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1.
Anther culture of an interspecific rice hybrid from a cross of Oryza sativa× O. rufipogon was attempted. Of the 117 regenerated pollen clones, 56 could survive to maturity. A majority of these were either haploids or doubled haploids and very few turned out to be chromosomal variants. Comparative study of doubled haploids and the seed derived F2 plants indicate the distinct advantages of anther culture techniques. (1) Androgenic plants, though few in number, showed greater ariation for all the traits with the exception of ear bearing tillers. (2) Predominance of recombinants with wild traits was observed in F2 segregation. (3) It was possible to recover indica type recombinants among the anther-derived plants with one or two traits introgressed from O. rufipogon. These results suggest the feasibility and utility of anther culture in distant hybridization for incorporation of alien variation into cultivated rice.  相似文献   

2.
Sexuality is correlated with diploidy and apomixis with polyploidy in the Brachiaria genus. Brachiaria ruziziensis is a key species in Brachiaria breeding due to its obligate sexuality and intrinsic agronomic qualities. Interspecific crosses in the genus became feasible only when a few diploid accessions of B. ruziziensis were artificially tetraploidized and remained sexual. Hybridization has been done since, using natural tetraploid apomictic accessions of B. brizantha or B. decumbens as pollen donors. Twenty two accessions of B. ruziziensis from the Embrapa Beef Cattle germplasm collection (Campo Grande, MS, Brazil) were cytologically analyzed: 16 are natural diploids (2n = 2x = 18) and six are artificially induced tetraploids (2n = 4x = 36). The meiotic behavior in the 16 diploid accessions varied. The mean of meiotic abnormalities per accession ranged from zero to 24.46%. Meiotic behavior in the induced tetraploid accessions also varied with the mean of meiotic abnormalities ranging from 5.20% to 54.71%. The most common abnormalities observed in both the diploid and the tetraploid accessions, were those related to irregular chromosome segregation. In one tetraploid accession, with a high frequency of those, other irregularities involving chromosome orientation at metaphase plate and chromosome convergence to the poles, a meiotic mutation known as divergent spindle, were recorded. Meiotic behavior should be considered in selecting potential genitors for breeding.  相似文献   

3.
Summary First- and second-cycle doubled haploids of burley tobacco (Nicotiana tabacum L.) were examined to ascertain the significance of source genotype on the performance of anther-derived material and to determine the magnitude of changes from the haploid-production and chromosome-doubling stages. The anther-derived lines evaluated in this study did not exhibit siginficant yield reductions. However, significant interactions between the cycle comparison and the source genotypes indicated that source genotype can affect the degree of vigor reduction observed. Significant variation was also observed among the second-cycle doubled haploids examined in this study. Partitioning of this variation indicates that most of it is due to alteration present at the haploid-production step instead of the chromosome-doubling step. In general, the variation present in the second-cycle doubled haploids was distributed around the values observed for the source first-cycle doubled haploids. Even though unexpected variation is often observed in anther-derived materials, these results suggest that reduced vigor is not intrinsically associated with androgenetic lines of burley tobacco. The most plausible explanations for the variation and vigor losses in anther-derived lines propose that natural phenomena, given the opportunity for expression via anther culture, are responsible. Spontaneous variants present in the gametic pool of inbreds or first-cycle doubled haploids offer one possible explanation for the performance observed in anther-derived lines of tobacco.Contribution from the Department of Agronomy, University of Kentucky, Lexington, KY 40546-0091. This research was supported, in part, by a grant from R. J. Reynolds Tobacco Co. This paper (no. 85-3-29) is published with the approval of the Director of the Kentucky Agricultural Experiment Station.  相似文献   

