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1.
Jacqueline B. F. Geervliet Annemarie I. Vreugdenhil Marcel Dicke Louise E. M. Vet 《Entomologia Experimentalis et Applicata》1998,86(3):241-252
Comparison of closely related species can elucidate adaptive differences in species characteristics. The present study compares the effect of experience on the host-finding behaviour of two Cotesia (Hymenoptera: Braconidae) parasitoid species that differ in their degree of specialization. After multiple experiences with host larvae, females of the generalist parasitoid Cotesia glomerata showed a clear preference for volatiles from Pieris brassicae-infested Brussels sprouts leaves over P. rapae-infested Brussels sprouts leaves in two-choice tests (preference learning at herbivore level). A single experience with a host did not lead to such preferences.Experience of adult C. glomerata with different P. brassicae-infested cabbage varieties or nasturtium (Tropaeolum majus L.) led to preferences for the experienced plant-host complex in most cases (preference learning at plant level). No effect of rearing plant (early adult learning) on plant preference was found.In contrast to the generalist C. glomerata, females of the specialist C. rubecula did not show preference learning at the herbivore level. At the plant level, experience with different P. rapae-infested cabbage varieties in no case resulted in a difference in preference between treatments. The results support the hypothesis that learning plays a more important role in searching in generalists than in specialist parasitoids. The behaviour of the generalist C. glomerata was more easily changed by experience than that of the specialist C. rubecula. 相似文献
2.
3.
P. Doak 《Oecologia》2000,122(4):556-567
Despite extensive research on parasitoid-prey interactions and especially the effects of heterogeneity in parasitism on stability,
sources of heterogeneity other than prey density have been little investigated. This research examines parasitism rates by
three parasitoid species in relationship to prey density and habitat spatial pattern. The herbivore Itame andersoni (Geometridae) inhabits a subdivided habitat created by patches of its host plant, Dryas drummondii, in the Wrangell Mountains of Alaska. Dryas colonizes glacial moraines and spreads clonally to form distinct patches. Habitat subdivision occurs both on the patch scale
and on the larger spatial scale of sites due to patchy successional patterns. Itame is attacked by three parasitoids: an ichneumonid wasp (Campoletis sp.), a braconid wasp (Aleiodes n. sp.), and the tachinid fly (Phyrxe pecosensis). I performed a large survey study at five distinct sites and censused Itame density and parasitism rates in 206 plant patches for 1–3 years. Parasitism rates varied with both plant patch size and isolation
and also between sites, and the highest rates of overall parasitism were in the smallest patches. However, the effects of
both small- and large-scale heterogeneity on parasitism differed for the three parasitoid species. There was weak evidence
that Itame density was positively correlated with parasitism for the braconid and tachinid at the patch scale, but density effects differed
for different patch sizes, patch isolations, and sites. At the site scale, there was no evidence of positive, but some indication
of negative density-dependent parasitism. These patterns do not appear to be driven by negative interactions between the three
parasitoid species, but reflect, rather, individual differences in habitat use and response to prey density. Finally, there
was no evidence that parasitism strongly impacted the population dynamics of Itame. These results demonstrate the importance of considering habitat pattern when examining spatial heterogeneity of parasitism
and the impacts of parasitoids.
Received: 3 June 1999 / Accepted: 4 October 1999 相似文献
4.
