Genetic diversity in an African plantain core collection using AFLP and RAPD markers

Fifteen AFLP primer pairs (EcoRI+3 and MseI+3) and 60 10-mer RAPD primers were used to detect polymorphisms and assess genetic relationships in a sample of 25 plantains from diverse parts of Western and Central Africa. The discriminatory power of the AFLP technique was greater than that of the RAPD technique, since the former produced markers with greater polymorphic information content (PIC) than the latter. Hence, AFLP analysis appeared to be a more-powerful approach for identifying genetic differences among plantain accessions. In this regard, significant genetic diversity within the plantains was shown by the unweighted pair-group method of arithmetic averages (UPGMA) and the multidimensional principal coordinate (PCO) analyses. The AFLP-derived clusters indicated closer relationships between similar inflorescence types than the RAPD-derived clusters. A small group of cultivars from Cameroon were separated from the bulk of other plantains, suggesting that Cameroon may harbour accessions with useful or rare genes for widening the genetic base of breeding populations derived from the plantains. A greater effort should be directed at collecting and characterizing plantain cultivars from Cameroon.     

Genetic diversity in Indian cucumber based on microsatellite and morphological markers

Genetic variation among 44 cucumber accessions was assessed using morphological and SSR markers. High genetic variability was observed for days to 50% female flowering (37–46 days from sowing), number of fruits per plant (1.4–6.0), individual fruit weight (0.04–0.552 kg) and root length (14.25–32.8 cm). The pair-wise Jaccard similarity coefficient ranged between 0.25 and 0.85 indicating that the accessions represent genetically diverse populations. The allelic diversity of polymorphic markers ranged from 0.001 to 0.9396 with an average of 0.31 based on polymorphic information content. The clustering pattern of SSR markers was not in consonance with the groupings based on quantitative traits. The accession of Indian state i.e.; Madhya Pradesh and Uttar Pradesh were diverged from the accessions of other parts of India. The study provides information for future exploration and collection of cucumber germplasm in India and utilization of diverse germplasm for developing cultivars/hybrids for specific traits.     

Velamen and exodermis characters of West African epiphytic orchids in relation to taxonomic grouping and habitat tolerance

The velamen and exodermis of roots of 76 species of epiphytic orchids occurring in West Africa were examined and evaluated for the following characters: number of velamen layers; wall striations and hairs of the velamen; wall thickening and lignification of velamen and exodermal cells; size, and uniformity in shape and size, of velamen and exodermal cells. The term epi-velamen is proposed for the distinctive outermost layer of multi-seriate velamen. High correlation is reported between the number of velamen layers and taxonomic as well as habitat-tolerance groupings, together with lower, but still appreciable, correlation between the other characters evaluated and taxonomic and habitat-tolerance groupings.     

Comparative analysis of phenotypic and genotypic diversity among plantain landraces (Musa spp., AAB group)

Genetic diversity amongst 76 plantain landraces has been studied using RAPD analysis at two levels of intensity and compared with groupings based on phenotypic indices and morphotype. There was a good correlation (R²=0.78) between estimates of genetic diversity based on 76 RAPD bands and 164 RAPD bands. However, there was a poor correlation between RAPD-based estimates of genetic diversity and a phenotypic index based on agronomic characters. There was also a poor correlation between RAPD analyses and morphotype group (based on bunch type and stature). These results suggest that the traditional designations of plantain landraces based on morphotype do not provide a true reflection of overall genetic divergence. Similarly, classification systems using phenotypic indices based on agronomic characters may not provide accurate taxonomic differentiation. The level of genetic divergence within morphogroups based on bunch type suggests that True Horn plantains are derived from False Horn plantains which in turn are derived from French plantains. Genetic divergence was found to be generally quite low within the plantain landrace genepool, which is consistent with the proposed evolution of this germplasm through somatic mutation of a relatively small number of introductions. However, putative synonyms/duplicates have been shown to be genetically distinct. In contrast, a group of 12 landraces have been identified that are highly distinct from one another (showing 20–35% dissimilarity). Fertile members of this group may be useful for generating genetically diverse 2x and 4x breeding populations that can be used in breeding secondary triploid hybrid plantain varieties. Received: 8 January 2000 / Accepted: 2 March 2000     

Infraspecific variation and systematics of cultivatedSetaria italica,foxtail millet (Poaceae)

