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1.
J. P. Wilson 《Plant Breeding》1997,116(3):239-243
Quantitative disease resistance should be exploited to complement the use of genes for qualitative or hypersensitive resistance. The expression and inheritance of partial rust resistance of pearl millet inbreds 700481-21-8 and ‘ICMP 501’ crossed to moderately susceptible Tift 383’ were evaluated in seedling assays in the greenhouse and in generation mean and single-seed descent populations in the field. Uredinium sizes on seedling leaves of hybrids were generally intermediate to those of the parental inbreds and consistent differences could be discerned in uredinium lengths. Area under the disease progress curves (AUDPCs) of individual plants of the parents, F1, F2, and backcross F1S to each parent were determined from field trials. Broad-sense heritability estimates for both crosses were 43%. In generation mean analyses, additive genetic effects were significant in the cross of 700481–21–8 × Tift 383′, whereas additive, dominance, and dominance × dominance epistatic effects were significant for ‘ICMP 501’בTift 383’. The number of genes conferring partial resistance was estimated to be two for 700481–21–8 and 2.5 for ‘ICMP 501’. A hierarchical single-seed descent analysis revealed significant differences in AUDPC among F3-derived F4 progenies in the F6 generation. Selection for progenies with greater resistance should be possible among F4 families. Higher levels of resistance were observed in progeny derived from ‘ICMP 501’. Because segregation of resistance differed among progeny derived from 700481–21–8 and ‘ICMP 501’, the genetic basis for resistance probably differs between the two inbreds.  相似文献   

2.
Summary Resistance toMeliodogyne chitwoodi races 1 (MC1) and 2 (MC2) andM. hapla (MH) derived fromSolanum bulbocastanum was introduced into the cultivated potato gene pool through somatic fusion. The initial F1 hybrids showed resistance to the three nematodes. Resistance to reproduction on roots by MC1 was accompanied by resistance to tuber damage in F1 clones. Tuber damage sometimes occurred, however, in hybrids of BC1 progeny resistant to reproduction on roots when MC2 and MH were the challenging nematodes. Resistance to reproduction was transferred into BC1 individuals, but a greater proportion of BC1 progeny was resistant to MC1 than to MC2 or MH. Resistance to MC1 appears to be dominant and discretely inherited. F1 and BC1 progeny were pollen sterile, but seed were produced from crosses using cultivated tetraploid pollen sources. Approximately 11 and 33 per cent of pollinations produced berries on F1 and BC1 pistillate parents, respectively. Seed yield increased fourfold overall in crosses with F1 compared to BC1 individuals.Abbreviations MC1 Meloidogyne chitwoodi race 1 - MC2 Meloidogyne chitwoodi race 2 - MH Meloidogyne hapla - Rf Reproductive factor  相似文献   

3.
Summary Sixty-six chrysanthemum (Dendranthema grandiflora) inbred selections, noninbred cultivars and hybrids, and D. makinoi were the base populations from which up to three generations of inbreds were obtained using multiple plant descent. Each parent possessed pseudo-self compatibility (PSC), which allowed seed set following self pollination. Rapid-generation cycling (laboratory seed ripening to heart stage and subsequent embryo rescue) reduced generation time and minimized confounding maternal with zygotic inbreeding depression during post heart-stage seed development. Selection criteria were male/female fertility and PSC. Two stages of the life cycle were chosen to evaluate inbreeding depression: germination (seed development to germination) and survivorship (fertile individuals at anthesis). PSC was environmentally interactive and genotype dependent, causing variable levels of self seed set between and within populations and generations. By the end of the second generation, families from all noninbred cultivars, D. makinoi, and one F1 hybrid were eliminated from the experiment due to self incompatibility and/or inbreeding depression. Post-germination inbreeding depression was severe in several advanced inbreds. Inbred progeny of most F1 or F2 hybrids expressed less or equal amounts of inbreeding depression compared to advanced inbreds. Linear regression coefficients for either germination or survivorship on percent homozygosity were negative. Correlation coefficients between percent germination and survivorship (as a percent of seed set) were highly significant for Minnesota inbreds (r=0.67, P0.002) and hybrids (r=0.67, P0.006). The correlation coefficient was higher when percent germination and survivorship (as a percent of germinated seedlings) were compared (r=0.95, P0.001).Abbreviations F Fisher's Coefficient of Inbreeding - IBD Inbreeding Depression - PSC Pseudo-self Compatibility - RGC Rapid Generation Cycle - SI Self Incompatibility  相似文献   