Herrera JC Combes MC Anthony F Charrier A Lashermes P 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(4):661-668
Transfer of desired characters from the diploid relative species such as Coffea canephora into the cultivated allotetraploid coffee species (Coffea arabica L.) is essential to the continued improvement of varieties. Behaviour of the C. canephora genome and its interaction with the C. arabica genome were investigated in tetraploid interspecific hybrids (C. arabica×C. canephora 4x) resulting from a cross between an accession of C. arabica and a tetraploid plant of C. canephora obtained following colchicine treatment. Segregation and co-segregation of restriction fragment length polymorphism (RFLP)
and microsatellite loci-markers were studied in two BC1 populations. These two populations of 28 and 45 individuals, respectively, resulted from the backcross of two tetraploid
F1 plants to C. arabica. The presence in BC1 plants of specific C. canephora markers was scored for 24 loci (11 RFLP and 13 microsatellites) distributed on at least 7 of the 11 linkage groups identified
in C. canephora. At almost all loci analysed, the segregation of C. canephora alleles transmitted by the (C. arabica×C. canephora 4x) hybrids conformed to the expected ratio assuming random chromosome segregation and the absence of selection. The recombination
fractions of C. canephora chromosome segments were estimated for seven marker intervals, and compared with the recombination fractions previously observed
in C. canephora for the equivalent marker intervals. The recombination frequencies estimated in both plant materials were rather similar,
suggesting that recombination in the (C. arabica×C. canephora 4x) hybrid is not significantly restricted by the genetic differentiation between chromosomes belonging to the different genomes.
The hybrid (C. arabica×C. canephora 4x) therefore appeared particularly favourable to intergenomic recombination events and gene introgressions.
Received: 26 March 2001 / Accepted: 29 June 2001 相似文献
5.
S. Steinberg M. Dicke L. E. M. Vet R. Wanningen 《Entomologia Experimentalis et Applicata》1992,63(2):163-175
Upon initiating a research project on the role of volatile infochemicals in the tritrophic system Cotesia (= Apanteles) glomerata (L.)-Pieris brassicae (L.)-cabbage, a bioassay was developed to investigate the response of C. glomerata. The bioassay should be effective in terms of high responsiveness and minimum variability and constructed through a comparative approach. Twenty seven treatments, organized in a factorial randomized block design, compared the effect of three bioassay set-ups (glasshouse flight chamber, wind-tunnel and Y-tube olfactometer), three parasitoid age groups (1–2, 4–5 and 8–9 days old females), three pre-treatment experiences (naive, damage experienced and oviposition experienced wasps) and the day-to-day effect on response of C. glomerata to clean cabbage (CC) and planthost complex (PHC) in a dual choice test.The best results with regard to the strength and consistency of response to the PHC were obtained in the glasshouse flight-chamber by 4–5 days old female wasps with either damage or oviposition experience (94 and 90%, respectively). It is therefore recommended as a suitable bioassay for studying the role of volatile infochemicals in host-habitat location by C. glomerata.A day-to-day variation in response was found in the glasshouse and wind-tunnel. It was correlated with the direction of change in barometric pressure within the time period of the experiment, showing that steadily increasing atmospheric pressure yields a significantly higher response than steadily decreasing or fluctuating barometric flux. To control for the day effect it is suggested to conduct further experiments in a block design, having day as a block. Several aspects of the infochemical ecology of C. glomerata are discussed. 相似文献
6.
Using the stable isotope marker 13C to study extrafloral nectar uptake by parasitoids under controlled conditions and in the field
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Anna Pollier Simon Dosdat Yann Tricault Armin Bischoff Manuel Plantegenest Bruno Jaloux 《Entomologia Experimentalis et Applicata》2016,161(2):131-140
Parasitic wasps are prominent natural enemies of crop pests. They usually feed on floral resources during the adult stage (nectar, pollen, or honeydew). Extrafloral nectar is an alternative source of sugar easily accessible to adult parasitoids. We developed an original method of nectar labelling based on the injection of labelled sugar solution into the plant stem in order to analyse the nectar uptake by parasitoids (cotton wick method). This method was used to artificially enrich extrafloral cornflower, Centaurea cyanus L. (Asteraceae), nectar with the stable isotope 13C. We analysed (1) the transfer of 13C from the sugar solution into extrafloral nectaries, (2) the uptake of labelled nectar by parasitoids under laboratory conditions, and (3) the ability of the method to discriminate, in an oilseed rape (Brassica napus L., Brassicaceae) field, between labelled parasitoids (i.e., those who have fed on labelled cornflowers located adjacent to the field) and unlabelled parasitoids to track parasitoid movements from the margin into the field. The extrafloral nectar of all test plants was 13C‐labelled. Most (66%) of the parasitoids were identified as marked after 96 h of exposure to labelled plants in the laboratory. We could also detect labelled parasitoids inside the field, but the detection rate was only 1%. The experiments clearly demonstrate that the cotton wick method is appropriate to label extrafloral nectar and parasitoids feeding on this labelled nectar. Further research is needed on the amount of labelled extrafloral nectar required to obtain a sufficient marker level to track parasitoid movements in the field. 相似文献
7.
