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1.
The present study was conducted to evaluate the importance of two environmental factors, year and geographic location, on the cultivar outcrossing rate and genetic structure of Vicia faba L. Under natural field conditions. Outcrossing rates were estimated for six cultivars using isozyme markers, the mixed mating model and the multilocus method. The genetic structure was described by Wright's fixation index and the inbreeding equilibrium coefficient. Faba bean outcrossing rate, as measured by multilocus estimates was relatively invariable among cultivars within locations. Our results suggest substantial variation in outcrossing rate associated with geographic location (Mediterranean subtropical and temperate climates enhancing the cross-pollination). Year variation was far less important than geographic variation.  相似文献   

2.
Our research assesses the feasibility of using artificial selection on pre-mating floral traits to modify the mating system of faba bean (Vicia faba). This analysis considered two synthetic populations, which were derived from different genetic pools and had undergone five years of multiplication. For these populations, we identified floral and inflorescence traits that influence outcrossing per plant and examined the relative importance of these traits in governing yield. Codominant isozyme loci and the mixed-mating model were used to estimate the multilocus female outcrossing rate. A maternal half-sib design was used to evaluate the additive genetic component of floral and inflorescence traits, yield and yield components. Multiple regression was used to assess the effects of floral and inflorescence traits on outcrossing and yield and components of yield. The two populations exhibited mixing mating. Self-fertilization appears to result from the action of pollinating bees, so that its incidence could be modified by selection on floral and inflorescence traits that affect pollination. Floral and inflorescence traits affected individual differences in outcrossing unequally, with most variation being associated with the numbers of displayed flowers and inflorescences. Variation among plants in reward traits and in shape, although statistically significant, had limited and inconsistent influences on individual differences in outcrossing. Yield and its components varied strongly with aspects of floral display and, to a lesser extent, floral design, except for seed weight. Overall, our results imply that both outcrossing and yield could be enhanced by selection for plants that produce more inflorescences, each with relatively few flowers.  相似文献   

3.
In this study, we used microsatellite loci to estimate the outcrossing rate of Centrosema pubescens in open-pollinated populations of 10 progenies that each contained 20 genotypes. The multilocus outcrossing rate was 27%, which suggested a mixed mating system with a predominance of autogamy. The single locus outcrossing rate was 13%. The difference was 0.040, which indicated that only 4% of outcrossing occurs in related individuals. A paternity correlation of 14% suggests that there is a low probability of finding full sibs in the progeny. Cross-amplification of the 26 microsatellite loci available for C. pubescens was evaluated across 11 different Centrosema species. Nineteen of the 26 tested microsatellites were successfully transferable across the Centrosema species. The polymorphism information content and discriminating power evaluated had averages of 0.64 and 0.77, respectively. A total of three clusters were assembled to demonstrate the genetic relationships between Centrosema species. The transferable microsatellite loci should be useful for exploiting the genetic resources of the Centrosema species and determining the outcrossing rate, which are essential for proposing effective approaches for conservation and for establishing strategies for the selection and improvement of Centrosema spp.  相似文献   

4.
Summary To assess the feasibility for synthetic varieties of Vicia faba L., 108 faba bean genotypes were screened for cross-fertilization rate in five field experiments carried out in 1989 and 1990 at Wageningen.Significant genotypic differences were observed for outcrossing rate, which ranged from 1 to 55%. These percentages, however, are thought to be not high enough for a commercially feasible production of synthetic varieties.The inheritance of cross-fertilization rate, determined by testing the F4 generation of a cross between two inbreds, both with high outcrossing rates, appeared to be of a polygenic nature, as was indicated by the wide variation in, and the continous distribution of, the cross-fertilization rates. Among the F4 lines tested some had a significantly higher cross-fertilization rate than the parents. However, this difference was not found when these lines were retested, indicating that possibilities for successful selection for higher outcrossing rates might be limited.  相似文献   

