bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear- and chloroplast-microsatellite variation in A-genome species of rice
Authors: Ishii T , Xu Y , McCouch S R
Published: April 2011

Simple sequence length polymorphism analysis was carried out to reveal microsatellite variation and to clarify the phylogenetic relationships among A-genome species of rice. Total DNA from 29 cultivars (23 Oryza sativa and 6 O. glaberrima) and 30 accessions of wild A-genome species (12 O. rufipogon, 5 O. glumaepatula, 2 O. longistaminata, 6 O. meridionalis, and 5 O. barthii) was used as a template for PCR to detect 24 nuclear and 10 chloroplast microsatellite loci. Microsatellite allelic diversity was examined based on amplified banding patterns. Microsatellites amplified clearly in all 59 accessions, with an average of 18.4 alleles per locus. The polymorphism information content (PIC) value ranged from 0.85 to 0.94, with an average of 0.89. At the species level, high average PIC values were observed in O. sativa (0.79) and O. rufipogon (0.80). For chloroplast microsatellites, the average number of alleles per locus and the average PIC value were 2.9 and 0.38, respectively. While the magnitude of diversity was much greater for nuclear microsatellites than for chloroplast microsatellites, they showed parallel patterns of differentiation for each taxonomic group. Using the ratio of common alleles (estimated as size of amplified fragments) as a similarity index, the average percentages of common microsatellite alleles were calculated between taxa. For both nuclear and chloroplast microsatellites, O. sativa showed the highest similarity values to O. rufipogon, and O. glaberrima was most similar to O. barthii. These data support previous evidence that these cultivars originated from the corresponding wild ancestral species.Key words: simple sequence length polymorphism, SSLP, microsatellite marker, rice, Oryza sativa, allelic diversity, phylogenetics.
Lateral asymmetry of paw usage: phenotypic survey of constitutive and experience-conditioned paw-usage behaviours among common strains of the mouse
Authors: Biddle Fred G , Eales Brenda A
Published: April 2011

Left-right direction of paw usage in the mouse is defined by the right-paw entry (RPE) score, which is the number of reaches with the right paw to retrieve food from a small food tube in a total of 50 right- and left-paw reaches. Two qualitatively different paw-usage behaviours can be identified by the difference in the RPE scores from naive mice in left- or right-biased test chambers and their retest, 1 week later, in the opposite-biased test chamber. In mice with constitutive paw usage, the RPE score may respond to the direction of a biased test chamber, but it returns to the value that is expected for naive mice in the opposite-biased test chamber. In mice with experience-conditioned paw usage, the RPE score responds to the direction of a biased test chamber and does not return to its expected value in the opposite-biased test chamber. In this report, we document the alternate paw usage behaviours in an extended phenotypic survey of different strains that will be useful for its genetic analysis. We also validate an alternate biometrical method to identify constitutive and experience-conditioned paw usage that is based on the mean average RPE score from the biased test and opposite-biased retest of individual mice. This alternate biometrical method demonstrated that, in some strains with experience-conditioned paw usage, there may be asymmetry or an interaction between genotype and the direction of the test sequence. In addition, the strain survey demonstrated that the qualitative difference between constitutive and experience-conditioned paw usage is independent of the well-known quantitative difference in the degree of lateralization of preferred-paw usage.Key words: mouse, lateral asymmetry of paw usage, left and right handedness, behavioural genetics, constitutive behaviour, experience-conditioned behaviour.
Low-activity allele of copper-zinc superoxide dismutase (CuZnSOD) inDrosophilaincreases paraquat genotoxicity but does not affect near UV radiation damage
Authors: Vontas John G , Tsakas Spyridon C , Loukas Michael , Hemingway Janet
Published: April 2011

Different types of mutations and DNA-damage profiles induced by near-UV radiation and the superoxide anion (O2-·) indicate separate lesions and (or) mechanisms of mutagenesis. Despite a wealth of data, it is still unclear whether variations in the activity levels of antioxidant enzymes naturally present in suboptimal concentrations are among the underlying causes of the increase of near UV radiation genotoxicity. We incorporated a low-activity allele of copperzinc superoxide dismutase (CuZnSOD), recovered from natural populations of Drosophila melanogaster, into standard marked strains and employed a somatic mutation and recombination test (SMART) to compare paraquat and near UV radiation genotoxicity in these strains. Our results show that, although the low-activity CuZnSOD allele of D. melanogaster confers hypersensitivity to paraquat, the near UV radiation damage was not affected.Key words: reactive oxygen species, near-UV radiation, superoxide dismutase, Drosophila, somatic mutation and recombination.
Candidate-gene cloning and targeted marker enrichment of wheat chromosomal regions using RNA fingerprinting - differential display
Authors: Gill Kulvinder S , Sandhu Devinder
Published: April 2011