A. M. Golmirzaie K. Bretschneider R. Ortiz 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(7):1129-1132
Inbreeding depression may affect the performance of consecutive generations of potatoes propagated by true potato seed (TPS).
The effect of inbreeding was established using selfed and sib-mated generations of five TPS families. Correlation coefficients
were calculated between the level of inbreeding and different traits. Inbreeding depression was expressed mainly by pollen
viability, as measured by its stainability (r=−0.912, P<0.01), and tuber yield (r=−0.837, 0.01<P<0.05). The results also indicated that without unavoidable selection inbreeding depression is expected to be more evident.
Furthermore, the TPS families responded quite differently to inbreeding depression. They did not show the same amount of depression
for yield as they did for the characters concerning fertility. The high tuber-yielding families displayed a greater inbreeding
depression for tuber yield than the lower-yielding families.
Received: 10 November 1997 / Accepted: 3 March 1998 相似文献
8.
We describe differences in life history of the intertidal arboreal snail, Littoraria filosa, among patches of mangroves ranging in size from isolated trees to large stands several square kilometres in area. Recruitment
of L. filosa occurred from mid spring (October) to early winter (June), recruits grew rapidly and copulating adults were found during
the following September–April. Populations within large patches of forest were annuals; all or most individuals died between
October–January (spring–midsummer). In contrast, those in smaller peripheral patches were more likely to survive over the
summer but survival differed among patches and years. These differences in life history were caused by a parasitoid fly (genus Sarcophaga) that attacked L. filosa 10 mm and longer and was present in all large patches, but absent from, or rare, in smaller peripheral patches. Experimental
introductions to isolated trees confirmed that the fly could kill L. filosa. Another sarcophagid parasitoid that attacked L. filosa from 4 to less than 10 mm long was also found in every patch. The combined effects of these parasitoids appear to determine
the metapopulation structure of L. filosa. Most adults in large patches were killed by the larger fly during early summer. Summer recruits were often killed by the
smaller fly within a month of settlement and when this happened effective recruitment of L. filosa was reduced to autumn. The planktotrophic larval stage of L. filosa lasts less than 1 month, so the source of autumn recruits to all patches must have been adults that survived the early summer,
most of which were in small patches or on isolated trees. Consequently these ”peripheral sources” are likely to be important
for persistence of the metapopulation of L. filosa. The results of this study demonstrate that metapopulation structure may be determined by complex interactions and that common
models cannot be assumed to apply in all habitats.
Received: 15 September 1999 / Accepted: 31 January 2000 相似文献
9.
Effects of small mammals and vertebrate predators on vegetation in the Chilean semiarid zone 总被引:4,自引:0,他引:4
J. R. Gutiérrez P. L. Meserve S. Herrera L. C. Contreras F. M. Jaksic 《Oecologia》1997,109(3):398-406
We monitored the cover and seed bank response of shrubs, perennial herbs, and ephemeral plants to experimental exclusion
of both the principal rodent herbivore, Octodon degus, and its vertebrate predators from 1989 to 1994 in a semiarid Chilean mediterranean site. Although both richness and species
composition of the plant community at the study site were largely determined by abiotic factors (mainly rainfall and soil
nutrients), predator and herbivore exclusion had significant effects on the relative abundance of several plant species. Experimental
exclusion of herbivores was associated with increased cover of some shrubs and a perennial grass, and decreased cover and
seed densities of several ephemerals, especially those exotic or restricted to areas underneath shrubs. Herbivores apparently
reduced shrubs through browsing and indirectly affected herb cover and seed densities by opening up areas under shrubs and/or
modifying physical and chemical conditions of the soil. Plant responses to predator exclusion were less clear. Nevertheless,
higher cover of some shrubs and ephemerals in the presence of predators suggests tritrophic effects through changes in small
mammal densities and/or foraging behavior.
