Cytogenetic analysis of Kengyilia mutica (Keng) J. L. Yang, Yen and Baum (Poaceae: Triticeae)

Kengyilia mutica (Keng) Yang, Yen et Baum is a hexaploid perennial grass of the tribe Triticeae native to western central China. The analyzer species with known genomic constitution used to produce interspecific hybrids with the target taxon were Roegneria kamoji Ohwi (StStHHYY), K. hirsuta (Keng) J. L. Yang, Yen et Baum (PPStStYY) and K. rigidula (Keng) J. L. Yang, Yen et Baum (PPStStYY). Analysis of metaphase I pairing configurations in the F₁ hybrids indicates that K. mutica possesses the P, St and Y genomes, with only minor structural rearrangements. Chromosome pairing in hybrids supports the inclusion of K. mutica in the genus Kengyilia.     

Allopatric distributions of tetraploid and hexaploid forms of Aegilops neglecta Req. ex Bertol.

The genus Aegilops L. comprises 22 annual wild species that are closely related to wheat (Hammer in Kulturpflanze 28: 33–180, 1980). Aegilops neglecta Req. ex Bertol. is a member of the Aegilops section of this genus and is distributed from Morocco and Spain in the west to Transcaucasia and western Iran in the east. This species includes tetraploid (2n = 28, genome UUMM) and hexaploid forms (2n = 42, UUMMNN). However, the geographical distributions of the two cytological forms remain unclear. Clarifying the distribution of the two cytological forms is essential for a better understanding of the diffusion of Ae. neglecta and its tetraploid and hexaploid forms. In the present study, chromosome numbers were determined for accessions of Ae. neglecta from a total of 137 populations, located in the western area of the species distribution from the Aegean Islands to Morocco. Taken together with previous studies, the present data reveal a difference in the geographical distribution of tetraploid and hexaploid forms: tetraploid form is distributed in the eastern part of the species area and hexaploid form predominantly occurs in the western part with their border on the western margin of the Aegean Sea. Near the border, tetraploid and mixed populations are sporadically found among hexaploid populations in the Balkan and Peloponnesus Peninsulas, while a few hexaploid and mixed populations are found among tetraploid populations in the East Aegean Islands and West Anatolia.     

Genetic diversity of HMW glutenin subunits in diploid,tetraploid and hexaploid <Emphasis Type="Italic">Triticum</Emphasis> species

The genetic variations of high-molecular-weight (HMW) glutenin subunits in 1051 accessions of 13 Triticum subspecies were investigated using sodium dodecyl sulfate polyacrylamide-gel electrophoresis. A total of 37 alleles were detected, resulting in 117 different allele combinations, among which 20, 68 and 29 combinations were observed in diploid, tetraploid and hexaploid wheats, respectively. Abundance and frequency of allele and combinations in tetraploid wheats were higher than these in hexaploid wheats. Allele Glu-A1c was the most frequent subunit at Glu-A1 locus in tetraploid and hexaploid wheats. Consequently, the results also suggested that the higher variations occurred at Glu-B1 locus compared to Glu-A1 and Glu-D1. Therefore, carthlicum wheat possessing the allele 1Ay could be presumed a special evolutional approach distinguished from other tetraploid species. Furthermore, this provides a convenient approach of induction of the 1Ay to common wheat through direct cross with carthlicum wheat. Alleles Glu-B1c and Glu-B1i generally absent in tetraploid wheats were also found in tetraploid wheats. Our results implied that tetraploid and hexaploid wheats were distinguished in dendrogram, whereas carthlicum and spelta wheats and however displayed the unique performance. In addition, founder effect, no-randomness of diploidization, mutation and artificial selection could cause allele distribution of HMW-GS in Triticum. All alleles of HMW-GS in Triticum could be further utilized through hybrid in the quality improvement of common wheat.     

