Comparison of genomes of eight species of sections <Emphasis Type="Italic">Linum</Emphasis> and <Emphasis Type="Italic">Adenolinum</Emphasis> from the genus<Emphasis Type="Italic"> Linum</Emphasis> based on chromosome banding,molecular markers and RAPD analysis

Karyotypes of species sects. Linum and Adenolinum have been studied using C/DAPI-banding, Ag-NOR staining, FISH with 5S and 26S rDNA and RAPD analysis. C/DAPI-banding patterns enabled identification of all homologous chromosome pairs in the studied karyotypes. The revealed high similarity between species L. grandiflorum (2n = 16) and L. decumbens by chromosome and molecular markers proved their close genome relationship and identified the chromosome number in L. decumbens as 2n = 16. The similarity found for C/DAPI-banding patterns between species with the same chromosome numbers corresponds with the results obtained by RAPD-analysis, showing clusterization of 16-, 18- and 30-chromosome species into three separate groups. 5S rDNA and 26S rDNA were co-localized in NOR-chromosome 1 in the genomes of all species investigated. In 30-chromosome species, there were three separate 5S rDNA sites in chromosomes 3, 8 and 13. In 16-chromosome species, a separate 5S rDNA site was also located in chromosome 3, whereas in 18-chromosome species it was found in the long arm of NOR-chromosome 1. Thus, the difference in localization of rDNA sites in species with 2n = 16, 2n = 30 and 2n = 18 confirms taxonomists opinion, who attributed these species to different sects. Linum and Adenolinum, respectively. The obtained results suggest that species with 2n = 16, 2n = 18 and 2n = 30 originated from a 16-chromosome ancestor.     

Predominance of <Emphasis Type="Italic">Ehrlichia chaffeensis</Emphasis> in <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> ticks from kennel-confined dogs in Limbe,Cameroon

Rhipicephalus sanguineus ticks (n = 63) collected from five dogs (two adults and three puppies) housed in a kennel were screened for Ehrlichial agents (Ehrlichia canis, E. chaffeensis, and E. ewingii) using a species-specific multicolor real-time TaqMan PCR amplification of the disulphide bond formation protein (dsb) gene. Ehrlichia chaffeensis DNA was detected in 33 (56%) ticks, E. canis DNA was detected in four (6%) ticks, and one tick was coinfected. The E. chaffeensis and E. canis nucleotide sequences of the amplified dsb gene (374 bp) obtained from the Cameroonian R. sanguineus ticks were identical to the North American genotypes.     

Identification of Diploid <Emphasis Type="Italic">Stylosanthes seabrana</Emphasis> Accessions from Existing Germplasm of <Emphasis Type="Italic">S. scabra</Emphasis> Utilizing Genome-Specific STS Markers and Flow Cytometry,and Their Molecular Characterization

Stylosanthes seabrana (Maass and ‘t Mannetje) (2n = 2x = 20), commonly known as Caatinga stylo, is an important tropical perennial forage legume. In nature, it largely co-exist with S. scabra, an allotetraploid (2n = 4x = 40) species, sharing a very high similarity for morphological traits like growth habit, perenniality, fruit shape and presence of small appendage at the base of the pod or loment. This makes the two species difficult to distinguish morphologically, leading to chances of contamination in respective germplasm collections. In present study, 10 S. seabrana accessions were discovered from the existing global germplasm stock of S. scabra represented by 48 diverse collections, utilizing sequence-tagged-sites (STS) genome-specific markers. All the newly identified S. seabrana accessions displayed STS phenotypes of typical diploid species. Earlier reports have conclusively indicated S. seabrana and S. viscosa as two diploid progenitors of allotetraploid S. scabra. With primer pairs SHST3F3/R3, all putative S. seabrana yielded single band of ~550 bp and S. viscosa of ~870 bp whereas both of these bands were observed in allotetraploid S. scabra. Since SHST3F3/R3 primer pairs are known to amplify single or no band with diploid and two bands with tetraploid species, the amplification patterns corroborated that all newly identified S. seabrana lines were diploid in nature. Flow cytometric measurement of DNA content of the species, along with distinguishing morphological traits such as flowering time and seedling vigour, which significantly differ from S. scabra, confirmed all identified lines as S. seabrana. These newly identified lines exhibited high level of similarity among themselves as revealed by RAPD and STS markers (>92% and 80% respectively). Along with the enrichment in genetic resources of Stylosanthes, these newly identified and characterized accessions of S. seabrana can be better exploited in breeding programs targeted to quality.     