Received: 22 April 1996 / Accepted: 14 August 1996 相似文献
10.
Interactions among three trophic levels: the influence of host plant on performance of Pieris brassicae and its parasitoid, Cotesia glomerata 总被引:2,自引:0,他引:2
The relative suitability of four host plants was determined both for unparasitized Pieris brassicae L. caterpillars and for Cotesia glomerata (L.) developing in P. brassicae. For unparasitized P. brassicae, growth rate and pupal weight were highest on Brussels sprouts and Swedish turnip, intermediate on rape, and lowest on nasturtium. In contrast, C. glomerata larval developmental rate and adult longevity were greatest for wasps from P. brassicae reared on nasturtium.On all four plants, the host-parasitoid complex attained a lower final weight than unparasitized P. brassicae, and it is argued that this difference is due primarily to reduced consumption by parasitized P. brassicae. Among parasitized caterpillars, however, complex weight was positively correlated with clutch size, suggesting that C. glomerata larvae are able to partially counteract the effect of parasitization per se on host consumption.The host plants of P. brassicae appear to face an evolutionary dilemma: in order to increase the total mass of parasitoids produced, they must suffer greater loss of foliage. This trade-off, if common in nature, may represent a formidable constraint on coevolution between host plants and parasitoids. 相似文献
11.
Quantifying pathways of energy transfer between plants, pests, and beneficial insects is a necessary step toward maintaining
pest stable agroecosystems in the absence of chemical subsidies. A diet switching experiment utilizing a predatory ladybird
beetle, Hippodamia variegata (Goeze), evaluated the use of naturally occurring stable C and N isotopes as an economically feasible and safe method for
quantifying pathways of energy flow within agroecosystems. Stable isotope values of the ladybird beetle Coleomegilla maculata lengi (Timberlake) collected from an agroecosystem were used to estimate the relative amount of C and N derived from agricultural
plants and incorporated by ladybird beetles based on mass balance equations. At the beginning of the diet-switching experiment
δ13C and δ15N values of H. variegata (–12.0‰ and 6.3‰, respectively) differed by –0.2‰ and 2.9‰ from the aphids that were provided exclusively as their diet. These
data are consistent with previous estimates of trophic level isotope effects. After switching the diet of H.
variegata to an alternative food, isotope values of H. variegata gradually shifted toward expected values for individuals fed this diet (–22.9‰ and 8.8‰ for δ13C and δ15N values, respectively). Isotope values of another ladybird beetle, C. maculata, collected from the field indicated that in May, alfalfa and maize (pollen) obtained in the previous year contributed 32%
and 68% of the C or N to the diets of these individuals and in August, 52%, 6%, and 42% of the C or N assimilated by these
insects was derived from alfalfa, wheat, and maize, respectively. These data are consistent with expectations based on the
relative abundance of C. maculata in various crops during the season. The field and laboratory data are a clear indication that isotope values are sensitive
to dietary changes on a relatively short time scale (days) and provide a strong basis for the use stable C and N isotope to
trace energy flow patterns of these beneficial organisms within agroecosystems.
Received: 17 November 1995 / Accepted: 20 June 1996 相似文献
12.
Huan-Xiang Zhou 《Journal of biological inorganic chemistry》1997,2(1):109-113
Factors that contribute to the control of reduction potential by protein matrix are examined within a spherical protein model.
