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1.
Longin CF Utz HF Reif JC Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,112(5):903-912
Optimum allocation of resources is of fundamental importance for the efficiency of breeding programs. The objectives of our
study were to (1) determine the optimum allocation for the number of lines and test locations in hybrid maize breeding with
doubled haploids (DHs) regarding two optimization criteria, the selection gain ΔG
k
and the probability P
k
of identifying superior genotypes, (2) compare both optimization criteria including their standard deviations (SDs), and
(3) investigate the influence of production costs of DHs on the optimum allocation. For different budgets, number of finally
selected lines, ratios of variance components, and production costs of DHs, the optimum allocation of test resources under
one- and two-stage selection for testcross performance with a given tester was determined by using Monte Carlo simulations.
In one-stage selection, lines are tested in field trials in a single year. In two-stage selection, optimum allocation of resources
involves evaluation of (1) a large number of lines in a small number of test locations in the first year and (2) a small number
of the selected superior lines in a large number of test locations in the second year, thereby maximizing both optimization
criteria. Furthermore, to have a realistic chance of identifying a superior genotype, the probability P
k
of identifying superior genotypes should be greater than 75%. For budgets between 200 and 5,000 field plot equivalents, P
k
> 75% was reached only for genotypes belonging to the best 5% of the population. As the optimum allocation for P
k
(5%) was similar to that for ΔG
k
, the choice of the optimization criterion was not crucial. The production costs of DHs had only a minor effect on the optimum
number of locations and on values of the optimization criteria.
C. Friedrich H. Longin and H. Friedrich Utz contributed equally to this work. 相似文献
2.
Longin CF Utz HF Reif JC Wegenast T Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,115(4):519-527
Early testing prior to doubled haploid (DH) production is a promising approach in hybrid maize breeding. We (1) determined
the optimum allocation of the number of S1 families, DH lines, and test locations for two different breeding schemes, (2) compared the maximum selection gain achievable
under both breeding schemes, and (3) investigated limitations in the current method of DH production. Selection gain was calculated
by numerical integration in two-stage breeding schemes with evaluation of testcross progenies of (1) DH lines in both stages
(DHTC), or (2) S1 families in the first and DH lines within S1 families in the second stage (S1TC-DHTC). Different assumptions were made regarding the budget, variance components, and time of DH production within S1 families. Maximum selection gain in S1TC-DHTC was about 10% larger than in DHTC, indicating the large potential of early testing prior to DH production. The optimum
allocation of test resources in S1TC-DHTC involved similar numbers of test locations and test candidates in both stages resulting in a large optimum number
of S1 families in the first stage and DH lines within the best two S1 families in the second stage. The longer cycle length of S1TC-DHTC can be compensated by haploid induction of individual S1 plants instead of S1 families. However, this reduces selection gain largely due to the current limitations in the DH technique. Substantial increases
in haploid induction and chromosome doubling rates as well as reduction in costs of DH production would allow early testing
of S1 lines and subsequent production and testing of DH lines in a breeding scheme that combines high selection gain with a short
cycle length.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Thilo Wegenast H. Friedrich Utz C. Friedrich H. Longin Hans Peter Maurer Baldev S. Dhillon Albrecht E. Melchinger 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,120(4):699-708
In hybrid maize (Zea mays L.) breeding, doubled haploids (DH) are increasingly replacing inbreds developed by recurrent selfing. Doubled haploids may
be developed directly from S0 plants in the parental cross or via S1 families. In both these breeding schemes, we examined 2 two-stage selecting strategies, i.e., considering or ignoring cross
and family structure while selection among and within parental crosses and S1 families. We examined the optimum allocation of resources to maximize the selection gain ΔG and the probability P(q) of identifying the q% best genotypes. Our specific objectives were to (1) determine the optimum number and size of crosses and S1 families, as well as the optimum number of test environments and (2) identify the superior selection strategy. Selection
was based on the evaluation of testcross progenies of (1) DH lines in both stages (DHTC) and (2) S1 families in the first stage and of DH lines within S1 families in the second stage (S1TC-DHTC) with uniform and variable sizes of crosses and S1 families. We developed and employed simulation programs for selection with variable sizes of crosses and S1 families within crosses. The breeding schemes and selection strategies showed similar relative efficiency for both optimization
criteria ΔG and P (0.1%). As compared with DHTC, S1TC-DHTC had larger ΔG and P (0.1%), but a higher standard deviation of ΔG. The superiority of S1TC-DHTC was increased when the selection was done among all DH lines ignoring their cross and family structure and using variable
sizes of crosses and S1 families. In DHTC, the best selection strategy was to ignore cross structures and use uniform size of crosses. 相似文献
4.
