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1.
Genetic divergence in two tropical maize composites after four cycles of reciprocal recurrent selection 下载免费PDF全文
Adesike O. Kolawole Abebe Menkir Melaku Gedil Essie Blay Kwadwo Ofori Jennifer G. Kling 《Plant Breeding》2017,136(1):41-49
Two tropical maize composites were subjected to four cycles of reciprocal recurrent selection to develop divergent inbred lines with good combining ability. This study was conducted to examine the extent of genetic diversity, changes in allele composition and genetic structure, of 100 randomly selected S1 lines each from the original (C0) and advanced (C4) selection cycles of TZL COMP3 and TZL COMP4, genotyped using single nucleotide polymorphism (SNP) markers. Results revealed that the proportion of alleles at both low and high frequencies decreased from C0 to C4, whereas those at intermediate frequencies increased at C4 in the two composites. More unique and other alleles were lost at C4 in TZL COMP3 relative to those in TZL COMP4. The changes in different measures of genetic diversity were either small or negligible with selection in the two composites. The proportion of markers departing from Hardy–Weinberg equilibrium (HWE) decreased with selection, whereas the total number of pairs of markers in linkage disequilibrium increased with selection in the two composites. Examination of changes in population structures using a model‐based approach as well as cluster and multivariate analyses found a high degree of concordance in stratifying the 400 S1 lines into four non‐overlapping groups corresponding to the two selection cycles each within the reciprocal composites. The observed molecular‐based divergence between cycles within the same composite and the clear differentiation between the complementary composites highlight the importance of reciprocal recurrent selection for preserving genetic diversity for long‐term selection. This increases the potential of the advanced selection cycles to sustain genetic gain in productivity of hybrids adapted to the savannas in West and Central Africa. 相似文献
2.
Mateus Figueiredo Santos Tassiano Maxwell Marinho Câmara Gustavo Vitti Moro Emiliano Fernandes Nassau Costa Cláudio Lopes De Souza Jr 《Euphytica》2007,157(1-2):185-194
This research reports responses to selection and changes in general (GCA) and specific (SCA) combining abilities after three
cycles of a modified reciprocal recurrent selection procedure (MRRS) in EPB-4 and EPB-5 maize populations. In the MRRS procedure
a cycle can be completed in 1 or 2 years depending on the availability of winter breeding nurseries. The original and the
three selection cycles of the two populations per se (eight entries) and the partial diallel developed from the crosses between
them (16 entries) were evaluated in six environments. Realized response to selection on the population cross was 7.25% cycle−1 for grain yield, −13.63% cycle−1 for plant lodging, and 11.93% cyle−1 for prolificacy, whereas plant and ear heights remained unchanged. GCA estimates increased with selection cycles for both
populations for grain yield and prolificacy, and decreased for plant lodging, indicating that the frequency of favorable alleles
with additive effects for these traits increased with the MRRS cycles in both populations. SCA estimates increased for grain
yield and prolificacy indicating that the frequency of favorable complementary alleles at loci with non-additive effects in
the reciprocal populations increased with the MRRS cycles. For grain yield, SCA effects increased more than GCA effects with
selection cycles, indicating that MRRS exploited more the non-additive effects than the additive effects for the improvement
of this trait. The overall results showed that the MRRS procedure was highly effective in improving the population cross,
exploiting both GCA and SCA effects. 相似文献
3.
In order to investigate the effect of long term recurrent selection on the pattern of gene diversity, thirty randomly-selected
individuals from the progenitors (p) and four selection cycles (C0, C3, C6 and C11) were sampled for DNA analysis from the
tropical maize (Zea mays L.) breeding populations, Atherton 1 (AT1) and Atherton 2 (AT2). Fifteen polymorphic Simple Sequence Repeat markers amplified
a total of 284 and 257 alleles in AT1 and AT2 populations, respectively. Reductions in the number of alleles were observed
at advanced selection cycles. About 11 and 12% of the alleles in AT1 and AT2 populations respectively, were near to fixation.
However, a higher number of alleles (37% in AT1 and 33% in AT2) were close to extinction. Fisher’s exact test and analysis
of molecular variance (AMOVA) showed significant population differentiations. Gene diversity estimates and AMOVA revealed
increased genetic differentiations at the expense of loss of heterozygosity. Population differentiations were mainly due to
fixation of complementary alleles at a locus in the two breeding populations. The estimates of effective population at an
advanced selection cycle were close to the population size predicted by the breeding method. 相似文献
4.