These include the nonpolar nature of protein matrices, solvent accessibility of the redox center, and net charges and dipoles
of surrounding amino acids. Simple rules on their effects are established. In particular, surface charges have little effect
on the reduction potential, and polar groups may either increase or decrease the reduction potential, depending on their orientations
relative to the redox center. The effects of complex formation, proton titration, and ionic strength are also discussed.
Received, accepted: 26 November 1996 相似文献
13.
B. Saal J. Plieske J. Hu C. F. Quiros D. Struss 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(5):695-699
Microsatellites are highly polymorphic and efficient markers for the analysis of plant genomes. Primer specificity, however,
may restrict the applicability of these markers even between closely related species for comparative mapping studies. We have
demonstrated that the majority of microsatellites identified in oilseed rape (Brassica napus L; AC genome) correspond to loci which can be easily assigned to the A and C progenitor genomes. A study with 63 primer pairs
has shown that 54% detect two loci, one from each genome, while 25% and 21%, respectively, are either A or C genome-specific.
The distribution of rapeseed microsatellites in the C genome was investigated by genetic mapping in Brassica oleracea L. Ninety two dinucleotide microsatellites were screened for polymorphism in an F2 population derived from a cross between collard and cauliflower, for which an RFLP map has been constructed previously. Thirty
three primer pairs (35.7%) have yielded either unspecific or no PCR products whereas the remaining primer pairs amplified
one or more distinct loci. The level of polymorphism found in the mapping population was 49.2%. A total of 29 primer pairs
disclosed 34 loci of which 31 are evenly distributed on 8 of the 9 B. oleracea linkage groups. For the remaining three markers linkage could not be established. Our results showed that microsatellite
markers from the composite genome of B. napus can serve as a useful marker system in genetic studies and for plant-breeding objectives in B. oleracea.
Received: 14 April 2000 / Accepted: 3 July 2000 相似文献
14.
Genetic variation within and among populations of a wild rice Oryza granulata from China detected by RAPD and ISSR markers 总被引:37,自引:0,他引:37
W. Qian S. Ge D.-Y. Hong 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(2-3):440-449
Genetic variation within and between five populations of Oryza granulata from two regions of China was investigated using RAPD (random amplified polymorphic DNA) and ISSR (inter-simple sequence
repeat amplification) markers. Twenty RAPD primers used in this study amplified 199 reproducible bands with 61 (30.65%) polymorphic;
and 12 ISSR primers amplified 113 bands with 52 (46.02%) polymorphic. Both RAPD and ISSR analyses revealed a low level of
genetic diversity in wild populations of O. granulata. Furthermore, analysis of molecular variance (AMOVA) was used to apportion the variation within and between populations both
within and between regions. As the RAPD markers revealed, 73.85% of the total genetic diversity resided between the two regions,
whereas only 19.45% and 6.70% were present between populations within regions and within a population respectively. Similarly,
it was shown by ISSR markers that a great amount of variation (49.26%) occurred between the two regions, with only 38.07%
and 12.66% between populations within regions and within a population respectively. Both the results of a UPGMA cluster, based
on Jaccard coefficients, and pairwise distance analysis agree with that of the AMOVA partition. This is the first report of
the partitioning of genetic variability within and among populations of O. granulata at the DNA level, which is in general agreement with a recent study on the same species in China using allozyme analysis.
Our results also indicated that the percentage of polymorphic bands (PPB) detected by ISSR is higher than that detected by
RAPD. It seems that ISSR is superior to RAPD in terms of the polymorphism detected and the amplification reproducibility.
Received: 29 March 2000 / Accepted: 15 May 2000 相似文献
15.