5.
Longin CF Utz HF Melchinger AE Reif JC 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2007,114(3):393-402
Optimum allocation of test resources is of crucial importance for the efficiency of breeding programs. Our objectives were
to (1) determine the optimum allocation of the number of lines, test locations, as well as number and type of testers in hybrid
maize breeding using doubled haploids with two breeding strategies for improvement of general combining ability (GCA), (2)
compare the maximum selection gain (ΔG) achievable under both strategies, and (3) give recommendations for the optimum implementation of doubled haploids in commercial
hybrid maize breeding. We calculated ΔG by numerical integration for two two-stage selection strategies with evaluation of (1) testcross performance in both stages
(BS1) or (2) line per se performance in the first stage followed by testcross performance in the second stage (BS2). Different
assumptions were made regarding the budget, variance components (VCs), and the correlation between line per se performance
and GCA. Selection gain for GCA increased with a broader genetic base of the tester. Hence, testers combining a large number
of divergent lines are advantageous. However, in applied breeding programs, the use of single- or double-cross testers in
the first and inbred testers in the second selection stage may be a good compromise between theoretical and practical requirements.
With a correlation between line per se performance and GCA of 0.50, ΔG for BS1 is about 5% higher than for BS2, if an economic weight of line per se performance is neglected. With increasing economic
weight of line per se performance, relative efficiency of BS2 increased rapidly resulting in a superiority of BS2 over BS1
already for an economic weight for line per se performance larger than 0.1. Considering the importance of an economic seed
production, an economic weight larger than 0.1 seems realistic indicating the necessity of separate breeding strategies for
seed and pollen parent heterotic groups.
C. Friedrich H. Longin and H. Friedrich Utz have contributed equally to this work. 相似文献
6.
Doubled haploid versus S1 family recurrent selection for testcross performance in a maize population
Bordes J Charmet G de Vaulx RD Pollacsek M Beckert M Gallais A 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,112(6):1063-1072
Theoretically, in a recurrent selection program, the use of doubled haploids (DH) can increase genetic advance per unit of
time. To evaluate the efficiency expected from the use of DH for the improvement of grain yield in a maize (Zea mays L.) population, two recurrent selection programs for testcross performance were initiated using testcross progenies from
DH lines and S1 families. In 4 years one selection cycle using DH and two selection cycles using S1 families were carried out with the same selection intensity for both methods. As expected, testcross genetic variance was
twice as high among DH lines as among S1 families. The predicted genetic gain was 8.2% for the DH selection cycle, and 10.6% for the two S1 selection cycles, giving a per year advantage of 29% for the S1 family method over the DH method with a cycle of 4 years. With a 3-year cycle for the DH method, both methods were expected
to be equivalent. Using a tester related to the one used for selection, the genetic gains obtained were equivalent for both
methods: 6.6% for the DH cycle and 7.0% for the two S1 cycles. With a 3-year cycle for the DH method, the advantage would have been in favor of DH method. Furthermore, the DH method
has the advantage of simultaneously producing lines that are directly usable as parents of a hybrid. Thus, if the genetic
advance per unit of time is evaluated at the level of developed varieties even with the same or with a lower genetic advance
in population improvement, the DH method appears to be the most efficient. 相似文献
7.
