Somatic embryogenesis and plant regeneration through cell suspensions inMusa acuminata

Summary Cell suspensions ofMusa acuminata sspburmannicoides andMusa acuminata sspmalaccensis were obtained by culturing embryogenic callus initiated from immature zygotic embryos in liquid medium. Plant regeneration was then achieved through somatic embryogenesis. Germination of these embryos occurred in a modified MS medium containing auxin and cytokinin. Plant recovery frequencies were 20 to 36%. This method may allow a better utilization of biotechnologies in genetic improvement of theMusa diploid species, essential for banana and plantain breeding.     

Somatic embryogenesis in plantain banana

Summary A cell suspension of French Sombre plantain banana (Musa spp. AAB genome) was initiated from callus obtained from young male flowers. Histological examination enabled us to describe and follow the evolution of the suspension consisting of: embryogenic aggregates, proembryos, nodules, and isolated cells. It demonstrated the unicellular origin of somatic embryos, either during maintenance of the suspension or after plating on a semisolid medium. The cells from which the embryos originated had no starch but only protein reserves. Plating 1 ml of packed cells from the suspension led to the formation of 10⁵ embryos of which 10 to 40% could be converted into plantlets.     

Histology of somatic embryo initiation and organogenesis from rhizome explants of Musa spp.

The origin of somatic embryos derived from rhizome explants of triploid Musa cv. Grand Nain was the subject of histological studies during different phases of ontogenetic development. The investigation revealed that the majority of somatic embryos showed normal root formation and consisted of highly vacuolated cells in the poorly structured shoot apex. The embryogenic mass and somatic embryos were mostly derived from several morphologically competent cells. Single cell origin depended on the presence of organogenetically functional vascular cells of rhizome explants and occurred infrequently. The implications of these findings for genetic improvement of banana and plantain by in vitro mutation breeding and gene technology are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Peroxidase activity of desiccation-tolerant loblolly pine somatic embryos

Summary Desiccation tolerance can be induced by culturing somatic embryos of loblolly pine (Pinus taeda L.) on medium supplemented with 50 μM abscisic acid (ABA) and/or 8.5% polyethylene glycol (PEG₆₀₀₀). Scanning electron microscopy of desiccated somatic embryos showed that the size and external morphology of the desiccation-tolerant somatic embryos recovered to the pre-desiccation state within 24–36 h, whereas the non-desiccation-tolerant somatic embryos did not recover and remained shriveled, after rehydration. Peroxidase activity of desiccated somatic embryos increased sharply after 1 d of desiccation treatment at 87% relative humidity (RH), and desiccation-tolerant somatic embryos had higher peroxidase activity compared to sensitive somatic embryos. Higher peroxidase activity of desiccation-tolerant somatic embryos may have allowed them to catalyze the reduction of H₂O₂ produced by drought stress, and protected them from oxidative damage.     

Induction of somatic embryogenesis and plant regeneration from cotyledon and hypocotyl explants of <Emphasis Type="Italic">eruca sativa</Emphasis> mill

Summary A protocol was developed for high frequency somatic embryogenesis and plant regeneration from cotyledon and hypocotyl explants of Eruca sativa. Explants grown on Murashige and Skoog (MS) medium supplemented with 4.52 μM 2,4-D formed embryogenic callus after 4 wk of culture. Secondary somatic embryos were also produced from primary somatic embryos on MS medium containing 0.56 μM 2,4-D. Somatic embryos developed into mature embryos on MS medium in the presence of 45 gl⁻¹ polyethylene glycol. After desiccation, somatic embryos developed into plantlets by culturing the mature somatic embryos on 1/2 x MS medium containing 0.24 μM indole-3-butyric acid.     

Banana and plantain production systems in Benin: ethnobotanical investigation,varietal diversity,pests, and implications for better production

Background

The cultivated banana and plantain (Musa spp.) are valuable for nutritional and socio-economic security for millions of people worldwide. In Benin, banana and plantain are among the most produced, consumed, and traded commodities. Its production is mainly for local consumption and remains insufficient to the demand. However, the varietal diversity of banana and plantain cultivated in Benin is not documented. This study aims at characterizing the banana and plantain cropping systems, genetic diversity, and production constraints as a baseline to the full utilization of this resource in crop improvement and to identify the potential production and agronomic qualities.