4.
Creeping bentgrass (Agrostis stolonifera L. or A. palustris Huds.) is a highly outcrossing allotetraploid species. It can form hybrids with a number of other Agrostis species and Polypogon genus. However, cytology and pollen grain fertility of the creeping bentgrass interspecific and intergeneric hybrids are not well known. In this research, chromosome pairing behaviors during meiosis I in F1 and pollen viability of F1 hybrids, as well as seed set rate and seed germination rate of backcrosses were studied in hybrids between creeping bentgrass, and other bentgrass species and three species of Polypogon genus. Abnormal chromosome pairing, laggard chromosomes, and premature segregation in F1 hybrids were found. Pollen viability ranged from 1.6 to 48.5% amongst F1 hybrids, significantly lower than that of the parents (85.5–94.1%). Some hybrids produced pollens of different sizes within the same anther. Seed set following backcrosses using F1 hybrids as the male parent and creeping bentgrass as the recurrent parent was significantly lower than their parents. The study of chromosome paring behaviors and progeny fecundity are important in utilizing the alien genes to improve bio-stress and abio-stress resistance, and in assessing the potential transgene risks of creeping bentgrass.  相似文献   

5.
Summary The relative yields of spaced plants of inbred lines derived from different seed stock of forage rape were compared with F1 hybrids among these lines. The hybrids between inbred lines derived from the same parental seed stock showed a mean superiority of 8.8% and the hybrids between inbreds from different stocks showed 19.6% superiority over the inbred lines in early vegetative growth. This hybrid superiority is discussed in relation to the development of superior varieties.  相似文献   

6.
Summary Cajanus platycarpus, an incompatible wild species from the tertiary gene pool of pigeonpea (C. cajan (L.) Millspaugh), has many desirable characteristics for the improvement of cultivated varieties. To necessitate such transfers, embryo rescue techniques were used to obtain F1 hybrids. The F1 hybrids were treated with colchicine to obtain tetraploid hybrids, that were selfed to obtain F2, F3 and F4 progenies. All of the hybrids and subsequent progenies had an intermediate morphology between the two parents. Backcrossing of the tetraploid hybrids with cultivated pigeonpea was not possible given embryo abortion, with smaller aborted embryos than those obtained in the F0 parental cross.As a route of introgression, diploid F1 hybrids were backcrossed with cultivated pigeonpea and BC1 progeny obtained by in vitro culture of aborting embryos. BC2 plants were obtained by normal, mature seed germination. Although embryo rescue techniques had to be used to obtain F1 and BC1 plants, it was possible to produce BC2 and subsequent generations through direct mature seed. Every backcross to cultivated pigeonpea increased pollen fertility and the formation of mature seeds.Special project assistant till December, 2003.  相似文献   

7.
Summary Isozyme phenotypes at four known genetic loci were determined in parental inbreds and corresponding F1 hybrid seed lots of four commercial broccoli, two cauliflower, and two cabbage varieties to determine seed purity. Most inbred lines were completely homozygous at all four loci but differed with respect to alleles at one to three loci. Several parental inbreds of the cabbage hybrids were segregating at two to three of the loci. Models were developed to estimate seed purity in cases where parents were either fixed or segregating at diagnostic loci. Estimates of contamination ranged from 1.5 to 40.1%. These estimates were comparable with those from commercial grow-outs with a tendency for the former estimates to be higher. It was concluded that more stable SI alleles or genetic male sterility should be used to reduce contamination. Electrophoretic variation was further discussed as a tool for selecting homozygous plants and for strong self-incompatibility.  相似文献   

8.
Summary Six isozyme genes were analyzed in seed samples of 65 commercial F1 hybrids of four horticultural groups of Brassica oleracea (cabbage, Brussels sprouts, sprouting broccoli and cauliflower). Results obtained from electrophoretic assays led to the following conclusions: 1) the electrophoretic test of F1 hybrid purity was possible in 59 (91%) of the hybrids analyzed, since their inbred parents were apparently fixed each for a different allele in at least on of the loci studied; 2) forty-eight (74%) of the hybrids were individually distinguished by their isozyme phenotype; 3) high levels of segregation in the inbred parents were inferred from the analysis of a sample of seeds of each hybrid.  相似文献   

