Some Evidence for Host Specificity in Arbuscnlar Myc-orrhizas

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Cryptic genetic diversity and host specificity of Bothriocephalus acheilognathi Yamaguti,1934(Eucestoda:Bothriocephalidea)

In this report, genetic variation and phylogeny of B. acheilognathi were analyzed based on 96 samples collected from 20 fish host species in 29 different localities by using the rDNA internal transcribed spacer （ITS） sequences. The ITS1 and ITS2 sequences of B. acheilognathi varied among 561-639 bp and 559-648 bp, and ten simple sequence repeat loci （microsatellites） were detected in the ITS regions, which contributed to significant sequence length variation. Phylogenetic analyses revealed 4 genetic clades （A, B, C, D） in samples with significantly different fish host spectra and geographic distribution. Clade A possessed a wide host range and geographic distribution, including all the samples ofB. acheilognathi determined in previous report. Clades B, C, and D only infected the small cyprinid fishes Opsariichthys bidens and Zacco platypus, and were limited to different locality. Interesting, Clades A and D were detected coexisting in same water body, and even in same fish host O. bidens in Danjiangkou Reservoir. The relatively higher genetic divergence and wide geographic distribution orB. acheilognathi parasitic in O. bidens indicated that O. bidens is likely to be the primary host. Sympatric occurrence of the two genetically distinct clades suggests the possibility of allopatric speciation and second encounter events.

Clupeid fish hosts a Peniculus sp.(Pennellidae,Siphonostomatoida, Copepoda)—First report on new host and season dependent prevalence

Pennellid copepod Peniculus fistula fistula(Nordmann, 1832)(Synonym: Peniculus fistula Nordmann, 1832,Aphia ID: 745880), a worldwide distributed species, has been recovered from at least 19 teleost families. The present paper reports for the first time from the Malabar coast(South India), not only the existence of a new host family, Clupeidae, hosting this parasitic copepod species(P. fistula fistula) but also their season dependent hosting. A total of 123 marine fish species, belonging to 77 genera and 38 families surveyed along the Malabar coast, only the clupeid, Anadontostoma chacunda(Hamilton, 1822) was shown to be infected by this copepod species;all the recovered(copepod) parasites were invariably found attached at the mid portion of the caudal fin lobes and lying parallel to the host body, indicating the strict site-specific parasitisation. There is a discrete seasonality in the prevalence(P<0.05) as the sign of infection was noticed during the period from September to May with relatively high prevalence during winter months(November–January). During the monsoon months(June–August), the host fish was found completely free from Peniculus infection. Interestingly, all the 229 recovered specimens(P. fistula fistula) were gravid females having paired uniserrate egg sacs with the length more than its own body length.

Electrophysiological responses of Plutella xylostella to 9 different plant volatiles

Plutella xylostella is the main pest of cruciferae plants in the worldwide fields.The volatiles released from host plants serve vital roles in host-finding and oviposition behavior.Electroantennograms were recorded from male and female Plutella xylostella to 9 different plant volatiles(cabbage Brassica oleracea L.var.capitata,baby bokchoi Brassica chinensis L.,broccoli Brassica oleracea L.var.botrytis L.,Chinese cabbage Brassica pekinensis Rupr.,Radish Raphanus sativus L.,towel gourd Luffa Cylindrica Roem.,eggplant Solanum melongena L.,tomato Solanum lycopersicum,pepper Capsicum annuum L.) in healthy/injured status.The statistic analysis show there is a significant difference of EAG relative values between cruciferae and non-cruciferae volatiles.The EAG relative values of injured plant volatiles to both male and female changed a lot during the tests.Multiple-ANOVA analysis represents cross factors(sex,host-plant,plant status) showed a great interactive impacts to the EAG-RV.

Research status of soybean symbiosis nitrogen fixation

Soybean(Glycine max)is one of the most important economic legume crops with largest planting area,and is also an important oil crop,as well as food and feed material.Soybean-rhizobia symbiosis plays important roles in plant cultivation and fertilizer application.However,there are many problems in agricultural application of soybean symbiotic nitrogen fixation.In this review,we summarized three restriction factors(host specificity,low nitrogen fixation efficiency and abiotic stress)and discussed research progresses of these factors.Clarification of host specific mechanism will help to select and apply rhizobia inoculants.Both maintaining high nitrogenase activity and delaying nodule senescence can improve the efficiency of symbiotic nitrogen fixation.Abiotic stress-tolerant rhizobia can improve the abiotic stress tolerance of soybean.Breeding stress tolerant genotypes of soybean and rhizobia,obtaining correlated genes are the common strategies to improve soybean symbiotic nitrogen fixation under extreme conditions.Regulatory mechanisms of these restriction factors are still poorly understood and needs further clarification.

Analysis of the Abnormal Segregation of Pathogenicity in Magnaporthe grisea by Using a Genetic Cross of Oryza and Eleusine Isolates

A genetic cross between Oryza isolate Y93-164a-1 and Eleusine isolate SA98-4 was established, and the pathogenicity of 151 F1 progeny isolates was investigated on both host plants rice and finger millet. Results showed that the segregation of pathogenicity in this genetic cross was abnormal, i.e., most of the progeny isolates were nonpathogenic on both host plants. However, no abnormal segregation was observed when middle repetitive sequence MGR586 and 31 single-copy RFLP markers from all of the chromosomes were genetically analyzed. At the same time, comparison of the chromosomal organization among two pairs of parental isolates did not find any genomic abnormity. These results suggested that the ＂abnormal＂ inheritance of pathogenicity in this cross was most likely due to the reassortment of numerous host species specificity genes but not the biased segregation of the host species specificity genes. The host species specificities in M. grisea were likely to be multigenically controlled, at least in the genetic cross involving rice pathogen and the grasses pathogen other than rice.

