Endopolyploidy in seed plants is differently correlated to systematics, organ, life strategy and genome size

Endopolyploidy is a systemic feature in seed plants. A negative correlation between genome size and endopolyploidization has been claimed previously, assuming that a minimum amount of DNA, necessary for certain cell functions, has to be acquired by endopolyploidization of the corresponding cells in plants with small genomes. This assumption was based on the analysis of only a limited set of data from few species. In the present study the endopolyploidization of several organs of 54 seed plant species belonging to two gymnosperm and 14 angiosperm families was investigated. The results revealed a low negative correlation between genome size and endopolyploidization. However, differences between the families, between the different organs of a given species and between the different life‐cycle types with regard to endopolyploidization became obvious. A three‐way analysis of variance with covariate to quantify the impact of the different factors on the extent of endopolyploidization suggested that taxonomic position is the major factor determining the degree of endopolyploidy within a species, while life cycle, genome size and organ type have a minor but also significant effect on endopolyploidization. The comparison of habitats of 16 investigated Central European species implies that endopolyploidization represents a mean to accelerate the growth of plant species in niches, which require and support fast development.     

Endopolyploidie und Ertrag bei diploiden und tetraploiden Zuckerrüben

Zusammenfassung Die Regression des Rübengewichts von diploiden und tetraploiden Zuckerrüben auf den tatsächlichen Ploidiegrad des Mesophylls, der sich aus der meristematischen Ploidiestufe und der Endopolyploidie zusammensetzt, wurde in einem nassen Jahr unter Feldbedingungen geprüft. Am wenigsten leisteten die Pflanzen mit dem höchsten Endopolyploidiegrad. Die Diploiden mit geringer bis mittlerer Endopolyploidie befriedigten im Mittel gleich gut, aber unter den Tetraploiden brachten nur die Pflanzen mit der kleinsten oder einer nur wenig höheren Tendenz zur Endopolyploidisierung den höchsten Ertrag. Das beste Rübengewicht wurde sowohl bei Diploiden als auch bei Tetraploiden mit etwa tetraploidem, im vorhergehenden Trockenjahr bei Diploiden sogar mit vorwiegend diploid gebliebenem Mesophyll erreicht. Deshalb erscheint es nützlich, bei tetraploiden Zukkerrüben gegen die Endopolyploidisierung zu züchten. Die genetischen Vorteile der Tetraploidie bleiben erhalten, während der Nachteil der großen Zellen verschwinden kann.

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Endopolyploidy and yield in diploid and tetraploid sugar beets

Summary The root weight of diploid and tetraploid sugar beets as related to the actual degree of ploidy of the mesophyll, a combination of meristematic level and subsequent endopolyploidization, was investigated under field conditions in a wet year. Plants with highest endopolyploidy showed the lowest yield. Diploids with low to intermediate endopolyploidy were about equally satisfactory, but among the tetraploids only those plants with the lowest tendency toward endopolyploidization exhibited maximum yield. The highest yield was produced by both diploids and tetraploids with about tetraploid mesophyll, in the preceding dry year this was achieved by diploids with predominantly diploid mesophyll. It seems, therefore, useful in tetraploid sugar beets to breed against endopolyploidization. The genetic advantages of tetraploidy are retained while the disadvantage of large cell size may be eliminated.

     

Endopolyploidie und Ertrag bei diploiden und tetraploiden Zuckerrüben

Zusammenfassung Ein verbessertes Verfahren zur Selektion auf niedrigen Endopolyploidiegrad in Zuckerrübenblättern durch Bonitur der Chloroplastenzahlen in Schwammparenchymzellen wird angegeben. Die bessere Leistungsfähigkeit der kleinzelligen (d. h. weniger hoch endopolyploiden) tetraploiden Zuckerrüben in den Populationen beruht nicht auf stärkerer Heterozygotie dieser Pflanzen.