The usefulness of the RNA fingerprinting  differential display technique in gene cloning and targeted marker enrichment in wheat is demonstrated. A small region of chromosome 5BL was targeted that contains Ph1, a chromosome-pairing regulator gene. The cultivar Chinese Spring (CS) and mutant ph1b are almost identical except for chromosome 5BL, which, in the mutant line, carries an interstitial deletion encompassing the Ph1 gene. Poly(A)+RNA of the two lines from anthers at developmental stages ranging from pre-meiotic mitosis to anaphase II was PCR-amplified using 38 pairwise combinations of 19 primers. The35S-labeled amplified products were size-separated on denaturing polyacrylamide-urea gels. A total of 3154 fragment bands were observed, of which 43 were present in CS but absent in the ph1b mutant. These 43 fragment bands were eluted, re-amplified, and used as probes in gel-blot DNA analyses of wheat group 5 nullisomic-tetrasomic lines and the ph1b mutant. Twenty-four of these 43 probes were single- or few-copy sequences. Eight of the 24 probes mapped to wheat group 5 and five mapped to the deletion of the ph1b mutant. Three of these five probes were further localized to the submicroscopic region containing the Ph1 gene, by using two deletion lines flanking the region. Northern-blot analysis revealed that the gene corresponding to one of these three probes expresses mainly during meiosis and is from the B genome.Key words: RNA fingerprinting  differential display, wheat, gene cloning, marker enrichment, Ph1 gene.
AFLP analysis of genetic polymorphism and evolutionary relationships among cultivated and wildNicotianaspecies
Authors: Ren Nan , Timko Michael P
Published: April 2011

Amplified fragment length polymorphism (AFLP) analysis was used to determine the degree of intra- and inter-specific genetic variation in the genus Nicotiana. Forty-six lines of cultivated tobacco (Nicotiana tabacum L.) and seven wild Nicotiana species, including N. sylvestris, N. tomentosiformis, N. otophora, N. glutinosa, N. suaveolens, N. rustica, and N. longiflora, were analyzed, using at least eight different oligonucleotide primer combinations capable of detecting a minimum of 50 polymorphic bands per primer pair. The amount of genetic polymorphism present among cultivated tobacco lines (N. tabacum) was limited, as evidenced by the high degree of similarity in the AFLP profiles of cultivars collected worldwide. Six major clusters were found within cultivated tobacco that were primarily based upon geographic origin and manufacturing quality traits. A greater amount of genetic polymorphism exists among wild species of Nicotiana than among cultivated forms. Pairwise comparisons of the AFLP profiles of wild and cultivated Nicotiana species show that polymorphic bands present in N. tabacum can be found in at least one of three proposed wild progenitor species (i.e., N. sylvestris, N. tomentosiformis, and N. otophora). This observation provides additional support for these species contributing to the origin of N. tabacum.Key words: AFLP, evolution, genetic diversity, Nicotiana, tobacco, wild relatives of tobacco.
Molecular and cytological analyses ofDeschampsia cespitosapopulations from Northern Ontario (Canada)
Authors: Nkongolo K K , Deck A , Michael P
Published: April 2011

Deschampsia cespitosa is widely dispersed around the globe, particularly in the northern hemisphere. A high tolerance to adverse environmental conditions allows D. cespitosa to colonize and dominate plots of land that are uninhabitable by other plants. The main objective of the present study was to determine the degree of genetic variation and relatedness among D. cespitosa populations from heavy metal contaminated sites and uncontaminated sites in Northern Ontario, using RAPD markers. Genomic DNA samples from individual plants were analyzed using 35 oligonucleotides of random sequence. Twenty-eight of these primers allowed amplification of random polymorphic DNA (RAPD) loci. Overall, 90% of RAPD bands were polymorphic. Analysis of molecular variance revealed that 72% of the variation could be attributed to individual differences within each of the populations. The within- and among-region variations accounted for 14 and 15% of the total molecular variance, respectively. Population-specific RAPD markers were identified. RAPD markers specific to D. cespitosa were isolated, cloned, and characterized. Cytogenetic analysis revealed a high level of aneuploidy in all the populations from Northern Ontario, with chromosome numbers varying from 2n = 18 to 2n = 26.Key words: Deschampsia, RAPD, genetic relationships, species-specific markers, population-specific markers.
Assessment of genetic variation and differentiation of hop genotypes by microsatellite and AFLP markers
Authors: Jake Jernej , Kindlhofer Katja , Javornik Branka
Published: April 2011

