Are Phenological Observations Sufficient to Estimate the Quality of Seed Crops from a <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> Open-pollinated Seed Orchard? Consequences for Seed Collections

Reproductive phenology was observed over three years in a Eucalyptus grandis seed orchard in Madagascar to determine the impact of geographic differences of parental selections on the expected genetic composition of seed crops. Pollen flow (observed pollen cloud) was deduced from a paternity assignment based on sampling from one year’s seed production. The two approaches were used to verify whether knowledge of phenology is sufficient to predict the genetic quality of the seeds collected. Despite the high flowering level, with a constant cycle over three years, the results demonstrated wide reproductive phenological differences associated with the parents’ origin, suggesting putative pollination disequilibrium. From both observed and expected pollen clouds, the results showed preferential mating among different provenances, which has consequences for seed crop composition. Phenological observations, which can be made inexpensively, can be used to promote methods of effective seed orchard management in order to improve the genetic quality of seeds.     

马达加斯加的热带森林

马达加斯加是非洲大陆的离岛。天然森林类型复杂多样。原生性的森林群落主要为常绿林，落叶林以及多刺、肉质的落叶灌木丛。在不同类型的岩石露头发育着岩生矮林；高山上可见山顶矮林，滨海湿地则为红树林。马达加斯加的森林有着独特的植物和动物种类，有着巨大的生物多样性。但由于人类长期对其生境的破坏，不少动物种类已处于濒危状态。到目前为止，60％－85％的森林植被已遭到破坏。非持续的农业轮作是森林植被完整性的主要威胁。在某些地区，火烧林地建立牧场业是引起森林面积减少的主要因素。     

Glomus mosseae bioprotection against aster yellows phytoplasma (16srI-B) and Spiroplasma citri infection in Madagascar periwinkle

The bio-control potential of arbuscular mycorrhizal fungus Glomus mosseae against two pathogenic microorganisms aster yellows (AY) phytoplasma and Spiroplasma citri has been examined in Madagascar periwinkle (Catharanthus roseus). G. mosseae had a positive influence on healthy C. roseus plants and S. citri infection. It provided bioprotection against S. citri pathogen and induced significant degree of resistance to spiroplasma infection. Besides, symptom expression significantly reduced and shoot height, leaves number, root fresh and dry weight increased in spiroplasma-infected plants treated with mycorrhiza fungus. Although, G. mosseae had no positive effect on phytoplasma disease. The root architectures were affected by the phytoplasma pathogen, and the root surface area dramatically decreased in G. mosseae treated AY-infected periwinkles compared with the control. Nitrogen and Phosphorus concentrations notably increased in spiroplasma + G. mosseae compared with control plants. Potassium concentration did not differ significantly in all mycorrhizal treated and untreated infected plants except in G. mosseae treated healthy plants. The spore density and root colonization rate did not vary in both pathogen treatments G. mosseae + spiroplasma and G. mosseae + phytoplasma. To our knowledge, this is the first report showing the bioprotective effect of G. mosseae on S. citri. The possible mechanisms involved in complex interaction between plants, cell wall-less bacteria and arbuscular mycorrhizal fungi (AMF) are discussed and the underlying mechanisms for the functioning of AMF are hypothesized.     

杂交水稻在马达加斯加的推广前景

马达加斯加为印度洋岛国,粮食不能自给.为了解决马达加斯加的粮食危机,推广中国杂交水稻技术,实现粮食产量翻番的目标,介绍了马达加斯加水稻生产现状,并对在马达加斯加推广杂交水稻面临的机遇及困难进行了分析.     

长春花ISSR-PCR 反应体系的正交优化

[目的]筛选最适的长春花ISSR-PCR反应体系。[方法]采用正交试验方法,对影响长春花ISSR-PCR反应体系的引物浓度、dNTP浓度、Mg2＋浓度、TaqDNA聚合酶浓度和模板DNA浓度5个因素在4个水平上进行正交试验,建立适合长春花ISSR-PCR的反应体系。[结果]长春花ISSR-PCR反应体系的最佳条件：引物浓度0.50μmol/L,dNTP浓度0.10 mmol/L,Mg2＋浓度3.00 mmol/L,Taq酶浓度0.75U/25μl,DNA模板浓度350 ng/25μl。采用该反应体系筛选出12对适合于长春花ISSR-PCR反应的引物。[结论]利用优化系统进行长春花的ISSR-PCR反应,可获得稳定性高、重复性好、背景清晰的电泳结果。     

Seasonal dependence of rooting success in cuttings from natural forest trees in Madagascar

Four ligneous species from the tropical forest in the east of Madagascar, with a proven or potentially high economic value, were subject to ‘low-tech’ vegetative propagation tests from stem cuttings. The species concerned were Aphloia theiformis, Ilex mitis, Prunus africana and Ravensara aromatica. The cuttings were three-node segments of stems on which one leaf was retained. All the species proved amenable to rooting. The maximum percentage of rooting ranged from 33% for P. africana to 60% for I. mitis. Rooting success was dependant on the season of cutting (high in the hot season, from October to May, and null in cold season). This study is the first successful attempt at propagating cuttings from Malagasy forest species. This result is of particular importance to P. africana, threatened by destructive exploitation in Madagascar. It goes a step further in the domestication of this species by demonstrating the ability of cutting from 10 year old ortets collected in natural forest to root as it offers the possibility of a reliable and effective method of reintroduction for the species in overexploited zones.     

