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1.
Douglas-fir trees from 39 open-pollinated families at four test locations were assessed to estimate heritability of modulus of elasticity (MOE) and basic density. After trees were felled, sound velocity was measured on 4-m logs with the Director HM200. Disks were taken to estimate dry and green wood density; dynamic MOE was estimated as green density × (sound velocity)2. Heritability estimates of MOE (across-site h
2=0.55) were larger than those for total height (0.15) and diameter at breast height (DBH; 0.29), and similar to those for density (0.59). Negative genetic correlations were found for MOE with height (r
A=−0.30) and DBH (r
A=−0.51), and were similar to those found for density with height (r
A=−0.52) and DBH (r
A=−0.57). The partial correlations of height with MOE and density, while holding DBH constant, were positive, implying that the observed negative correlations between height and the wood properties were a function of the high positive correlation between height and DBH and the strong negative correlations between DBH and the wood properties. Taper [DBH/(height−1.4)] was found to be negatively associated with MOE. Selection for MOE may produce greater gains than selection for density because MOE had a larger coefficient of additive variation (9.6%) than density (5.1%). Conversely, selection for growth may have a more negative impact on MOE than density because of the greater genetic variation associated with MOE. Family mean correlations of the wood quality traits with stem form and crown health were mostly nonsignificant. 相似文献
2.
R. Ortiz S. Madsen W. W. Wagoire J. Hill S. Chandra O. Stølen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(6-7):1103-1106
Diallel mating designs have proved informative in determining the inheritance of quantitative traits of interest to plant
breeders. Apart from the well-established analyses of a complete diallel, the two-way factorial data structure of this design
lends itself to analysis by the additive-main-effects-and-multiplicative-interaction (AMMI) model. This research article describes
the joint application of the AMMI model and Griffing’s method 1, model I, to gain insight into the breeding value of inbred
lines in a self-pollinated crop such as disomic, hexaploid bread wheat. Data from a multi-environment trial of a complete
diallel cross between eight lines adapted to the East African highlands were analyzed to provide an example of this joint
analysis. This combined approach identified not only the direction of a cross, i.e. which parent should be male or female,
but also which crosses produce offspring showing F1 heterosis.
Received: 10 June 2000 / Accepted: 31 July 2000 相似文献
3.
Milled rice (Oryza sativa L.) is composed of approximately 90% starch. The properties of starch have considerable effects on cooked rice palatability and consumer acceptability. Starch pasting viscosity parameters serve as important indices in the estimation of eating, cooking, and processing qualities of rice. In the present study, four cytoplasmic male-sterile (CMS) lines and eight restorer (R) lines have been used in an incomplete diallel cross to analyze seed effects, cytoplasmic effects, maternal gene effects, and their genotype × environment (GE) effects on the following starch pasting viscosity parameters: breakdown (BD), consistency (CS), and setback (SB). The results demonstrated that the total main genetic variances (VG) accounted for over 64% of the total genetic variance (VG + VGE) for the three traits, indicating that these traits were mainly controlled by the main genetic effects in addition to the GE interaction effects. The estimated total narrow-sense heritability were 67.8%, 79.5%, and 79.5% for BD, CS, and SB, respectively. The general heritability (h2G) accounted for over 75% of the total heritability (h2G + h2GE), indicating that early selection would be effective for those traits and the selection efficiencies were relatively stable in different environments. 相似文献
4.
Ordas B Butron A Alvarez A Revilla P Malvar RA 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(7):1183-1191
Reciprocal recurrent selection (RRS) was proposed for simultaneously improving two populations and their cross. A modification
of the classical full-sib RRS (FS-RRS) was proposed in which the performance of full-sibs and S2 families is combined in a selection index (FS-S2-RRS). The Mediterranean corn borer (MCB) is the main corn borer species in the Mediterranean and adjacent areas and produces
important yield losses. We started two RRS programs (FS-RRS and FS-S2-RRS) from the same maize population in which the selection criterion was grain yield under artificial infestation with MCB
eggs. Original populations, two cycles of selection derived from them by both RRS methods, and population crosses were evaluated
under MCB attack and under insecticide treatment in three different environments. The objective was to compare the efficiency
of the FS-RRS and the FS-S2-RRS methods for improving grain yield. We found that the FS-S2-RRS method was successful for improving the yield of the population cross under optimum conditions (the regression coefficient
over cycles was b = 0.87** Mg ha−1 cycle−1) without losing yield under high pressure of MCB attack (b = 0.07). On the contrary, FS-RRS failed to improve the yield of the population cross under optimum conditions (b = 0.65) and tended to decrease the yield under high levels of MCB attack (b = −0.26). We conclude that for developing high yielding and stable varieties, FS-S2-RRS is more efficient than the classical FS-RRS method. 相似文献
5.