Evaluation of geographic distribution of high-molecular-weight glutenin subunits (HMW-GS) in wild and cultivated Triticum species

Variation of high-molecular-weight glutenin subunit (HMW-GS) in 632 wild and cultivated Triticum accessions was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. A total of 11 alleles of HMW-GS in diploid species, 22 in tetraploid species, and 15 in hexaploid species were detected. Diploid species on Glu-1A locus and tetraploid species Glu-1B locus showed the highest diversity, respectively. Tetraploid species had the highest level of diversity on three Glu-1 loci, followed by hexaploid and diploid, based on Shannon’s information index, Nei’s genetic diversity, and percentage of polymorphic loci. Molecular variance analysis confirmed main variance of HMW-GS within species, regions, and locations, respectively. Variance among species and regions was enhanced gradually with the increase of ploidy. Significant non-random distributions between the phylogenic trees of HMW-GS and the locations of accessions were tested by GenGIS software, indicated that geographic factors played an important role along the different orientations in the spread of Triticum species. We found one original diversified center in diploid what located around Elazig, Malatya, Gaziantep, Urfa, and Kiziltepe in Turkey, and three diversified centers in tetraploid wheat, including Turkey–Armenia–Georgia–Iran, Portugal–Spain, and Ethiopia, respectively, and two diversified adjacent areas between Turkey and Switzerland and around Turkey, Georgia, and Armenia. The original center of diploid species located in southeast Turkey, where the unexpressed 1Ay subunit was mainly distributed in T. urartu, could be one of the candidate regions of polyploidization of Triticum L. The regional distribution of HMW-GS and species also provided geographic evidences for the existence of founder effect on the spread of Triticum species. The present study suggests that integrating genetic diversity with geographic characterization in Triticum could very useful for collection, conservation, and utilization, as well as for research microevolution and domestication.     

Ploidy levels of Dioscorea alata L. germplasm determined by flow cytometry

Dioscorea alata L. is a highly important crop, widely distributed in the humid and semi-humid tropics. Flow cytometry was used to determine the ploidy levels of 74 D. alata genotypes collected mainly from West African countries. Sixty three of the genotypes were found to be tetraploid, one was hexaploid and ten were octoploid. The high percentage of tetraploids together with the small percentage of hexaploid individuals and the absence of diploid individuals gives us some more clues on the possible origin of these species. No association between ploidy level and place of cultivation was found for the tested material. The obtained results represent important knowledge for enhancing the breeding methodologies and optimize germplasm management of this species. It also offers further insights to the phylogeny and evolution of Dioscorea species.     

DNA Fingerprinting and Genetic Characterization of Anatolian Triticum spp. using AFLP Markers

In this study, genetic analysis of Triticum spp. was carried out using AFLP markers. Six AFLP selective combinations were scored as presence and absence of bands for all the individual samples obtained from a single seed of each accession (70 accessions); T. baeoticum (21), T. monococcum (5), T. urartu (16), T. araraticum (7), T. dicoccoides (16) and T. dicoccon (5), resulting in 506 polymorphic AFLP bands. The phylogenetic tree showed two major clusters; one was composed of T. monococcum (AA) and T. baeoticum (AA), and the other cluster included T. araraticum (AAGG), T. dicoccon (AABB), T. dicoccoides (AABB), and T. urartu (AA). T. urartu, although having a diploid AA genome, did not cluster with other A genome diploids such as T. monococcum and T. baeoticum; instead it clustered together with the tetraploid species, confirming that T. urartu is the A genome progenitor. The extent of variations within and among species is discussed.     

Genetic Variation Among Portuguese Landraces of ‘Arrancada’ Wheat and <Emphasis Type="Italic">Triticum petropavlovskyi</Emphasis> by AFLP-based Assessment