A. Mohanty J. P. Martín I. Aguinagalde 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,100(8):1304-1310
High chloroplast DNA (cpDNA) diversity was found within and among populations of Prunus spinosa sampled from seven European deciduous forests. A study of 12% of the total chloroplast genome detected 44 mutations, which
were distributed over 24 haplotypes; four were common to two or more populations and the rest were unique haplotypes. The
most-abundant and widely distributed haplotype was H2 (frequency = 41% approximately). Six of the seven populations were polymorphic.
All of the six polymorphic populations had ”private” haplotypes (frequency < 5%) in addition to common haplotypes. The UPGMA
dendrogram demonstrated a correlation between populations and their geographical locations. The total diversity was high (hT = 0.824) and a major portion of it was within populations (hs = 0.663). The level of population subdivision for unordered alleles was low (GST = 19.5%) and for ordered alleles was lower (NST = 13.6%). No phylogeographic structure could be demonstrated in the present geographical scale. High polymorphism in the cpDNA
of P. spinosa has to be considered carefully when planning phylogenetic studies involving this species.
Received: 20 September 1999 / Accepted: 10 November 1999 相似文献
16.
Effects of habitat fragmentation on species diversity and herbivore-parasitoid interactions were analyzed using the insect
community of seed feeders and their parasitoids in the pods of the bush vetch (Vicia sepium L.). Field studies were carried out on 18 old meadows differing in area and isolation. The area of these meadows was found
to be the major determinant of species diversity and population abundance of endophagous insects. Effects of isolation were
further analyzed experimentally using 16 small plots with potted vetch plants isolated by 100–500 m from vetch populations
on large old meadows. The results showed that colonization success greatly decreased with increasing isolation. In both cases,
insect species were not equally affected. Parasitoids suffered more from habitat loss and isolation than their phytophagous
hosts. Minimum area requirements, calculated from logistic regressions, were higher for parasitoids than for herbivores. In
addition, percent parasitism of the herbivores significantly decreased with area loss and increasing isolation of Vicia sepium plots, supporting the trophic-level hypothesis of island biogeography. Species with high rates of absence on meadows and
isolated plant plots were not only characterized by their high trophic level, but also by low abundance and high spatial population
variability. Thus conservation of large and less isolated habitat remnants enhances species diversity and parasitism of potential
pest insects, i.e., the stability of ecosystem functions.
Received: 4 January 1999 / Accepted: 8 September 1999 相似文献
17.
C. Grenier P. J. Bramel-Cox M. Noirot K. E. Prasada Rao P. Hamon 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(1-2):190-196
A large collection, such as the sorghum [Sorghum bicolor (L.) Moench] landrace collection held at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT),
represents a challenge for the maintenance of both the accessions of and the information documented for the germplasm collection.
The accessibility and knowledge of the landrace collection are the essential factors for an efficient utilization of the genetic
resources by both breeders and farmers. Different sampling strategies, either random or non-random, were proposed to obtain
subsets of reduced size (core collection). Three subsets were established; a random sampling within a stratified collection
(logarithmic strategy: L); a sample based upon morpho-agronomic diversity (principal component score strategy: PCS); and a
sample based upon an empirical knowledge of sorghum (taxonomic strategy: T). Comparisons of these three samples for morpho-agronomic
characterization and passport information were assessed to determine their impact on phenotypic diversity. For their overall
diversity, the three subsets did not differ, as shown with the two-dimensional representation of the morpho-agronomic diversity
and the Shannon-Weaver diversity indices. When comparisons for morpho-agronomic and passport data were considered, the PCS
subset looked similar to the entire landrace collection. The L subset showed differences for characters associated with the
photoperiod reaction that was considered in the stratification of the collection. The T subset was the most distinct from
the entire landrace collection as it over-represented the landraces selected by farmers for specific uses and covered the
widest range of geographical adaptation and morpho-agronomic characteristics.
Received: 5 October 1999 / Accepted: 3 November 1999 相似文献
18.