Different fertility and meiotic regularity in allohexaploids derived from trigenomic hybrids between three cultivated <Emphasis Type="Italic">Brassica</Emphasis> allotetraploids and <Emphasis Type="Italic">B</Emphasis>. <Emphasis Type="Italic">maurorum</Emphasis>

The wild species Brassica maurorum Durieu (MM, 2n = 16) is useful for the improvement of Brassica crops. Herein, interspecific reciprocal crosses between B. maurorum and three cultivated Brassica allotetraploids were carried out with the aid of embryo rescue. Trigenomic hybrids with Brassica napus (AACC, 2n = 38) and Brassica carinata (BBCC, 2n = 34) were produced from reciprocal crosses, but the hybrids with Brassica juncea (AABB, 2n = 36) were obtained only when B. maurorum was used as female. All the hybrids were morphologically intermediate between their parents, and were male and female sterile. By in vitro chromosome doubling of the trigenomic hybrids, the allohexaploids (AACC.MM/MM.AACC, 2n = 54; BBCC.MM, 2n = 50; MM.AABB, 2n = 52) were established and characterized for their phenotype and cytology. The fertilities of three allohexaploids were different, for AACC.MM and MM.AACC failed to produce seeds by selfing, but BBCC.MM showed low seed-set and MM.AABB had good seed-set. They also expressed variable extents of male meiotic regularity as to chromosome pairing and segregation, with MM.AABB > BBCC.MM > AACC.MM/MM.AACC, the same order as their fertility. So their meiotic behavior contributed to the fertility. Finally, the potential of these allohexaploids as a bridge for genetic improvement of Brassica crops was discussed.     

Urban Pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>) as a Potential Source of Pathogenic Yeasts: A Focus on Antifungal Susceptibility of <Emphasis Type="Italic">Cryptococcus</Emphasis> Strains in Northeast Brazil

To investigate pigeons as a potential source of pathogenic yeast species, 47 samples of pigeon droppings and 322 samples from pigeon cloacae were evaluated. The samples were also collected from trees located near the pigeon habitats, in the city of Fortaleza, Ceará, Northeast Brazil. In addition, we evaluated the in vitro antifungal susceptibility of these environmental Cryptococcus strains to amphotericin B, azoles and caspofungin. C. neoformans var. neoformans (n = 10), C. laurentii (n = 3), Candida spp. (n = 14), Rhodotorula mucilaginosa (n = 6) and Trichosporon sp. (n = 3) were isolated from pigeon droppings. In contrast, only Candida spp. (n = 4), Trichosporon sp. (n = 3) and R. mucilaginosa (n = 2) were recovered from cloacae specimens. Only Candida glabrata (n = 1) was recovered from plant samples. Azole resistance was detected in only one environmental strain of Cryptococcus, which was resistant to itraconazole (MIC = 1 μg/ml). As expected, all Cryptococcus strains were resistant to caspofungin. In summary, the present study confirms that urban pigeons are a potential source of Cryptococcus spp. and other pathogenic yeasts. Additionally, antifungal resistance was observed in one environmental strain of Cryptococcus neoformans var. neoformans in Northeast Brazil.     