Portuguese wheat landraces, ‘Arrancada’ were collected from the Aveiro region, Portugal before the 1950s. We found in eight accessions of `Arrancada' hexaploid wheat with the long glume phenotype. We assessed the comparative genetic diversity among Portuguese `Arrancada' wheat and Triticum petropavlovskyi Udacz. et Migusch. using AFLP assays and discuss the origin of long glumed `Arrancada' wheat. With the four primer pairs a total of 4885 visible bands were scored corresponding to 99 AFLP markers as putative loci, of which 55 markers (54%) were polymorphic. UPGMA clustering and PCO grouping showed that long glumed ‘Arrancada’ wheat and T. petropavlovskyi were genetically diverse. Long glumed ‘Arrancada’ hexaploid wheat separated into two clusters (groups) in both the UPGMA dendrogram and in PCO analysis. Four long glumed accessions fell in the cluster of tetraploid wheat. A similar argument could be made for another four accessions which belong to the cluster of hexaploid wheat. The substantial level of genetic variation indicated that long glumed ‘Arrancada’ wheat and T. petropavlovskyi originated independently. It is most likely that the P-gene of long glumed ‘Arrancada’ hexaploid wheat was introduced from T. turgidum ssp. polonicum (L.) Thell. to T. aestivum via natural introgression or breeding. We suggest that the long glumed ‘Arrancada’ hexaploid wheat did not originate from T. aestivum through spontaneous mutation at the P locus     

Stomatal frequency and size differentiate ploidy levels in Aegilops neglecta

Aegilops neglecta Req. ex Bertol. is a forage goatgrass that has tetraploid and hexaploid forms. No morphological trait is known to distinguish between the two forms. Accessions of Ae. neglecta representing diverse germplasm were characterized for stomatal frequency and size on the adaxial surface of leaves. Stomatal frequency among tillers within a plant and among leaves on a tiller was measured. Significant variation was found in stomatal frequency between the ploidy levels for basal leaves 2 and 3 and the penultimate and flag leaves. Mean stomatal frequency for basal leaves ranged from 50.24 to 54.80 per mm² for tetraploid and from 39.24 to 40.50 per mm² for hexaploid accessions. For upper leaves, it varied from 52.88 to 53.50 per mm² for tetraploid and from 46.12 to 46.40 per mm² for hexaploid accessions. The two ploidy forms also exhibited clear differences for stomatal size on the basal and upper leaves of the main tiller. Mean stomatal size for the basal leaves ranged from 41.42 to 46.09 m for tetraploid and from 53.59 to 54.97 m for hexaploid accessions. For upper leaves, stomatal size varied from 47.29 to 53.29 m in tetraploid and from 64.76 to 66.84 m for hexaploid accessions. None of the individual accession ranges overlapped between the ploidy levels. Stomatal frequency and size were highly negatively correlated. Increased ploidy in Ae. neglecta has resulted in fewer but larger stomata per unit leaf area. Stomatal size and/or frequency on the adaxial surface of leaves could be used to distinguish tetraploid from hexaploid cytotypes in Ae. neglecta in fresh material from Turkey collected in the field.     

Size homoplasy and mutational behavior of chloroplast simple sequence repeats (cpSSRs) inferred from intra- and interspecific variations in four chloroplast regions of diploid and polyploid <Emphasis Type="Italic">Triticum</Emphasis> and <Emphasis Type="Italic">Aegilops</Emphasis> species

Chloroplast simple sequence repeats (cpSSRs) are widely distributed in the chloroplast genomes of all plant species, and are frequently employed for genotypic and phylogenetic analysis. However, information on intra- and interspecies variation in cpSSRs is lacking. In this study, we sequenced four intergenic (non-coding) chloroplast DNA regions in 57 accessions of 12 tetraploid, and 16 accessions of 4 hexaploid species of Triticum and Aegilops. These sequence data added to our previous data for diploid species in the same chloroplast regions. Intra- and interspecific genetic variation was analyzed for a total of 189 accessions of 13 diploid, 12 tetraploid, and 4 hexaploid species of Triticum and Aegilops, such that all species were represented by multiple accessions. The data were used to infer phylogenetic relationships within and among Triticum and Aegilops species. Based on this robust phylogenetic tree, seven of eight cpSSR loci clearly exhibited “size homoplasy,” referring to the fact that cpSSRs of identical size and DNA sequence can arise even if the alleles are not descended from a common ancestor. These data indicate that cpSSRs should be used with caution in phylogenetic analyzes. Interestingly, as observed from several previous studies, our data also suggest that observed mutation rates may increase significantly when mononucleotide (homopolymer) repeat numbers reach or exceed 9 bp. In the present report, using this sequence data set involving cpSSRs, 81 unique haplotypes among 189 accessions were detected, and five tetraploid Triticum and Aegilops species were successfully identified and genotyped. Our results indicate that combinations of nucleotide substitutions, indels and SSRs of chloroplast nucleotide sequences are available for genotyping at the species accession level.     