Mi X Wegenast T Utz HF Dhillon BS Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(1):1-10
With best linear unbiased prediction (BLUP), information from genetically related candidates is combined to obtain more precise
estimates of genotypic values of test candidates and thereby increase progress from selection. We developed and applied theory
and Monte Carlo simulations implementing BLUP in 2 two-stage maize breeding schemes and various selection strategies. Our
objectives were to (1) derive analytical solutions of the mixed model equations under two breeding schemes, (2) determine
the optimum allocation of test resources with BLUP under different assumptions regarding the variance component ratios for
grain yield in maize, (3) compare the progress from selection using BLUP and conventional phenotypic selection based on mean
performance solely of the candidates, and (4) analyze the potential of BLUP for further improving the progress from selection.
The breeding schemes involved selection for testcross performance either of DH lines at both stages (DHTC) or of S1 families at the first stage and DH lines at the second stage (S1TC-DHTC). Our analytical solutions allowed much faster calculations of the optimum allocations and superseded matrix inversions
to solve the mixed model equations. Compared to conventional phenotypic selection, the progress from selection was slightly
higher with BLUP for both optimization criteria, namely the selection gain and the probability to select the best genotypes.
The optimum allocation of test resources in S1TC-DHTC involved ≥10 test locations at both stages, a low number of crosses (≤6) each with 100–300 S1 families at the first stage, and 500–1,000 DH lines at the second stage. In breeding scheme DHTC, the optimum number of test
candidates at the first stage was 5–10 times larger, whereas the number of test locations at the first stage and the number
of test candidates at the second stage were strongly reduced compared to S1TC-DHTC. 相似文献
8.
J. S. C. Smith T. Hussain E. S. Jones G. Graham D. Podlich S. Wall M. Williams 《Molecular breeding : new strategies in plant improvement》2008,22(1):51-59
Through the concerted use of doubled haploidy (DH), molecular markers and off-season nurseries, maize (Zea mays L.) breeders have unprecedented capabilities to quickly and precisely create progeny with desired levels of similarity to
either parents of a commercial hybrid. Genotypic data from both simulated and from actual populations created either by single
seed descent or through doubled haploidy were examined for the initial and subsequent generations. Simulation data showed
that DH progeny inherited larger blocks of parental chromosomes; approximately seven out of 10 chromosomes had intact segments
of 50% or greater. By the third DH generation progeny can be selected that are more than 90% similar to either parent of the
initial commercial hybrid. Actual marker data from the initial DH generation showed a maximum parental contribution of 88.4%
compared to 78.7% for progeny developed by single seed descent (SSD). The number of intact chromosomes was higher among DH
progeny than among progeny bred by SSD. Use of DH facilitates access to germplasm that is already present in commercial maize
hybrids. Available technologies coupled with the intellectual property protection regime will influence decisions made by
plant breeders in the balance of exotic compared to well-adapted germplasm they choose to access for further cycles. 相似文献
9.
Katarzyna Niemirowicz-Szczytt 《Acta Physiologiae Plantarum》1997,19(2):155-167
The utility of haploids and DH lines for breeding programmes and basic research is discussed here. High effectiveness of haploid
induction from random responding gametes and from valuable donor plants is not sufficient to ensure success in breeding. DH
lines often appeared inferior to conventionally obtained inbred lines. One of the causes may be a very high level of homozygosity,
in this paper referred to as excessive homozygosity. Besides, colchicine treatment as well as gametoclonal and somaclonal
variation could have a negative effect on the agronomic performance of DH plants. Lack of natural selection in the first stages
of haploid development is another important factor, negatively influencing haploid utility.
On the other hand, there is a wide range of possibilities of using haploids as model plants for basic research. Among different
applications, including mapping, genetic analysis, mutations, transformation, somatic hybridisation, biochemical and physiological
studies, artificial seed production and germplasm storage, the first seems to be explored most effectively and give promising
results. 相似文献
10.