9.
Agronomic Traits and Chromosome Behavior of Autotetraploid Sorghums   总被引:2,自引:0,他引:2  
Y. W. Luo    X. C. Yen    G. Y. Zhang  G. H. Liang 《Plant Breeding》1992,109(1):46-53
The agronomic performance and chromosome behavior of autotetraploid sorghum [Sorghum bicolor (L.) Moench] inbreds and F1 hybrids were investigated. Autotetraploids have possible commercial use and can serve as bridging species in crosses to natural tetraploids. Autotetraploid sorghum inbreds (2n = 40) had higher kernel weight, seed yield, and protein and amino acid content than their diploid counterparts. Stalk height and panicle length of the autotet-raploids, however, were not different from those of the diploids, and seed set of autotetraploids was lower in early generations. Seed set of autotetraploid Ft hybrids was related to and higher than that of the autotetraploid parental inbred lines. Frequency of quadrivalents, anaphase I and II laggards, and quartet micronuclei varied among autotetraploids. Frequency of quadrivalents did not appear to be an important factor in seed set nor was it significantly associated with frequency of laggards. Aneuploids (2n = 39, 41) had higher percentages of laggards and micronuclei than did euploids (2n = 40). Methods of pollination significantly affected seed set in autotetraploid S4 lines. Differences in seed set among autotetraploid lines indicated the feasibility of selecting for lines with high seed set and utilizing those lines for hybrid production.  相似文献   

10.
Summary A subjective rating scale was used to select tomato inbreds with inserted stigmas (inserted) for crossing with inbreds possessing exserted stigmas (exserted) in a combining a bility study. Six inserted parents were inbred to F5 or F6, but were not stable for stigma position in most cases. The exserted x inserted hybrids were all slightly exserted and it appeared stigma exsertion was incompletely dominant to stigma insertion. No reciprocal cross differences were detected for stigma position indicating the absence of cytoplasmic inheritance. There was no clear relationship between hybrid stigma positions and the level of insertion of the inserted parents. Stigma insertion was more consistently detrimental to fruit set than was stigma exsertion. Hybrids were either heterotic or dominant for yield.The inability to attain hybrids with standard stigma positions by crossing exserted x inserted genotypes could limit fruit-set under some environmental conditions. Furthermore, difficulty in breeding stable inserted lines and the incomplete dominance of exserted over inserted genotypes limits the feasibility of using heterostyly alone for producing reliable hybrids.Ohio Agricultural Research and Development Center Article No. 166-78.  相似文献   

11.
Success in obtaining an interspecific hybrid between B. pekinensis and B. oleracea var. acephala was possible through the use of the Chinese cabbage as the seed parent and the use of the growth regulator, N-m-tolylphthalamic acid. The hybrids appeared vegetatively intermediate between the parents except for the inflorescence which appeared more like the kale parent. The F1 was backcrossed with ease to the Chinese cabbage parent using the hybrid either as the pollen or seed parent. No backcross was made to the kale parent. Segregation in the F2 was continuous for most characters studied.Michigan Agricultural Experiment Station, Journal Article Number 2588.  相似文献   

12.
A series of field experiments was undertaken in order to determine whether resistance to bean common mosaic virus (BCMV) could be incorporated into genotypes of the common bean (Phaseolus vulgaris L.) suitable for cultivation in Zimbabwe without recourse to backcrossing. Six inbred genotypes carrying the resistance-conferring alleles at the loci I and Bc-3 were crossed with five locally-adapted inbred genotypes. The first experiment comprised F3 progeny rows, each derived from a single unselected F2 plant, the second, F3 bulks selected for resistance, and the third, a comparison of selected and unselected F2-derived F4 lines. The number of days to flowering and to maturity, the incidence of mosaic and necrosis symptoms, seed yield and seed size were recorded. There was evidence that late flowering and maturity were associated with BCMV resistance in some crosses, though not strongly enough to present an obstacle to plant breeding. The incidence of virus symptoms and seed yield were influenced by genetic factors additional to the major resistance genes, and variation in seed yield was present not only between bulk populations of crosses, but also between single-row plots of lines within crosses. This indicates that early-generation selection for yield in the presence of BCMV, even among progeny selected for BCMV-resistace, is likely to be effective. However, the variation in yield among F4 lines was least in the highest-yielding crosses, which may represent a limit to successful selection for yield. Seed size was partly under additive genetic control, but there was also evidence of non-allelic interactions. There was no association between large seed size, preferred by consumers, and susceptibility to BCMV in the progeny, indicating that the association between these characters in the parent lines is fortuitous and will not present an obstacle to plant breeding. It is noted that a considerable amount of useful genetic information can be obtained without recourse to elaborate crossing schemes, provided that unselected progeny are included in experiments as controls. The evidence presented indicates that resistance to BCMV can be combined with appropriate values of maturity date, yield and seed size without the need for backcrossing.  相似文献   