Maize (Zea mays L.) production has significantly expanded into very short-season environments where germination and growth in cooler environments
is essentially a pre-requisite. Therefore, an important goal for maize breeders is to improve local germplasm sources of inbred
lines that are able to grow under these challenging conditions. The objective of this research was to evaluate direct and
correlated responses in two improved early maturing maize populations [NDSCD(M)C10 and BS22(R)C7] after two cycles of S1 and full-sib intra-population recurrent selection for cold tolerance. The S1 and full-sib progenies were obtained by self-pollinating 100 random plants and by intercrossing 200 random plants, respectively.
Ten percent of the families were selected, based on an index that included emergence percentage, seedling vigor, and root
lodging percentage, and recombined at the same time in a summer nursery based upon data across northern North Dakota locations.
The essential benefit of this breeding methodology was to achieve one year per cycle of selection based upon progenies. However,
direct response to selection was not significant while some correlated responses were significant. We decided to report these
results in order to encourage other scientists the evaluation of additional sources of germplasm, the screening at various
dates, and the selection of target environments with more intensive cold stress before initiating long-term selection programs
for cold tolerance. In addition, further research on the current and alternative long-term selection methods for cold tolerance
is recommended for continuous genetic improvement of advanced cycles in the northern U.S. Corn Belt.
Part of the thesis submitted by B. Sezegen in partial fulfillment of the requirements for a MS degree at North Dakota State
University. 相似文献
5.
Luc Baudouin Claire Baril André Clément-Demange Thierry Leroy Didier Paulin 《Euphytica》1997,96(1):101-114
The recurrent selection schemes recommended by CIRAD for 6 tropical tree crops are presented and compared. Breeding programmes
are carried out under cooperation between CIRAD and its partners in regions where the crops are grown. The crops are cacao,
coffee, rubber tree, oil palm, coconut and eucalyptus. After a short look at the background, the reasons behind the options
chosen are given and the main characteristics of the schemes are described and illustrated. The state of progress and some
major results are discussed. Over and above the differences linked to plant biology, the genetic diversity available and the
type of varietal output, common characteristics are emphasized. The time taken for each generation means simplifying the intercrossing
phases between successive breeding cycles, and thus, the parents tested are heterozygous: whenever possible, a clonal varietal
output is an additional source of progress. The use of biotechnologies to study diversity is a valuable asset, and their application
for early selection (QTL) is also promising. The preponderance of combining ability coexists with marked heterosis, which
poses the problem of the latter's origin. As a result, all of the schemes described, but one, are reciprocal recurrent selection
schemes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Summary Phenotypic and genotypic correlations were examined for four traits in seven populations of maize (Zea mays L.) undergoing recurrent selection. Correlations among grain yield and percentage of grain moisture, root lodging, and stalk lodging were low (|r|<0.3) except for the correlation between grain yield and stalk lodging, which was high and negative. The phenotypic and genotypic correlations agreed well from cycle to cycle within populations. Variation of correlations among populations was not significantly larger than variation among cycles. Heritabilities of these traits generally were high (h2>0.5). Two indices, one that used heritabilities as index weights and one that used relative economic weights (base index) as index weights, were compared with the Smith-Hazel index (optimim index). Relative efficiencies of the two indices, in terms of predicted gains for the individual traits and the composite trait, compared with the Smith-Hazel index, were high. The use of an index in which heritabilities were used as index weights was recommended because:1) the heritabilities were the same as the optimum weights when the traits were uncorrelated, and for the data examined the correlations were low; and 2) heritabilities were computed in routine data analyses and were available at no additional cost.Joint contribution: USDA-SEA-AR and Journal Paper No. 10152 of the Iowa Agriculture and Home Economics Exp. Stn., Ames, Iowa. Project 2194. 相似文献
7.
A. S. Khehra B. S. Dhillon N. S. Nalhi S. S. Pal V. K. Saxena V. V. Malhotra 《Euphytica》1986,35(3):817-822
Summary Reciprocal recurrent selection was carried out with two populations of maize (Zea mays L.) having good combining ability. We selected for higher grain yield, early maturity, shorter plant height and lodging resistance. Two cycles were completed in two years (four seasons), by resorting to late planting of S1 lines for recombination in the main season in which top-cross families were assessed. Top-crosses and selfings were made in the off-season. The original and improved versions of the populations and their crosses were evaluated in multilocation trials. The superiority of the population hybrid was 10.3% for grain yield, 5.5% for plant height and 1.8 days to silk. The improved hybrid had delayed leaf senescence and better resistance to lodging and post-flowering stalk rots. Among the yield components, only ear girth showed improvement. Syn 2 of the improved population cross showed a yield reduction of 6.2% in comparison to Syn 1. Intrapopulation gains were not significant except for lodging resistance in one population. 相似文献
8.