Complementary fruiting phenologies facilitate sharing of one pollinator fig wasp by two fig trees

Aims most pollinator fig wasps are host plant specific,with each spe-cies only breeding in the figs of one fig tree species,but increasing numbers of species are known to be pollinated by more than one fig wasp,and in rare instances host switching can result in Ficus species sharing pollinators.in this study,we examined factors facilitating observed host switching at Xishuangbanna in southwestern(sW)China,where Ficus squamosa is at the northern edge of its range and lacks the fig wasps that pollinate it elsewhere,and its figs are colonized by a Ceratosolen pollinator that routinely breeds in figs of F.heterostyla.Methods We recorded the habitat preferences of F.squamosa and F.heterost-yla at Xishuangbanna,and compared characteristics such as fig size,location and colour at receptive phase.Furthermore,the vegetative and reproductive phenologies in the populations of F.squamosa and F.heterostyla were recorded weekly at Xishuangbanna Tropical botanical garden for 1 year.Important Findings Ficus squamosa is a shrub found near fast-flowing rivers,F.heterostyla is a small tree of disturbed forest edges.although preferring different habitats,they can be found growing close together.both species have figs located at or near ground level,but they differ in size when pollinated.Fig production in F.squamosa was concentrated in the colder months.F.heterostyla produced more figs in summer but had some through-out the year.The absence of its normal pollinators,in combination with similarly located figs and partially complementary fruiting patterns appear to have facilitated colonization of F.squamosa by the routine pollinator of F.heterostyla.The figs probably also share similar attractant volatiles.This host switching suggests one mechanism whereby fig trees can acquire new pollinators and emphasizes the likely significance of edges of ranges in the genesis of novel fig tree-fig wasp relationships.

The Colletotrichum orbiculare species complex: Important pathogens of field crops and weeds

Colletotrichum orbiculare causes anthracnose of Cucurbitaceae and is phylogenetically closely related to pathogens of several other herbaceous hosts belonging to the Asteraceae,Fabaceae and Malvaceae.Most of them are known for their hemibiotrophic infection strategy and as destructive pathogens either of field crops or weeds.In order to study the phylogenetic relationships of these fungi,a multilocus analysis(ITS,GAPDH,CHS-1,HIS3,ACT,TUB2,GS)of 42 strains of C.orbiculare and related species was conducted.The analysis resulted in nine clades that confirmed the four species previously known as belonging to this species complex,C.lindemuthianum,C.malvarum,C.orbiculare and C.trifolii,and recognised four new species from weeds,namely C.bidentis,C.sidae,C.spinosum and C.tebeestii.The name C.orbiculare itself is widely used in plant pathology and science,but is invalid according to current nomenclatural rules.Therefore we described a new species with the same epithet and a type specimen that agrees with our current understanding of this species,and is linked to a living culture.Following the recent epitypification of C.lindemuthianum,we chose appropriate specimens with associated strains to serve as epitypes of C.malvarum and C.trifolii,and selected an authentic specimen of C.trifolii as lectotype.

Multigene phylogeny and taxonomy of the genus Melanconiella(Diaporthales)

Molecular phylogenetic analyses of LSU rDNA demonstrate monophyly of the genus Melanconiella,and its status as a genus distinct from Melanconis is confirmed.Data of macro-and microscopic morphology,pure cultures and phylogenetic analyses of partial SSU-ITS-LSU rDNA,tef1 and rpb2 sequences revealed 13 distinct species of Melanconiella,six of which are described as new(M.chrysodiscosporina,M.chrysomelanconium,M.chrysorientalis,M.echinata,M.elegans,M.meridionalis).Melanconiella hyperopta var.orientalis is described as a new variety.Diaporthe carpinicola,D.ellisii,D.flavovirens,D.hyperopta and D.ostryae are formally combined into Melanconiella.The name Melanconiella chrysostroma is excluded from Melanconiella,as it is an obligate synonym of Wuestneia xanthostroma.The type of Melanconiella is confirmed as M.spodiaea.Several species are lecto-and/or epitypified.A key to all treated species ofMelanconiella is provided,and the circumscriptions of the genera Melanconis and Melanconiella are emended.Most Melanconiella species revealed by molecular phylogenetic analyses can be well characterised by a suite of morphological traits including ascospore shape,length and width,colour,absence/presence and shape of appendages and the anamorph.Anamorph-teleomorph connections were confirmed by pure culture and DNA data,revealing the presence of a single melanconium-or discosporina-like anamorph for each species.Colony growth was found to be characteristic of the respective species.Melanconiella is shown to be confined to the host family Betulaceae,and all species are found to be highly host-specific,mostly confined to a single host species.The biodiversity ofMelanconiella was determined to be centred on the genus Carpinus with nine species,five of which have been confirmed on C.betulus.Europe appears to be the geographic centre of Melanconiella biodiversity.

European Species of Hebeloma Section Theobromina

This paper addresses section Theobromina within the genus Hebeloma(Agaricales).We recognise seven European species within this section,three of which are described as new:Hebeloma alboerumpens,H.griseopruinatum and H.parvicystidiatum.The first two of these species appear to be ectomycorrhizal with Cistaceae:Cistus and Helianthemum.Hebeloma parvicystidiatum is more likely to be in mycorrhizal association with Quercus spp.We also provide a key to the European species within sect.Theobromina and an updated key of known Hebeloma associates of Cistus.Molecular analyses based on multiple loci further illustrate the distinctness of the newly described taxa and provide molecular evidence,supporting the morphological evidence,for the relationship that exists among species of this section.The ITS is the only one from the sequenced loci that,alongside with morphology,distinguishes among all of the species of sect.Theobromina.The section gains most of its molecular support from the MCM7 locus,followed by RPB2.