin and 1-naphthaleneacetic acid (NAA). Elongated shoots were rooted in the presence of zeatin or 3-indole-butyric acid (IBA) alone or in combinations. The highest number of explants forming shoots (100%) as well as the highest number of shoots per explant (3.4) and the longest shoots (22 mm) were recorded on medium containing 4.0 mg·dm−3 BAP, 2.0 mg·dm−3 NAA, and 1.0 mg·dm−3 zeatin. About 76% of shoots formed roots on half-strength MS medium free of plant growth regulators. The best root formation (approximately 88%) was recorded on the medium containing 1.0-1.5 mg·dm−3 IBA. The micropropagated shoots with well-developed roots were efficiently acclimatized under greenhouse conditions. The random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) amplification products were monomorphic in micropropagated plants and similar to those of mother plant showing their genetic uniformity. This is the first report of micropropagation of S. biafrae, which will facilitate in vitro mass propagation, conservation, and germplasm exchange of this endangered African vegetable.

Somatic embryogenesis and regeneration of five multipurpose cassava landraces extensively integrated in African cropping system

ABSTRACT Successful development and adoption of transgenic cassava (Manihot esculenta Crantz) varieties in Africa depend on in vitro regeneration of landraces because of their agronomic value and amenability to genetic modification. The study investigated somatic embryogenesis from axillary bud and immature leaf-lobe explant and regeneration via shoot organogenesis in five cassava landraces. Landraces exhibited significant (P < 0.05) differences in frequencies of primary somatic embryo production, number of embryos per explant, and frequency of secondary embryos. The frequency of primary somatic embryogenesis ranged from 7.8 to 14.5%, whereas the number of embryos per explant varied from 5.3 to 10.6. However, only frequency of primary somatic embryos and number of embryos per explant showed significant (P < 0.05) differences when immature leaf lobe was used as explant. The frequency of primary somatic embryogenesis ranged from 42.7 to 49.2%, whereas number of embryos per immature leaf-lobe explant varied from 9.5 to 15.2 per explant. Secondary embryogenesis was cultivar-independent in the case of immature leaf-lobe explant. Cyclic and green (mature) embryogenesis showed no significant (P < 0.05) landrace differences in both axillary bud and immature leaf-lobe explants. Shoot regeneration from cotyledon of somatic embryos had significant (P < 0.05) landrace differences. The mean shoot-bud formation frequency of axillary bud and immature leaf-lobe explants was 51.4% and 37.2%, respectively. Root formation was efficient, with greater than 70% of shoots forming root in all landraces. Similarly, landrace differences were detected for the survival of acclimatized regenerated plants, with a mean of 94.7% for both explants. In conclusion, somatic embryos were produced from immature leaf and axillary bud explants of the landraces and the embryos were converted to plantlets via shoot organogenesis.

Tissue- and Organ-Specific Promoters for Expression of Heterologous Genes inTransgenic Cassava (Manihot Esculenta Crantz) Plants

Promoters are regions of DNA that initiates transcription of genes. A number of promoters have been identified that confer high level of expression of heterologous genes in transgenic plants. Some promoters have constitutive expression as they are active in all circumstances in the cell, while others are regulated, becoming active in certain cell or in response to specific stimuli. Despite the availability of tissue- and organ-specific promoters, most transgene expressions in Cassava are driven by constitutive cauliflower mosaic virus promoter. This paper examines the availability of promoters for transgene expression in plants, assesses the use of promoters for transgene expression in Cassava and establishes the need for tissue- and organ-specific promoters for expression of heterologous genes in Cassava.

Shoot Induction from Axillary Bud of β-Carotene Enriched Manihot esculenta Crantz and Molecular Stability of Regenerants

Abstract Inadequacy of planting materials is limiting the distribution of three high-β-carotene (pro-vitamin A) cassava varieties released in Nigeria to increase public vitamin A intake. However, studies have established the suitability of in vitro shoot culture for mass propagation of elite crop varieties for quick distribution to farmers. We investigated multiple shoot induction from axillary bud of three β-carotene enriched cassava varieties using BAP and assessed the genetic stability of the regenerated plants to establish mass propagation system. Multiple shoots were induced from BAP-enlarged axillary bud on basal medium supplemented with 10 mg/l BAP. Shootbuds were elongated on basal medium supplemented with 1.0 mg/l BAP and 10.0 IBA mg/l. Genetic stability of regenerated plants was assessed byeight RAPD markers. There were significant (P < 0.05) differences in survival of isolated axillary bud, shootbud formation, survival of shootbud, regenerated shoots, root formation and survived regenerated plants among cassava varieties. The order of shootbud formation among the cassava varieties was UMUCASS 37 > UMUCASS 36 >TMS 30555 > UMUCASS 38. The best (83.4%) shoot regeneration was recorded in TMS 30572 and lowest (47.8%) in UMUCASS 37, however, UMUCASS 36 recorded the best (98.5%) survival of regenerated shoot after hardening. Eight RAPD primers produced 56 bands, ranging from 200 to 3000 bp in size. RAPD analysis showed a uniform profile among regenerants and between mother plant and regenerants. The study concluded that multiple shoot formation could be induced in pro-vitamin A cassava varieties using BAP from axillary bud with no genetic infidelity of the regenerants.