Characterization of the missing diploid progenitors of the common oat

Summary The genomic formula ACD of the hexaploid oat,Avena saliva, AC for the tetraploid speciesA. magna andA. murphyi, and the hypothesis that the A genome was contributed byA. strigosa group and C genome byA. ventricosa—A. eriantha group, have derived from karyotype studies. Cytogenetic evidence, however, does not support any of the known diploid oats as possible progenitors of the hexaploid oats.A. magna, and to a lesser extent,A. murphyi, are closer to the hexaploids than other tetraploids. Morphologically, these tetraploids resemble thesterilis type, which is apparently the genuine form of the hexaploid oats, with a few important differences. Spikelet morphology of these three wild oats indicates some features that must also occur in one or more of their diploid progenitors: 1. Ventricose diaspore containing the entire spikelet, 2. Long and broad callus with blunt tip, 3. Awn insertion at the lower one quarter of the lemma, 4. Close proximity of lemma tips of the two lower florets.A. magna andA. murphyi have narrow ecological ranges and are restricted to heavy alluvial soils which are now mostly under cultivation. It is likely that on similar soil type the diploid progenitors would grow as well and a search for them should be attempted there. Morocco is the most promising area for finding the missing diploids. Not onlyA. magna andA. murphyi grow there, but except one, all other annual oat species as well.     

Chromosome N-banding polymorphism in Aegilops geniculata Roth

The chromosome morphology and the variation in the N-band distribution along the chromosomes were studied in 13 accessions of the wild wheat Aegilops geniculata Roth (2n=28, genome formula UUM°M°). The karyotype consisted of four metacentric, five submetacentric, three subtelocentric, and two satellited pairs of chromosomes. The N-banding technique stained differentially all 14 chromosome pairs. The most prominent bands were observed near the centromeres and in the intercalary regions of both arms. Telomeric bands were found in only seven chromosomes. All chromosomes produced a specific banding pattern, permitting their identification. Polymorphism for presence or absence of particular bands was observed among the different accessions. The variable bands were located predominantly at the terminal and subterminal chromosome regions, and were also unevenly distributed over chromosomes. This polymorphism resulted in up to eight distinct banding pattern variants for each of the Ae. geniculata chromosomes. Each accession in this study showed a unique overall karyotype, sharing 0 to 8 chromosomes of identical banding pattern with the other accessions. A generalized idiogram of Aegilops geniculata is presented.     

Rediscovery of a diploid cytotype of Dasypyrum breviaristatum in Morocco

The chromosome numbers of a total of 273 Dasypyrumbreviaristatum plants sampled from 20 Moroccan and one Greek naturalpopulations were examined. 270 plants from all of the populations weretetraploids. Among them, 223 were eu-tetraploids with 28 chromosomes and 47 wereaneuploids with 25, 27 and 29 chromosomes. Besides, three plants were found tobe diploids among 16 plants from a population in the Moyen Atlas Mountains ofMorocco. This is the second report of a diploid cytotype ofD. breviaristatum since the firstcommunication in 1957. Morphologically, the diploids were similar to but smallerthan the tetraploids in plant height, spike length, spikelet number and leafepidermis cell size. However, it was not possible to distinguish between the twocytotypes based on those morphological characteristics alone. A distinctdifference was found between the two cytotypes only in the number of trichomeson the leaf surfaces. The karyotype of the diploid cytotype consisted of a pairof SAT-chromosomes, five pairs of metacentric and a pair of submetacentricchromosomes. Based on the similarity in karyotype and in plant morphologybetween the two cytotypes of D.breviaristatum, we suggest that the diploid cytotype is themost probable candidate for the ancestral form of the tetraploid cytotype.     

Cytogenetic affinities between populations of Avena insularis Ladizinsky from Sicily and Tunisia

The wild tetraploid oat Avena insularis, which was recently discovered in Sicily has now been detected in two regions in Tunisia. It grows there in a similar habitat as in Sicily and is confined to uncultivated patches. Hybrids between Tunisian populations from Temime and Bargou were partly sterile due to a chromosomal rearrangement and probably other genetic factors. Hybrids between representatives of these populations and Sicilian populations from Gela and Mt. Bubonia were also partial sterile. This sterility suggests that the Sicilian populations of A. insularis have not originated directly from the Tunisian populations.     

A reevaluation of karyotype in cucumber (Cucumis sativus L.)

