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91.
Biological control of Chenopodium album L. in Europe 总被引:2,自引:0,他引:2
J. Netland L.C. Dutton M.P. Greaves M. Baldwin M. Vurro A. Evidente G. Einhorn P.C. Scheepens L.W. French 《BioControl》2001,46(2):175-196
Ascochyta caulina (P. Karst) v.d. Aa and v. Kest is aplant pathogenic fungus which is specific to Chenopodium albumL. It has been suggested as a potential mycoherbicide to this weed,which is important and wide spread in arable crops throughout Europe. Toinvestigate its potential as a biocontrol agent, the fungus has beentested in glasshouse and field experiments. Formulations containingdifferent combinations of A. caulina conidia, the phytotoxinsfrom the fungus and low doses of herbicides have been tested.Significant improvement in the efficacy of the fungus was achieved inglasshouse trials with an aqueous formulation containing PVA(0.1% v/v), Psyllium (0.4% w/v), Sylgard 309(0.1% v/v), nutrients and conidia (5 ×106/ml). The extracellular, hydrophilic phytotoxinsproduced by A. caulina were purified and their structuresdetermined. The main toxin, named ascaulitoxin, was characterised as theN2--D-glucopyranoside of the unusual bis-aminoacid2,4,7-triamino-5-hydroxyoctandioic acid. Two other toxins proved to betrans-4-amino-D-proline and the aglycone of ascaulitoxin. Thesetoxins have shown promising herbicidal properties. Field trials haveinvestigated the performance of A. caulina conidia applied atdifferent developmental stages of C. album either as a singletreatment or combined with sub-lethal doses of herbicides or with thefungal phytotoxins. With the available formulation, favourable weatherconditions are needed to obtain infection in the field. The efficacy ofthe strain of A. caulina used so far has proved to beinadequate to justify its development as a bioherbicide. This isprobably due to its low virulence. 相似文献
92.
Avise JC; Shapira JF; Daniel SW; Aquadro CF; Lansman RA 《Molecular biology and evolution》1983,1(1):38-56
We address the problem of the possible significance of biological
speciation to the magnitude and pattern of divergence of asexually
transmitted characters in bisexual species. The empirical data for this
report consist of restriction endonuclease site variability in maternally
transmitted mitochondrial DNA (mtDNA) isolated from 82 samples of
Peromyscus polionotus and P. leucopus collected from major portions of the
respective species' ranges. Data are analyzed together with previously
published information on P. maniculatus, a sibling species to polionotus.
Maps of restriction sites indicate that all of the variation observed can
be reasonably attributed to base substitutions leading to loss or gain of
particular recognition sites. Magnitude of mtDNA sequence divergence within
polionotus (maximum approximately equal to 2%) is roughly comparable to
that observed within any of five previously identified mtDNA assemblages in
maniculatus. Sequence divergence within leucopus (maximum approximately
equal to 4%) is somewhat greater than that within polionotus. Consideration
of probable evolutionary links among mtDNA restriction site maps allowed
estimation of matriarchal phylogenies within polionotus and leucopus.
Clustering algorithms and qualitative Wagner procedures were used to
generate phenograms and parsimony networks, respectively, for the
between-species comparisons. Three simple graphical models are presented to
illustrate some conceivable relationships of mtDNA differentiation to
speciation. In theoretical case I, each of two reproductively defined
species (A and B) is monophyletic in matriarchal genealogy; the common
female ancestor of either species can either predate or postdate the
speciation. In case II, neither species is monophyletic in matriarchal
genotype. In case III, species B is monophyletic but forms a subclade
within A which is thus paraphyletic with respect to B. The empirical
results for mtDNA in maniculatus and polionotus appear to conform closely
to case III. These theoretical and empirical considerations raise a number
of questions about the general relationship of the speciation process to
the evolution of uniparentally transmitted traits. Some of these
considerations are presented, and it is suggested that the distribution
patterns of mtDNA sequence variation within and among extant species should
be of considerable relevance to the particular demographies of speciation.
相似文献
93.
94.
Klaus Fischer Jürgen Kreyling Michaël Beaulieu Ilka Beil Manuela Bog Dries Bonte Stefanie Holm Sabine Knoblauch Dustin Koch Lena Muffler Pierick Mouginot Maria Paulinich J. F. Scheepens Raijana Schiemann Jonas Schmeddes Martin Schnittler Gabriele Uhl Marieke van der Maaten-Theunissen Julia M. Weier Martin Wilmking Robert Weigel Phillip Gienapp 《Heredity》2021,126(1):23
Assessing the genetic adaptive potential of populations and species is essential for better understanding evolutionary processes. However, the expression of genetic variation may depend on environmental conditions, which may speed up or slow down evolutionary responses. Thus, the same selection pressure may lead to different responses. Against this background, we here investigate the effects of thermal stress on genetic variation, mainly under controlled laboratory conditions. We estimated additive genetic variance (VA), narrow-sense heritability (h2) and the coefficient of genetic variation (CVA) under both benign control and stressful thermal conditions. We included six species spanning a diverse range of plant and animal taxa, and a total of 25 morphological and life-history traits. Our results show that (1) thermal stress reduced fitness components, (2) the majority of traits showed significant genetic variation and that (3) thermal stress affected the expression of genetic variation (VA, h2 or CVA) in only one-third of the cases (25 of 75 analyses, mostly in one clonal species). Moreover, the effects were highly species-specific, with genetic variation increasing in 11 and decreasing in 14 cases under stress. Our results hence indicate that thermal stress does not generally affect the expression of genetic variation under laboratory conditions but, nevertheless, increases or decreases genetic variation in specific cases. Consequently, predicting the rate of genetic adaptation might not be generally complicated by environmental variation, but requires a careful case-by-case consideration.Subject terms: Evolutionary genetics, Climate-change ecology, Biodiversity 相似文献
95.
96.
Opportunities for biological weed control in Europe 总被引:1,自引:0,他引:1
The development and application of biological weed control offer greatopportunities not only for farmers, nature conservationists and othervegetation managers but also for institutions and companies that wish tosell plant protection services and products, and for the general publicthat demands safe food and a visually attractive and diverseenvironment. Despite the obvious opportunities for biological weedcontrol, few control agents are actually being used in Europe. Potentialagent organisms have features that make them particularly strong anduseful for biological control, but they also have weaknesses. Weaknessesinclude a too narrow or too wide host specificity, lack of virulence, orsensitivity to unfavourable environmental conditions.Developing specific knowledge on the interaction between weeds andpotential biological control agents, as well as expertise to increasethe effect of control agents and so achieve sufficient weed control in acost-effective manner, should have the highest priority in researchprogrammes. From 1994 to 2000 most ongoing research on biological weedcontrol in Europe was combined in a cooperative programme. This COSTAction concentrated on the interactions between five target crop weedsand their antagonists (pathogens and insects), on furthercharacterisation of the specific blems and potential control agents andon the most suitable biological control approach.The next major challenge will be to apply the findings provided byCOST-816 to the development of practical control solutions. The leadingobjective of a new concerted research programme with European dimensionswill be to stabilise or even promote biodiversity in the most importantEuropean ecosystems by integrating biological weed control in themanagement of these systems. 相似文献