Methods

A baseline investigation of ethnobotanical attributes of banana cultivars was done in 51 randomly chosen villages in southern Benin. Interviews with randomly selected representative farmers were carried out. Key informant interviews and focus group discussions were used for global confirmatory investigation of survey data. Socio-demographic data and indigenous knowledge on the farmer uses of banana and plantain diversity, such as cultural practices, origin, and availability of banana and plantain planting materials, and the constraints and criteria of varietal preference cited by farmers were ranked.

Results

Eighty-seven locally recognized cultivars were found: 73 of banana and 14 of plantain groups. The most popular cultivars were Sotoumon (banana) (52.94%), Aloga (plantain) (41.17%), Planta (banana) (33.33%), and Adjangan (plantain) (27.45%). Of the eleven production constraints identified, the main biotic challenges were banana weevil Cosmopolites sordidus Germar and banana bunchy top virus (BBTV), while abiotic problems were drought and the wind. Some local varieties like Amandan, Assonwonnou, Coleti, and Ninkouin are extremely rare owing to agronomic and economic preference perceptions.

Conclusion and implications

This study provides a baseline for banana diversity in Benin and the West African region and entry points for biological characterization and production improvement. This would enable the exploitation of this resource for plant breeding towards biotic and abiotic challenges facing banana production.

     

A historical overview of the appearance and spread of Musa pests and pathogens on the African continent: highlighting the importance of clean Musa planting materials and quarantine measures

The genus Musa is not native to Africa. It evolved in tropical Asia, from southwest India eastward to the island of New Guinea. There is a growing circumstantial evidence which suggests that the East African Highland banana and the tropical lowland plantain were cultivated on the African continent since before 1 AD. It is also probable that ABB cooking and AB and AAB dessert cultivars were brought to the continent from India by Arabian traders from 600 AD, and that these were disseminated throughout East Africa. During the colonial era, the main centres of distribution for banana cultivars were botanical gardens, such as Zomba in Malawi, Entebbe in Uganda and Amani in Tanzania. It appears that the very early introductions of Highland banana and plantain arrived in Africa as a relatively clean material without the conspicuous pests and diseases that affect them in Asia. In contrast, several devastating problems now impact the crop in Africa, including nematodes, the borer weevil and diseases, most notably banana bunchy top, banana streak, Sigatoka leaf spots, Xanthomonas wilt and Fusarium wilt. We (a) provide chronological overviews of the first reports/observations of different Musa pests and pathogens/diseases in Africa, (b) highlight specific examples of when a pest or pathogen/disease was introduced via planting materials and (c) give recent examples of how the pests and pathogens spread to new regions via planting materials. In total, these production constraints threaten banana and plantain production throughout the continent and impact those who can ill afford lost production, the small‐holder producer. Our intent in this review is to highlight the significance of these problems and the great importance that infested planting materials have played in their development.     

Relationships between nematodes, weevils, banana and plantain cultivars and damage

Infestation of banana and plantain suckers by nematodes (Pratylenchus good-eyi, Radopholus similis and Helicotylenchus multicinctus) and weevils (Cosmopolites sordidus) increased with time from establishment in a field of eight different cultivars. There was a strong association between nematode and weevil infestation; suckers infested with nematodes were more than four times more likely to be infected by weevil than suckers without nematodes. Weevil damage, measured by percentage coefficient of infestation (PCI) at harvest of the bunch, was higher on a plantain (cv. Gonja) and on an east African highland cooking banana (cv. Lusumba) than on the sweet and multi-purpose cultivars. There was a correlation between numbers of male weevils caught in a plot and the mean PCI measured in the plot, but no correlation with female numbers.     