Agronomic and Quality Performance of Progeny Lines Derived from Spring Wheat by Durum Wheat Crosses

Hard red spring wheat (Triticum aestivum L. subsp. aestivum) and durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn) have both been selected for dryland yield potential and high grain protein, although end uses of flour are different. For this study, 14 tetraploid and 10 hexaploid lines were derived from crosses between tetraploid durum wheat and hexaploid hard red spring wheat. Our objective was to determine the impact of genetic exchange between the two classes on agronomic and quality attributes of derived progeny lines. Yield potential of both the tetraploid and hexaploid progeny was lower than the parental types. Polyphenol oxidase levels were higher by almost twofold in the hexaploid group. The tetraploid progeny group had better noodle color than did the hexaploid group. Bread quality of hexaploid group was superior, with loaf volume 362 cm³ higher than that of tetraploid progeny group. In general, the presence of durum wheat genes in the derived hexaploid lines had little impact on most quality traits. The presence or absence of the D genome tended to be the major influence on end use quality traits. Our results suggest that genetic exchange between the two groups has a small effect on end use quality, but low yield potential in the progeny suggests obtaining desirable genetic combinations for plant improvement may be challenging.     

Development of new sources of tetraploid <Emphasis Type="Italic">Arachis</Emphasis> to broaden the genetic base of cultivated groundnut (<Emphasis Type="Italic">Arachis hypogaea</Emphasis> L.)

Groundnut, an important crop of many countries of the world, is susceptible to a range of diseases and pests. High levels of resistances are not available in the cultivated gene pool as the crop is said to have a narrow genetic base. Narrow genetic base is attributed to the evolution of the crop which took place by the combination of A and B genome species, and later doubling their chromosome number, giving rise to tetraploid cultivated groundnut. Direct utilization of cross-compatible wild relatives, which are diploids, to broaden the genetic base and introduction of useful traits, is not a straight-forward process due to ploidy differences between the cultivated species and wild relatives. Hence amphiploids and autotetraploids were created by not only combining the putative genomes, but many other A and B genome species, thus producing a highly variable population of tetraploid groundnuts also called new sources of Arachis hypogaea. This study describes the development and characterization of newly generated tetraploid groundnuts and the level of molecular diversity as assessed by DArT markers.     

Characterization of a world collection of <Emphasis Type="Italic">Agropyron cristatum</Emphasis> accessions

The genetic diversity was studied of 115 Agropyron cristatum accessions from 17 countries. Tetraploids were the most common (74.8%), followed by diploid (16.3%) and hexaploid (6.9%). We observed a relation between geographic distribution and ploidy level. The tetraploids, the most widespread, were found from Europe through Russia to East Asia. The diploids appeared over the same general range, except in Turkey, Iran and Georgia where no diploid accessions were found. Hexaploid accessions mainly came from a region comprising the east of Turkey, the north of Iran and Georgia. A selection of 71 accessions, including all three ploidy levels, were analyzed by capillary electrophoresis using six wheat simple sequence repeat (SSR) markers. All markers presented high levels of polymorphism, generating 166 different alleles ranging in size between 84 and 256 bp. Based on polymorphic information content values obtained (0.579–0.968), all the SSRs were classified as informative markers (values?>?0.5). According to the dendrogram generated, all the A. cristatum accessions were distinctly classified. Diploid, tetraploid and hexaploid accessions are not clearly differentiated from each other on the basis of SSR markers. A field experiment was conducted to morphologically characterize 18 accessions including the three ploidy levels. Significant differences were found between the accessions in spike length, spike width and number of spikelets per spike. All the cytological, molecular, and morphological data demonstrate the high genetic diversity present in A. cristatum, making it a valuable resource for future breeding programs.     