The objective of this study was to investigate the effect of individual durum wheat (Triticum turgidum L.) chromosomes on crossability with maize (Zea mays L.) and to cytologically characterize the haploids recovered. Fourteen 'Langdon' (LDN) D-genome disomic substitution lines, a LDN Ph mutant (Ph1b ph1b), and normal 'Langdon' were pollinated with maize pollen. After pollination, hormonal treatment was given daily for up to 14 days. Haploid embryos were obtained from all lines and were aseptically cultured. From a total of 55,358 pollinated florets, 895 embryos were obtained. Only 14 of the embryos germinated and developed into healthy plants. Different substitution lines showed varying degrees of success. The most successful was the substitution 5D(5B) for both embryo formation and haploid plantlet production. These results indicate that the substitution of 5D for 5B confers on durum wheat a greater ability to produce haploids. Fluorescent genomic in situ hybridization (GISH) showed that the substitution haploids consisted of 7 A-genome chromosomes, 6 B-genome chromosomes, and 1 D-genome chromosome. Triticum urartu Turn. genomic DNA was efficient in probing the 7 A-genome chromosomes, although the D-genome chromosome also showed intermediate hybridization. This shows a close affinity between the A genome and D genome. We also elucidated the evolutionary translocation involving the chromosomes 4A and 7B that occurred at the time of evolution of durum wheat. We found that the distal segment translocated from chromosome 7B constitutes about 24% of the long arm of 4A. 相似文献
11.
Melchinger AE Technow F Dhillon BS 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2011,123(8):1269-1279
Recent progress in genotyping and doubled haploid (DH) techniques has created new opportunities for development of improved
selection methods in numerous crops. Assuming a finite number of unlinked loci (ℓ) and a given total number (n) of individuals to be genotyped, we compared, by theory and simulations, three methods of marker-assisted selection (MAS)
for gene stacking in DH lines derived from biparental crosses: (1) MAS for high values of the marker score (T, corresponding to the total number of target alleles) in the F2 generation and subsequently among DH lines derived from the selected F2 individual (Method 1), (2) MAS for augmented F2 enrichment and subsequently for T among DH lines from the best carrier F2 individual (Method 2), and (3) MAS for T among DH lines derived from the F1 generation (Method 3). Our objectives were to (a) determine the optimum allocation of resources to the F2 ( n1* \, n_{1}^{*} ) and DH generations (n - n1* ) (n - n_{1}^{*} ) for Methods 1 and 2 by simulations, (b) compare the efficiency of all three methods for gene stacking by simulations, and
(c) develop theory to explain the general effect of selection on the segregation variance and interpret our simulation results.
By theory, we proved that for smaller values of ℓ, the segregation variance of T among DH lines derived from F2 individuals, selected for high values of T, can be much smaller than expected in the absence of selection. This explained our simulation results, showing that for Method
1, it is best to genotype more F2 individuals than DH lines ($ n_{1}^{*} :n > 0.5 $ n_{1}^{*} :n > 0.5 ), whereas under Method 2, the optimal ratio n1* :n n_{1}^{*} :n was close to 0.5. However, for ratios deviating moderately from the optimum, the mean [`(X)] \overline{X} of T in the finally selected DH line (
T\textDH* T_{\text{DH}}^{*} ) was hardly reduced. Method 3 had always the lowest mean [`(X)] \overline{X} of
T\textDH* T_{\text{DH}}^{*} except for small numbers of loci (ℓ = 4) and is favorable only if a small number of loci are to be stacked in one genotype and/or saving one generation is of
crucial importance in cultivar development. Method 2 is under most circumstances the superior method, because it generally
showed the highest mean [`(X)] \overline{X} and lowest SD of
T\textDH* T_{\text{DH}}^{*} for the finally selected DH. 相似文献
12.
Grieder C Dhillon BS Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(6):971-980
Biofuels have gained importance recently and the use of maize biomass as substrate in biogas plants for production of methane
has increased tremendously in Germany. The objectives of our research were to (1) estimate variance components and heritability
for different traits relevant to biogas production in testcrosses (TCs) of maize, (2) study correlations among traits, and
(3) discuss strategies to breed maize as a substrate for biogas fermenters. We evaluated 570 TCs of 285 diverse dent maize
lines crossed with two flint single-cross testers in six environments. Data were recorded on agronomic and quality traits,
including dry matter yield (DMY), methane fermentation yield (MFY), and methane yield (MY), the product of DMY and MFY, as
the main target trait. Estimates of variance components showed general combining ability (GCA) to be the major source of variation.