Recurrent selection facilitated by dominant male sterility has been conducted to broaden the genetic basis for cultivar development in Brassica napus. This study aimed to evaluate the genetic variation in four base populations (C0‐C3) and breeding lines from two of the populations produced during recurrent selection by random amplified polymorphic DNA (Rapd) markers. Genetic variation in four populations declined gradually with the advance of selection cycles as measured by expected genetic heterozygosity (from 0.2058 in C0 to 0.1536 in C3) but the decline was not statistically significant. When compared with the average genetic distances for 21 germplasm collections with wide geographical and genetic origins (0.4712) and seven breeding lines from pedigree selection (0.2059), seven breeding lines selected from the C1 population and 11 from the C3 population had a larger average genetic distance (0.5339 and 0.5486, respectively). Clustering analysis indicated that the lines from recurrent selection had a much lower genetic similarity than lines from pedigree selection. Our results suggest that base populations derived from recurrent selection could provide a wider genetic variation for selection of breeding lines with more broad genetic bases. 相似文献
9.
Summary Maize (Zea mays L.) breeders are interested in the effects of recurrent selection for grain yield on other traits. Changes in plant traits could alter agronomic acceptability of the populations under selection, and observed improvements in grain yield could be explained by changes in ear traits. We evaluated changes in combining ability for plant and ear traits of BS10(FR), BS11(FR), BSSS(R), BSCB1(R), and Lancaster Surecrop associated with recurrent selection for grain yield.Recurrent selection procedures generally did not change plant and ear heights or date of silking of testcrosses of populations or of the population crosses, BS10(FR)×BSS11(FR) and BSSS(R)×BSCB1(R). Grain yield improvements, however, were associated with increases in ear-sink size.Journal Paper No. J 9517 of the Iowa Agriculture and Home Economics Exp. Stn., Ames, Iowa. Project 2152. 相似文献
10.
The effect of introgression of temperate germplasm into an elite tropical maize population, EV8443SR, was studied for different
traits. Two temperate lines, FS14 and DEA, were crossed with EV8443SR. The F1 of each cross was backcrossed to EV8443SR to
produce the BC1. F1 and BC1 were subjected to two cycles of random mating. Random sets of S1 families were derived from the
tropical-temperate populations and the tropical parent for evaluation in two tropical locations. Introgression of FS14 and
DEA into EV8443SR significantly increased earliness, and reduced plant height, number of grains per ear, 1000 grains weight
and grain yield. Significant harvest index increases were observed. The effect of introgression on genetic variance of EV8443SR
varied with trait and sometimes with cross and location. The highest expected genetic progress was obtained in a tropical-temperate
population for most of the traits studied. EV8443SR appeared better than, or pratically equal to, the tropical-temperate populations
as a foundation population to improve grain yield and husk cover.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
12.
Summary Experiments were conducted during the growing seasons of 1975 and 1976 to determine changes in morphological and physiological traits associated with recurrent selection for grain yield in maize (Zea mays L.). Four variety hybrids, BSSS(R)CO x BSCB1(R)CO, BSSS(R)C7 x BSCB1(R)C7 [from a reciprocal recurrent selection program involving Iowa Stiff Stalk Synthetic (BSSS) and Iowa Corn Borer Synthetic #1 (BSCB1)], BS12CO x B14A, and BS12C6 x B14A [from a half-sib selection program involving the open-pollinated variety Alph (BS12) and the inbred tester B14A] were grown at 59 300 and 98 800 plants/ha near Ames, Iowa We obtained data on CO2-exchange rate (an estimate of photosynthetic rate), grain yield, grain-yield components, flowering dates, maturity traits, light interception and use, shelling percentage, harvest index, and various other plant traits.CO2-exchange rate did not change appreciably with recurrent selection for yield. Grain yield per hectare and per plant were larger for the improved than unimproved hybrids. Grain-yield components did not change significantly with recurrent selection. Kernel weight of BSSS(R)C7 x BSCB1 (R)C7, however, was larger than that of BSSS(R)C0 x BSCB1(R)C0. Pollen-shed-to-silking interval was shorter for the improved than the unimproved hybrids, and grain-filling duration was longer in C7 x C7 than in C0 x C0 of the reciprocal recurrent selection program. Furthermore, improved hybrids were characterized by smaller tassels and more upright canopies. Usually, plant traits and leaf-area-related traits were similar for all hybiids.Although dry-matter productivity was similar for all hybrids, those that were improved by recurrent selection produced more grain per unit leaf area and per unit light interception. Also, BS12C6 x B14A was characterized by a higher harvest index than BS12CO x B14A.We concluded that the source (i.e., photosynthetic capacity) was not limiting grain yield in BSSS(R) x BSCB1(R) and BS12. Increased grain yields that resulted from recurrent selection were consequences of longer grain-filling duration for BSSS(R) x BSCB1(R) and increased translocation of photosynthate from source to sink for both BSSS(R) x BSCB1(R) and BS12.Journal Paper J-8953 of the Iowa Agriculture and Home Economics Exp. Stn., Ames, Iowa. Project No. 2152. 相似文献
13.