Foxtail millet (Setaria italica,) is grown as a cereal in southern Europe and in temperate, subtropical, and tropical Asia. Its closest wild relative isS. italica ssp.viridis (green foxtail). Green foxtail is native to temperate Eurasia, but was introduced and became widely established as a weed in temperate and warmer parts of the Americas. Spontaneous and cultivatedS. italica cross to produce fertile hybrids. Derivatives of such crosses, resembling foxtail millet in some inflorescence traits but with efficient natural seed dispersal, accompany the cereal across its range of cultivation. Giant green foxtail of Europe and the American corn belt is a weed of hybrid origin. Foxtail millet was domesticated in the highlands of central China; remains of cultivated foxtail millet are known from the Yang-shao culture period dating back some 5,000 yrs. Comparative morphology suggests that foxtail millet spread to Europe and India as a cereal soon after its domestication. Three cultivated races are recognized. Moharia, from Europe and southwestern Asia, includes cultivars with 5–52 culms, each bearing several, small, more or less erect inflorescences. Cultivars in race maxima are characterized by plants with 1–8 usually unbranched culms that bear large inflorescences; they occur in Transcaucasian Russia and the Far East. Race indica is intermediate in culm number (ave. 6.6) and inflorescence size between races moharia and maxima, and is cultivated in southern Asia.     

Autosomal and mtDNA Markers Affirm the Distinctiveness of Lions in West and Central Africa

The evolutionary history of a species is key for understanding the taxonomy and for the design of effective management strategies for species conservation. The knowledge about the phylogenetic position of the lion (Panthera leo) in West/Central Africa is largely based on mitochondrial markers. Previous studies using mtDNA only have shown this region to hold a distinct evolutionary lineage. In addition, anthropogenic factors have led to a strong decline in West/Central African lion numbers, thus, the conservation value of these populations is particularly high. Here, we investigate whether autosomal markers are concordant with previously described phylogeographic patterns, and confirm the unique position of the West/Central African lion. Analysis of 20 microsatellites and 1,454 bp of the mitochondrial DNA in 16 lion populations representing the entire geographic range of the species found congruence in both types of markers, identifying four clusters: 1) West/Central Africa, 2) East Africa, 3) Southern Africa and 4) India. This is not in line with the current taxonomy, as defined by the IUCN, which only recognizes an African and an Asiatic subspecies. There are no indications that genetic diversity in West/Central Africa lions is lower than in either East or Southern Africa, however, given this genetic distinction and the recent declines of lion numbers in this region, we strongly recommend prioritization of conservation projects in West/Central Africa. As the current taxonomic nomenclature does not reflect the evolutionary history of the lion, we suggest that a taxonomic revision of the lion is warranted.     

荷花品种比较试验

从始蕾、始花期、群体花期、着花密度、株型、花型等方面对41个荷花品种进行比较试验。结果表明,大株型荷花品种以祝福、西湖红莲最好;中小株型以金珠落玉盘、小精灵、绿云、小碧台、玉碗、红宝石、醉半熏、淡云、雨花、桃红小碗、红碗莲、瑶池春暖等12个品种最好,具有较高的观赏价值和商品价值。     

甘蓝型油菜若干农艺性状与单株产量的关系分析

以38个甘蓝型油菜品种为材料,对单株产量、有效分枝部位高度、主轴花序长度等11个农艺性状进行了方差分析、通径分析和聚类分析．结果显示:所有调查性状在品种间存在显著的差异;主花序长度、主序有效角果数与单株产量都有显著的遗传相关性,两者都通过有效分枝部位高度对单株产量产生较大的正向间接作用;有效分枝部位高度对单株产量的影响也较显著,高产品种具有相对较高的有效分枝部位高度;总角果数对单株产量的直接遗传通径系数虽小,但它具有最大的直接表型通径系数,它通过主序有效角果数和有效分枝数对单株产量产生了两个较大的间接作用;要获得3130kg/hm~2的产量,重点应具备果多、枝多的特征,总角果数不少于657个,有效分枝数不少于18个．     

QTL analysis for pseudostem pungency in bunching onion (Allium fistulosum)

Low pungency is one of the most important agronomic traits in bunching onion (Allium fistulosum L.). Although the degree of pungency can be evaluated indirectly using a colorimetric test for pyruvic acid, DNA markers linked to low-pungency quantitative trait loci (QTLs) are still desired. In this study, we evaluated pungency in the bunching onion pseudostem through six trials conducted over 3?years using an F _2:3 population. QTL analysis based on the genetic linkage map revealed that the major pungency QTL was located within a 24.2-cM interval on Chr. 2a. The low-pungency parent-derived allele at AFAT04B03, a simple sequence repeat locus linked to the pungency QTL, was rare among commercial bunching onion cultivars. In addition, individuals homozygous for the low-pungency parent-derived allele at AFAT04B03 were significantly less pungent than those that were homozygous or heterozygous. Thus, these findings suggest that AFAT04B03 is an effective selection marker for low pungency in bunching onion breeding.     