D. S. Virk A. S. Khehra Parminder S. Virk B. S. Dhillon 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,69(3):325-328
Summary For studying the inheritance of metric traits, diallel cross and factorial mating designs are commonly used. Since factorial mating design is less restrictive in crossing plans, the genetic information drawn from it was compared with that from a diallel cross. The comparison was made using graphical, genetic components and combining ability analyses for grain yield, grain weight and spike length in a field experiment of bread wheat (Triticum aestivum L.). Analyses were made on a nine parent diallel cross and a 4 × 5 factorial mating design which was sampled from the diallel cross. In general, there was a high degree of agreement between the results obtained from factorial mating design and diallel cross analyses showing thereby that the former provides almost equivalent genetic information to the latter. 相似文献
6.
The growth performance of malolactic fermenting bacteria Oenococcus oeni NCIMB 11648 and Lactobacillus brevis X2 was assessed in continuous culture. O. oeni grew at a dilution rate range of 0.007 to 0.052 h−1 in a mixture of 5:6 (g l−1) of glucose/fructose at an optimal pH of 4.5, and L. brevis X2 grew at 0.010 to 0.089 h−1 in 10 g l−1 glucose at an optimal pH of 5.5 in a simple and safe medium. The cell dry weight, substrate uptake and product formation
were monitored, as well as growth kinetics, yield parameters and fermentation balances were also evaluated under pH control
conditions. A comparison of growth characteristics of two strains was made, and this showed significantly different performance.
O. oeni has lower maximum specific growth rate (μmax=0.073 h−1), lower maximum cell productivity (Q
x
max=17.6 mg cell l−1 h−1), lower maximum biomass yield (Y
x/s
max=7.93 g cell mol−1 sugar) and higher maintenance coefficient (m
s=0.45 mmol−1 sugar g−1 cell h−1) as compared with L. brevis X2 (μmax=0.110 h−1; Q
x
max=93.2 g−1 cell mol−1 glucose; Y
x/s
max=22.3 g cell mol−1 glucose; m
s=0.21 mmol−1 glucose g−1 cell h−1). These data suggest a possible more productive strategy for their combined use in maturation of cider and wine. 相似文献
7.
J. Hill R. Ortiz W. W. Wagoire O. Stølen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(2):305-309
Effectiveness of indirect selection for grain yield was investigated among eight bread wheat lines, selected in a stress
environment in the East African Highlands, where they showed a wide response to yellow rust, the biotic factor causing the
stress. The lines were intercrossed to give an 8×8F1 diallel, which was grown in this same environment for three consecutive growing seasons during 1994 and 1995. Half of the
last trial was sprayed with fungicide. From the estimates of narrow-sense heritabilities for yield and yellow rust severity,
and the genetic correlation between them, indirect selection for yield in the unsprayed plots, obtained by choosing the most
resistant 5% of this material was, on average, 12% higher than selecting for yield itself. In the fungicide-treated plots,
indirect selection was only 73% as efficient as direct selection. The implications of these results for selecting for yield
in stress environments are discussed.
Received: 10 April 1998 / Accepted: 5 August 1998 相似文献
8.
Desmond J. Stackpole René E. Vaillancourt Marcelo de Aguigar Brad M. Potts 《Tree Genetics & Genomes》2010,6(2):179-193
Genetic parameters for stem diameter and wood density were compared at selection (4–5 years) and harvest (16–17 years) age
in an open-pollinated progeny trial of Eucalyptus globulus in Tasmania (Australia). The study examined 514 families collected from 17 subraces of E. globulus. Wood density was assessed on a subsample of trees indirectly using pilodyn penetration at both ages and directly by core
basic density at harvest age. Significant additive genetic variance and narrow-sense heritabilities (
h\textop2 h_{\text{op}}^2 ) were detected for all traits. Univariate and multivariate estimates of heritabilities were similar for each trait except
harvest-age diameter. Comparable univariate estimates of selection- and harvest-age heritabilities for diameter masked changes
in genetic architecture that occurred with stand development, whereby the loss of additive genetic variance through size-dependent
mortality was countered by the accentuation of additive genetic differences among survivors with age. Regardless, the additive
genetic (r
a) and subrace (r
s) correlations across ages were generally high for diameter (0.95 and 0.61, respectively) and pilodyn penetration (0.77 and
0.96), as were the correlations of harvest-age core basic density with selection- and harvest-age pilodyn (r
a −0.83, −0.88; r
s −0.96, −0.83). While r
s between diameter and pilodyn were close to zero at both ages, there was a significant change in r
a from adverse at selection age (0.25) to close to zero (−0.07) at harvest age. We argue that this change in the genetic correlation
reflects a decoupling of the genetic association of growth and wood density with age. This result highlights the need to validate
the use of selection-age genetic parameters for predicting harvest-age breeding values. 相似文献
9.