Microsatellites have many desirable marker properties and have been increasingly used in crop plants in genetic diversity studies. Here we report on the characterisation of microsatellite markers and on their use for the determination of genetic identities and the assessment of genetic variability among accessions from a germplasm collection of hop. Thirty-two polymorphic alleles were found in the 55 diploid genotypes, with an average number of eight alleles (3.4 effective alleles) for four microsatellite loci. Calculated polymorphic information content values classified three loci as informative markers and two loci as suitable for mapping. The average observed heterozygosity was 0.7 and the common probability of identical genotypes was 3.271 × 104. An additional locus, amplified by one primer pair, was confirmed by segregation analysis of two crosses. The locus discovered was heterozygous, with a null allele in the segregating population. The same range of alleles was detected in nine triploid and five tetraploid hop genotypes. Cultivar heterozygosity varied among all 69 accessions, with only one cultivar being homozygous at four loci. Microsatellite allele polymorphisms distinguished 81% of all genotypes; the same allelic profile was found mainly in clonally selected cultivars. Cultivar-specific alleles were found in some genotypes, as well as a specific distribution of alleles in geographically distinct hop germplasms. The genetic relationship among 41 hop accessions was compared on the basis of microsatellite and AFLP polymorphisms. Genetic similarity dendrograms showed low correlation between the two marker systems. The microsatellite dendrogram grouped genetically related accessions reasonably well, while the AFLP dendrogram showed good clustering of closely related accessions and, additionally, separated two geographically distinct hop germplasms. The results of microsatellite and AFLP analysis are discussed from the point of view of the applicability of the two marker systems for different aspects of germplasm evaluation.Key words: Humulus lupulus L., germplasm collection, molecular markers, genetic diversity.
Chloroplast DNA phylogeography ofCunninghamia konishii(Cupressaceae), an endemic conifer of Taiwan
Authors: Lu Sheng-You , Peng Ching-I , Cheng Yu-Ping , Hong Kuo-Hsiang , Chiang Tzen-Yuh
Published: April 2011

In this study, we investigated the genetic structure and phylogeographic pattern of the genus Cunninghamia, a member of the Cupressaceae restricted to mainland China and Taiwan, based on sequences of the trnDtrnT noncoding spacer of the chloroplast DNA. Maternal inheritance of chloroplasts was determined experimentally. No paternal leakage was detected. Both parsimony and neighbor-joining analyses revealed the polyphyly of Cunninghamia konishii, populations of which were nested in clades of C. lanceolata from mainland China. The nucleotide diversity of chloroplast DNA sequences within C. konishii (0.0118) was higher than that between species (0.0104), which agrees with a previous allozyme investigation. Based on mutational differences between sequences, a minimum spanning network consisting of five clades was constructed. Significant genetic differentiation (ΦST= 0.130, P < 0.001) was detected between the clades based on AMOVA analyses. We infer several possible refugia in the Yunnan, Zhejiang, and Guangdong provinces of south China, all located in the minimum network as interior nodes. We also infer possible migration routes of Cunninghamia populations. The phylogeographic pattern shown in the reconstructed network suggests that the present-day Cunninghamia populations in Taiwan were derived from six different sources in continental Asia via long-distance seed dispersal. A migrant-pool model explains the heterogeneous composition of the organelle DNA in Taiwan's populations and the low differentiation between populations of Taiwan and China (ΦCT= 0.012, P = 0.454). In contrast with the genetic heterogeneity within geographic populations, many local populations have attained coalescence at the trnDtrnT alleles, which has led to significant differentiation at the population level.Key words: AMOVA, coalescence, cpDNA, Cunninghamia konishii, Cunninghamia lanceolata, minimum spanning network, phylogeography.
Pericentric inversion in natural populations ofOligoryzomys nigripes(Rodentia: Sigmodontinae)
Authors: Bonvicino Cibele R , D'Andrea Paulo S , Borodin Pavel M
Published: April 2011