13.
Crop improvement in sorghum has progressed extensively availing the variation available in the primary gene pool of S. bicolor. Crossing further, the yield plateau can be accomplished by bringing in the genes from tertiary gene pool into the cultivated gene pool. Earlier efforts for wide hybridization in sorghum with tertiary gene pool were not successful due to inhibition of wild pollen germination on the stigma of cultivated species. In the current study, elite lines of cultivated Sorghum species were pollinated with wild species using different floral treatments. The results showed that spray with the synthetic auxin, 2,4-dichlorophenoxyacetic acid, has promoted the seed set. Overall, 76% crosses showed seed set, but many seeds were underdeveloped and deformed. F1 progeny showed traits of both cultivated and wild parents. Hybrids were confirmed through PCR analysis. Many (80%) F1 plants were sterile, and 20% of F1s were advanced to F2 generation. Wide variation was observed in F2 progeny, and the phenotype selections were made and are being evaluated in the field.  相似文献   

14.
S. Woods  D. A. Thurman 《Euphytica》1976,25(1):707-712
Summary Starch gel electrophoresis of single seeds of five different F1 hybrids of Brussels sprouts showed that they possessed three cathodal acid phosphatases. By comparison with cathodal acid phosphatases present in their inbred parents these have been interpreted as the two parental types plus a hybrid enzyme. All of the parental material could be classified into two groups depending upon whether or not their cathodal acid phosphatase was fast or slow moving. It was shown that these acid phosphatases are suitable for the determination of sibs in F1 hybrid sprout seed provided that one of the parents possesses the slow moving cathodal acid phosphatase and the other the fast moving one. A survey of 35 different F1 hybrids showed that 18 could be analysed for sibs using this method, those which could not were assumed to have had parents who possessed cathodal acid phosphatases of the same mobilities.  相似文献   

15.
Summary Interspecific triploid hybrids were obtained betweenArachis hypogaea L. andA. stenosperma Krapov. and W.C. Gregory by adopting hybridization coupled with rescue of the developing hybrid embryos. Two hexaploid hybrid populations were generated from triploids, somatically doubled (SD) and sexually polyploidized (SP) hexaploids. Microscopic screening for the occurrence of 2n gametes in triploid hybrids was useful to predict the production of spontaneous hexaploids. In order to facilitate maximum intergenomic recombination, the hexaploids were allowed to self for several generations (F4) in the greenhouse. Prolific vegetative growth, pollen stainability, and seed set were observed to decline with each selfed generation. Individuals of the F3 generation from the two hexaploid populations were evaluated for resistance to nematode (Meloidogyne arenaria Chitwood, race 1) and late leafspotCercosporidium personatum (Berk. & Curt.) Deighton under greenhouse conditions. Both SD and SP populations performed significantly better than their cultivated parent, Sunbelt Runner, and a susceptible cultivar, Florunner. At the DNA level, no significant differences were detected among hybrid individuals using cDNA clones and RAPD primers polymorphic for the two parents. Seven cDNA clones were used to probe DNA from 17 F2 individuals and two parents and 45 RAPD primers were used to amplify DNA from 21 F2 and F3 individuals. No significant differences in banding patterns were observed among hybrid individuals which suggested that little or no detectable intergenomic recombination had occurred.  相似文献   

16.
Summary The inheritance of seed weight in cowpea was examined in a field planting of the parents, reciprocal F1s, F2s and backcrosses to both parents of a cross between TVu 1977-OD (small seeded) and ACC 70002 (large).Seed weight was inherited quantitatively and small seed was partially domiminant to large seed size. Gene action was predominantly additive but dominance and additive × additive epistatic effects were also significant.Broad and narrow sense heritabilities were 85.1±5.3% and 75.4±18.6% respectively. The minimum number of loci involved in the inheritance of seed size was eight, and each gene pair contributed up to 1.02 g increase to seed weight. The estimate of genetic advance from F2 to F3 generations with 5% selection intensity was 3.58 g.International Institute of Tropical Agriculture, Semi-Arid Food Grain Research and Development Project/National Cowpea Improvement Program, B.P. 1783, Ouagadougou, Upper Volta.Department of Primary Industries, Hermitage Research Station, Warwick 4370, Queensland, Australia.International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), ICRISAT Center, Patancheru, P.O. 502 324, A.P., India.  相似文献   

17.
S. Varotto    L. Pizzoli    M. Lucchin  P. Parrini 《Plant Breeding》1995,114(6):535-538
As a result of an incompatibility mechanism which prevents both self-fertilization and intermating between plants with identical genotypes, inbreeding does not occur in Cichorium intybus. This self-incompatibility system complicates the production of inbred lines and the generation of F1 hybrids in Italian red chicory. Histological observations on pollinated stigmas show that the incompatibility reaction in chicory is very rapid and either prevents pollen adhering to the stigmatic papillae or determines the arrest of pollen-tube growth on the stigmatic surface; incompatible pollen cannot reach the transmitting tissue of the style. Both histological and genetic analyses of F1 progeny from a reciprocal cross between two unrelated plants suggest the occurrence of a sporophytic incompatibility system in Italian red chicory.  相似文献   