5.
Summary To elucidate the role of leaf surface structures as first barriers to confer resistance to bacterial blight, leaf stomata and their occlusion with leaf waxes were studied in cassava genotypes. For the first time, cassava leaf waxes were quantitatively and qualitatively analysed. Comparing the susceptible and resistant standard genotypes BEN86052 and TMS30572, respectively, the total quantity of triterpenes was significantly higher in the resistant genotype, grown in three ecozones of Benin. In cuticular leaf waxes of seven cassava genotypes the triterpenes beta amyrins, epi-taraxerol, taraxerone and taraxerol were dominant constituents across genotypes, and alkanes (C25-C33) and acids (C30 and C32) occurred in minor concentrations. Comparing seven genotypes, no clear relation between resistance or ecozones and total quantities of the major wax constituents was observed. Only the highly resistant genotype TMS30572 showed high triterpene levels irrespective of ecozone. Scanning electron-microscopy revealed a regular distribution of waxes at the abaxial leaf surface, covering and occluding stomatal pores of susceptible and resistant genotypes, while on the adaxial leaf surface waxes were in form of crystalloids and did not occlude the stomata. The number of stomata on the abaxial surfaces was about 7–11 fold higher than on the adaxial surfaces, where stomata were located along the midrib and major veins. No significant differences in stomata number were observed between genotypes varying in resistance to bacterial blight. It is suggested, that stomata on the adaxial surface might be portals of entry for the bacteria.  相似文献   

6.
Knowledge of the origin, organization and nature of the cassava (Manihot esculenta Crantz) germplasm collection in Brazil is incomplete due to lack of critical information on several aspects of the collection. This study verifies the utility of SSR-primed PCR markers for germplasm assessment and then utilizes these markers as well as RAPD's to characterize the Brazilian collection. We specifically address the following questions: 1)what is the relationship of morphologically closely related species to cultivated cassava? 2) What is the genetic diversity of cultivars within and between different habitats in Brazil? 3) Do agronomic traits and molecular markers reveal the same relationship among cassava accessions? 4) How complete is the Brazilian cassava collection and how well is it represented in the Word Core Collection of cassava, maintained by CIAT? Results of the interspecific studies of cassava and its wild relatives confirms the close relationship of cassava, Manihot esculenta ssp. esculenta to Manihot esculenta ssp. flabellifolia as well identifying several other closely related wild species. Next, PCR-based markers indicate a strong grouping of varieties related to the region of cultivation in Brazil. Moreover, important regions such as Cerrados and Amazon are relatively poorly represented in germplasm collections. Interestingly, the relationships of accessions based on agronomic traits are not fully congruent with relationships revealed with RAPD markers. Finally, the genetic diversity of the Brazilian cassava collection is not fully represented in the Core of the Word Core Collection of CIAT.  相似文献   

7.
The Asian wild rice, Oryza rufipogon, has partial outcrossing behavior and shows high levels of genetic variation. To estimate an accurate outcrossing rate of annual form of O. rufipogon, two backcross lines (Lines R1 and R2) between Oryza sativa Nipponbare and O. rufipogon W630 were examined under field conditions. A chromosome survey confirmed that these lines had wild chromosomal segments at more than 92% of marker loci. As for the traits of glume, stamen and pistil, Line R1 showed similar floral morphology as that of O. rufipogon W630, whereas Line R2 had larger glumes. In 2005, 2006 and 2008, a total of 22 backcross plants were planted in the middle of wild rice plots. The successive progenies of each plant were examined using microsatellite markers that could clearly detect self-pollination and outcrossing. The outcrossing rates of Line R1 plants ranged from 4.04% to 25.50% with an average of 10.20%. This indicates that cross-pollination of wild rice is a chance event affected by many environmental factors. The outcrossing rates of Line R2 plants also varied, however, no significant difference was observed between the averages of Lines R1 and R2, suggesting that the glume sizes are not critical for outcrossing ability.  相似文献   

8.
Summary Six populations of Coix lacryma-jobi with distinct characters were studied to evaluate the presence of autonomous apomixis and pseudogamy, and to determine its implications and effects in the calculations of the rate of breeding. For this reason, two types of genetic markers were used-morphological markers and isozymatic markers.The results show that autonomous apomixis does not seem to occur in these populations. Further experiments are necessary to prove the presence of pseudogamy in one of the populations. The rate of natural outcrossing in the grain types Rosario, Rosadlay and I-47 fluctuated around 35.9% using estimates based on isozymatic markers. The rate of natural outcrossing was 37.4% in the Adlay population using morphological markers. A population composed of tall individuals, named Tailândia, which has a greater vegetative mass and fewer grains, presented a high level of natural outcrossing at 72.8%. This information is important for many reasons, such as: 1) guiding sampling strategies of genetic material, 2) in the organization and upkeep of germplasm banks, and 3) for plant breeding programs.  相似文献   