We analysed polymorphism for pericentric inversion in chromosome 3 of Oligoryzomys nigripes (Rodentia: Sigmodontinae) in several populations in Brazil and examined the meiotic behaviour of this chromosome in heterozygotes. We observed an orderly pairing of all chromosomes at pachytene in heterozygotes for the inverted chromosome 3. No indication of meiotic arrest and germ-cell death was found. Electron microscopy of synaptonemal complexes and conventional meiotic analysis indicated strictly nonhomologous synapsis and crossing-over suppression in the inverted region in the heterozygotes, which prevent the formation of unbalanced gametes. Thus, the pericentric inversion in chromosome 3 does not apparently result in any selective disadvantages in heterozygous carriers. In the majority of the populations studied, the frequencies of acrocentric homozygotes, metacentric homozygotes, and heterozygotes were in HardyWeinberg equilibrium. However, in some populations, we detected an excess of heterozygotes and a deficiency of acrocentric homozygotes.Key words: chromosome rearrangements, inversion, meiosis, Oligoryzomys nigripes.
A bacterial artificial chromosome based physical map of theUstilago maydisgenome
Authors: Meksem Khalid , Shultz Jeffry , Tebbji Faiza , Jamai Aziz , Henrich Jürgen , Kranz Harald , Arenz Monika , Schlueter Thomas , Ishihara Hirofumi , Jyothi Lavu N , Zhang Hong-Bin , Lightfoot David A
Published: April 2011

Ustilago maydis, a basidiomycete, is a model organism among phytopathogenic fungi. A physical map of U. maydis strain 521 was developed from bacterial artificial chromosome (BAC) clones. BAC fingerprints used polyacrylamide gel electrophoresis to separate restriction fragments. Fragments were labeled at the HindIII site and codigested with HaeIII to reduce fragments to 50–750 bp. Contiguous overlapping sets of clones (contigs) were assembled at nine stringencies (from P ≤ 1 x 10–6to 1 x 10–24). Each assembly nucleated contigs with different percentages of bands overlapping between clones (from 20% to 97%). The number of clones per contig decreased linearly from 41 to 12 from P ≤ 1 x 10–7to 1 x 10–12. The number of separate contigs increased from 56 to 150 over the same range. A hybridization-based physical map of the same BAC clones was compared with the fingerprint contigs built at P ≤ 1 × 10–7. The two methods provided consistent physical maps that were largely validated by genome sequence. The combined hybridization and fingerprint physical map provided a minimum tile path composed of 258 BAC clones (18–20 Mbp) distributed among 28 merged contigs. The genome of U. maydis was estimated to be 20.5 Mbp by pulsed-field gel electrophoresis and 24 Mbp by BAC fingerprints. There were 23 separate chromosomes inferred by both pulsed-field gel electrophoresis and fingerprint contigs. Only 11 of the tile path BAC clones contained recognizable centromere, telomere, and subtelomere repeats (high-copy DNA), suggesting that repeats caused some false merges. There were 247 tile path BAC clones that encompassed about 17.5 Mbp of low-copy DNA sequence. BAC clones are available for repeat and unique gene cluster analysis including tDNA-mediated transformation. Program FingerPrint Contigs maps aligned with each chromosome can be viewed at http://www.siu.edu/~meksem/ustilago_maydis/.Key words: Ustilago maydis, physical map, bacterial artificial chromosomes, whole-genome sequencing.
Genetic characterization of QTL associated with resistance to Fusarium head blight in a doubled-haploid spring wheat population
Authors: Yang Zhuping , Gilbert Jeannie , Fedak George , Somers Daryl J
Published: April 2011

Fusarium head blight (FHB) is one of the most important fungal wheat diseases worldwide. Understanding the genetics of FHB resistance is the key to facilitating the introgression of different FHB resistance genes into adapted wheat. The objectives of the present study were to detect and map quantitative trait loci (QTL) associated with FHB resistance genes and characterize the genetic components of the QTL in a doubled-haploid (DH) spring wheat population using both single-locus and two-locus analysis. A mapping population, consisting of 174 DH lines from the cross between DH181 (resistant) and AC Foremost (susceptible), was evaluated for type I resistance to initial infection during a 2-year period in spray-inoculated field trials, for Type II resistance to fungal spread within the spike in 3 greenhouse experiments using single-floret inoculation, and for resistance to kernel infection in a 2001 field trial. One-locus QTL analysis revealed 7 QTL for type I resistance on chromosome arms 2DS, 3AS, 3BS, 3BC (centromeric), 4DL, 5AS, and 6BS, 4 QTL for type II resistance on chromosomes 2DS, 3BS, 6BS, and 7BL, and 6 QTL for resistance to kernel infection on chromosomes 1DL, 2DS, 3BS, 3BC, 4DL, and 6BS. Two-locus QTL analysis detected 8 QTL with main effects and 4 additive by additive epistatic interactions for FHB resistance and identified novel FHB resistance genes for the first time on chromosomes 1DL, 4AL, and 4DL. Neither significant QTL by environment interactions nor epistatic QTL by environment interactions were found for either type I or type II resistance. The additive effects of QTL explained most of the phenotypic variance for FHB resistance. Marker-assisted selection for the favored alleles at multiple genomic regions appears to be a promising tool to accelerate the introgression and pyramiding of different FHB resistance genes into adapted wheat genetic backgrounds.Key words: Triticum aestivum, Fusarium graminearum, microsatellite, additive effect, additive by additive epistatic effect.
Genetic diversity among varieties and wild species accessions of pea (Pisum sativumL.) based on molecular markers, and morphological and physiological characters
Authors: Tar'an B , Zhang C , Warkentin T , Tullu A , Vandenberg A
Published: April 2011