Distribution, status, and conservation of radiated tortoises (Geochelone radiata) in Madagascar

The radiated tortoise, Geochelone radiata, one of Madagascar’s four endemic tortoises, occupies a narrow band of xeric spiny forest along the island’s southwest coast. Traditionally avoided by indigenous tribes, these tortoises are now routinely harvested for food. An accurate assessment of human exploitation remains problematic, however, hindered by limited, dated statistics available on tortoise populations. To update the radiated tortoise’s status and distribution, we established a series of line transects at seven localities across its range and implemented a mark-recapture study at one of these localities (Cap Sainte Marie). Tortoises currently range from south of Tulear to east of Cap Sainte Marie, at density estimates spanning 27-5744 tortoises/km². The mark-recapture estimate for Cap Sainte Marie (1905-2105 tortoises/km²) was substantially higher than its transect estimate (654 tortoises/km²) though comparable to actual tortoise captures (1438) there. Thus, our transect density values probably err as underestimates, and from these data, we calculate a conservative total population size of 12 million radiated tortoises. We also examined mitochondrial DNA sequences (ND4 gene) for two individuals/locality in a preliminary assessment of genetic variation across the species’ range. Only two ND4 haplotypes were recovered, the more common haplotype representing 13 of the 14 individuals. We offer several conservation recommendations in light of our survey results.     

Methodological considerations in reserve system selection: A case study of Malagasy lemurs

Although data quality and weighting decisions impact the outputs of reserve selection algorithms, these factors have not been closely studied. We examine these methodological issues in the use of reserve selection algorithms by comparing: (1) quality of input data and (2) use of different weighting methods for prioritizing among species. In 2003, the government of Madagascar, a global biodiversity hotspot, committed to tripling the size of its protected area network to protect 10% of the country’s total land area. We apply the Zonation reserve selection algorithm to distribution data for 52 lemur species to identify priority areas for the expansion of Madagascar’s reserve network. We assess the similarity of the areas selected, as well as the proportions of lemur ranges protected in the resulting areas when different forms of input data were used: extent of occurrence versus refined extent of occurrence. Low overlap between the areas selected suggests that refined extent of occurrence data are highly desirable, and to best protect lemur species, we recommend refining extent of occurrence ranges using habitat and altitude limitations. Reserve areas were also selected for protection based on three different species weighting schemes, resulting in marked variation in proportional representation of species among the IUCN Red List of Threatened Species extinction risk categories. This result demonstrates that assignment of species weights influences whether a reserve network prioritizes maximizing overall species protection or maximizing protection of the most threatened species.     

Molecular epidemiology of cassava mosaic disease in Madagascar

Cassava is the staple food for hundreds of millions of people in Africa but its cultivation is seriously constrained by cassava mosaic disease (CMD) in Madagascar, and in Africa in general. This study identified the cassava mosaic geminiviruses (CMGs) involved in CMD in Madagascar and their associated epidemiological characteristics from countrywide surveys. Molecular characterization of CMGs in Madagascar revealed an unprecedented diversity and co‐occurrence of six viruses: African cassava mosaic virus (ACMV), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic virus (EACMV), South African cassava mosaic virus (SACMV) and the recently described Cassava mosaic Madagascar virus (CMMGV). Distinct geographical distributions were observed for the six viruses. While ACMV was more prevalent in the central highlands, EACMV and EACMKV were prevalent in lowlands and coastal regions. Both EACMCV and SACMV occurred in almost all the localities visited. PCR diagnosis revealed that mixed infection (up to four co‐infected viruses) occurred in 21% of the samples and were associated with higher symptom severity scores. Pairwise comparisons of virus associations showed that EACMCV was found in mixed infections more often than expected while ACMV and SACMV were mostly found in single infections. A greater abundance of whiteflies was observed in lowland and coastal areas. Nevertheless, infected cuttings remain the primary source of CMD propagation (95%) in Madagascar.     

Dynamics of mangrove forests in the Mangoky River delta,Madagascar, under the influence of natural and human factors

Mangroves in Madagascar cover 327 000 ha to 340 300 ha. Several authors have studied these mangroves, but we do not yet have a complete knowledge of these ecosystems. The present study is an attempt to respond to this concern by analyzing dynamics and changes in the extent of the mangrove forest in the Mangoky delta (SW Madagascar) between 1951 and 2000. The comparison between base maps and Landsat TM images shows that the mangrove area remained relatively stable, even increasing slightly (+189 ha) between 1951 and 1979. From 1979 to 1994, its area decreased from 21 426 ha to 11 706 ha (−9720 ha). It then increased again (+84 ha) between 1994 and 2000. The balance was a decrease of 41.74% between 1951 and 2000. These figures may be compared with national (−15% in 56 years) and world (−35% for the last 20 years) statistics. Three main reasons are given to explain these changes: (1) the hydrological and sedimentological behavior of the Mangoky River; (2) the mechanism of plant succession, which depends on tides and on the characteristics of the substratum and (3) human activities and logging, which have increased since the 1980s in the Mangoky delta.