A recombination-derived mitochondrial genome retained stoichiometrically only among Solanum verrucosum Schltdl. and Mexican polyploid wild potato species

We previously found a specific DNA fragment, designated Band 1, in the cytoplasm of a Mexican hexaploid wild potato species, Solanum demissum, and varieties with the S. demissum cytoplasm. In this study, we show that Band 1 also occurs substoichiometrically in various species and varieties. The S. demissum DNA sequence harboring Band 1 was extended by genome walking to 7,040 bp, and whole-genome sequencing of the S. verrucosum genome generated a 10,794-bp contig with the corresponding sequence. Their 3′-terminal end sequences had 100 % homology with segment 2 of the S. tuberosum mitochondrial genome, proving that Band 1 originated from a recombination-derived mitochondrial genome. Both normal and recombination-derived mitochondrial genomes co-existed in Band 1 carriers. The presence or absence of Band 1 was surveyed for four accessions of tomato and wild relatives and 172 accessions of 38 Solanum species or potato and tuber-bearing wild relatives, mostly from Mexican species. Together, with the results of our previous survey (mostly for South American species), we conclude that Band 1 is retained stoichiometrically only among S. verrucosum and Mexican polyploid species, supporting S. verrucosum as a maternal ancestor for all Mexican polyploid species. The presence or absence of Band 1 was not uniform within these species and was not associated with ploidy, geographical distribution, or latitude. Several evolutionary hypotheses to explain intraspecific variation were discussed.     

Geographical pattern and ploidy levels of the weed Solanum elaeagnifolium (Solanaceae) from Argentina

A total of 106 samples taken from natural Argentinean populations of the weedy Solanum elaeagnifolium (subgenus Leptostemonum) were studied cytologically to understand the impact of the different ploidy levels in its distribution and origin. Classical Feulgen staining was employed to determine mitotic chromosome numbers in all samples. 2C nuclear DNA content was determined by means of PI flow cytometry in eight samples of different ploidy levels. Principal component analysis and GIS tools were employed to compare altitude, annual precipitation and annual mean temperature among accessions. Three cytotypes were found: diploid (2n?=?24) which is widespread, tetraploid (2n?=?48) centered in western and southern Argentina, and hexaploid (2n?=?72) which predominates in central Argentina extending as well to the east. The annual precipitation is significantly different between tetraploids and hexaploids. Cx-values ranged from 1.231 to 1.275?pg, with statistical differences (of about 24.5–50.9?Mbp, p?≤?0.05) among accessions. Diploids are the most widespread cytotype and have adapted to a number of very different habitats. Tetraploids live in arid or semi-arid regions with a mean annual rainfall less than 500?mm. Hexaploids are successful in colonizing wetter areas, where no tetraploids were found. Thus, the distribution of cytotypes may be associated with habitat differences, particularly soil moisture. The observed cytotype pattern and the differences in DNA content suggest multiple places of origin for the polyploidy of S. elaeagnifolium in Argentina.     

Breeding system, genetic diversity and clonal structure in the sub-alpine forb Rutidosis leiolepis F. Muell. (Asteraceae)

Genetic markers, controlled pollinations and chromosome analysis were used to examine the breeding system, clonal structure, genetic diversity and cytological complexity of populations of the endangered sub-alpine forb Rutidosis leiolepis. Results show that R. leiolepis: (1) has a strong sporophytic self-incompatibility system; (2) exhibits significant clonality and that the importance of vegetative reproduction increases at higher altitudes; (3) is genetically diverse, but that variation within populations decreases and differentiation among populations increases with altitude; and (4) is diploid with 2n=22 throughout its geographic range. Based on these results, low altitude populations around Cooma and Happy Valley should be made priority areas for in situ conservation in the Species Recovery Plan currently being developed by the New South Wales National Parks and Wildlife Service because they exhibit the most sexual reproduction and highest levels of genetic variation within the species. They may also be demographically more viable in the long term, having larger effective population sizes and less likelihood of mate limitation due to low S allele richness than high altitude populations. Sampling strategies for ex situ conservation should vary from large collections within populations at low altitudes to smaller collections spread across populations at higher altitudes where more of the genetic diversity is partitioned among sites. This should give maximum representation of the species' gene pool for minimum sampling effort.     