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Endopolyploidy and yield in diploid and tetraploid sugar beetsIII. Methodological results

Summary An improved procedure is described for selection for a lower degree of endopolyploidy in leaves of sugar beets by means of scoring chloroplast numbers in spongy parenchyma cells. The higher yield of the tetraploid sugar beets with smaller cells (i.e. with a lower degree of endopolyploidy) in the populations is not a result of an increased heterozygosity of these plants.

     

Endopolyploidie und Ertrag bei diploiden und tetraploiden Zuckerrüben. II.

Zusammenfassung Bei diploiden Zuckerrüben entsprechen die Zellgrößen des Mesophylls, die durch Endotetraploidisierung entstehen, im Mittel dem Erfordernis für einen optimalen Ertrag. Bei tetraploiden Zuckerrüben jedoch werden die Zellen der meisten Pflanzen endooktoploid und damit zu groß. Es ist nicht ratsam, die Endopolyploidie der Tetraploiden ganz wegzüchten zu wollen; nur eine Verminderung ihres Ausmaßes erscheint vorteilhaft.

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Endopolyploidy and yield in diploid and tetraploid sugar beets II

Summary In diploid sugar beet the mesophyll cell sizes, arising from endotetraploidization, are well adapted to optimal yield requirements. In tetraploid sugar beet, however, the mesophyll cells of most plants become endooctoploid and hence too large. Trying to eliminate all endopolyploidy from tetraploids is not advisable, but some reduction of its extent seems advantageous.

     

Endopolyploidy is a common response to UV-B stress in natural plant populations,but its magnitude may be affected by chromosome type

Background and AimsUltraviolet-B radiation (UV-B) radiation damages the DNA, cells and photosynthetic apparatus of plants. Plants commonly prevent this damage by synthetizing UV-B-protective compounds. Recent laboratory experiments in Arabidopsis and cucumber have indicated that plants can also respond to UV-B stress with endopolyploidy. Here we test the generality of this response in natural plant populations, considering their monocentric or holocentric chromosomal structure.MethodsWe measured the endopolyploidy index (flow cytometry) and the concentration of UV-B-protective compounds in leaves of 12 herbaceous species (1007 individuals) from forest interiors and neighbouring clearings where they were exposed to increased UV-B radiation (103 forest + clearing populations). We then analysed the data using phylogenetic mixed models.Key ResultsThe concentration of UV-B protectives increased with UV-B doses estimated from hemispheric photographs of the sky above sample collection sites, but the increase was more rapid in species with monocentric chromosomes. Endopolyploidy index increased with UV-B doses and with concentrations of UV-B-absorbing compounds only in species with monocentric chromosomes, while holocentric species responded negligibly.ConclusionsEndopolyploidy seems to be a common response to increased UV-B in monocentric plants. Low sensitivity to UV-B in holocentric species might relate to their success in high-UV-stressed habitats and corroborates the hypothesized role of holocentric chromosomes in plant terrestrialization.     

Genetic relationship among Paspalum species of the subgenus Anachyris: Taxonomic and evolutionary implications