Somatic embryogenesis and plant regeneration from floral explants of cacao (Theobroma cacao L.) using thidiazuron

Summary A procedure for the regeneration of cacao (Theobroma cacao) plants from staminode explants via somatic embryogenesis was developed. Rapidly growing calli were induced by culturing staminode explants on a DKW salts-based primary callus growth (PCG) medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and thidiazuron (TDZ) at various concentrations. Calli were subcultured onto a WPM salts-based secondary callus growth medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and 1.4 nM kinetin. Somatic embryos were formed from embryogenic calli following transfer to a hormone-free DKW salts-based embryo development medium containing sucrose. The concentration of TDZ used in PCG medium significantly affected the rate of callus growth, the frequency of embryogenesis, and the number of somatic embryos produced from each responsive explant. A TDZ concentration of 22.7 nM was found to be the optimal concentration for effective induction of somatic embryos from various cacao genotypes. Using this procedure, we recovered somatic embryos from all 19 tested cacao genotypes, representing three major genetic group types. However, among these genotypes, a wide range of variation was observed in both the frequency of embryogenesis, which ranged from 1 to 100%, and the average number of somatic embryos produced from each responsive explant, which ranged from 2 to 46. Two types of somatic embryos were identified on the basis of their visual appearance and growth behavior. A large number of cacao plants have been regenerated from somatic embryos and established in soil in a greenhouse. Plants showed morphological and growth characteristics similar to those of seed-derived plants. The described procedure may allow for the practical use of somatic embryogenesis for clonal propagation of elite cacao clones and other applications that require the production of a large number of plants from limited source materials.     

Somatic embryogenesis and plant regeneration from cell suspension cultures of Rajeli (AAB), an endangered banana cultivar

Rajeli (AAB), a commercially valuable Indian banana cultivar, is presently under the threat of extinction due to various diseases, warranting development of the strategies for its conservation and incorporation of disease resistance. This elite genotype was successfully regenerated in vitro via establishment of cell suspensions followed by somatic embryogenesis. The immature male flower buds were cultured on gelled Murashige and Skoog medium supplemented with 4 mg/l 2,4-D, 1 mg/l each of IAA and NAA, D-Biotin, 100 mg/l Malt Extract, 100 mg/l L-Glutamine and 30 g/l sucrose. Embryogenic calli with translucent somatic embryos were observed after 4 months of male flower bud culturing. Fine embryogenic cell suspensions were established in the liquid medium of same composition but with 45 g/l sucrose. Of the various sugars tested, maltose in the maintenance medium yielded better growth of plated cells as compared to sucrose, fructose and dextrose. Embryos differentiated at a high frequency and mature somatic embryos developed into plantlets on MS medium supplemented with 0.5 mg/l BAP. Approximately 40 % of the torpedo stage somatic embryos germinated and developed into complete plants. The regenerated plants exhibited normal phenotype during acclimatization in the greenhouse. The technique can be employed for conservation of this endangered cultivar and its improvement via mutagenesis and genetic transformation.     

Structure and composition of snake assemblages across three types of plantation in south‐eastern Nigeria

Assemblage structure, diversity measures and diversity/dominance patterns of snakes were studied between 1996 and 2013 in three types of plantation in the Niger River delta of southern Nigeria. The investigated plantation types were pineapple, banana/plantain, and cassava/yam. Over 74% of the census species (n = 27) were found in all three plantation types, with, overall, just two singletons (Bitis nasicornis, Lamprophis olivaceus) being observed. Despite an overall similarity in the taxonomic species composition, a principal component analysis placed the three plantation types in distinct zones of the multivariate space. Diversity/dominance diagrams for the three plantation types showed that banana/plantain and cassava/yam were nearly identical in terms of evenness profile, whereas the pineapple plantation had a higher evenness.     