Ancestral state reconstruction reveals multiple independent evolution of diagnostic morphological characters in the "Higher Oribatida" (Acari), conflicting with current classification schemes

Background  

The use of molecular genetic data in phylogenetic systematics has revolutionized this field of research in that several taxonomic groupings defined by traditional taxonomic approaches have been rejected by molecular data. The taxonomic classification of the oribatid mite group Circumdehiscentiae ("Higher Oribatida") is largely based on morphological characters and several different classification schemes, all based upon the validity of diagnostic morphological characters, have been proposed by various authors. The aims of this study were to test the appropriateness of the current taxonomic classification schemes for the Circumdehiscentiae and to trace the evolution of the main diagnostic traits (the four nymphal traits scalps, centrodorsal setae, sclerits and wrinkled cuticle plus octotaxic system and pteromorphs both in adults) on the basis of a molecular phylogenetic hypothesis by means of parsimony, likelihood and Bayesian approaches.     

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 new species of the wild dragon tree, Dracaena (Dracaenaceae) from Gran Canaria and its taxonomic and biogeographic implications

The arborescent taxa of Dracaena which form the dragon tree group comprise five species found in Macaronesia, Morocco (D. draco), East Africa (D. ombet, D. schizantha), Arabia (D. serrulata) and the island of Socotra (D. cinnabari). A new species of dragon tree, Dracaena tamaranae A. Marrero, R. S. Almeida & M. Gonzalez-Martin, is described from Gran Canaria, Canary Islands. This new species differs from D. draco, the only other Dracaena species currently known in Macaronesia, in having a growth form and inflorescence type and leaves more similar to the East African and Arabian species of Dracaena. In contrast, D. draco appears to be related to D. cinnabari. In this paper, we also present a study of the taxonomy, habitat and ecology of all the species of the dragon tree group. These are found in thermo-sclerophyllous plant communities of tropical-subtropical regions which are rather xerophilous and have a rainfall range of 200–500 mm. Our study indicates two independent colonization events for Dracaena in Macaronesia. In addition, we suggest that the dragon tree group provides an example of two major biogeographical disjunctions between East and West Africa. We postulate that this group has a Tethyan origin, a hypothesis supported by fossil and palaeoclimatic data, and thus parallels the distribution and dispersal pattern of other taxonomic groups.     

Wood anatomy and vessel characteristics of spiny monkey orange (Strychnos spinosa) in Benin (West Africa)

The response of plant species to varying climate conditions in tropical Africa remains poorly understood but can be assessed using wood anatomical traits. These traits play an important role for the adaptive capacity of a species to environmental stress, since environmental conditions can modify the proportion, size, and morphology of wood anatomical elements. This study reports quantitative data on vessel characteristics of the diffuse porous angiosperm Spiny monkey orange (Strychnos spinosa Lam.) in Benin in tropical West Africa. The vessel-related anatomical traits varied with high amplitude (coefficient of variation CV ˃ 25%) between different sites located in different climate zones. The variability of the traits is higher within one climatic zone than between climatic zones, and even more pronounced within trees. Consequently, the climatic zones have less influence on the studied features than local site conditions. However, the study showed that S. spinosa individuals that have numerous vessels also have a high lumen fraction and total ring area. On the other hand, individuals presenting a high vessel density also display vessels of smaller size. The correlation between vessel number and total ring area on the one hand, and between vessel size and lumen fraction on the other hand are highly significant and positive. In Benin, S. spinosa wood anatomical traits are likely linked to local site factors rather than to regional climatic factors.     

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.     

紫丁香195个实生单株花表型性状变异分析

为了准确掌握紫丁香资源花部性状的变异程度及表型多样性水平,为紫丁香优良品种的选育提供理论依据。本研究以195株紫丁香实生单株为材料,对其5个数量性状和4个质量性状的变异、性状间相关性和聚类关系等进行了分析。结果表明,5个数量性状在群体内表现出极显著差异(P<0.01),且符合正态分布,变异系数为19.72%~30.22%,平均24.97%,其中花序长变异最大;根据ISCC-NBS色彩名称表示法将群体花色划分为白色系、浅粉色系、紫色系、紫红色系、紫粉色系和蓝紫色系等6个色系,其中紫色系(54.35%)和紫红色系(32.31%)所占比例最大;4个质量性状的多样性指数为0.36~1.09,平均0.86,其中花冠裂片(状态)最大,表明群体中质量性状变异类型丰富。相关性分析表明,5个数量性状之间均呈现极显著正相关,其中花序长与花序宽相关系数最大,为0.767。聚类分析表明,195株紫丁香基于欧氏距离可分为3大类,第一类群主要性状表现为花冠筒长;第二类群表现为花序长;第三类群表现为花冠裂片长。参试紫丁香资源花部性状表型变异丰富。     