Estimates of heritability exceeded 0.67 for all traits and were even much greater in most instances. Methane yield was perfectly
correlated with DMY but not with MFY, indicating that variation in MY is primarily determined by DMY. Further, DMY had a larger
heritability and coefficient of genetic variation than MFY. Hence, for improving MY, selection should primarily focus on DMY
rather than MFY. Further, maize breeding for biogas production may diverge from that for forage production because in the
former case, quality traits seem to be of much lower importance. 相似文献
13.
A. E. Melchinger R. K. Gumber R. B. Leipert M. Vuylsteke M. Kuiper 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(3-4):503-512
Prediction of the means and genetic variances in segregating generations could help to assess the breeding potential of base
populations. In this study, we investigated whether the testcross (TC) means and variances of F3 progenies from F1 crosses in European maize can be predicted from the TC means of their parents and F1 crosses and four measures of parental genetic divergence: genetic distance (GD) determined by 194 RFLP or 691 AFLPTM
1 markers, mid-parent heterosis (MPH), and absolute difference between the TC means of parents (∣P1−P2∣). The experimental materials comprised six sets of crosses; each set consisted of four elite inbreds from the flint or dent
germplasm and the six possible F1 crosses between them, which were evaluated for mid-parent heterosis. Testcross progenies of these materials and 20 random
F3 plants per F1 cross were produced with a single-cross tester from the opposite heterotic group and evaluated in two environments. The characters
studied were plant height, dry matter content and grain yield. The genetic distance between parent lines ranged between 0.17
and 0.70 for RFLPs and between 0.14 and 0.57 for AFLPs in the six sets. Testcross-means of parents, F1 crosses, and F3 populations averaged across the six crosses in a particular set generally agreed well for all three traits. Bartlett’s test
revealed heterogeneous TC variances among the six crosses in all sets for plant height, in four sets for grain yield and in
five sets for dry matter content. Correlations among the TC means of the parents, F1 crosses, and F3 populations were highly significant and positive for all traits. Estimates of the TC variance among F3 progenies for the 36 crosses showed only low correlations with the four measures of parental genetic divergence for all traits.
The results demonstrated that for our material, the TC means of the parents or the parental F1 cross can be used as predictors for the TC means of F3 populations. However, the prediction of the TC variance remains an unsolved problem.
Received: 4 August 1997 / Accepted: 17 November 1997 相似文献
14.
M. Stange T. A. Schrag H. F. Utz C. Riedelsheimer E. Bauer A. E. Melchinger 《Molecular breeding : new strategies in plant improvement》2013,32(3):533-546
Grain yield (GY) is a genetically complex and physiologically multiplicative trait which can be decomposed into the components kernel number (KN) and 100-kernel weight (HKW). Genetic analysis of these less complex yield component traits may give insights into the genetic architecture and predictive ability of complex traits. Here, we investigated how the incorporation of component traits and epistasis in quantitative trait locus (QTL) mapping approaches influences the accuracy of GY prediction. High-density genetic maps with 7,000–10,000 polymorphic single nucleotide polymorphisms were constructed for four biparental populations. The populations comprised between 99 and 227 doubled haploid maize lines which were phenotyped in field trials in two environments. Heritability was highest for HKW (88–89 %), intermediate for KN (72–80 %), and lowest for GY (64–83 %). Mapped QTL explained in total 21–55 %, 22–67 %, and 24–75 % of the genotypic variance for GY, KN, and HKW, respectively. Support intervals of QTL were short, indicating that QTL were located with high precision. Co-located QTLs with same parental origin of favorable alleles were detected within populations for different traits and between populations for the same traits. Using GY predictions based on the detected QTL, prediction accuracies (r) determined by cross validation ranged from 0.18 to 0.52. Epistatic models did not outperform the corresponding additive models. In conclusion, models based on QTL positions of component traits support the identification of favorable alleles for multiplicative traits and provide a basis to select superior inbred lines by marker-assisted breeding. 相似文献
15.