<Emphasis Type="Italic">Saturnispora serradocipensis</Emphasis> sp. nov. and <Emphasis Type="Italic">Saturnispora gosingensis</Emphasis> sp. nov., two ascomycetous yeasts from ephemeral habitats

Two novel ascomycetous yeast species, Saturnispora serradocipensis and Saturnispora gosingensis, were isolated from leaf detritus in a tropical stream of Southeastern Brazil and a mushroom collected in Taiwan, respectively. Analysis of the D1/D2 domains of the large-subunit of the rRNA gene of these strains showed that these species are related to Saturnispora hagleri, their closest relative. Saturnispora serradocipensis and S. gosingensis differed from S. hagleri, respectively, by seven nucleotide substitutions and two indels and three nucleotide substitutions and three indels in D1/D2 rRNA sequences. The two new species differ from each another by four nucleotide substitutions and one indel in D1/D2 rRNA sequences. However, the ITS sequences of S. serradocipensis, S. gosingensis and S. hagleri were quite divergent, showing that they are genetically separate species. The type strain of S. serradocipensis is UFMG-DC-198^T (=CBS 11756^T = NRRL Y-48717^T), and of S. gosingensis GA4M05^T is (CBS 11755^T = NRRL Y-48718^T).     

Population genetic structure of the endangered and endemic medicinal plant <Emphasis Type="Italic">Commiphora</Emphasis><Emphasis Type="Italic">wightii</Emphasis>

Commiphora wightii is a medicinally important endangered species endemic to the Thar Desert of Rajasthan, India and adjoining areas of Pakistan. The populations of this species are declining sharply because of its extensive use as a natural herb. Random amplified polymorphic DNA analysis was conducted to find the genetic variation among 7 populations of C. wightii. Of the 100 random primers screened, 44 primers yielded 220 loci. Statistical analysis indicated low genetic diversity (H _pop = 0.0958; I = 0.1498; mean polymorphic loci = 14.28%), and high genetic differentiation among the populations (G _ST = 0.3990; AMOVA Φ _ST of 0.3390; Bayesian θ ^(II) = 0.3002). The low genetic diversity may be due to geographic isolation and restricted gene flow (N _m = 0.7533) between the fragmented populations. Unsustainable utilization of the plant has fragmented the population continuum which served the purpose of genetic exchange between populations. Mantel’s test was performed which revealed a highly significant positive correlation between genetic and geographic distance (r ² = 0.614, P = 0.023) among the populations studied. Low variation can also be attributed to poor seed setting and the slow growth pattern of the species, which is also an apomict. In UPGMA dendrogram the Commiphora wightii samples were divided into two major and one minor cluster. These findings can serve as a guide to preserving the genetic resources of this medicinal plant species.     

Cytogenetic characterization of <Emphasis Type="Italic">Hydrangea involucrata</Emphasis> Sieb. and <Emphasis Type="Italic">H. aspera</Emphasis> D. Don complex (Hydrangeaceae)<Emphasis Type="Italic">:</Emphasis> genetic,evolutional, and taxonomic implications

The subsection Asperae of genus Hydrangea L. (Hydrangeaceae) has been investigated for three reasons: several ambiguous classifications concerning Hydrangea aspera have been published, unexpected differences in genome size among seven accessions have been reported Cerbah et al. (Theor Appl Genet 103:45–51, 2001), and two atypical chromosome numbers (2n = 30 for Hydrangea involucrata and 2n = 34 for H. aspera) have been found when all other species of the genus present 2n = 36. Therefore, these two species and four subspecies of Hydrangea in all 29 accessions were analyzed for their genome size, chromosome number, and karyotype features. This investigation includes flow cytometric measurements of nuclear DNA content and bases composition (GC%), fluorochrome banding for detection of GC- and AT-rich DNA regions, and fluorescent in situ hybridisation (FISH) for chromosome mapping of 5 S and 18 S-5.8 S-26 S rDNA genes. In the H. aspera complex, the genome size ranged from 2.98 (subsp. sargentiana) to 4.67 pg/2C (subsp. aspera), an exceptional intraspecific variation of 1.57-fold. The mean base composition was 40.5% GC. Our report establishes the first karyotype for the species H. involucrata, and for the subspecies of H. aspera which indeed present different formulae, offering an element of discrimination. FISH and fluorochrome banding revealed the important differentiation between these two species (H. involucrata and H. aspera) and among four subspecies of the H. aspera complex. Our results are in agreement with the Chinese classification that places the groups Kawakami and Villosa as two different species: Hydrangea villosa Rehder and Hydrangea kawakami Hayata. This knowledge can contribute to effective germplasm management and horticultural use.     