Paspalum is one of the most important genera of the Poaceae family due to its large number of species and diversity. The subgenus Anachyris comprises six species mainly from South America grouped together by sharing rare spikelet characteristics. A genetic analysis using ISSR markers, compared with the morphological and phenotypic variation observed in each one species, was used to establish genetic relationships among 40 accessions with several ploidy levels, belonging to 5 species of the subgenus Anachyris. Fourteen accessions of Paspalum malacophyllum (2x and 4x), 12 of P. simplex (2x, 3x, 4x and 6x), 4 of P. procurrens (2x and 4x), 4 of P. usterii (4x) and 6 of P. volcanensis (4x) were analysed. A total of 227 ISSR loci (98.7% polymorphic) were detected among all accessions, with variable loci number and percentages of polymorphism according to species delimitations. Six main groups were identified by cluster analysis based on Jaccard's genetic distance and UPGMA, four of which matched all the respective accessions of P. simplex, P. procurrens, P. usterii and P. volcanensis, while the other two were consistent with two different groups of accessions of P. malacophyllum, one involving most tetraploid accessions, and the other one grouping together a tetraploid and two diploid accessions. The distinctive morphological characteristics and the separate clustering of these tetraploid and diploid cytotypes suggest to consider a new multiploid species complex inside the subgenus Anachyris. Both cytotypes of P. procurrens, and the four co-specific cytotypes of P. simplex consistently clustered together forming two specific groups for the two multiploid taxons. This is in agreement with the existence of high phenotypic similarities between diploid and tetraploid cytotypes of P. procurrens, and among diploid, triploid, tetraploid and hexaploid cytotypes of P. simplex. Since the polyploid cytotypes of these species are reproduced by apomixis, the specific genetic clustering by ISSR markers and morphological and cytological results support the hypothesis that the two multiploid species were originated by autopolyploidy. Our results confirm previous studies suggesting a monophyletic origin for the subgenus Anachyris and are concordant with previous data regarding genomic homologies and phylogenetic analyses in the genus.     

Ploidy analysis of Cymbidium,Phalaenopsis, Dendrobium and Paphiopedillum (Orchidaceae), and Spathiphyllum and Syngonium (Araceae)

Endopolyploidy is typical and wide-spread in the Orchidaceae. In this study, an attempt was made to quantify the ploidy of mature callus and mature protocorm-like bodies (PLBs) of nine hybrid Cymbidium cultivars cultured in vitro, as well as different flower parts (dorsal sepal, petal, lateral sepal, labellum, pedicel, column, anther cap, stigmatic surface) and youngest leaf of Phalaenopsis and Paphiopedillum and in leaf tissues of in vitro Spathiphyllum and Syngonium plants. Polyploidy was detected in in vitro cultures, primarily in PLBs, ant to a limited extent in floral tissue: 8C was detected in the pedicel and column, but never exceeding 3%. This study expands on the number and breadth of cases of endopolyploidy in orchids, with novel information about Paphiopedillum. These findings may be useful for better understanding developmental processes in vitro or in planta, and may be the first step to revealing evolutionary or adaptive mechanisms of survival of orchids in response to environmental or abiotic stresses.     

Variation in flavonoid patterns in relation to chromosome changes in Gibasis schiedeana

The distribution of $\text{C-}\text{glycoflavones}$ has been examined in the leaves of plants from five diploid and 12 tetraploid populations of Gibasis schiedeana. Five different chromatographic patterns were found; one occurs only in a single population of diploid plants, two were found in seven populations of tetraploids and the other two in the remaining plants from both diploid and tetraploid populations. Flavonoids were also investigated in three different types of artificially produced triploids. The effects of the changes in ploidy, which are accompanied by Robertsonian fusion and variation in the number of B chromosomes as contributory factors in the observed differences in flavonoid patterns are discussed.     

Endopolyploidy in Diploid and Tetraploid Maize (Zea mays L.)

Nuclei from different tissues such as stem, mesocotyl, nodalroot and root tip of diploid and tetraploid maize were isolated,stained with propidium iodide and passed through an EPICS-751flow-cytometer cell sorter. Variations in flow histograms wereobserved in different tissues. Stem tissues of both the diploidand tetraploid had two peaks representing G1 and G2 somaticnuclei. The remaining tissues in both the diploids and tetraploidsexhibited three peaks. The first peak observed in these tissuesrepresents G1 somatic nuclei of the lowest ploidy level. Thesecond peak represent G2 somatic nuclei of the lowest ploidylevel+G1 somatic nuclei of the next ploidy level. The thirdpeak represents G2 of the higher ploidy level+G1 somatic nucleiof the next higher ploidy level. Statistically significant differenceswere observed between the diploid and tetraploid maize tissueswith respect to nuclei distribution in the higher ploidy levelpeaks implying variation in the degree of endopolyploidy inthe diploid and tetraploid maize. The results of this studysuggest that the amount of endopolyploid observed in maize genotypeshas an effect on their overall agronomic performance under thefield conditions.Copyright 1993, 1999 Academic Press Zea mays L., maize, endopolyploidy, diploid, tetraploid, flow cytometry     