Gynogenesis was investigated on gentian (Gentiana triflora, G. scabra and their hybrids), which is an important ornamental flower. When unfertilized ovules were cultured in 1/2 NLN medium containing
a high concentration of sucrose (100 g/l), embryo-like structures (ELS) were induced. Although genotypic variation was observed
in ELS induction, all four genotypes produced ELSs ranging from 0.93 to 0.04 ELSs per flower bud. The ovules collected from
flower buds of later stages (just before anthesis or flower anthesis) tended to exhibit higher response. The dark culture
condition produced more than four times as many ELSs than in 16-h light condition. A significant number of plantlets were
directly regenerated from ELSs on MS regeneration medium. The ploidy levels of 179 regenerated plants were determined by flow
cytometry, revealing that the majority of them were diploid (55.9%) and haploid (31.3%). When a total of 54 diploid plants
were examined by molecular genetic markers, 52 (96.3%) were considered as doubled haploids (DHs). This is the first report
showing successful gynogenesis in gentian. The production of haploids and DHs by unfertilized ovule culture opens a novel
prospect in gentian F1 hybrid breeding. 相似文献
16.
Grieder C Dhillon BS Schipprack W Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,124(6):981-988
Breeding maize for use as a biogas substrate (biogas maize) has recently gained considerable importance. To optimize hybrid
breeding programs, information about line per se performance (LP) of inbreds and its relation to their general combining ability
(GCA) is required. The objectives of our research were to (1) estimate variance components and heritability of LP for agronomic
and quality traits relevant to biogas production, (2) study correlations among traits as well as between LP and GCA, and (3)
discuss implications for breeding of biogas maize. We evaluated 285 diverse dent maize inbred lines in six environments. Data
were recorded on agronomic and quality traits, including dry matter yield (DMY), methane fermentation yield (MFY), and their
product, methane yield (MY), as the main target trait. In agreement with observations made for GCA in a companion study, variation
in MY was mainly determined by DMY. MFY, which showed moderate correlation with lignin but only weak correlation with starch,
revealed only low genotypic variation. Thus, our results favor selection of genotypes with high DMY and less focus on ear
proportion for biogas maize. Genotypic correlations between LP and GCA [r
g (LP, GCA)] were highest (≥0.94) for maturity traits (days to silking, dry matter concentration) and moderate (≥0.65) for
DMY and MY. Multistage selection is recommended. Selection for GCA of maturity traits, plant height, and to some extent also
quality traits and DMY on the level of LP looks promising. 相似文献
17.
PEDRO P. OLEA 《Ibis》2011,153(4):832-845
Animals can select breeding sites using non‐social information (habitat characteristics) and social information (conspecific presence or abundance). The availability of both types of information is expected to vary over time during the colonization of a new area, conditioning their use by colonizers. However, if and how both types of information are exploited during the colonization process remains unclear. We hypothesized that non‐social information should be predominant at the beginning of a colonization episode (when conspecific presence is low) and that social information should gain in importance as the colonization progresses. We tested this hypothesis by studying habitat selection by the Griffon Vulture Gyps fulvus, a long‐lived colonial raptor, during a natural colonization process spanning 40 years. In NW Spain, the population showed a sharp increase from 15 breeding pairs in three colonies in the 1970s to 586 breeding pairs in 120 colonies in 2008, expanding its range from 90 km2 in the 1970s to 6403 km2 in 2008, with directions of expansion following areas rich in nesting cliffs. The main determinants of habitat selection varied over time. Livestock density and the characteristics of nesting cliffs were the main predictors of settlement at the onset of colonization. Breeding density of conspecifics increased its importance over time, having the greatest relative weight in habitat selection later in the colonization process. Our results indicated a prevalent use of non‐social information during the early stages of the colonization and an increasing role of social information as the expansion progressed. 相似文献
18.