Emitted and endogenous floral scent compounds of Prunus mume and hybrids

Prunus mume is the only species of Prunus known to produce a strong floral fragrance. Most interspecific hybrids between P. mume and other species of Prunus lack the fragrance. The analysis of variations in emitted and endogenous compounds among genetically close cultivars is a powerful approach for revealing the mechanisms underlying floral scent emission. Compounds emitted by flowers from five cultivars were collected using the static headspace method, and endogenous compounds in the flowers were extracted with ethyl acetate. Samples were analysed quantitatively and qualitatively using gas chromatography-mass spectrometry. The result showed that benzenoids were the dominant compounds, of which benzyl acetate was the principal component contributing to the floral scent of P. mume. A clustering analysis of the floral volatiles from the different cultivars suggested that the scent traits of hybrids are related to the taxonomic relationship between their parents. The correlations between the amount of the endogenous and emitted compounds revealed that benzyl acetate had a stronger tendency to be volatile than the other compounds and the volatilisation rate of volatile compounds varied greatly among different cultivars. The importance of the biosynthetic pathway and the function of benzaldehyde are discussed.     

广东大蕉分类位置的探讨

本文从形态特征,减数分裂,染色体配对以及核型分析等三个方面探讨了广东大蕉在属内的分类位置问题,根据１５个形态特征的比较评分,染色体组同源性和核型特征的分析结果,广东大蕉应属ＢＢＢ类型。它的学名应为Ｍｕｓａ ｂａｌｂｓｉａｎａ Ｃｏｌｌａ（ＢＢＢｇｒｏｕｐ）。     

Flowering dynamics in Arum italicum (Araceae): relative role of inflorescence traits, flowering synchrony, and pollination context on fruit initiation

We studied the relative role of inflorescence traits, flowering synchrony, and pollination context for infructescence and fruit initiation in two Spanish populations of Arum italicum, a species in which inflorescences are the pollination unit. In this species, a specialized inflorescence organ, the appendix, is important for pollinator attraction. However, the short floral longevity and the production of mostly one inflorescence per plant make its pollination potentially dependent on strong flowering synchrony and on external factors not controlled by the plant (the pollination context). The flowering period in both sites lasted >3 mo. Day-to-day variation in simultaneous antheses was high, and 11-50% of antheses occurred on days during which no pollen donor was present. Inflorescence traits, flowering synchrony, and between-plant distance all influenced infructescence and fruit initiation, but their relative importance differed between sites. In one large population, infructescence initiation was positively related to inflorescence traits; in a smaller population infructescence initiation increased with the number of donor inflorescences. In both sites, percentage of fruits initiated per infructescence was dependent on a combination of inflorescence traits, flowering synchrony, and between-plant distance. Plants producing 2-4 inflorescences had higher probability of infructescence initiation and overlapped their antheses with more plants than single-inflorescence ones.     

Enzyme diversity in pearl millet (Pennisetum glaucum)

Summary The survey of enzyme polymorphism in West African pearl millet cultivars reported by Tostain et al. 1987 has been extended to include populations from other regions of Africa and from India. The eight enzyme systems studied included: alcohol dehydrogenase, -esterase, catalase, phosphoglucoisomerase, phosphoglucomutase, 6-phosphogluconate dehydrogenase, glutamate oxaloacetate transaminase, and malate dehydrogenase. One-hundred-ninety-nine populations of millet were analyzed, including 74 populations studied earlier. No new enzyme diversity was observed. Intrapopulation diversity ranged from 70%–90% of the total diversity, depending on their regions of origin. Four principal groups were distinguished in the following decreasing order of diversity: early-maturing cultivars from West and East Africa, late — maturing cultivars from West and East Africa, cultivars from India, and cultivars from southern Africa. The early-maturing cultivars were distributed between two principal focal points from East Africa in the East to Mali in the West. In the center were found millets from Niger which were most diverse. Indian and southern African cultivars were distinct, with the former appearing relatively similar to those of Niger, and the latter somewhat similar to late-maturing cultivars from West Africa, a diverse group that included late-maturing cultivars from East Africa. Based on the results obtained, an evolutionary hypothesis proposed here includes: multiple domestications in the Sahel, creation of early-maturing cultivars and their migration eastwards to India plus a southwards migration to Sudanian zone, and creation of late-maturing cultivars and their migration simultaneously westwards, eastwards, and southwards to southern Africa.