A karyotype analysis was conducted on the mitotic chromosomes of cucumber (Cucumis sativus L.; 2n = 2 × = 14), using improved chromosome preparation and C-banding techniques. Chromosome pairs were characterized on the basis of length and arm ratio value. The length of metaphase chromosomes ranged from 1.48 to 2.31 m, and the total length of the haploid chromosome complement was 13.06 m. The karyotype of this species was symmetric, and consisted of six metacentric and one submetacentric chromosomes. All chromosomes were defined by their unique C-banding patterns. The C-banded karyotype included centromeric, telomeric, and intercalary bands depending on chromosome pair leading to a precise identification of each pair. The C-banding patterns were distinctly different from observations made in previous study.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Karyomorphology of eighteen species of genus <Emphasis Type="Italic">Epimedium</Emphasis> (Berberidaceae) and its phylogenetic implications

The karyomorphology of 18 Epimedium species were reported in this study. Among 18 species, the karyomorphology of eight taxa, namely E. ecalcaratum, E. pauciflorum, E. lishihchenii, E. dolichostemon, E. pudingense, E. baojingense, E. yingjiangense and E. shuichengense were reported for the first time. The chromosome numbers of all species studied are 2n = 2x = 12, except E. yingjiangense 2n = 4x = 24. Tetraploid was reported in genus Epimedium for the first time. All the Epimedium species, investigated in the present research, have a uniform karyotype with two types of chromosome, metacentric and submetacentric, except E. leptorrhizum and E. sagittatum, of which the sixth pair of chromosomes were subteleocentric. A secondary constriction was commonly found on the proximal side of the short arm of the chromosome pair 1 or 2. The karyotype symmetry of all investigated species was relatively primitive 1A, 2A or 3A. The speciation, infrageneric and intergeneric relationship of Epimedium in Berberidaceae were discussed.     

Trait inheritance,fertility, and genomic relationships of some n = 9 Brassica species

Summary Karyotypic differences among n = 9 Brassica species, as well as the inheritance of some morphological characteristics, are reported. Annual habit, anthocyanin pigmentation in leaf and stem, enlarged stem, glossy foliage, dark green foliage, white flower and leaf pubescence were all expressed as dominant characteristics and in most cases were determined by one or two genes. 172 intra- and interspecific hybrids of the species belonging to the Brassica oleracea cytodeme were analyzed for fertility and meiotic chromosome behavior. B. alboglabra, B. bourgeaui, B. cretica spp. cretica, B. montana and B. oleracea produced fertile interspecific hybrids, indicating that geographical isolation is the only barrier to gene exchange. Interspecific hybrids generated from crosses of B. incana, B. insularis and B. rupestris to other n = 9 species were semi-sterile. This was shown to be associated with abnormal meiotic behavior. The former two species, when crossed, produced fully fertile hybrids. Therefore, three different karyotypes are identified among the n = 9 Brassica species. Frequent changes in the genome of the species belonging to the Brassica oleracea cytodeme could have led to the formation of accessory chromosomes present in certain accessions.     

RFLP analysis of Aegilops species belonging to the Sitopsis section

The phylogenetic relationships among theAegilops species belonging to the Sitopsis section were investigated using RFLP (restriction-fragment-length polymorphism) analysis. Twenty-five probes, each of which hybridised to oneor more restriction fragments located in the B-genomechromosomes of cultivated wheats, were used. At least one and in most cases two fragments were located in every B genome chromosome arm. Adendrogram derived from a cluster analysis of the complete RFLP dataset showed a subdivision of the species belonging to the Sitopsis section into one group comprising the species of the Truncata subsection and another group comprised of the species of theEmarginata subsection. Dendrograms also were produced using RFLP data from loci located in different combinations of only three chromosomes, and some of these showed different subdivisions of the species. This demonstrates the importance in obtaining reliable classification data of using probes that detect loci evenly distributed in the genome and located in each chromosomearm.     

A novel genome of C and the first autotetraploid species in the <Emphasis Type="Italic">Setaria</Emphasis> genus identified by genomic <Emphasis Type="Italic">in situ</Emphasis> hybridization

Genomic in situ hybridization (GISH) was used to investigate the genomic relationships among some newly collected species of genus Setaria. Previous work identified that S. viridis and S. adhaerens carry genomes A and B, respectively. GISH patterns obtained in this report clearly distinguished the genome of S. grisebachii from the known genomes A and B, and indicated its new genomic constitution which we suggest to name genome C of the Setaria genus. The two sets of chromosomes of tetraploid S. queenslandica hybridized well with the A genome of S. viridis indicating its autotetraploid nature. This is the first autotetraploid identified in the Setaria genus, which should be classified into the primary A genome gene pool rather than the tertiary gene pool as previously classified. GISH patterns did not distinguish the genome of S. leucopila from the A genome of S. viridis and S. italica, suggesting its close relation with foxtail millet. Strong hybridization signals were observed when S. adhaerens genomic DNA was used as probe to hybridize the chromosomes of diploid S. verticillata, inferring its B genome nature. Combined with morphological observation and previous work, we deduce that diploid S. verticillata and S. adhaerens are probably taxonomically the same species with different names. Y. Wang and H. Zhi contributed equally to this article.     