Ploidy doubling by in vitro culture of excised protocorms or protocorm-like bodies in <Emphasis Type="Italic">Phalaenopsis</Emphasis> species

Endopolyploidy was observed in the protocorms of diploid Phalaenopsis aphrodite subsp. formosana with ploidy doubling achieved by in vitro regeneration of excised protocorms, or protocorm-like bodies (PLBs). Thirty-four per cent of the PLBs regenerated from the first cycle of sectioned protocorms were found to be polyploids with ploidy doubled once or twice as determined by flow-cytometry. The frequency of ploidy doubling increased as the sectioning cycles increased and was highest in diploid followed by the triploid and tetraploid. Regeneration of the endopolyploid cells in the tissue of the protocorms or PLBs is proposed as the source of the development of ploidy doubled plantlets. The frequency of ploidy doubling was similar in seven other Phalaenopsis species, although the rate of increase within cycles was genotype specific. In two species, a comparison of five parameters between 5-month-old diploid and tetraploid potted plants showed only the stomata density differed significantly. The flowers of the tetraploid plant were larger and heavier than those of the diploids. This ploidy doubling method is a simple and effective means to produce large number of polyploid Phalaenopsis species plants as well as their hybrids. The method will be beneficial to orchid breeding programs especially for the interspecific hybridization between varieties having different chromosome sizes and ploidy levels.     

Most organs of sugar-beet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.) plants at the vegetative and reproductive stages of development are polysomatic

Polysomaty was studied using flow cytometry in different organs of diploid, triploid and tetraploid sugar-beet (Beta vulgaris L.) plants, in the first (at harvest) and the second (at the height of the blooming period) year of development. Of the organs/parts of organs of the vegetative plant that developed during the first year, only the leaf lamina did not contain endopolyploid cells; in all others, one to three endocycles had occurred. The second-year seed-crop plant was also highly polysomatic; even in reproductive organs such as the flower and pericarp the endopolyploid cells were present (up to 8C and 32C, respectively). At this stage of development no endocycles occurred in the leaf lamina, flower bract, and inflorescence bract. The parts of the plant with no endopolyploid cells are recommended for ploidy estimation, and as a material suitable for micropropagation and genetic manipulations. Endoreduplication, up to 32C (64Cx), was organ-specific and correlated negatively with plant ploidy. The highest mean C-value, over 7, was in the diploid, in the basal part of the oldest leaf petiole in the first-year plant, and in the storage parenchyma of the root in the second-year seed-crop plant. The results confirm that higher endopolyploidy occurs in plants with a smaller 2C DNA amount than in those with a larger one. The significance of endopolyploidization in development of sugar-beet plant organs is discussed.     

Essential mycorrhizal partners of the endemic Chilean orchids Chloraea collicensis and C. gavilu

Orchids are obligate mycoheterotrophic plants, relying on fungal nutrient resources to grow for their entire life or until they develop into photosynthetic seedlings. In Chile, orchids are represented by 7 genera and 63 species, 27 of which are endemic. Some Chilean species are considered endangered or rare, but many are insufficiently known. This study aims to isolate, culture, and identify fungal species found in symbiosis with the endemic Chilean orchids Chloraea collicensis Kraenzl. and Chloraea gavilu Lindl. for their potential to be used in future conservation programs. Roots of both species of orchids were collected in the field and those presenting pelotons were firstly cultured in agar-water and thereafter sub-cultured in potato dextrose agar media. Fungal colony growth was measured under the dissecting microscope. Fungal isolates from C. gavilu showed a higher growth rate than isolates from C. collicensis and could be used as inoculum for seed germination in further studies. Isolated colonies showed morphological characteristics of the form genus Rhizoctonia and presented two nuclei per cell. The ITS-nrDNA sequences confirmed their morphological identification as species of Tulasnella.     