Body mass (BM) and resting metabolic rates (RMR) are two inexorably linked traits strongly related to mammalian life histories. Yet, there have been no studies attempting to estimate heritable variation and covariation of BM and RMR in natural populations. We used a marker‐based approach to construct a pedigree and then the ‘animal model’ to estimate narrow sense heritability (h2) of these traits in a free‐living population of weasels Mustela nivalis—a small carnivore characterised by a wide range of BM and extremely high RMR. The most important factors affecting BM of weasels were sex and habitat type, whereas RMR was significantly affected only by seasonal variation of this trait. All environmental factors had only small effect on estimates of additive genetic variance of both BM and RMR. The amount of additive genetic variance associated with BM and estimates of heritability were high and significant in males (h2 = 0.61), but low and not significant in females (h2 = 0.32), probably due to small sample size for the latter sex. The results from the two‐trait model revealed significant phenotypic (rP = 0.62) and genetic correlation (rA = 0.89) between BM and whole body RMR. The estimate of heritability of whole body RMR (0.54) and BM corrected RMR (0.45) were lower than estimates of heritability for BM. Both phenotypic and genetic correlations between BM corrected RMR and BM had negative signals (rP = ?0.42 and rA = ?0.58). Our results indicate that total energy expenditures of individuals can quickly evolve through concerted changes in BM and RMR. 相似文献
10.
11.
Mapping QTL controlling fatty acid composition in a doubled haploid rapeseed population segregating for oil content 总被引:2,自引:0,他引:2
Jianyi Zhao Zoran Dimov Heiko C. Becker Wolfgang Ecke Christian Möllers 《Molecular breeding : new strategies in plant improvement》2008,21(1):115-125
Increasing oil content and improving the fatty acid composition in the seed oil are important breeding goals for rapeseed
(Brassica napus L.). The objective of the study was to investigate a possible relationship between fatty acid composition and oil content
in an oilseed rape doubled haploid (DH) population. The DH population was derived from a cross between the German cultivar
Sollux and the Chinese cultivar Gaoyou, both having a high erucic acid and a very high oil content. In total, 282 DH lines
were evaluated in replicated field experiments in four environments, two each in Germany and in China. Fatty acid composition
of the seed oil was analyzed by gas liquid chromatography and oil content was determined by NIRS. Quantitative trait loci
(QTL) for fatty acid contents were mapped and their additive main effects were determined by a mixed model approach using
the program QTLMapper. For all fatty acids large and highly significant genetic variations among the genotypes were observed.
High heritabilities were determined for oil content and for all fatty acids (h
2 = 0.82 to 0.94), except for stearic acid content (h
2= 0.38). Significant correlations were found between the contents of all individual fatty acids and oil content. Closest genetic
correlations were found between oil content and the sum of polyunsaturated fatty acids (18:2 + 18:3;
r
G = −0.46), the sum of monounsaturated fatty acids (18:1 + 20:1 + 22:1; r
G = 0.46) and palmitic acid (16:0; r
G = −0.34), respectively. Between one and eight QTL for the contents of the different fatty acids were detected. Together, their
additive main effects explained between 28% and 65% of the genetic variance for the individual fatty acids. Ten QTL for fatty
acid contents mapped within a distance of 0 to 10 cM to QTL for oil content, which were previously identified in this DH population.
QTL mapped within this distance to each other are likely to be identical. The results indicate a close interrelationship between
fatty acid composition and oil content, which should be considered when breeding for increased oil content or improved oil
composition in rapeseed. 相似文献
12.
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
13.