9.
FLP site-specific recombination has been shown in transgenic plants to excise DNA sequences between target FRT sites, and thereby activate transgenes in plants. In previous reports, crossing of tobacco plants expressing FLP recombinase from a CaMV-35s promoter with plants containing the target FRT sites, hybrid plants with deletion sectors were generated, which were infrequently transmitted to progeny. In this report we evaluate the occurrence of recombination in F1 hybrid seed derived from crosses of different FLP and FRT-reporter target lines and the germinal transmission of recombined loci from these hybrids to F2 progeny. Twenty hybrids were generated from crosses of independent five FLP-active lines and four FRT-reporter target lines. In one hybrid, FLP deletions occurred at an early stage, prior to seed maturation, and the deletions from this hybrid were more efficiently transmitted to F2 progeny. The demonstration of FLP-mediated recombination activity and germinal inheritance of the recombined FRT loci are supported by both molecular and enzymatic evidence. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

10.
Summary Fertility restoration genes in Triticum aestivum L. in Texas Restorer Composite (TRC), D6301, and four CIMMYT restorer lines were studied, and selection was made for higher fertility in TRC. Mean-while, outcrossing percentages of seed set for 27 spring habit cytoplasmic male sterile (cms) varieties were evaluated for 3 to 5 years at Davis. The winter-habit TRC material did not restore reasonably good fertility, and the response to selection for higher fertility seemed to be slow. This poor fertility could be partly due to its late winter growth habit causing flowering at a period of high temperature and low humidity at Davis. The highest F1 fertility was 46.6% in the cross cms Ramona x TRC-6, and its F2 segregated into the ratio of 15 fertile to 1 sterile, with fertility ranging from 3.2 to 100%. Suggested for its improvement was intensive selection in the original TRC material and in the segre-gating F2 population, followed by intercrossing. D6301 has 2 fertility restoration genes with different strengths which restore fertility up to 45.2% when both genes are heterozygous. D6301 is quite likely heterogeneous for these genes. Four CIMMYT restorer lines, D7464, D7465, D7466, and D7467, had satisfactory F1 fertility restoration after crossing with cms Ramona 50. In 1975, the fertilities of the F1's ranged from 71 to 85% and were over 90% in 1976. The F2 population of the cross cms Ramona 50 × D7464 segregated into a ratio of 3 fertile to 1 sterile, indicating that D7464 has a single dominant gene for fertility restoration. The F2's of crosses cms Ramona 50 × D7465, cms Ramona 50 × D7466, and cms Ramona 50 × D7467 gave a ratio of 15 fertile to 1 sterile, indicating that two gene pairs in these three lines were responsible for the fertility restoration. The best of this group was D7467 which restored fertility fully after being crossed with cms Ramona 50 (T. timopheevi cytoplasm).The early-flowering cms male-sterile varieties had higher outcrossing rates (16 to 38%) than late varieties (6 to 30%) over a 5-year period. This was due to hot and dry weather during the late growing season as well as to the rarity of windborne pollen. In 1970, 1971, 1972, and 1976, the variation among varieties was rather great. Some of them such as Roque 66 and Bajio 67, had consistently high outcrossing rates. This outcrossing ability seemed to be inherited and probably associated with the open-flowering characteristics of each variety.  相似文献   

11.
B. Horneburg 《Plant Breeding》2006,125(6):638-640
Knowledge about the degree of outcrossing is essential for onfarm crop management and breeding schemes and for lentil (Lens esculenta Medik.) only restricted evidence was available. Three varieties were investigated in two central European locations to foster research into on farm maintenance and development of cultivars. To determine outcrossing rates, the complete dominance of ‘orange cotyledons’ over ‘yellow cotyledons’ was used as a marker. The degree of outcrossing ranged from 0.06% to 5.12%. Results were strongly influenced by cultivar, year and location. The outcrossing rate of individuals also varied within cultivars, the extremes being 0% and 22.2%. There is evidence that the degree of outcrossing can be heritable. The potential for evolutionary changes in lentil cultivars can be considerable. Growing cultivars close together or as a mixture can lead to natural or even conscious selection and local adaptation. On the other hand, spatial separation may be necessary to avoid undesirable cross‐pollination.  相似文献   