Teosinte comprises different Zea species (Zea mays, Zea diploperennis, Zea perennis, Zea luxurians) that can be crossed with cultivated maize (Z. mays ssp. mays). Nine microsatellites from maize were applied to different teosinte species in order to evaluate their usefulness in markerbased exploitation of these genetic resources. The same microsatellites were tested with rye, barley, and sorghum as potential molecular markers for these species. Almost all microsatellite × teosinte combinations yielded polymerase chain reaction (PCR) fragments in the range of cultivated maize. Using an F2 population of a cross between maize inbred A188 and an individual of Zea mays ssp. mexicana, amplification products for maize and teosinte originated from the same genomic location for each of nine microsatellites investigated. PCR fragments of reduced intensity were generally obtained by applying maize microsatellites to rye, barley and sorghum. Polymorphisms among accessions within teosinte (sub)species occurred frequently. In contrast, no polymorphisms were obtained within rye, barley, and sorghum. Hence, application of maize microsatellites to teosinte for fingerprinting or marker-assisted introgression of genomic regions from teosinte into cultivated maize appears promising. 相似文献
14.
Selection and random genetic drift are the main forces affecting selection response in recurrent selection (RS) programmes. The correct assessment of both forces allows a better comparison of the efficiency of different RS schemes. The objective of this study was to extend the population diallel analysis proposed by Hammond and Gardner in 1974 and the model proposed by Smith in 1979 with full consideration of inbreeding depression due to random genetic drift. The effect of random genetic drift is expected to be large, particularly in studies with many selection cycles and/or high rates of inbreeding. Therefore, the extension of the population diallel allows a better assessment of the selection response in RS programmes. 相似文献
15.
Accelerated recurrent selection (ARS), in which selection is carried out on the predicted value of the progeny rather than
on the observed performance of the parents, has been proposed as a method of increasing response to selection and of reducing
cycle time. ARS schemes based on test cross evaluation of full-sib families have been compared by stochastic computer simulation.
The difference in genetic and economic time scales is emphasised, with the economic long term (21 years) being only 21 or
fewer cycles of selection. ARS schemes are shown frequently to offer improvements over standard recurrent selection methods
under these circumstances, since they allow more cycles of selection in a given time frame. Schemes with very low effective
population sizes often give the greatest response to selection over the time scales considered here. It is suggested that
evaluation of cumulative responses to selection over defined periods of time, either by Monte Carlo simulation or by stochastic
theory, is the best method of ranking alternative selection schemes. Evaluating response to selection by deterministic methods,
or by attempting to take drift into account by evaluating schemes with identical effective population sizes can be misleading.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
Improvement of maize populations for resistance to downy mildew 总被引:1,自引:0,他引:1
Upgrading levels of disease resistance are a primary objective of maize breeding programmes. Efficacy of S1 recurrent selection in improving levels of resistance to downy mildew (DM) infection was assessed in Nigeria from 1997 to 2000 in six maize populations. Improvement procedures consisted of evaluating S1 progenies under artificial infection with DM spores and in disease‐free environments and using a selection index to combine selection for reduced DM infection with appropriate agronomic characters from more than one environment. Three to four cycles of selection were completed in each of the populations. Products from the different cycles of selection were evaluated and data collected on DM infection parameters and agronomic traits. Result obtained showed 3–4 cycles of selection were adequate to reduce DM infection levels significantly and increase grain yield. Downy mildew infection decreased by between 58 and 100% while grain yield increases ranged from 10 to 98% for the 2‐4 cycles of selection relative to the C0 (original). Selection increased grain yield with acceptable changes in plant height while maintaining maturity in disease‐free environments. 相似文献
17.