4.
Tetraploid plants were induced successfully from diploid bananas Musa acuminata (AA genome) ‘Kluai Leb Mu Nang’ and ‘Kluai Sa’ (2n = 2x = 22) with in vitro oryzalin treatment. Calluses from in vitro-grown shoot tips of both cultivars were treated with oryzalin at concentrations of 1.5 or 3 mg l−1 for 24, 48 and 72 h, respectively. The oryzalin treatments produced tetraploids at a frequency of 15.6% in ‘Kluai Leb Mu Nang’ and 16.7% in ‘Kluai Sa’ as detected by flow cytometry. Chromosome counting showed that the tetraploid plant chromosome number was (2n = 4x = 44). The selected tetraploid plants were transplanted in the field and variations in the morphological characteristic of leaf shape and fruit bunch compared to normal diploid plants were found under the same growing condition even after 3 years of cultivation.  相似文献   

5.
St. Augustinegrass is well suited for lawns and commercial landscapes. While many genotypes are cross‐fertile, all cultivars are propagated vegetatively in sod production. To ensure varietal purity, development of sterile triploid hybrids by crossing tetraploid and diploid genotypes has been successfully used in other warm‐season turfgrasses. Applying this model in St. Augustinegrass would be beneficial to sod producers and turf managers who require purity for certification and uniformity for performance, respectively. This study was conducted to develop colchicine‐induced tetraploid lines of St. Augustinegrass. Seeds of cultivar ‘Raleigh’ were treated with four colchicine concentrations at four exposure times. A non‐treated control was included among the treatments. Seedlings that germinated were screened for genome size changes using flow cytometry. Line DSA 13005 and two progeny lines derived through selfing, DSA 16001 and DSA 16016, were corroborated as tetraploids (2n = 4x = 36) through chromosome counts. These lines will be used in future breeding efforts to attempt development of sterile triploid cultivars of St. Augustinegrass.  相似文献   

6.
We report the accurate determination of the allelic configurations of a total of eight new citrus tetraploid hybrids by means of SSR analysis, coupled with capillary electrophoresis, and PCR based dosage effects. Tetraploid hybrids were spontaneously obtained from different interploid crosses (2x × 4x) between diploid ‘Femminello’ lemon and the allotetraploid somatic hybrid (2n = 4x = 36) ‘Key’ lime + ‘Valencia’ orange, and between diploid ‘Wilking’ and ‘Fortune’ mandarins and an autotetraploid ‘Dancy’ mandarin (2n = 4x = 36). To understand the opportunity to employ them in further backcross programs, the cytological mechanisms underlying their ploidy level were unambiguously determined using six SSR primers. PCR conditions were optimized and skewness in template/product ratios were verified. Tetraploid allelic configurations were determined from PCR based dosage effects using electropherogram peak heights to estimate the copy number per allele. In all the tetraploid hybrids we found out that diploginy (2n eggs) has occurred, contributing the extra haploid genome in the tetraploids. According to the marker genotypes, it was further inferred that the 2n eggs in ‘Femminello’ lemon resulted from first division restitution (FDR), while in ‘Wilking’ and ‘Fortune’ mandarins 2n eggs occurred in second division restitution (SDR). These new genotypes, with their improved genetic female background, can be therefore considered very valuable in our citrus genetic improvement program as pollen donors in backcrosses suitable to eliminate negative traits.  相似文献   

7.
Double haploid (DH) plants of Brassica spp. can be produced via anther culture or culture of microspores. This paper reviews the uses of double haploids in crop improvement research in vegetable brassicas (B. oleracea). Applications of DH lines are described for breeding; construction of linkage maps; genetic analysis of quantitative traits and capturing genetic variation. The advantages and disadvantages of DH lines are discussed  相似文献   

8.
Summary Adventitious shoots were obtained from the diploid watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] cultivars Dixielee, Jubilee II, Mickylee, Minilee, and Royal Sweet by culturing excised cotyledons on shoot regeneration medium for six weeks. Tetraploid and diploid regenerants were identified by counting the number of chloroplasts per guard cell pair from leaves of regenerated plants. Cross fertilization of putative tetraploids with diploid pollinators and the production of triploid seed confirmed the efficacy of this approach. The mean number of chloroplasts for tetraploid regenerants was 19.1 whereas diploids averaged 11.2. These values were similar to tetraploid and diploid plants from seed. Ovary diameter, petal, and anther diameter of male flowers, and leaf length by width ratio were also good indicators of plant ploidy. Progeny obtained from self-fertile tetraploids of Mickylee were crossed with various diploid pollinators to produce triploid hybrid seed. All triploid plants from tissue culture-derived tetraploids produced fruit comparable in quality to fruit produced by currently-available triploid hybrids, demonstrating that in vitro tetraploid induction can be used to produce high quality tetraploid plants for use in triploid hybrid seed production.  相似文献   