12.
The potential of transferring herbicide resistance from transgenic rice (Oryza sativa L.) varieties to sexually compatible weeds is of paramount importance for development of effective weed control strategies. The objective of this research was to determine the genetic control and frequency of natural outcrossing between a transgenic, glufosinate-resistant rice line and a Louisiana biotype of red rice (Oryza sativa L.). Molecular and phenotypic data showed that outcrossing in field plots between a non-transgenic purple marker line and red rice did occur within one field season, but at a low rate of <1%. Similarly, molecular and phenotypic data demonstrated that glufosinate resistance was transferred from the transgenic line to the red rice biotype in the field within one year at a low frequency of 0.3%. Compared to parental lines, the transgenic-red rice hybrids were extremely late, tall, and never set seed during the normal field season. Genetic analyses in all F2 populations showed glufosinate resistance behaved in a Mendelian fashion as a single, dominant gene. Presence of the bar gene for glufosinate resistance did not increase fitness or seed fecundity in hybrids or subsequent progeny. The genetic analyses and outcrossing results from this study suggest that an effective management program can be developed to prolong the usefulness of transgenic, glufosinate herbicide technology. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
Summary Backcross populations of maize (Zea mays L.) were produced by crossing the early maturing inbred line W153R with the highland Mexican race Cónico then backcrossing to W153R (Q1 population) and by crossing W153R with the highland Peruvian race San Gerónimo then backcrossing to W153R (Q3 population). The populations were recombined by one generation of random mating. Testcrosses were produced from S0 plants in the original and recombined versions and these were evaluated in New Zealand for grain yield, grain moisture and other traits.Unexpected changes occurred during recombination for increased grain yield in the Q1 population and for decreased grain moisture in the Q3 population. This indicates strong, unplanned selection. Many testcrosses were higher yielding than check hybrids of W153R, but most were later maturing.S1 lines selected for high grain yield and acceptable grain moisture in testcrosses were advanced to the S2 generation and re-tested. All produced testcrosses with lower grain moisture than late maturing hybrid checks. Testcross grain yields of one Q1 line were equivalent to those of late maturing checks and its testcross had a lower grain moisture. The high yield potential of hybrids of this line was confirmed in the S4 generation.  相似文献   

14.
Summary Two cloned cassava genes (pCAS6, pHNL) and a barley gene (pBLT63) which is highly conserved in higher plants, were evaluated as potential multilocus probes for RFLP analysis of phylogenetic relationships of species within the genus Manihot. For M. rubricaulis, M. chlorosticta and M. esculenta subsp. flabellifolia dendrograms based on 13 probe-restriction enzyme combinations show very little variation between accessions of the same species. A close relationship is demonstrated between the Mexican species M. chlorosticta and the M. esculenta subsp. flabellifolia accessions, which does not support the classification of flabellifolia as a true South American wild species.  相似文献   

15.
Outcrossing rates of barley landraces from Syria   总被引：1，自引：0，他引：1  
Diversity levels in populations of barley landraces may be influenced by varying levels of natural outcrossing caused by environmental conditions. Outcrossing was studied in 10 accessions of the barley landrace Arabi Aswad from different environments in Syria. Electrophoretic variation at two codominant isoenzymes (Est1 and Est2) in six seeds of 50 families per population were analysed and multilocus outcrossing rates calculated. Results were correlated with interpolated environmental conditions. Outcrossing was, on average, 1.7% and not significantly different from the outcrossing rate of wild barley. A significant increase of outcrossing was observed with increasing inter‐annual variation in rainfall and decreasing minimum temperatures of the coldest month.  相似文献   

16.
Summary Cassava (Manihot esculenta) is a tropical crop that is grown in Africa, Latin America and Southeast Asia. Cassava was introduced from Latin America into West and East Africa at two independent events. In Uganda a serious threat to cassava's survival is the cassava mosaic disease (CMD). Uganda has had two notable CMD epidemics since the introduction of cassava in the 1850s causing severe losses. SSR markers were used to study the effect of CMD on the genetic diversity in five agroecologies in Uganda with high and low incidence of CMD. Surprisingly, high gene diversity was detected. Most of the diversity was found within populations, while the diversity was very small among agroecological zones and the high and low CMD incidence areas. The high genetic diversity suggests a mechanism by which diversity is maintained by the active involvement of the Ugandan farmer in continuously testing and adopting new genotypes that will serve their diverse needs. However, in spite of the high genetic diversity we found a loss of rare alleles in areas with high CMD incidence. To study the effect of the introgression history on the gene pool the genetic differentiation between East and West Africa was also studied. Genetic similarities were found between the varieties in Uganda and Tanzania in East Africa and Ghana in West Africa. Thus, there is no evidence for a differentiation of the cassava gene pool into a western and an eastern genetic lineage. However, a possible difference in the genetic constitution of the introduced cassava into East and West Africa may have been diminished by germplasm movement.  相似文献   