Summary Genetic parameters were estimated in trials planted in connection with a reciprocal recurrent selection programme applied to Coffea canephora in Côte d'Ivoire. Narrow sense heritability values, estimated from a breakdown of the analysis of variance, were high for architectural characters (0.22 to 0.78) and medium for tree vigour (0.13 to 0.40) and for bean weight (0.15 to 0.28). Calculated heritability values for the first two harvests were high (h2>0.7), but much lower for the following harvests (less than 0.2). Heritability estimates by parent-offspring regressions gave variable results, though they were often similar to those obtained by variance analysis, especially for bean weight. Phenotypic and genetic correlations between tree vigour traits and productivity were high. Bean weight was not correlated with vigour or production. Canopy diameter of 4 year-old trees was closely correlated with cumulated productivity from 2 to 5 years in the absence of development competition between trees, but the correlation was low if trees were in competition with each other. The consequences of the results for the choice of characters to be selected among intergroup hybrids or the parents of both populations are discussed. 相似文献
18.
Lucas Rafael de Souza Camacho Marlon Mathias Dacal Coan Carlos Alberto Scapim Ronald Jos Barth Pinto Dauri Jos Tessmann Rodrigo Ivn Contreras‐Soto 《Plant Breeding》2019,138(6):770-780
Southern corn rust (SCR) is a fungal disease found on corn in several countries worldwide. In Brazil, the disease can result in productivity losses of 65%, especially in areas with a history of the disease. In this study, the genetic architecture and identification of genomic regions associated with SCR resistance was investigated by performing a genome‐wide association study. Genotyping‐by‐sequencing was performed to carry out the association between single nucleotide polymorphism (SNP) markers and phenotypic data from two environments on a panel of 164 maize inbred lines. Eight SNPs were identified as significant for SCR resistance. These SNPs were colocalized with QTL regions, some of which underlie candidate resistance genes with functions that play an important role in the stress response during pathogen recognition. These candidate genes, involved in plant defense pathways, could be associated with partial resistance to SCR and provide a partial comprehensive insight into the genetic architecture of this trait. After validation of the SNPs, they will be useful for marker–assisted selection and for a better understanding of maize resistance to SCR. 相似文献
19.
C.A. Mangolin C.L. de Souza Jr. A.A.F. Garcia A.F. Garcia S.T. Sibov A.P. de Souza 《Euphytica》2004,137(2):251-259
Maize cultivars often have low kernel oil content. To increase the oil content, efficient maize breeding programs have to be developed, which require the knowledge of the inheritance of this trait. Thus, the objective of this research was to map quantitative trait locus (QTLs) and estimate their effects for kernel oil content in a tropical maize population. Two maize inbred lines, contrasting for kernel oil content, were used to develop an F2 population. Four hundred and eight F2 plants were self-pollinated, and their kernels (F2:3 progenies) were used for kernel oil evaluation. A genetic map with 75 microsatellites was developed, and the QTLs were mapped using the composite interval map (CIM); also, estimates of genetic and phenotypic variances, and heritability coefficient were computed. The map presented 10 linkage groups, spanned 1,438.6 cM in length with an average interval of 19.18 cM between adjacent markers. The kernel oil content averaged 58.40 g kg–1, and the broad-sense heritability was high (h2= 0.98). Thirteen QTLs were mapped, which were distributed into eight chromosomes, and explained 26.64% of the genetic variation. QTLs in chromosomes 1, 5, and 6 contributed the most for kernel oil content. Nine out of 13 QTLs with favorable alleles were from the parental inbred with the highest kernel oil content. The average level of dominance was partial, but gene action of the QTLs ranged from additive to overdominance. Eight out of 13 mapped QTLs were already reported for temperate maize populations. 相似文献
20.
Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers 总被引:13,自引:0,他引:13
L. L. Benchimol C. L. de Souza Jr A. A. F. Garcia P. M. S. KONO C. A. Mangolin A. M. M. Barbosa A. S. G. Coelho A. P. de Souza 《Plant Breeding》2000,119(6):491-496
Tropical maize inbred lines, eight derived from a Thai synthetic population (BR‐105) and 10 from a Brazilian composite population (BR‐106), were assayed for restriction fragment length polymorphisms with 185 clone‐enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR‐105×BR‐106 lines (0.77) than for BR‐106×BR‐106 (0.71) and for BR‐105×BR‐105 (0.69) lines. Cluster analysis resulted in a clear separation of BR‐105 and BR‐106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP‐based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP‐based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups. 相似文献