Genetic analysis of wheat (Triticum aestivum L.) and related species with SSR markers

Genetic diversity among 19 Triticum aestivum accessions and 73 accessions of closely related species was analyzed using simple sequence repeat (SSR) markers. Forty-four out of 497 SSR markers were polymorphic. In total 274 alleles were detected (mean 6.32 alleles per locus). The polymorphic information content (PIC) of the loci ranged from 0.3589 to 0.8854 (mean 0.7538). The D genome contained the highest mean number of alleles (6.32) followed by the A and B genomes (6.13 and 5.94, respectively). The correlation between PIC and allele number was significant in all genome groups (0.7540, 0.7361 and 0.7482 for A, B and D genomes, respectively). Among the seven homologous chromosome groups, genetic diversity was lowest in group 7 and highest in group 5. In cluster and principal component analyses, all accessions grouped according to their genomes were consistent with their taxonomic classification. Accessions with the A and D genomes were clustered into two distinct groups, and AABB accessions showed abundant genetic diversity and a close relationship. Triticum durum and T. turgidum were clustered together, consistent with their morphological similarity. Cluster analysis indicated emmer is closely related to hexaploid wheat. Compared with common wheat, higher genetic variation was detected in spelt, T. aestivum subsp. yunnanense and subsp. tibetanum. In addition, a close genetic relationship between T. polonicum and T. macha was observed. The results of the clustering and principal component analyses were essentially consistent, but the latter method more explicitly displayed the relationships among wheat and closely related species.     

Genetic diversity and species delimitation in the cultivated and wild Guinea yams (Dioscorea spp.) from Southwest Ethiopia as determined by AFLP (amplified fragment length polymorphism) markers

Yams (Dioscorea spp.) rank as the fourth most important root and tuber crop after potatoes, cassava and sweet potatoes. They are an economic crop in most of the tropics especially in West Africa, which produces over 95 % of the world output. Despite their cultural and economic importance there is taxonomic confusion regarding Guinea yams. The currently used classification scheme, which relies on vegetative and inflorescence characters, does not consistently delimit species boundaries between members of Guinea yams (D. cayenensis Lam.–D. rotundata Poir. complex), their wild relatives (D. abyssinica Kunth and D. praehensilis Benth.,) and D. sagittifolia Pax. Establishing the taxonomic identity of the germplasm and understanding the systematic relationships among crops is vital to the management of genetic resources and the utilization of accessions. In this study, amplified fragment length polymorphism (AFLP) genetic fingerprinting was used to evaluate and characterize 43 individual plants, belonging to different populations of wild and cultivated Guinea yams. The three primer combinations used in the AFLP analyses generated 158 scorable bands, with an overall polymorphism of 78 %. Ordination and cluster analyses of AFLP data failed to produce any clear species boundary between either the Guinea yam accessions or between them and their wild relatives. The average genetic similarity between the study individuals of Guinea yams and their wild relatives ranged from 60 to 100 %. The first, second and third principal coordinates axes cumulatively account for 77.45 % of the total variation. AFLP analyses also revealed a higher genetic divergence among cultivated Guinea yam accessions of the Sheko cultivars. Ordination and cluster analysis using UPGMA revealed no clear species boundaries between members of the complex. Thus, the taxonomy of these “species” needs to be revisited using other markers.     