Determination of Ploidy Level and Nuclear DNA Content in Tunisian Populations of Atriplex halimus L.

Atriplex halimus L. (Chenopodiaceae) (Saltbush) is a perennial species used as a fodder shrub for livestock in arid and semi-arid areas, particularly in North Africa. The aim of this work was to determine whether differences in ploidy level and/or nuclear DNA content exist among populations from widely-separated sites in Tunisia. We determined nuclear DNA content and chromosome numbers for populations of A. halimus from seven different locations (Gabes, Medenine, Tataouine, Monastir, Tunis, Sidi Bouzid, Kairouan). The chromosome counts showed that all the Tunisian populations, plus a population from Eraclea (Italy), were tetraploid (2n = 4x = 36) whereas a population from Cala Tarida (Spain) was diploid (2n = 2x = 18). With respect to nuclear DNA, the 2C DNA content of population Cala Tarida was estimated to be 2.41 pg. There was no significant difference among the tetraploid populations (or among plants within populations), whose 2C DNA content ranged from 4.92 to 4.97 pg.     

Karyotypic studies in wild germplasm of <Emphasis Type="Italic">Arachis</Emphasis> (Leguminosae)

The karyomorphology for eight diploid species of Arachis belonging to three sections has been described for the first time, Sect. Extranervosae: A. macedoi (2n = 20m) and A. retusa (2n = 14m + 6sm); Sect. Heteranthae: A. sylvestris (2n = 16m + 4sm); Sect. Procumbentes: A. chiquitana (2n = 18m + 2sm); Sect. Arachis: A. cruziana (2n = 18m + 2sm), A. herzogii (2n = 18m + 2sm), A. simpsonii (2n = 20m) and A. williamsii (2n = 20m). A pair of satellited chromosomes was observed in all species. A chromosomes were found in A. chiquitana, A. herzogii and A. simpsonii. Karyotypic differences between sections were observed, but not enough to establish a characteristic karyotype pattern for each section. However, the species may be differentiated by the presence of A chromosomes, the type and position of satellites, and the karyotype formulae. These results are discussed with regard to karyotype evolution in Arachis to contribute to understanding the role of chromosome changes in the evolution of the genus.     

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.     

Identification of genomic constitutions of <Emphasis Type="Italic">Oryza</Emphasis> species with the B and C genomes by the PCR-RFLP method

Oryza officinalis complex is the largest and the most complicated group in the genus Oryza L., consisting of about ten species with the B, C, BC, CD, and E genomes. Taxonomy and identification of the species, particularly those with the B, C and BC genomes, are difficult due to the similar morphology and overlapping distribution of some species. The difference in ploidy levels of some species adds more complexity. In the present study, we surveyed 64 accessions of rice germplasm in the O. officinalis complex using RFLP analysis of PCR-amplified Adh genes in addition to chromosome counting. The results confirmed that all O. rhizomatis accessions are diploids with the C genome, whereas all O. minuta accessions are tetraploids having the BC genome. However, both diploid and tetraploid forms were found for the accessions identified in the genebank as O. officinalis, O. punctata and O. eichingeri. The tetraploid form of O. officinalis with the BC genome is exclusively distributed in India and has been described as O. malampuzhaensis. The tetraploid form of O. punctata which has been called O. schweinfurthiana by some workers was found to be as widely distributed as its diploid form in Africa. It is noteworthy that two accessions that had been determined as tetraploid O. officinalis were actually belonging to a species with the CD genome (O. latifolia). Our results promote a better understanding of the genomic constitutions of many accessions in the O. officinalis complex and correct determination of the genebank material, which serves as an important basis of germplasm cataloguing for further research and utilization.     

Observations on interspecific compatibility and meiotic chromosome behavior of Capsicum buforum and C. lanceolatum

The wild species, Capsicum buforum Hunz. and C. lanceolatum(Greenm. ex J.D. Sm.) Morton and Standl. were hybridized to nine different Capsicum species to understand their taxonomic and genetic relationships. With C. buforum as the male parent, the compatibility to the nine species varied from species to species and ranged from producing under-developed embryo, seed coat, seedless fruit, to no fruit set. When C. buforum was the female parent, it was incompatible (no fruit set) to the nine Capsicum species tested. When C. lanceolatum was the female parent, the hybridizations to the other species ranged from aborted embryo, seed coat, seedless fruit or no fruit. As a pollen parent, C. lanceolatum was incompatible (no fruit set) to the species investigated. In pollen mother cells (PMCs) of C. buforum, 24 chromosomes (n = 12) paired as 12 bivalents with chromosome lagging at meiotic anaphase-I. Twenty-six chromosomes (n = 13) were detected in PMCs of C. lanceolatum. In C. lanceolatum most chromosomes paired as bivalents, but one quadrivalent was observed in some cells. C. buforum was found to be self-incompatible, while C. lanceolatum was self-compatible.     