9.
A triploid hybrid, which was obtained from interspecific crosses between tetraploid Primula denticulata (2n = 4x = 44) and P. rosea (2n = 2x = 22), successfully produced 11 plants by backcrossing with pollen of tetraploid P. denticulata. Analysis of ploidy level using flow cytometry and chromosome counting in the 11 BC1 plants revealed that all progeny had much larger DNA contents and chromosome number than both parents. In this triploid-tetraploid (3x–4x) crossing, progeny was predominantly true or near pentaploid presumably produced by the fertilization between true or near triploid female gamete produced from triploid hybrid and diploid pollen of tetraploid P. denticulata. These results suggest that unreduced (3x) or near triploid female gametes were partially produced by single step meiosis, either first-division restitution or second-division restitution process. The zygotes formed by the fertilization between true or near triploid egg produced by single step meiosis in triploid hybrid and diploid pollen produced by normal meiosis of tetraploid P. denticulata might be the only survivors in embryogenesis.  相似文献   

10.
To transfer new traits into the gene pool of garden dahlias (Dahlia variabilis), crosses between garden dahlias (2n = 64) and the epiphytic species Dahlia macdougallii (2n = 32) from the section Epiphytum were conducted. Six hybrid plants were obtained. The hybrid status was verified using three SSR markers. In addition, flow cytometry was performed to determine the genome size of the hybrids and to show that the hybrids were hexaploid as expected from crosses between tetraploids and octoploids. The open pollinated progeny of the hybrids produced four progeny with octoploid genomes. The hybrids exhibited indeterminate vegetative growth and the formation of flowers from axillary buds, similar to the father D. macdougallii. This result is of interest for breeding new varieties of dahlia with traits that are not present in the current gene pool.  相似文献   

11.
Helleborus species are members of the family of the Ranunculaceae. These popular perennials are all diploids (2n = 2x = 32). This study investigates polyploidy induction by different antimitotic agents. Colchicine, oryzalin and trifluralin were tested in vitro on shoots of Helleborus niger, H. orientalis and H. × nigercors. Furthermore the effect of the antimitotic agents on the viability and the multiplication rate of cultured plantlets were analyzed. Flow cytometry demonstrated that polyploidisation was genotype dependent: using H. niger, tetraploids were obtained using either oryzalin (3 μM) or trifluralin (3 or 10 μM), whereas for H. × nigercors only trifluralin (3 or 10 μM) induced polyploidisation. For H. orientalis neither treatment was effective to produce tetraploids or mixoploids. For these three species, colchicine (100 μM) was ineffective. The polyploidisation events in H. niger and H. × nigercors were confirmed by chromosome counts of mounted nuclei derived from root tips (2n = 4x = 64).  相似文献   

12.
Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombination.  相似文献   

13.
Shelley Jansky 《Euphytica》2011,178(2):273-281
Valuable genetic diversity in diploid wild Solanum species can be accessed through crosses to haploids (2n = 2×) of the tetraploid cultivated potato, Solanum tuberosum. Haploid-wild species hybrids segregate for the ability to tuberize in the field. In addition, they vary in male fertility, vine size, stolon length, and tuber size. In this study, three haploids were crossed with nine diploid wild Solanum species and 27 hybrid families were evaluated in the field for two years. The proportion of male fertile hybrid clones varied depending on the wild species parent. A large effect of the female parent was detected for vine size, stolon length, tuber size, percent tuberization, and percent plants selected for agronomic quality. An exceptional haploid (US-W4) was identified for the production of agronomically desirable haploid-wild species hybrids. In hybrids derived from US-W4, differences among wild species parents were observed for agronomic quality. Superior hybrids were produced by S. berthaultii and S. microdontum. Reciprocal crosses were evaluated for a subset of families. When the wild species was used as the female parent, male fertility was restored, but tuberization and tuber size were reduced. Careful selection of both haploid and wild species parents can result in a large proportion of fertile, agronomically desirable hybrid offspring.  相似文献   