Taiaro Atoll Lagoon is normally isolated from the ocean, but at least 125 marine fish species of 31 families are present
there. We sampled fish larvae in Taiaro Lagoon and the nearby ocean in February 1994 with plankton net, neuston net and light
trap to investigate which taxa were completing their life cycles in the lagoon. Concentrations of fish eggs and larvae were
very high in the lagoon indicating intense spawning, but larvae of only 18 taxa of 10 families were present. Only six, a callionymid,
gobiids, a hemiramphid, a microdesmid, and two pomacentrids, were present across a full range of pelagic sizes, and were clearly
completing their pelagic stage in the lagoon. Four other taxa, an apogonid, two labrids and a scarid, were common, but the
largest individuals were small (<5 mm) postflexion larvae. These may have been completing their pelagic stage in the lagoon.
The remaining lagoonal larvae (eight taxa) were rare and at the preflexion stage, so we could only conclude that they hatched
from eggs spawned in the lagoon. Nineteen taxa of 15 families found as adults in the lagoon were present outside the lagoon
as larvae, but not inside, suggesting that they may not normally complete their life cycles in the lagoon. Horizontal distributions
of larvae in the lagoon are apparently due to the interaction of larval vertical distribution behaviour with a wind-driven
countercurrent system.
Accepted: 16 October 1996 相似文献
19.
North American study on essential derivation in maize: inbreds developed without and with selection from F2 populations 总被引:2,自引:0,他引:2
R. Bernardo A. L. Kahler 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(6-7):986-992
An essentially derived variety largely retains the characteristics of a parental or ancestral variety. A consensus has not
been reached regarding the threshold for declaring essential derivation in maize (Zea mays L.), partly because benchmark data are lacking. Our objective in this study, commissioned by the American Seed Trade Association,
was to determine the range of parental contribution among maize inbreds developed without and with selection. Seed companies
in North America contributed existing proprietary data on the molecular marker similarity of 100 or more families, developed
without selection from F2 populations, with each of their parents. The companies also sent us seed samples of elite inbreds, developed with selection
from F2 populations, for analysis using 60 RFLP marker loci and 20 SSR marker loci. Among the families developed without selection,
the average parental contribution was close to the expected value of 0.50 for F2 populations. Specific families received up to 79% of their alleles from one parent. Although selection tended to increase
the frequency of such transgressive segregants, it did not necessarily increase the maximum parental contribution in an F2 population. Parental contributions were consistent between the elite inbreds and their early-generation families. We conclude
that inbreds with 70% to nearly 80% of their genome derived from one parent can be obtained from an F2 population. Further empirical data would be valuable particularly for backcross populations, which were not available in
this study.
Received: 21 June 2000 / Accepted: 28 July 2000 相似文献
20.
Assessing the genetic divergence of Pinus leucodermis Ant. endangered populations: use of molecular markers for conservation purposes 总被引:2,自引:0,他引:2
G. Bucci G. G. Vendramin L. Lelli F. Vicario 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(7):1138-1146
In this study, 23 previously identified Mendelian RAPD markers and 16 polymorphic allozymic markers were used to assess divergence
among two Greek populations and five Italian populations of Pinus leucodermis. Confidence intervals of observed genetic divergence were obtained using bootstrap analysis. Divergence among Italian populations
was found to be about as large as that between Italian and Greek populations. Since it is likely that the split of two nuclei
took place more than 10,000 years ago, a larger differentiation between, rather than within, the above nuclei was expected.
If genetic drift was responsible for the larger divergence of Italian populations, large randomly generated disequilibrium
between alleles at neutral, unlinked loci was expected. Indeed, the proportion of pairs of loci showing a non-random association
of alleles within each of the Italian populations was larger than what was expected by pure chance (7.95–10.88%). Effective
population size based on randomly generated disequilibrium was quite small for three out of the five populations considered
(N
e
=17.31±1.88, 16.57± 1.73, and 31.41±7.26, respectively). The implications of the results with respect to the conservation
of endangered species of trees are discussed.
Received: 27 April 1997 / Accepted: 14 June 1997 相似文献