Systemic endopolyploidy in <Emphasis Type="Italic">Spathoglottis plicata</Emphasis> (Orchidaceae) development

Background  

Endopolyploidy is developmentally regulated. Presence of endopolyploidy as a result of endoreduplication has been characterized in insects, mammals and plants. The family Orchidaceae is the largest among the flowering plants. Many of the members of the orchid family are commercially micropropagated. Very little has been done to characterize the ploidy variation in different tissues of the orchid plants during development.     

Endopolyploidy in seed plants

Two main attempts have been suggested for the biological significance of endopolyploidy: (i) provision of high DNA amounts to support high synthetic demands in certain cells and (ii) compensation for a lack of nuclear DNA in species with small genomes. However, in seed plants, the positive correlation between DNA content and cell volume of endopolyploid cells suggests other possibilities. Cell size paralleled by the endopolyploidy level has an impact on growth and development. Endopolyploidy levels in turn are characteristic for a given species and even families, reflecting the adaptation to certain habitats during phylogeny. Furthermore, endopolyploidy levels vary to some degree between individuals of one species in response to different environmental conditions. In addition, endopolyploidy differs between different tissues suggests that a certain cell size is advantageous for a given cell function. This article reviews these findings and discusses more conclusive possible functions of endopolyploidy.     

Hybridisation between oilseed rape (Brassica napus) and tetraploid Brassica rapa under field conditions

Cross-compatible relatives of crop species contribute to the uncertainty regarding the potential risk of transgene escape from genetically modified varieties. The most successful crossing partner of oilseed rape (Brassica napus L.) is diploid Brassica rapa L. Variation of ploidy level among B. rapa cultivars has, until recently, been neglected in the context of gene flow and hybridisation with oilseed rape. We estimated the extent of hybridisation between autotetraploid B. rapa varieties (female) and B. napus (pollen donor) under experimental field conditions. Morphology, variation of relative DNA amount, and microsatellite markers were used to distinguish between intraspecific offspring of tetraploid B. rapa and interspecific hybrids with B. napus. Of 517 seed progenies of tetraploid B. rapa, 45 juvenile plants showed species specific morphological traits of oilseed rape. The detection of putative hybrids based on variation in relative DNA amounts was problematic due to the occurrence of aneuploidy. In total, 84 offspring showed relative DNA amounts deviating from tetraploid B. rapa, four of which were hexaploids. Of the 205 offspring analysed at three microsatellite loci, 67 had oilseed rape alleles. Based on molecular evidence a minimum hybridisation rate of 13.0% was estimated. A few mother plants accounted for the majority of hybrids. The mean pollen viability of hybrids between B. napus and tetraploid B. rapa (80.6%) was high in comparison with mean pollen viability of triploid hybrids between B. napus and diploid B. rapa. Therefore, the occurrence of tetraploid B. rapa should be taken into consideration when estimating the likelihood of gene flow from oilseed rape to close relatives at the landscape level. Tetraploid B. rapa is a common component of several seed mixtures and establishes feral populations in northwest Germany. Assuming a similar abundance of diploid and tetraploid B. rapa, gene flow from B. napus to tetraploid may be more likely than gene flow to diploid B. rapa.     

Tetraploidization events by chromosome doubling of nucellar cells are frequent in apomictic citrus and are dependent on genotype and environment

Background and Aims

Polyploidy is a major component of plant evolution. The citrus gene pool is essentially diploid but tetraploid plants are frequently encountered in seedlings of diploid apomictic genotypes. The main objectives of the present study were to establish the origin of these tetraploid plants and to ascertain the importance of genotypic and environmental factors on tetraploid formation.