17.
Knowledge about the degree of spontaneous outcrossing of diverse genotypes is essential for breeding programmes, maintenance breeding, and seed production. For tomato (Lycopersicon esculentum Mill.), very limited scientific evidence for genotypic differences is available and evidence from Europe is scarce. To close this knowledge gap, six cultivars were investigated in three Central European locations as part of the Organic Outdoor Tomato Project. To determine outcrossing rates, the monogenetic “cut‐leaf” trait, which is dominant over the “potato‐leaf” trait, was used as morphological marker. The observed range of outcrossing was 0.0%–5.2%. Outcrossing was significantly influenced by cultivar and environment. The outcrossing rate of individual flowers varied within cultivars ranging from 0% to 37%. The potential of newly opened flowers to accept foreign pollen varied largely with the cultivar. Genotypic differences could partly be linked to flower morphology traits. The potential for recombination between tomato genotypes is generally very low but can be a source for new variation in on‐farm management.  相似文献   

18.
M. W. Humphreys 《Euphytica》1989,42(1-2):105-116
Summary Using phosphoglucoisomerase (PGI/2) as a genetic marker, it has been shown to be possible to transfer genes from Festuca arundinacea into diploid Lolium multiflorum using the pentaploid hybrid L. multiflorum (4x) x F. arundinacea (6x). The pentaploid hybrid was sufficiently fertile to be used in reciprocal crosses with diploid. L. multiflorum. When used as the male parent, only two backcross generations were then required to reconstitute the diploid genotype. Intergeneric recombinants including a F. arundinacea PGI/2 allele were found among the diploid BC2. Cytological data indicates that although the majority of chromosome associations involve only homologous Lolium chromosomes, associations involving Lolium and Festuca chromosomes also occur.Interpollinating the pentaploid hybrids prior to commencing a backcrossing programme increases the number of cycles of recombination and improves the chance of recovering intergeneric recombinants. The crossing programme described is proposed to be an effective method of introducing F. arundinacea genes into L. multiflorum.  相似文献   

19.
F. Lefèvre  A. Charrier 《Euphytica》1992,66(1-2):73-80
Summary Isozyme diversity is described among a collection of 365 Manihot esculenta cultivars plus 109 accessions from wild relatives (M. glaziovii and spontaneous hybrids) from Africa. The study is based on 17 polymorphic loci. A natural hybrid swarm is detected between the two species. Although they were recently introduced, M. esculenta and M. glaziovii show high levels of polymorphism: heterozygosity estimates are 0.225 and 0.252 respectively. For the wild species, diversity is structured at the unilocus level, and the multilocus approach reveals a geographical pattern. The organization of the diversity is not so clear for the cultivated cassava, but a multilocus approach, based on both common and rare alleles, led us to identify different groups of clones with many intermediate genotypes between them. Elements of the secondary diversification process of Manihot in Ivory Coast are discussed.  相似文献   

20.
Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess the extent of natural outcrossing was undertaken for two years at Morden and Portage la Prairie, Manitoba using the semi-dwarf character, which is due to a homozygous genotype with regard to a single recessive gene, as a marker. The semi-dwarf genotype was grown in 100 m rows running in four directions at 90 ° from a central 36 m2 plot of a normal, tall variety. At maturity, seed samples were taken from the semi-dwarf population at designated intervals. At least 200 F1 seeds from each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwarf plants were immediately next to the normal plants and then the proportion decreased with increasing distance. Although outcrossing occurred throughout the distance tested, there were no significant differences from 12 m onward from the pollen source. Lack of directional influence in outcrossing and a sharp reduction in the proportion of tall plants within a 3 m distance from the pollen source suggested that wind was not a major factor in dispersing the buckwheat pollen over long distances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend the minimum isolation distance required to meet certain standards for buckwheat seed production. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

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