A broad regional understanding of tropical forest leaf photosynthesis has long been a goal for tropical forest ecologists,
but it has remained elusive due to difficult canopy access and high species diversity. Here we develop an empirical model
to predict sunlit, light-saturated, tropical leaf photosynthesis using leaf and simulated canopy spectra. To develop this
model, we used partial least squares (PLS) analysis on three tropical forest datasets (159 species), two in Hawaii and one
at the biosphere 2 laboratory (B2L). For each species, we measured light-saturated photosynthesis (A), light and CO2 saturated photosynthesis (A
max), respiration (R), leaf transmittance and reflectance spectra (400–2,500 nm), leaf nitrogen, chlorophyll a and b, carotenoids, and leaf mass per area (LMA). The model best predicted A [r
2
= 0.74, root mean square error (RMSE) = 2.9 μmol m−2 s−1)] followed by R (r
2
= 0.48), and A
max (r
2
= 0.47). We combined leaf reflectance and transmittance with a canopy radiative transfer model to simulate top-of-canopy
reflectance and found that canopy spectra are a better predictor of A (RMSE = 2.5 ± 0.07 μmol m−2 s−1) than are leaf spectra. The results indicate the potential for this technique to be used with high-fidelity imaging spectrometers
to remotely sense tropical forest canopy photosynthesis. 相似文献
14.
A family of 10 competing, unstructured models has been developed to model cell growth, substrate consumption, and product formation of the pyruvate producing strain Escherichia coli YYC202 ldhA::Kan strain used in fed-batch processes. The strain is completely blocked in its ability to convert pyruvate into acetyl-CoA or acetate (using glucose as the carbon source) resulting in an acetate auxotrophy during growth in glucose minimal medium. Parameter estimation was carried out using data from fed-batch fermentation performed at constant glucose feed rates of
qVG=10 mL h–1. Acetate was fed according to the previously developed feeding strategy. While the model identification was realized by least-square fit, the model discrimination was based on the model selection criterion (MSC). The validation of model parameters was performed applying data from two different fed-batch experiments with glucose feed rate
qVG=20 and 30 mL h–1, respectively. Consequently, the most suitable model was identified that reflected the pyruvate and biomass curves adequately by considering a pyruvate inhibited growth (Jerusalimsky approach) and pyruvate inhibited product formation (described by modified Luedeking–Piret/Levenspiel term).List of symbols cA
acetate concentration (g L–1)
- cA,0
acetate concentration in the feed (g L–1)
- cG
glucose concentration (g L–1)
- cG,0
glucose concentration in the feed (g L–1)
- cP
pyruvate concentration (g L–1)
- cP,max
critical pyruvate concentration above which reaction cannot proceed (g L–1)
- cX
biomass concentration (g L–1)
- KI
inhibition constant for pyruvate production (g L–1)
- KIA
inhibition constant for biomass growth on acetate (g L–1)
- KP
saturation constant for pyruvate production (g L–1)
- KP
inhibition constant of Jerusalimsky (g L–1)
- KSA
Monod growth constant for acetate (g L–1)
- KSG
Monod growth constant for glucose (g L–1)
- mA
maintenance coefficient for growth on acetate (g g–1 h–1)
- mG
maintenance coefficient for growth on glucose (g g–1 h–1)
- n
constant of extended Monod kinetics (Levenspiel) (–)
- qV
volumetric flow rate (L h–1)
- qVA
volumetric flow rate of acetate (L h–1)
- qVG
volumetric flow rate of glucose (L h–1)
- rA
specific rate of acetate consumption (g g–1 h–1)
- rG
specific rate of glucose consumption (g g–1 h–1)
- rP
specific rate of pyruvate production (g g–1 h–1)
- rP,max
maximum specific rate of pyruvate production (g g–1 h–1)
- t
time (h)
- V
reaction (broth) volume (L)
- YP/G
yield coefficient pyruvate from glucose (g g–1)
- YX/A
yield coefficient biomass from acetate (g g–1)
- YX/A,max
maximum yield coefficient biomass from acetate (g g–1)
- YX/G
yield coefficient biomass from glucose (g g–1)
- YX/G,max
maximum yield coefficient biomass from glucose (g g–1)
-
growth associated product formation coefficient (g g–1)
-
non-growth associated product formation coefficient (g g–1 h–1)
-
specific growth rate (h–1)
- max
maximum specific growth rate (h–1) 相似文献
15.