Demonstration of IS<Emphasis Type="Italic">711</Emphasis> transposition in <Emphasis Type="Italic">Brucella ovis</Emphasis> and <Emphasis Type="Italic">Brucella pinnipedialis</Emphasis>

Background  

The Brucella genome contains an insertion sequence (IS) element called IS711 or IS6501, which is specific to the genus. The copy number of IS711 varies in the genome of the different Brucella species, ranging from 7 in B. abortus, B. melitensis and B. suis to more than 30 in B. ovis and in Brucella strains isolated from marine mammals. At present, there is no experimental evidence of transposition of IS711, but the occurrence of this element with a high copy number in some species, and the isolation of Brucella strains with "ectopic" copies of IS711 suggested that this IS could still transpose.     

Genetic characterization of ticks from southwestern Romania by sequences of mitochondrial <Emphasis Type="Italic">cox</Emphasis>1 and <Emphasis Type="Italic">nad</Emphasis>5 genes

In the present study, samples representing three hard tick species and one soft tick species, namely Dermacentor marginatus, Haemaphysalis punctata, Ixodes ricinus and Argas persicus from southwestern Romania, and one hard tick, Haemaphysalis longicornis, from China were characterized genetically by a portion of mitochondrial cytochrome c oxidase subunit 1 gene (pcox1) and a portion of nicotinamide adenine dinucleotide dehydrogenase subunit 5 gene (pnad5). The pcox1 and pnad5 were amplified separately from individual ticks by PCR, sequenced and analyzed. The length of pcox1 and pnad5 sequences of all samples was 732 and 519 bp, respectively. The intra-specific sequence variation in De. marginatus was 0.1–1.0% for pcox1 and 0.2–1.2% for pnad5, whereas in Ha. punctata it was 0.4–1.9% for pcox1 and 0.4–1.0% for pnad5. For the tick species examined in the present study, sequence comparison revealed that the inter-specific sequence differences were higher: 15.9–27.6% for pcox1 and 20.3–42.4% for pnad5. This suggests that the cox1 and nad5 sequences could provide useful genetic markers for the specific identification and genetic characterization of ticks in Romania and elsewhere.     

<Emphasis Type="Italic">Ogataea phyllophila</Emphasis> sp. nov., <Emphasis Type="Italic">Candida chumphonensis</Emphasis> sp. nov. and <Emphasis Type="Italic">Candida mattranensis</Emphasis> sp. nov., three methylotrophic yeast species from phylloplane in Thailand

Five strains (LN12, LN14^T, LN15^T, LN16 and LN17^T) representing three novel methylotrophic yeast species were isolated from the external surface of plant leaves by three-consecutive enrichments. On the basis of morphological, biochemical, physiological and chemotaxonomic characteristics, the sequence analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene and the phylogenetic analysis, the five strains were assigned to be one novel Ogataea species and two novel Candida species. Three strains (LN12, LN14^T and LN16) represent a single novel species of the genus Ogataea, for which the name Ogataea phyllophila sp. nov. is proposed. The type strain is LN14^T (= BCC 42666^T = NBRC 107780^T = CBS 12095^T). Strain LN15^T was assigned to be Candida chumphonensis sp. nov. (type strain LN15^T = BCC 42667^T = NBRC 107781^T = CBS 12096^T). Strain LN17^T represented another novel species of Candida that was named Candida mattranensis sp. nov. (type strain LN17^T = BCC 42668^T = NBRC 107782^T = CBS 12097^T).     