Methods

Tetraploid seedlings from 30 diploid apomictic genotypes were selected by flow cytometry and genotyped with 24 single sequence repeat (SSR) markers to analyse their genetic origin. Embryo rescue was used to grow all embryos contained in polyembryonic seeds of ‘Tardivo di Ciaculli’ mandarin, followed by characterization of the plantlets obtained by flow cytometry and SSR markers to accurately establish the rate of tetraploidization events and their potential tissue location. Inter-annual variations in tetraploid seedling rates were analysed for seven genotypes. Variation in tetraploid plantlet rates was analysed between different seedlings of the same genotype (‘Carrizo’ citrange; Citrus sinensis × Poncirus trifoliata) from seeds collected in different tropical, subtropical and Mediterranean countries.

Key Results

Tetraploid plants were obtained for all the studied diploid genotypes, except for four mandarins. All tetraploid plants were identical to their diploid maternal line for SSR markers and were not cytochimeric. Significant genotypic and environmental effects were observed, as well as negative correlation between mean temperature during the flowering period and tetraploidy seedling rates. The higher frequencies (20 %) of tetraploids were observed for citranges cultivated in the Mediterranean area.

Conclusions

Tetraploidization by chromosome doubling of nucellar cells are frequent events in apomictic citrus, and are affected by both genotypic and environmental factors. Colder conditions in marginal climatic areas appear to favour the expression of tetraploidization. Tetraploid genotypes arising from chromosome doubling of apomictic citrus are extensively being used as parents in breeding programmes to develop seedless triploid cultivars and have potential direct use as new rootstocks.     

Morphological, physiological, cytological and phytochemical studies in diploid and colchicine-induced tetraploid plants of Echinacea purpurea (L.)

Echinacea purpurea (L.) is one of the important medicinal plant species. To obtain the tetraploid plants of Echinacea purpurea with improved medicinal qualities, the root tips of two true leaves seedlings were imbibed in 0.25 % (w/v) colchicine solution for 24, 48, 72, 96 and 168 h. The ploidy level of plants was determined by chromosome counting of root tip cells, and confirmed by flow cytometric analysis. Tetraploid induction occurred in seedlings treated for 24, 48 and 72 h at colchicine solution. The morphological, physiological, cytological, and phytochemical characteristics of diploid and colchicine-induced tetraploid plants were compared. Results indicated that tetraploid plants had considerable larger stomata, pollen grain, seed and flower. Moreover, chloroplast number in guard cells, amount of chlorophyll (a, b, and a + b), carotenoids as well as width and thickness of leaves were increased in tetraploids. However, stomata frequency, leaf index, plant height, and quantum efficiency of photosystem II in tetraploid were lower than diploid plants. High-performance liquid chromatography analysis showed that leaves of the tetraploid plants had more cichoric acid (45 %) and chlorogenic acid (71 %) than diploid plants. It was concluded that morphological and physiological characteristics can be used as useful parameters for preliminary screening of putative tetraploids in this species.     

铁皮石斛种子的室内共生萌发

由于人为的采挖和原生境的破坏,使得铁皮石斛野生资源已濒临灭绝。因此,保护铁皮石斛野生资源及其生境,加快其野生资源的繁殖显得非常重要。以铁皮石斛种子(TTC染色显示种子生活力为77.65%)为材料,与分离自2种野生兰科植物根部的4株共生真菌 (C20来自铁皮石斛,L12,L24b 和 L28来自美花石斛)在燕麦培养基上进行共生萌发。经过18周的共生培养,4株真菌均不同程度地促进了铁皮石斛种子的萌发,其中菌株L24b (Epulorhiza)和L28 (Epulorhiza)显著提高了种子的萌发率,分别比对照高出26.51%和12.20%,但未形成幼苗,只是处于原生分生组织阶段(阶段3);菌株C20(Epulorhiza)和L12 (Alternaria) 虽没有显著提高种子的萌发率,但对原球茎的发育和幼苗的生长有明显的促进作用;而对照的种子仍然处于膨大转绿期,即萌发阶段(阶段2)。同时发现,TTC染色显示的铁皮石斛种子生活力要高于种子共生萌发的萌发率(除了菌株L24b)。研究结果表明:种子生活力染色检测的活力值只代表种子所具有的潜在的萌发能力,而不能代表实际的萌发率。在异地条件下,铁皮石斛与共生真菌间没有严格的专一性,可以与瘤菌根菌属、链格孢属真菌形成共生关系。菌株C20和L12能促进萌发后的种子进一步分化成幼苗。这两个菌株为铁皮石斛的人工优质栽培和野外种群的建立提供了可能。     