Dietary fibre components and pectin chemical features of peels during ripening in banana and plantain varieties

The effects of the ripeness stage of banana (Musa AAA) and plantain (Musa AAB) peels on neutral detergent fibre, acid detergent fibre, cellulose, hemicelluloses, lignin, pectin contents, and pectin chemical features were studied. Plantain peels contained a higher amount of lignin but had a lower hemicellulose content than banana peels. A sequential extraction of pectins showed that acid extraction was the most efficient to isolate banana peel pectins, whereas an ammonium oxalate extraction was more appropriate for plantain peels. In all the stages of maturation, the pectin content in banana peels was higher compared to plantain peels. Moreover, the galacturonic acid and methoxy group contents in banana peels were higher than in plantain peels. The average molecular weights of the extracted pectins were in the range of 132.6-573.8 kDa and were not dependant on peel variety, while the stage of maturation did not affect the dietary fibre yields and the composition in pectic polysaccharides in a consistent manner. This study has showed that banana peels are a potential source of dietary fibres and pectins.     

Somatic Embryogenesis and Bud Formation on Cultured Fagopyrum esculentum Hypocotyls

An indirect somatic embryogenesis via the development of proembryogenic cell complexes (PECC) was observed in the in vitro cultured hypocotyl explants of 4–5-day-old buckwheat (Fagopyrum esculentum Moench.) seedlings. PECC development was shown to depend on culturing conditions, including 2,4-D concentration and the period of explant exposure to 2,4-D, sucrose concentration, and explant density. The culturing protocol was designed to ensure the development of buckwheat somatic embryos in two-month period. The cytogenetic analysis demonstrated that this protocol did not affect the chromosome numbers in the regenerated plants.     

A tissue culture technique for rapid clonal propagation and storage under minimal growth conditions of Musa (Banana and plantain)

A tissue culture technique for rapid clonal propagation and storage under minimal growth conditions is presented in this paper. Shoot-tip cultures of Musa cultivars (both banana and plantain) are induced by culturing small excised shoot apices on modified MS semisolid medium supplemented with various concentrations and combinations of auxins and cytokinins. The effects of cytokinin concentration in the medium as well as the genotypic configuration of the cultivars on the rate of shoot-bud proliferation have been tested. The established shoot-tip cultures grown on modified MS semisolid medium supplemented with IAA (0.18 mg/l) and BA (2.30 mg/l) have been successfully stored at 15°C with 1000 lux light intensity up to 13–17 months depending on the cultivar. The cultivars tested in the present investigation seem to vary in their ability to withstand minimal growth temperature.Abbreviations BA Benzyladenine - IAA Indoleacetic acid - IBA Indolebutyric acid - MS Murashige and Skoog     

Ultrastructural changes and the distribution of arabinogalactan proteins during somatic embryogenesis of banana (Musa spp. AAA cv. 'Yueyoukang 1')

A better understanding of somatic embryogenesis in banana (Musa spp.) may provide a practical way to improve regeneration of banana plants. In this study, we applied scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to visualize the ultrastructural changes during somatic embryogenesis of banana (Musa AAA cv. 'Yueyoukang 1'). We also used histological and immunohistochemical techniques with 16 monoclonal antibodies to study the spatial distribution and cellular/subcellular localization of different arabinogalactan protein (AGP) components of the cell wall during somatic embryogenesis. Histological study with periodic acid-Schiff staining documented diverse embryogenic stages from embryogenic cells (ECs) to the late embryos. SEM revealed a mesh-like structure on the surface of proembryos which represented an early structural marker of somatic embryogenesis. TEM showed that ECs were rich in juvenile mitochondria, endoplasmic reticulum and Golgi stacks. Cells in proembryos and early globular embryos resembled ECs, but they were more vacuolated, showed more regular nuclei and slightly more developed organelles. Immunocytochemical study revealed that the signal of most AGP epitopes was stronger in starch-rich cells when compared with typical ECs. The main AGP component in the extracellular matrix surface network of banana proembryos was the MAC204 epitope. Later, AGP immunolabelling patterns varied with the developmental stages of the embryos. These results about developmental regulation of AGP epitopes along with developmental changes in the ultrastructure of cells are providing new insights into the somatic embryogenesis of banana.     