Production and cytogenetic characterization of intertribal somatic hybrids between <Emphasis Type="Italic">Brassica napus</Emphasis> and <Emphasis Type="Italic">Isatis indigotica</Emphasis> and backcross progenies

Intertribal somatic hybrids between Brassica napus (2n = 38, AACC) and a dye and medicinal plant Isatis indigotica (2n = 14, II) were obtained by fusions of mesophyll protoplasts. From a total of 237 calli, only one symmetric hybrid (S2) and five asymmetric hybrids (As1, As4, As6, As7 and As12) were established in the field. These hybrids showed some morphological variations and had very low pollen fertility. Hybrids S2 and As1 possessed 2n = 52 (AACCII), the sum of the parental chromosomes, and As12 had 2n = 66 (possibly AACCIIII). Hybrids As4, As6 and As7 were mixoploids (2n = 48–62). Genomic in situ hybridization analysis revealed that pollen mother cells at diakinesis of As1 contained 26 bivalents comprising 19 from B. napus and 7 from I. indigotica and mainly showed the segregation 26:26 at anaphase I (AI) with 7 I. indigotica chromosomes in each polar group. Four BC₁ plants from As1 after pollinated by B. napus resembled mainly B. napus in morphology but also exhibited some characteristics from I. indigotica. These plants produced some seeds on selfing or pollination by B. napus. They had 2n = 45 (AACCI) and underwent pairing among the I. indigotica chromosomes and/or between the chromosomes of two parents at diakinesis. All hybrids mainly had the AFLP banding patterns from the addition of two parents plus some alterations. B. napus contributed chloroplast genomes in majority of the hybrids but some also had from I. indigotica. Production of B. napus–I. indigotica additions would be of considerable importance for genome analysis and breeding.     

Physiological effects upon <Emphasis Type="Italic">Amblyomma americanum</Emphasis> (Acari: Ixodidae) infected with <Emphasis Type="Italic">Beauveria bassiana</Emphasis> (Ascomycota: Hypocreales)

Unfed adult Amblyomma americanum were exposed to the entomopathogenic fungus Beauveria bassiana. Ticks exposed to the fungus exhibited reduced survival and increased water loss as indicated by change in weight. Treated ticks survived 7.2 ± 0.22 days (mean ± SE) and controls survived 17.9 ± 0.73 days (P = 0.01; df = 57). At death, ticks exposed to the fungus had lost 25.2 ± 0.84% of their starting weight; control ticks had lost 14.1 ± 0.85% of their starting weight (P = 0.01; df = 96). Water loss was highest immediately following inoculation, although losses continued to be higher than in uninoculated ticks. This suggests that fungal penetration causes sufficient cuticle damage to cause desiccation, although other water-loss avenues exist, including increased time of spiracular opening. Additionally this study did not eliminate the possibility of a negative impact on water vapor uptake. This is the first study to investigate the effect of an entomopathogenic fungus on the water balance of a tick.     

Karyotypic and molecular polymorphisms in <Emphasis Type="Italic">Ctenomys</Emphasis><Emphasis Type="Italic">torquatus</Emphasis> (Rodentia: Ctenomyidae): taxonomic considerations

The rodent genus Ctenomys (tuco-tucos) comprises more than 60 described species, and shows extraordinary inter- and intraspecific karyotypic variation. The most widely distributed species of Ctenomys in Brazil is C. torquatus. Although several cytogenetic studies have been done, the karyotypic variability of this species is still poorly known. In this paper we report two new diploid numbers for C. torquatus: 2n = 40 and 2n = 42, both showing AN = 72. The new distribution limits of C. torquatus here reported include localities in the southern, central and western parts of Rio Grande do Sul (RS) State in southern Brazil. The phylogenetic relationship between C. torquatus from Alegrete, RS, and Ctenomys sp. from Corrientes, Argentina, is described by means of mtDNA cytochrome b analysis. Although both entities share similar karyotypes and sperm morphology, these two species are not phylogenetically close.     