M. N. Inagaki G. Varughese S. Rajaram M. van Ginkel A. Mujeeb-Kazi 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(4):550-556
Yield performance of each group of ten spring bread wheat lines selected by doubled haploid (DH), single-seed descent (SSD)
and pedigree selection (PS) methods from three F1 crosses was compared with the aim of evaluating the DH method in breeding programs. Populations of 65–97 DH lines and 110
SSD lines per cross were used for selection. PS lines were developed by repeated selections from 1500 F2 plants. Yield evaluation was performed at the F6 generation of SSD and PS lines along with DH lines in a 2-year field experiment. It took only 2 years from the planting of
wheat materials for DH production to the planting of selected DH lines for yield evaluation. There was no significant difference
in grain yield between DH lines and PS lines selected from an F1 cross whose parental varieties were closely related in their pedigrees. In two crosses with low coefficients of parentage
and a large variation in their progenies, grain yield of selected DH lines was significantly lower than those of selected
SSD and PS lines. These results confirm that the DH method can save time in obtaining recombinant inbred lines ready for yield
evaluation. However, a larger DH population is required to achieve the same level of genetic advance with the PS method in
crosses containing greater genetic variation.
Received: 23 December 1997 / Accepted: 12 March 1998 相似文献
16.
《Animal : an international journal of animal bioscience》2015,9(1):35-42
Profitability of beef production can be increased by genetically improving carcass traits. To construct breeding value evaluations for carcass traits, breed-specific genetic parameters were estimated for carcass weight, carcass conformation and carcass fat in five beef cattle breeds in Finland (Hereford, Aberdeen Angus, Simmental, Charolais and Limousin). Conformation and fat were visually scored using the EUROP carcass classification. Each breed was separately analyzed using a multitrait animal model. A total of 6879–19 539 animals per breed had phenotypes. For the five breeds, heritabilities were moderate for carcass weight (h2=0.39 to 0.48, s.e.=0.02 to 0.04) and slightly lower for conformation (h2=0.30 to 0.44, s.e.=0.02 to 0.04) and carcass fat (h2=0.29 to 0.44, s.e.=0.02 to 0.04). The genetic correlation between carcass weight and conformation was favorable in all breeds (rG=0.37 to 0.53, s.e.=0.04 to 0.05), heavy carcasses being genetically more conformed. The phenotypic correlation between carcass weight and carcass fat was moderately positive in all breeds (rP=0.21 to 0.32), implying that increasing carcass weight was related to increasing fat levels. The respective genetic correlation was the strongest in Hereford (rG=0.28, s.e.=0.05) and Angus (rG=0.15, s.e.=0.05), the two small body-sized British breeds with the lowest conformation and the highest fat level. The correlation was weaker in the other breeds (rG=0.08 to 0.14). For Hereford, Angus and Simmental, more conformed carcasses were phenotypically fatter (rP=0.11 to 0.15), but the respective genetic correlations were close to zero (rG=−0.05 to 0.04). In contrast, in the two large body-sized and muscular French breeds, the genetic correlation between conformation and fat was negative and the phenotypic correlation was close to zero or negative (Charolais: rG=−0.18, s.e.=0.06, rP=0.02; Limousin: rG=−0.56, s.e.=0.04, rP=−0.13). The results indicate genetic variation for the genetic improvement of the carcass traits, favorable correlations for the simultaneous improvement of carcass weight and conformation in all breeds, and breed differences in the correlations of carcass fat. 相似文献
17.
Analysis of a combined F1/F2 diallel cross in wheat 总被引:2,自引:0,他引:2
J. Hill W. W. Wagoire R. Ortiz O. Stølen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(6-7):1076-1081
Analysis of a conventional diallel cross offers only perfect-fit estimates of the genetic components of variation, but no
test for the goodness of fit of the model based on these estimates. When F2 progenies are available, however, combining F1 and F2 diallels in a single experiment overcomes these problems. Least-squares estimates of these components can be calculated,
errors attached to them and the goodness of fit of the resultant model tested. This analysis was applied to data on the severity
of yellow rust infection in an F1/F2 half-diallel cross among eight bread wheat lines adapted to the East African highlands. After removing two interacting arrays,
genetic analysis indicated that an additive/dominance model of gene action satisfactorily explained the variation observed
among the remaining six parents and their progenies, in both the individual F1 and F2 diallels and the combined F1/F2 diallel. Resistance to yellow rust was dominant to susceptibility and genes for increased resistance were more frequent.
Received: 25 May 2000 / Accepted: 31 July 2000 相似文献
18.