毛百合根尖染色体Giemsa C-带分析

本研究利用Giemsa C-带方法对毛百合（Lilium dahuricum Ker-Gawl）根尖染色体进行了分析。研究结果表明毛百合试管苗的染色体倍性变异丰富,染色体倍性变异包括二倍体（2n=2×=24）、三倍体（2n=3×=36）、四倍体（2n=4×=48）到六倍体（2n=6×=72）。对二倍体毛百合的C-带结果进行分析,其带型公式为：2n=2×=24=2CI＋＋2CI＋T＋T＋＋6I＋2I＋＋2I＋＋2I＋T＋＋2I＋T＋＋2I＋T＋＋2T＋＋2T＋。每条染色体上都显示出显著的特征带,而且带纹的深浅差异明显。强带主要集中在长短臂上。因此,GiemsaC-带方法可以将毛百合（L.dahuricum）的每条染色体区分开。     

Genetic Diversity of the Greater Yam (<Emphasis Type="Italic">Dioscorea alata</Emphasis> L.) and Relatedness to <Emphasis Type="Italic">D. nummularia</Emphasis> Lam. and <Emphasis Type="Italic">D. transversa</Emphasis> Br. as Revealed with AFLP Markers

Amplified fragment length polymorphism markers were used to assess the genetic relatedness between Dioscorea alata and nine other edible Dioscorea. These species include D. abyssinica Hoch., D. bulbifera L., D. cayenensis-rotundata Lamk. et Poir., D. esculenta Burk., D. nummularia Lam., D. pentaphylla L., D. persimilis Prain. et Burk., D. transversa Br. and D. trifida L. Four successive studies were conducted with emphasis on the genetic relationship within D. alata and among species of the Enantiophyllum section from Vanuatu. Study 1 was carried out to select a set of polymorphic primer pairs using 11 combinations and eight species belonging to five distinct sections. The four most polymorphic primer pairs were used in study 2 among six species of the Enantiophyllum section. Study 3 focussed mainly on the genetic relationship among 83 accessions of D. alata, mostly from Vanuatu (78 acc.) but also from Benin, Guadeloupe, New Caledonia and Vietnam. The ploidy level of 53 accessions was determined and results indicated the presence of tetraploid, hexaploid and octoploid cultivars. Study 4, included 35 accessions of D. alata, D. nummularia and D. transversa and was conducted using two primer pairs to verify the taxonomical identity of the cultivars `langlang', `maro' and `netsar' from Vanuatu. The overall results indicated that each accession can be fingerprinted uniquely with AFLP. D. alata is an heterogeneous species which shares a common genetic background with D. nummularia and `langlang', `maro' and `netsar'. UPGMA cluster analysis revealed the existence of three major groups of genotypes within D. alata, each assembling accessions from distant geographical origins and different ploidy levels. The analysis also revealed that `langlang', `maro' and `netsar' clustered together with the cultivar `wael' (D. transversa) from New Caledonia. Results are discussed in the paper.     

Variation for stomatal characteristics and water use efficiency among diploid,tetraploid and hexaploid Iranian wheat landraces

Wheat is one of the most important crops in the world. Its study has involved anatomy, ecology, physiology, molecular biology, biotechnology, and cultivation. Knowledge of the relationship of diploid, tetraploid and hexaploid wheat with stomatal characteristics and water-use efficiency is spare and is subject to argument. The present study was aimed to examine different characteristics of stomata in 28 Iranian landraces belonging to the species Triticum monococcum (2n = 2x = 14), Triticum durum (2n = 4x = 28) and Triticum aestivum (2n = 6x = 42), respectively and investigated a possible relationship between these characteristics and water use efficiency by pot cultivation experiments. The results revealed large variation among landraces as well as between the different species for stomatal frequency and size. The diploid wheat species had the highest stomatal frequency and the lowest stomatal length and width. The hexaploid species had a lower stomatal frequency than the tetraploid species. A highly significant relationship was noted between the value of those traits on the adaxial and abaxial surfaces of the leaf. The ratio of adaxial to abaxial values appeared to be constant for a given species. Both stomatal frequency and size were associated with ploidy level, but also with the nature of the constituting genomes of the species. A highly significant negative association was found among accessions between stomatal frequency and size. As a consequence, the variation for stomatal area per unit leaf area was less than for the other traits. Diploid and hexaploid wheat have significantly higher water use efficiency, compared to tetraploid wheat. No clear association was found, however, between water use efficiency and stomatal characteristics.