Purification and characterization of chitinases from <Emphasis Type="Italic">Paecilomyces</Emphasis><Emphasis Type="Italic">variotii</Emphasis> DG-3 parasitizing on <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> eggs

Two extracellular chitinases were purified from Paecilomyces variotii DG-3, a chitinase producer and a nematode egg-parasitic fungus, to homogeneity by DEAE Sephadex A-50 and Sephadex G-100 chromatography. The purified enzymes were a monomer with an apparent molecular mass of 32 kDa (Chi32) and 46 kDa (Chi46), respectively, and showed chitinase activity bands with 0.01% glycol chitin as a substrate after SDS-PAGE. The first 20 and 15 N-terminal amino acid sequences of Chi32 and Chi46 were determined to be Asp-Pro-Typ-Gln-Thr-Asn-Val-Val-Tyr-Thr-Gly-Gln-Asp-Phe-Val-Ser-Pro-Asp-Leu-Phe and Asp-Ala-X-X-Tyr-Arg-Ser-Val-Ala-Tyr-Phe-Val-Asn-Trp-Ala, respectively. Optimal temperature and pH of the Chi32 and Chi46 were found to be both 60°C, and 2.5 and 3.0, respectively. Chi32 was almost inhibited by metal ions Ag⁺ and Hg²⁺ while Chi46 by Hg²⁺ and Pb²⁺ at a 10 mM concentration but both enzymes were enhanced by 1 mM concentration of Co²⁺. On analyzing the hydrolyzates of chitin oligomers [(GlcNAc) _n , n = 2–6)], it was considered that Chi32 degraded chitin oligomers as an exo-type chitinase while Chi46 as an endo-type chitinase.     

Additions to the cytologically investigated species of <Emphasis Type="Italic">Potentilla</Emphasis> L. (Rosaceae) from India

At present 14 species of Potentilla L. have been cytologically worked out from different geographical areas of Kashmir and Himachal Pradesh in the Western Himalayas. New chromosome numbers in nine species—Potentilla argyrophylla (n = 14), P. atrosanguinea (n = 7, 14), P. desertorum (n = 7), P. gerardiana (n = 14), P. indica (n = 14), P. micropetala (n = 14), P. nepalensis (n = 14), P. sibbaldia (n = 14) and P. thomsonii (n = 7)—have been reported on a worldwide basis for the first time. Additional chromosomal races of polyploid cytotypes for P. argyrophylla (n = 28) and P. desertorum (n = 14) along with a diploid cytotype for P. micropetala (n = 7) plus diploid cytotypes for the five species as P. fulgens (n = 7), P. gelida (n = 7), P. kleiniana (n = 7), P. sibbaldia (n = 7) and P. sundaica (n = 7) as well as a tetraploid cytotype for P. fruticosa (n = 14) all have been cytologically worked out from India for the first time. The course of meiosis varies from normal to abnormal in different populations of the majority of the species, such as P. argyrophylla, P. atrosanguinea, P. desertorum, P. fruticosa, P. fulgens, P. gelida, P. indica, P. nepalensis, P. sibbaldia and P. sundaica, except for normal meiosis observed in P. gerardiana, P. kleiniana, P. micropetala and P. thomsonii. The anomalous taxa are marked with meiotic abnormalities in the form of cytomixis, chromosomal stickiness, unoriented bivalents, formation of laggards and bridges resulting in abnormal microsporogenesis, and production of heterogenous-sized fertile pollen grains along with reduced pollen fertility. All the taxa with normal meiotic courses show nearly one hundred percent pollen fertility.     