燕麦属不同倍性种质资源抗旱性状评价及筛选

盆栽控水试验测定了燕麦属13个二倍体、7个四倍体和5个六倍体物种共106份材料的主要抗旱性状表现,用GGEbiplot软件的主成分分析法比较了各性状之间的关系及其对抗旱鉴定的贡献,综合评价燕麦属野生资源在燕麦抗旱育种中的潜能和利用价值。结果表明,干旱处理后植株的死亡率和萎蔫程度与可溶性糖含量的增加幅度呈显著正相关关系(r>0.5, P<0.05),而胁迫后植株的丙二醛(MDA)含量和植株相对电导率与抗旱能力也明显相关(r>0.5, P<0.01)。综合考虑抗旱的相关形态和生理指标,筛选到二倍体Avena atlantica、A. wiestii 和A. strigosa,四倍体种A. murphyi,以及六倍体栽培燕麦A. sativa和普通野燕麦A. fatua的部分居群具有优良的综合抗旱性。基于A. wiestii,A. strigosa和A. murphyi与栽培燕麦较近的亲缘关系,其抗旱性可通过远缘杂交的方式在普通燕麦育种中加以利用。而对于具有明显抗旱优势的野生二倍体材料A. atlantica,则可通过克隆其抗旱基因进而遗传转化的方法将其应用于栽培燕麦的抗旱性改良。同时该研究表明燕麦的抗旱性不具有种属和分布区域的特异性,因此其抗旱性并非简单的由基因或环境决定,在确定抗旱材料时需要对个体进行全面的抗旱性评价和鉴定,以期在利用抗旱材料或通过克隆抗旱基因来改善干旱地区生态环境的实践中能更准确和有效。     

Genetic and morphologic variability of annual glassworts (Salicornia L.) from the Gulf of Trieste (Northern Adriatic)

The genetic variability of four pre-determined morphotypes of Salicornia (S. patula, S. emerici, S. veneta and the “saline type”) from 10 locations on the Gulf of Trieste coast were studied by means of ploidy level estimation using flow cytometry and by molecular DNA analysis of ITS regions of nrDNA and cpDNA. Two groups, the diploids and tetraploids, with matching nrDNA sequences, were recognized. Two types of cpDNA emerged among the diploids; one the same as in tetraploids. This incongruence between nrDNA and cpDNA sequences indicates a hybridization with tetraploid maternal progenitors and demonstrates the evidence for reticulate evolution. The morphometry, based on generative morphological traits, did not clearly separate the four morphotypes. However, the most important characters—length of the middle fertile segment, length of the lateral flower, width of the scarious margin of the fertile segment in the floral region, conform to two genetically recognized types: diploid S. patula and the widely distributed tetraploid S. emerici, also comprising the “saline type” and morphotype, known as a charismatic endemic S. veneta, a flagship species for nature conservation. Other discriminative traits for diploid and tetraploid morphotypes are parameters of the flowers (comparison of length of the central vs. lateral flower) and stomatal index. The determination key is also given. The tetraploid S. emerici is by far the most common species of annual glassworts in the area, occupying more extreme habitats than a diploid S. patula, which mostly forms monodominate stands.