Plant regeneration,developmental pattern and genetic fidelity of somatic embryogenesis derived Musa spp.

Multiplication of banana cvs. Grand Naine (Musa AAA, Cavendish-sub group) and Rasthali (Musa AAB, Silk-sub group) were attempted through somatic embryogenesis. The influence of position of male flower buds, amino acid supplements in the induction of somatic embryogenesis and field performance of embryogenic cell suspension (ECS) derived banana plants were studied. Differentiated immature male flower buds positioned at 6–8?th bract whorl as explants showed better callus induction and somatic embryogenesis. Supplementation with glutamine at 400?mg?L^?1 along with 20:20?g?L^?1sucrose: maltose in maturation media induced a 10-fold increase in somatic embryo formation compared to control. Cotyledonary stage somatic embryos desiccated for 2?h showed higher germination compared to non-desiccated embryos. The plantlets generated were hardened, and the genetic fidelity of the plantlets was confirmed using ISSR marker. To check the field performance of ECS derived plants, plantlets were hardened and planted in the field along with meristem and sucker. During the field growth, these ECS derived plants were morphologically similar to those of control plants. In this experiment, it was observed that ECS derived banana plants displayed normal phenotype as that of plants grown from meristem and sucker. The protocol developed could be useful highly for large-scale micropropagation or genetic manipulation studies in these commercially important banana cultivars.     

Somatic embryogenesis, plant regeneration and cyanogenesis in Manihot glaziovii Muell. Arg. (ceara rubber)

 The report describes a system for somatic embryogenesis and direct plant regeneration from the embryos of Manihot glaziovii. Somatic embryos were obtained by culturing young leaf lobes (3–6 mm long) adjacent to the apex in Murashige and Skoog medium containing 18 μm 2,4-dichlorophenoxy acetic acid for 20 days and then transferring them to a maturation medium with 0.5 μm 6-benzylaminopurine. Secondary embryogenesis was induced from cotyledonary segments of somatic embryos by using the same protocol as that for primary embryogenesis. For regeneration, somatic embryos were cultured in medium supplemented with 10⁻⁴ m kinetin and 53.4% of them developed into plantlets. Linamarin and linamarase were not detected in calli or in somatic embryos. Linamarin content was found to be highest in leaves of regenerated plantlets, followed by stem and root tissues. Levels of linamarase activity were almost the same in leaves and stem tissues and very low in roots. Received: 19 April 1999 / Revision received: 11 August 1999 / Accepted: 17 August 1999     

Somatic embryo formation and germination from immature embryo-derived suspension-cultured cells of Angelica sinensis (Oliv.) Diels

Embryogenic callus was induced from immature embryos of Angelica sinensis cultured on Murashige and Skoog (MS) basal medium. Embryogenic callus growth was more rapid on MS basal medium than on B5 or White medium. Embryogenic callus was used to establish a suspension culture and somatic embryos and germinating embryos developed during the culture. A shaking speed of 80 rpm was found to be optimal for establishing suspension cultures, while 100 rpm produced more somatic embryos and germinating embryos with an initiation cell density of 0.2 ml packed cell volume/25 ml medium. Adding 0.3% agar to the liquid medium also stimulated the formation of somatic and germinating embryos. While no plant growth regulators were needed for culture initiation and plant regeneration, the addition of 0.5–1 mg/l 2,4-dichlorophenoxyacetic acid was needed to maintain the embryogenic suspension culture by preventing embryo germination. Forty percent of the germinating embryos survived after culturing on filter paper moistened with liquid half-strength MS medium containing 3% sucrose. The plants were successfully transferred into soil. Received: 19 March 1997 / Revision received: 21 November 1997 / Accepted: 19 January 1998     

大豆体细胞胚系培养及其微卫星DNA稳定性研究(简报)

植物离体培养是植物基因操作中的重要一环,也是植物个体发育研究中基因表达研究的有益参考体系。在继代培养过程中发生的遗传变异有时会使再生植株丧失优良的性状而需加以控制和避免。为此,首先需要了解培养过程中的遗传变异情况。