Ecological implications on the aggregation of <Emphasis Type="Italic">Amblyomma fuscum</Emphasis> (Acari: Ixodidae) on <Emphasis Type="Italic">Thrichomys laurentius</Emphasis> (Rodentia: Echimyidae), in northeastern Brazil

We investigated the Amblyomma fuscum load on a pullulating wild rodent population and the environmental and biological factors influencing the tick load on the hosts. One hundred and three individuals of Thrichomys laurentius were caught in an Atlantic forest fragment in northeastern Brazil, as part of a longitudinal survey on ticks infesting non-volant small mammals. Ticks (n = 342) were found on 45 individuals and the overall mean intensity of infestation was 7.6 ticks per infested rodent. Ticks were highly aggregated in the host population and the negative binomial distribution model provides a statistically satisfactory fit. The aggregated distribution was influenced by sex and age of the host. The microhabitat preference by T. laurentius probably increases contact opportunities between hosts and aggregated infesting stages of the ticks and represents important clues about the habitat suitability for A. fuscum.     

Molecular mapping of resistance gene to English grain aphid (<Emphasis Type="Italic">Sitobion avenae</Emphasis> F.) in <Emphasis Type="Italic">Triticum durum</Emphasis> wheat line C273

The English grain aphid, Sitobion avenae (Fabricius), is one of the most important insect pests causing substantial yield losses in wheat production in China and other grain-growing areas in the world. The efficient utilization of wheat genes for resistance to English grain aphid (EGA) provides an efficient, economic and environmentally sound approach to reduce the yield losses. In the present study, the wheat line C273 (Triticum durum AABB, 2n = 4x = 28), is resistant to EGA in greenhouse and field tests. To identify the resistance gene, designated RA-1 temporarily, C273 was crossed with susceptible genotype Poland 305 (T. polonicum, AABB, 2n = 4x = 28). The F₁, F₂ and F_2:3 lines were tested with EGA in the field and greenhouse. The results indicated that RA-1 is a single dominant gene, closely linked to the microsatellite markers (SSR) Xwmc179, Xwmc553 and Xwmc201 on chromosome 6AL at genetic distances of 3.47, 4.73 and 7.57 cM, respectively. The three SSR markers will be valuable in marker-assisted selection for resistance to EGA as well as for cloning this gene in the future.     

Fine genetic mapping of greenbug aphid-resistance gene <Emphasis Type="Italic">Gb3</Emphasis> in <Emphasis Type="Italic">Aegilops tauschii</Emphasis>

The greenbug, Schizaphis graminum (Rondani), is an important aphid pest of small grain crops especially wheat (Triticum aestivum L., 2n = 6x = 42, genomes AABBDD) in many parts of the world. The greenbug-resistance gene Gb3 originated from Aegilops tauschii Coss. (2n = 2x = 14, genome D^tD^t) has shown consistent and durable resistance against prevailing greenbug biotypes in wheat fields. We previously mapped Gb3 in a recombination-rich, telomeric bin of wheat chromosome arm 7DL. In this study, high-resolution genetic mapping was carried out using an F_2:3 segregating population derived from two Ae. tauschii accessions, the resistant PI 268210 (original donor of Gb3 in the hexaploid wheat germplasm line ‘Largo’) and susceptible AL8/78. Molecular markers were developed by exploring bin-mapped wheat RFLPs, SSRs, ESTs and the Ae. tauschii physical map (BAC contigs). Wheat EST and Ae. tauschii BAC end sequences located in the deletion bin 7DL3-0.82–1.00 were used to design STS (sequence tagged site) or CAPS (Cleaved Amplified Polymorphic Sequence) markers. Forty-five PCR-based markers were developed and mapped to the chromosomal region spanning the Gb3 locus. The greenbug-resistance gene Gb3 now was delimited in an interval of 1.1 cM by two molecular markers (HI067J6-R and HI009B3-R). This localized high-resolution genetic map with markers closely linked to Gb3 lays a solid foundation for map based cloning of Gb3 and marker-assisted selection of this gene in wheat breeding.