18.
Summary Self incompatibility (SI) can be used to alleviate costly hand emasculation and pollination in F1 hybrid chrysanthemum seed production. SI, however, disrupts the progression of inbreedig (selfing or full-sib mating). Consequently, inbreds are selected for breakdown of the SI system or the presence of pseudo-self compatibility (PSC). PSC inbreds, recombinant inbreds, and noninbred cultivars were selfed and/or intercrossed to determine PSC expression across environments and generate 1–3 inbred generations (I1–I3). Percent PSC ranged from 0–68.8% for inbred parents, 0.2–99.7% for recombinant inbreds, and 0.6–25.7% for noninbred cultivars. There was no indication of end-of-season PSC. The majority of parents (78%) were classified as low PSC and this trend continued in the I1 (70.1%), I2 (65.6%), and I3 (83.6%) generations; mid PSC was rarer (11.9–18.8%) and high PSC the least common (4.5–15.6%). PSC distributions were primarily continuous, rather than discrete, indicating quantitative inheritance. In several inbred families, 100% of the I1 individuals were SI; this was not correlated with parental PSC level. Inbred families derived from selfing low and mid PSC parents were the most likely to reach extinction due to inbreeding depression. High PSC was not highly heritable, since I1 progeny were predominantly SI or had low to mid PSC levels. Most 153-1 values for PSC:SI segregations (1:1, 1:3, 3:1) were not significant at the 5% level. Realized heritability (H R ) estimates for PSC ranged from a low of 0.05% to 10.19%, although increased H R values did not account for inbreeding depression or genetic mechanisms preventing selection for high PSC. The highest individual %PSC increased over the high parent with SI × low PSC or SI × mid PSC parents in all cases; progeny means did so only in SI × low PSC. Low × low crosses were split evenly between an increase and decrease in progeny or highest individual mean. Since all low × low crosses and low selfs produced 43–50% of the progeny with PSC levels higher than the parents, it appears that most low parents possess some unexpressed PSC genes. Mid PSC parents responded similarly to low PSC genotypes. An increase in PSC was found when crossing SI × PSC parents, illustrating a threshold effect. PSC × PSC crosses (high × low, low × low) produced SI, low, and mid PSC I1 individuals but did not show a heterotic effect, since the PSC parents had already surpassed the PSC threshold. Selfing high PSC parents, however, suggested different genetic control. Progeny and highest individual means behaved the same; 83% decreased and 17% remained the same for PSC levels. The drop in PSC indicated non-additive gene action. Thus, the PSC threshold with additive gene action holds when selection for higher PSC levels is being done from low and mid PSC parents, but once high PSC levels are obtained, non-additive gene action prevails.Abbreviations self pollinated - H R Realized Heritability - PSC Pseudo-Self Compatibility - SC Self Compatibility - SI Self Incompatibility  相似文献   

19.
Interspecific hybrids between Trifolium uniflorum and cultivated white clover (Trifolium repens) have highly useful characteristics for temperate pastoral systems derived from both parent species. However, the early hybrids (F1 and BC1) also have unacceptably poor seed production for commerce. This study analysed the basis for the poor seed production and investigated breeding strategies for overcoming the problem. The BC1F1 generation produced lower‐than‐expected numbers of heads per plant and seeds per floret. Backcrossing of selected hybrids to white clover corrected these deficiencies and created new variation. Seed numbers were also returned to near target levels by recurrent selection within the BC1 generation. Thus, it was possible to retain a theoretical average of 25% of T. uniflorum genome and still achieve high seed production per plant. The BC1F2 and BC2F1 generations produced high seed numbers per plant, along with reasonable variation. Both of these second‐generation hybrid forms have high reproductive potential and should be the focus for the selection of the desired combinations of agronomic and seed production traits.  相似文献   

20.
Summary Apomixis has been reported in a few lines of sorghum, among them R473 which was originally reported to be an obligate apomict. Although this line has multiple embryo sacs, the frequency of apomictic seed formation has not been determined because a progeny test has not been possible. R473 does not cross as a female with other lines except when its own pollen is present. In the present study mutations were induced in R473 by hydrazine and irradiation. Crosses were made between male-sterile mutants as females and normal R473 as males. Plants of R473 produced F1 hybrids sexually, thus indicating that they were not obligate apomicts. These F1's also reproduced sexually, as indicated by segregation for male sterility and male fertility in F2 progenies.  相似文献   

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