Biocontrol potential of native Trichoderma isolates against root-knot nematodes in West African vegetable production systems

Seventeen isolates of the free-living soil fungus Trichoderma spp., collected from Meloidogyne spp. infested vegetable fields and infected roots in Benin, were screened for their rhizosphere competence and antagonistic potential against root-knot nematodes, Meloidogyne incognita, in greenhouse pot experiments on tomato. The five isolates expressing greatest reproductive ability and nematode suppression in pots were further assessed in a typical double-cropping system of tomato and carrot in the field in Benin. All seventeen isolates were re-isolated from both soil and roots at eight weeks after application, with no apparent crop growth penalty. In pots, a number of isolates provided significant nematode control compared with untreated controls. Field assessment demonstrated significant inhibition of nematode reproduction, suppression of root galling and an increase of tomato yield compared with the non-fungal control treatments. Trichoderma asperellum T-16 suppressed second stage juvenile (J₂) densities in roots by up to 80%; Trichoderma brevicompactum T-3 suppressed egg production by as much as 86%. Tomato yields were improved by over 30% following the application of these biocontrol agents, especially T. asperellum T-16. Although no significant effects were observed on carrot galling and yield, soil J₂ densities were suppressed in treated plots, by as much as 94% (T. asperellum T-12), compared with the non-fungal controls. This study provides the first information on the potential of West-African Trichoderma spp. isolates for use against root-knot nematodes in vegetable production systems. The results are highly encouraging, demonstrating their strong potential as an alternative and complementary crop protection component.     

生物多样性与生态系统功能的关系研究进展

在国内外研究生物多样性与生态系统功能的关系基础上 ,系统分析了物种多样性与生产力之间相互作用关系及其影响因子 ,探讨了生物多样性与稳定性的关系。     

Discovery of c-SNPs in Anemone coronaria L. and Assessment of Genetic Variation

Single nucleotide polymorphisms (SNPs) were discovered in 44 cDNA clones from leaves by comparison of the commercial cultivar ‘Mona Lisa‘ with a wild population of Anemone coronaria L. One hundred and fifty five SNPs were discovered with an average frequency of one SNP per 167 bp. Forty nine percent of the SNPs are transitions, 43 are transversions, 26 are heterozygotes and 9% are InDels. Eighty two (68%) of the SNPs located in the ORF, resulted in a change of amino acid while 39 (32%) did not affect the amino acid. Thirty eight SNPs (46%), which change the amino acid, resulted in similar amino acid, while 44 SNPs (54%) resulted in a non-similar amino acid. Nine polymorphic sites were genotyped by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) using genomic DNA. Phylogenetic analysis of 50 individuals from six wild populations and the commercial cultivar revealed high polymorphism within and low polymorphism between A. coronaria L. wild populations. The phylogenetic tree revealed only one clear cluster of the ‘Mona Lisa’ cultivar. All the other individuals from the various wild populations are distributed on different nodes indicating that the genetic variation within the wild populations is high while the commercial cultivar is quite homogenous and genetically different from all other populations.     

江河源区生物多样性问题研究

江河源区西部、南部、东南部和东北部都毗邻生物多样性中心,生态系统多样,物种较丰富。这种生物多样性是随着青藏高原的隆起而产生和发展起来的并以其环境为生存条件,因而比较独特,不乏特有种、珍禽异兽、名贵药材和受到国家保护的物种。全面了解江河源区特殊的生物多样性将有利于该区的生态环境保护和区内自然保护区的建设。     

土壤微生物多样性实验研究方法概述

对有关土壤微生物多样性,包括微生物类群多样性、群落结构多样性、功能多样性以及基因多样性等的描述与表征方法进行了探讨,同时,对当前国内外土壤微生物多样性的一些实验研究方法,包括土壤微生物分离培养方法、Biolog 微平板方法、FAME 分析方法和分子生物学方法等进行了介绍和评述。并指出在土壤微生物多样性研究中,如果可能的话,需要将各种方法结合起来使用,方可得到有关土壤生物多样性的较为全面的信息和理解。     

Species compositional similarity and ecoregions: Do ecoregion boundaries represent zones of high species turnover?

The concept of an ecoregion, a discrete spatial area where species composition is presumed to be relatively homogeneous compared to that between areas, has become an increasingly common conservation tool. We test the effectiveness of one ecoregion delineation (World Wildlife Fund) in capturing patterns of change in species composition of birds, mammals, and trees across the United States (excluding Hawaii) and Canada, and describe the extent to which each ecoregion boundary is concurrent with relatively large changes in species composition. Digitized range maps were used to record presence/absence in 50 × 50 km equal-area grid cells covering the study area. Jaccard’s index of similarity was calculated for all pairs of cells in the same or adjacent ecoregions. The average rate at which similarity declined with geographic distance was calculated using pairs of cells within the same ecoregion (intra-ecoregion turnover) or using pairs of cells in adjacent ecoregions (inter-ecoregion turnover). The intra-ecoregion rate varies widely among ecoregions and between taxa, with trees having a faster rate of similarity decline than mammals or birds. For all three species groups, most ecoregion boundaries have similar rates across them (inter-ecoregion) than that within each adjacent ecoregion (intra-ecoregion), with the exception of zones of transition between biomes and major geographical features. Although the ecoregion concept is useful for many other conservation applications, the lack of systematic, high turnover rates along ecoregion boundaries suggests that ecoregions should not be used as a quantitative basis for delineating geographic areas of a particular taxonomic group.     

Endangered economic species of Indian desert

The economically important, naturally occurring species of the Indian desert was surveyed on the basis of the perception of local plant scientists. About one-fourth of the total 84 taxa were seen to be facing varying stages of risk. Of these, 17 species and 8 botanical varieties are endemic to Indian desert. Eighteen species in Bikaner, 21 in Jaisalmer and 19 in Jodhpur divisions were reported to be at risk. Factors responsible for the loss of species diversity have been discussed and appropriate strategies have been suggested for their conservation.     

Polypore diversity in managed and old-growth boreal Picea abies forests in southern Finland

Polypore communities were compared between mature managed, overmature managed, and old-growth spruce-dominated forests in southern Finland. A total of 85 polypore species, with 6000 records, were found in 16 sample plots, each 4 ha in size. Old-growth stands had on average 80% more species than mature stands, and 38% more species than overmature managed stands. Variation in polypore species richness was best explained by diversity of dead wood and the number and volume of dead trees. The best predictor for the number of threatened polypore species was the number of cut stumps. Threatened species were practically confined to old-growth forests and to stands in which the amount of dead wood exceeded 20 m³/ha. This figure appears to represent a stand-level threshold value for the amount of dead wood, below which the persistence of threatened species becomes unlikely. Our results suggest that a significant increase in the amount of dead wood (e.g. by leaving large retention trees and even by killing trees) is needed in managed forests before they become suitable habitats for threatened polypores.