14.
Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.  相似文献   

15.
The aim of this research was to improve our understanding of how ploidy level influences phenotype and gene expression in Chinese cabbage (Brassica rapa L. ssp. pekinensis). Haploid plants (2n = 10) was induced by 0.2% colchicine to produce diploid (2n = 20) and tetraploid plants (2n = 40). The aneuploid (2n = 24) was also obtained by hybridization between diploid plants as the female and tetraploid plants. The ploidy levels of all plants were identified through chromosome counts and flow cytometry. Leaves and petals became larger as the ploidy level increased from haploid to diploid, and from aneuploid to tetraploid. Similarly, expression of ARGOS was regulated by genome size, increasing in parallel with the level of ploidy. Among the four ploidy types, expression was stronger in the floral buds than in the leaves. Expression by ASY1 also differed according to ploidy level, being highest in diploid plants, followed in order by tetraploids. Expression was similar between haploids and aneuploids at two stages—prior to and after meiosis—but was higher in the haploids during meiosis. When buds were compared within the same ploidy type at different stages, ASY1 expression was obviously higher during meiosis than either before or after. Our study demonstrated the generation and phenotype of a ploidy Chinese cabbage series derived from one haploid. Expression of genes ARGOS and ASY1 were modulated by genome size in this ploidy series, and the regulated patterns of the two genes was different.  相似文献   

16.
The New Zealand hop breeding programme is based solely on the development of seedless triploid cultivars. This relies on the use of tetraploid parents. While a sexually derived tetraploid parents have been used successfully, sexually derived tetraploids offer a useful alternative. They may have a higher level of heterozygosity and are easier to obtain. Methods for the identification of tetraploids from seedling populations by flow cytometry are described. Two studies were conducted; one on field-grown plants, the other on plants grown in a glasshouse. Approximately 15%of seedlings in the two studies were identified as tetraploids (2n = 4x = 40). Between 70 and 80% were identified as either diploid (2n =2x = 20) or triploid (2n = 3x = 30). Remaining plants were haploid, pentaploid or probably aneuploid. Within triploid and tetraploid populations from 40to 50% of seedlings were female, 30 to40% were monoecious, with the remainder being males and non-flowering plants. Sexually derived tetraploid parents have been used successfully in the breeding programme, from which several promising triploid selections have subsequently been made. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
Prem P. Jauhar 《Euphytica》2006,148(3):341-344
Summary Durum or macaroni wheat (Triticum turgidum L., 2n = 4x = 28; AABB genomes) arose as a natural hybrid between two wild species, Aegilops speltoides Tausch (2n = 2x = 14; BB genome) and Triticum urartu Tumanian (2n = 2x = 14; AA genome). The two progenitors hybridized in nature about half a million years ago and gave rise to tetraploid wheat, presumably in one step as a result of functioning of unreduced gametes in their hybrid BA (amphihaploid). It is easily possible to go back on the evolutionary scale and obtain durum haploids BA, and then regenerate tetraploid durum plants from them. Interestingly, such a reversion to haploidy does occur in nature as well, although at a very low frequency. This article reports on the occurrence of two spontaneous durum haploids and describes their chromosomal characteristics. The haploids (euhaploids, to be precise) had 14 somatic chromosomes, which, on fluorescent genomic in situ hybridization (fl-GISH), could be distinguished as 7 A-genome and 7 B-genome chromosomes. At meiosis, only 2.3 and 2.7% of the chromosomes paired in the two haploids, because of the presence of the homoeologous pairing-suppressor gene, Ph1. The Ph1-induced lack of pairing is a prerequisite for chromosome doubling through the formation of unreduced gametes that give rise to tetraploid durum wheats.Mention of trade names or commercial products in this publication is solely to provide specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.  相似文献   