Isozyme polymorphism and genetic differentiation in natural populations of an endemic tetraploid species <Emphasis Type="Italic">Avena maroccana</Emphasis> in Morocco

A wild tetraploid oat Avena maroccana Gdgr. was collected from the 11 populations in the periphery of Rommani and Casablanca geographic groups of Morocco. Genetic diversity of the species was investigated using six allozyme systems. Allelic frequencies were scored representing eight polymorphic and five monomorphic loci. Coefficient of gene differentiation (Gst) was 0.3019, which indicated great genetic differentiation. The number of alleles per locus was 2.6154, the percentage of polymorphic loci was 61.54, and the expected heterozygosity was 0.2462 in all populations. Genetic diversity in A. maroccana was high in comparison to self-pollinated species. In total, nine heterozygotes resulting from outcrossing were found in the progeny from M1, M3, M4, M22 and M26. The population of M7 had peculiar alleles Pgd–2SS and Pgd-1SS in high frequency. M9 had the lowest level of diversity out of the 11 populations. Geographic and genetic distances between all the populations were not significantly correlated with each other (r = 0.0996). Cluster analysis showed that two groups, (M1, M22, M2 and M4) and (M3, M23, M8, M5 and M26) were apparently differentiated. Two populations of the Casablanca group, M7 and M9 were independent from each other, and were separated distinctly from the other populations. Genetic diversity of the Rommani and Casablanca groups was almost the same in all the parameters. This was due to the similar man-made habitat such as roadside or rich fertile soil and brown clay soils. The population size of A. maroccana was small and restricted to the narrow central Morocco with great genetic differentiation so that genetic diversity may be reflected from the results of genetic drift and outcrossing heterozygote segregation.     

The Distribution of <Emphasis Type="Italic">Perilla</Emphasis> Species

Perilla (Lamiaceae) contains one tetraploid species, P. frutescens (L.) Britt. and three diploid species, P. citriodora (Makino) Nakai, P. hirtella Nakai and P. setoyensis G. Honda. Tetraploid species have been traditionally cultivated in Asia for their seed oil and for their fragrant leaves that are used as medicine or as a garnish for fish. The center of diversity is still obscure. To conserve the genetic resources, it is important to know the diversity of the tetraploid species. The three diploid species, which are possible parents of the tetraploid species, are all believed to be indigenous to Japan. Their distribution in China and Korea was clarified on the basis of herbarium and field surveys. The tetraploid species is assumed to have originated somewhere around the mid-to downstream area of the Changjiang River. Though Perilla is not cultivated as often in these areas as in northern China, Korea, the Himalayan region, or Myanmar, these areas should also be important for the conservation of genetic resources of tetraploid Perilla crops because of the expected high genetic diversity.     

Genetic Characterization of Brazilian Annual <Emphasis Type="Italic">Arachis</Emphasis> Species from Sections <Emphasis Type="Italic">Arachis</Emphasis> and <Emphasis Type="Italic">Heteranthae</Emphasis> using RAPD Markers

The genus Arachis is divided into nine taxonomic sections. Section Arachis is composed of annual and perennial species, while section Heteranthae has only annual species. The objective of this study was to investigate the genetic relationships among 15 Brazilian annual accessions from Arachis and Heteranthae using RAPD markers. Twenty-seven primers were tested, of which nine produced unique fingerprintings for all the accessions studied. A total of 88 polymorphic fragments were scored and the number of fragments per primer varied from 6 to 17 with a mean of 9.8. Two specific markers were identified for species with 2n = 18 chromosomes. The phenogram derived from the RAPD data corroborated the morphological classification. The bootstrap analysis divided the genotypes into two significant clusters. The first cluster contained all the section Arachis species, and the accessions within it were grouped based upon the presence or absence of the ‘A’ pair and the number of chromosomes. The second cluster grouped all accessions belonging to section Heteranthae.     

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     

Collection and conservation of ‘Morado de Huetor’ Spanish tetraploid asparagus landrace

A cultivated tetraploid asparagus landrace ‘Morado de Huetor’ growing in the South of Spain has been collected and conserved ex situ in two experimental plots. This landrace has been reported to have an interspecific hybrid origin (A. officinalis × A. maritimus). A 59% of the total farmer plots cultivated in the region were visited and ripe fruits collected from 10 female plants per plot. Fruits from a total of 300 plants were collected and two half sibs descendents from each one were sown separate in two plots. Of the 88 farmer plots visited, the landrace was growing only in 34, in the rest the crop had been removed. Hence, ‘Morado de Huetor’ is in a very high risk of disappearing. Now this landrace is conserved ex situ in two experimental plots with sufficient number of plants to represent their maximum variability in order to be used in plant breeding.