Bo Peng Yongxiang Li Yang Wang Cheng Liu Zhizhai Liu Yan Zhang Weiwei Tan Di Wang Yunsu Shi Baocheng Sun Yanchun Song Tianyu Wang Yu Li 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2013,126(3):773-789
Simultaneous improvement in grain yield and related traits in maize hybrids and their parents (inbred lines) requires a better knowledge of genotypic correlations between family per se performance (FP) and testcross performance (TP). Thus, to understand the genetic basis of yield-related traits in both inbred lines and their testcrosses, two F 2:3 populations (including 230 and 235 families, respectively) were evaluated for both FP and TP of eight yield-related traits in three diverse environments. Genotypic correlations between FP and TP, $ \hat{r}_{\text{g}} $ (FP, TP), were low (0–0.16) for grain yield per plant (GYPP) and kernel number per plant (KNPP) in the two populations, but relatively higher (0.32–0.69) for the other six traits with additive effects as the primary gene action. Similar results were demonstrated by the genotypic correlations between observed and predicted TP values based on quantitative trait loci positions and effects for FP, $ \hat{r}_{\text{g}} $ (M FP, Y TP). A total of 88 and 35 QTL were detected with FP and TP, respectively, across all eight traits in the two populations. However, the genotypic variances explained by the QTL detected in the cross-validation analysis were much lower than those in the whole data set for all traits. Several common QTL between FP and TP that accounted for large phenotypic variances were clustered in four genomic regions (bin 1.10, 4.05–4.06, 9.02, and 10.04), which are promising candidate loci for further map-based cloning and improvement in grain yield in maize. Compared with publicly available QTL data, these QTL were also detected in a wide range of genetic backgrounds and environments in maize. These results imply that effective selection based on FP to improve TP could be achieved for traits with prevailing additive effects. 相似文献
19.
Developmental stability reflects the ability of individualsto cope with their environment during ontogeny given their geneticbackground. An inability to cope with environmental and geneticperturbations is reflected in elevated levels of fluctuatingasymmetry and other measures of developmental instability. Bothtrait size and symmetry have been implicated as playing an importantrole in sexual selection, although their relative importancehas never been assessed. We collected information on the relationshipbetween success in sexual competition and size and asymmetry,respectively, to assess the relative importance of these twofactors in sexual selection. Studies that allowed comparisonof the relationships for the same traits' size and symmetryand success in sexual competition constituted the data, whichtotaled 73 samples from 33 studies of 29 species. The averagesample-size weighted correlation coefficients between matingsuccess or attractiveness and size and asymmetry, respectively,were used as measures of effect size in a meta-anatysis. Analysiswas conducted on samples, studies, and species separately. Wefound evidence of an overall larger effect of symmetry at thespecies level of analysis, but similar effects at the sampleor study levels. The difference in effect size for charactersize and character symmetry was larger for secondary sexualcharacters than for ordinary morphological characters at thelevel of analysis of samples. The results lend support to theconclusion that symmetry plays an important general role insexual selection, especially symmetry of secondary sexual characters. 相似文献
20.
J. E. Bradshaw M. F. B. Dale G. E. L. Swan D. Todd R. N. Wilson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,97(8):1331-1339
In 1992, 72 seedlings from each of 198 pair crosses were grown in a glasshouse, and the tubers produced by each plant were
visually assessed on a 1–9 scale of increasing preference. Three groups of four progenies with high, medium and low mean scores
were chosen to progress, without selection via tuber progenies and four-plant plots at a high-grade seed site, to replicated
yield trials in the third clonal generation. The three groups maintained their high, medium and low scores for visual preference
over the three clonal generations and also had high, medium and low scores in the second and third clonal generations for
yield, size and appearance of tubers, all of which were components of visual preference. The three groups were predicted to
have 13.6%, 1.8% and 0.2% of their clones exceeding the mean of 13 control cultivars for visual preference in the replicated
trials, and 12.1%, 4.9% and 1.4% for yield, and 56.8%, 37.1% and 14.8% for appearance. The experiment confirmed that selection
for visual preference within crosses in the seedling and first clonal generations is very ineffective, but that worthwhile
progress can be made from selection in the second clonal generation, with correlated responses for faster emergence, earlier
maturity, higher yield and greater regularity of shape (appearance). Combining selection of the high group of progenies with
selection in the second clonal generation of the best 34 out of the 120 clones in this group, produced a response in visual
preference in the third clonal generation of 1.00 compared with a maximum possible of 1.74. Ways of achieving further improvements
in early-generation selection are discussed.
Received: 26 May 1998 / Accepted: 9 June 1998 相似文献