18.
Sexual hybridization is an important generator of biodiversity and a powerful breeding tool. Hybridization can also overcome ploidy barriers when it involves 2n gametes, as in the case of unilateral sexual polyploidization (USP) that has been utilized in several crops, among which alfalfa. This research was aimed at gaining insights into the effects of USP on genome methylation and on phenotypic traits in alfalfa, an important forage species. The Methylation-Sensitive Amplified Polymorphism technique was used to estimate the cytosine methylation changes occurring in a tetraploid (2n = 4x = 32) USP progeny from crosses between a diploid Medicago sativa subsp. falcata genotype that produces 2n eggs and a cultivated tetraploid Medicago sativa subsp. sativa variety. De novo methylation or demethylation in the USP progeny were observed for 13% of the detected genomic sites, indicating that methylation changes can be relevant. USP plants showed larger surface area of the leaf epidermis cells than both parents, but this did not result in larger leaf size or higher plant biomass. They displayed significant higher ovule sterility than the tetraploid parent, but normal fertility was observed in crosses with unrelated male testers. We conclude that hybridization and sexual polyploidization resulted in novel variation in terms of remodeling of the methylation landscape as well as changes in phenotypic traits in alfalfa.  相似文献   

19.
Tetraploid red clover (Trifolium pratense L.) often produces insufficient seed to be economically interesting. Numerous studies have identified poor pollination due to long corolla tubes as its cause, but other studies disagree. Therefore, we investigated seed yield, corolla tube length and flowering traits in 244 plants from five diploid and five tetraploid cultivars during 2 years. Tetraploids produced fewer seeds, fewer flower heads and fewer seeds per head, but an equal number of flowers per head when compared to diploids. Although corolla tubes were longer in tetraploid than in diploid red clover (P < 0.001), no correlation between corolla tube length and seed yield was detected. Therefore, the corolla tube length is likely neither the main nor only cause of low seed yield in tetraploid red clover. Instead, three putative causes for low seed yield were identified: tetraploids produced less inflorescences per plant, possessed a lower degree of determinacy and had markedly less seeds per head when compared to diploids. Possible causes for such differences include lower pollen viability and higher rates of embryo abortion.  相似文献   

20.
Doubling the chromosome number of bahiagrass via tissue culture   总被引：2，自引：0，他引：2  
Crop improvement in bahiagrass (Paspalum notatum Flüggé) is limited by apomixis in most natural tetraploids, however, diploid sexual types occur. Production of sexual tetraploids by chromosome doubling will allow hybridization with apomictic tetraploids. Diploid bahiagrass (Paspalum notatum Flüggé) embryogenic callus tissue was exposed to three concentrations of three antimitotic chemical agents, colchicine, oryzalin and trifluralin. Callus was generated to plants and ploidy was evaluated by stomata size, mitotic chromosome counts, and flow cytometry. A total of 310 plants were verified as tetraploid of 1,432 plants that reached transplanting size. All treatments yielded 4x plants. The mean percentage success over all treatments was 22%, with means of 31% for oryzalin, 24% for colchicine and 16% for trifluralin. The high rates of success indicate that all agents can be successfully used to double chromosome numbers in bahiagrass. The percentage of 4x plants ranged from 9% (20 μM trifluralin) to 43% (20 μM oryzalin). Several treatments adversely affected regeneration. Mitotic chromosome counts are difficult and labor intensive in bahiagrass. Therefore, leaf stomata measurements were used as a preliminary screen. Data gave a bimodal distribution with overlapping tails and based on chromosome counts would have given an error rate of 12%. Flow cytometry analysis of regenerated plants resulted in mean nucleus fluorescence distributions consistent with control diploid or tetraploid values. These values agreed with chromosome counts, and this method is recommended for determining bahiagrass ploidy level. Research goals and available resources should be taken into consideration when selecting a treatment for chromosome doubling in bahiagrass.  相似文献   

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