A. N. Sharpley 《Plant and Soil》1987,102(2):201-205
The effect of successive annual fertilizer P applications (30 kg P ha−1yr−1) on A values (plant availability) for four soils cropped with winter wheat, was investigated over a four-year period under
field conditions in the Southern Plains, USA, using P-32 as a tracer. With successive annual fertilizer P applications, winter
wheat dry matter yield and A value increased. This increase was linear for wheat yield on each soil (r2=0.77 to 0.97). For A value, the increase was a positive linear function of residual Bray-I P (r2=0.99 to 1.00) and a negative linear function of P-sorption index of the soil (r2=0.94 to 0.98). This was attributed to the fact that continued fertilizer P applications, by decreasing P-sorption index,
increased amounts of available P. Consequently, utilization of fertilizer P decreased with successive applications and A value,
thus, represents total soil P availability, including native and residual (carry over) fertilizer P. These results confirm
earlier suggestions that the A value may be used as a quantitative measurement of environmental and soil factors influencing
P availability. 相似文献
19.
Johan Kroon Tore Ericsson Gunnar Jansson Bengt Andersson 《Tree Genetics & Genomes》2011,7(6):1099-1111
We reviewed the genetic parameter estimates carried out from 1992 to 2006 for height increment in genetic tests of Norway
spruce and Scots pine, to describe patterns of genetic variation, heritability, and genetic correlations. The material included
seedling and clonal tests in Sweden, aged between 5 and 20 years. Multiple regression was used to explore relationships between
parameter values and test environments. Results showed moderate narrow-sense heritabilities ([^(h)]2 {\hat{h}^2} : mean =0.29 in Norway spruce; mean =0.23 in Scots pine) that decreased with test site latitude for both species. In Norway
spruce, [^(h)]2 {\hat{h}^2} increased with better growth and decreased with tree age, while for Scots pine, [^(h)]2 {\hat{h}^2} increased with tree age and southward transfer. The additive genetic coefficient of variation (; mean 15%), in Norway spruce, decreased with growth as well as site latitude. in Scots pine (mean =8.5%) increased with southward transfer and more southerly test latitude. Additive and genotypic within-site
genetic age-age correlations in Norway spruce were high, with mean r
A
and r
G
of 0.92 and 0.85, respectively. Corresponding across-sites estimates were on average lower. Genetic parameters were better
expressed on favorable sites, at younger ages in Norway spruce and at older ages in Scots pine. The results imply that gain
calculations should be based on different parameters in the two species. For maximizing genetic gain in the Swedish breeding
program, testing times could be shorter for Norway spruce than for Scots pine. The investigation showed a large variation
in parameter estimates from different field experiments, highlighting the importance of testing over multiple sites. 相似文献
20.
Physical Factors Control Phytoplankton Production and Nitrogen Fixation in Eight Texas Reservoirs 总被引:1,自引:0,他引:1
Margaret G. Forbes Robert D. Doyle J. Thad Scott Jacob K. Stanley Hui Huang Bryan W. Brooks 《Ecosystems》2008,11(7):1181-1197
We compared regression tree analyses and multiple linear regression models to explore the relative importance of physical
factors, land use, and water quality in predicting phytoplankton production and N2 fixation potentials at 85 locations along riverine to lacustrine gradients within eight southern reservoirs. The regression
tree model (r
2 = 0.73) revealed that differences in phytoplankton production were primarily a function of water depth. The highest rates
of production (mg C m−3 h−1) occurred at shallow sites (<0.9 m), where rates were also related to total phosphorus (TP) levels. At deeper sites, production
rates were higher at sites with relative drainage area (RDA, ratio of drainage area to water surface area) below 45, potentially
due to longer hydraulic residence times. In contrast, multiple linear regression selected TP, RDA, dissolved phosphorus, and
percent developed land as significant model variables (r
2 = 0.63). The regression tree model (r
2 = 0.67) revealed that N2 fixation potentials (mg N m−3 h−1) were substantially higher at sites with relatively smaller drainage areas (RDA < 45). Within this subgroup, fixation rates
were additionally related to TP values (threshold = 41 μg l−1). The multiple linear regression model (r
2 = 0.67) also selected RDA as the primary predictor of N2 fixation. Regression tree models suggest that nutrient controls (phosphorus) were subordinate to physical factors such as
depth and RDA. We concluded that regression tree analysis was well suited to revealing nonlinear trends in data (for example,
depth), but yielded large uncertainty estimates when applied to linear data (for example, phosphorus). 相似文献