Random amplified polymorphic DNA, simple sequence repeat, and inter-simple sequence repeat markers were used to estimate the genetic relations among 65 pea varieties (Pisum sativum L.) and 21 accessions from wild Pisum subspecies (subsp.) abyssinicum, asiaticum, elatius, transcaucasicum, and var. arvense. Fifty-one of these varieties are currently available for growers in western Canada. Nei and Li's genetic similarity (GS) estimates calculated using the marker data showed that pair-wise comparison values among the 65 varieties ranged from 0.34 to 1.00. GS analysis on varieties grouped according to their originating breeding programs demonstrated that different levels of diversity were maintained at different breeding programs. Unweighted pair-group method arithmetic average cluster analysis and principal coordinate analysis on the marker-based GS grouped the cultivated varieties separately from the wild accessions. The majority of the food and feed varieties were grouped separately from the silage and specialty varieties, regardless of the originating breeding programs. The analysis also revealed some genetically distinct varieties such as Croma, CDC Handel, 1096M-8, and CDC Acer. The relations among the cultivated varieties, as revealed by molecular-marker-based GS, were not significantly correlated with those based on the agronomic characters, suggesting that the 2 systems give different estimates of genetic relations among the varieties. However, on a smaller scale, a consistent subcluster of genotypes was identified on the basis of agronomic characters and their marker-based GS. Furthermore, a number of variety-specific markers were identified in the current study, which could be useful for variety identification. Breeding strategies to maintain or enhance the genetic diversity of future varieties are proposed.Key words: Pisum sativum, molecular markers, genetic relationships, cluster analysis.
Application of ISSR, RAPD, and cytological markers to the certification of Picea mariana, P. glauca, and P. engelmannii trees, and their putative hybrids
Authors: Nkongolo K K , Michael P , Demers T
Published: April 2011

Picea glauca (white spruce) and P. engelmannii (Engelmann spruce) are so similar and integrated that it is impossible to distinguish between them and their hybrids using morphological characteristics. Although natural hybrids between P. glauca and P. mariana (black spruce) do not generally occur, even though the 2 species are sympatric in North America, a first-generation hybrid, called the Rosendahl spruce, has been reported in the literature. In this study, several inter-simple sequence repeat (ISSR) markers were developed, as were randomly amplified polymorphic DNA (RAPD) markers, to certify spruce trees and their hybrids. ISSR fingerprinting was more efficient than RAPD assay; it detected 70% polymorphic DNA markers among the spruce species analyzed, whereas RAPD fingerprinting detected only 53%. Species-diagnostic ISSR and RAPD markers differentiating P. glauca from P. engelmannii and P. mariana were cloned and sequenced. Molecular certification of the spruce samples analyzed confirmed that all the seeds from interior spruce populations were true hybrids of P. glauca and P. engelmannii. But the analysis of seeds derived from the putative Rosendahl spruce indicated that this tree is likely a pure P. glauca genotype, rather than a hybrid of P. glauca and P. mariana. These data were confirmed by cytological analyses. Further analysis, using a more sensitive DNA amplification method with designed primers flanking the species-diagnostic ISSR and RAPD markers, revealed that such sequences are not generally species-specific because they are present in other spruce species.Key words: ISSR and RAPD markers, cloning, species-diagnostic markers, spruce hybrids, Picea spp.
Variation in nuclear DNA content in Malus species and cultivated apples
Authors: Tatum Tatiana C , Stepanovic Svetlana , Biradar D P , Rayburn A Lane , Korban Schuyler S
Published: April 2011

The nuclear DNA content for a group of 40 Malus species and hybrids has been estimated using flow cytometry. Estimates of nuclear DNA content for this germplasm collection range from 1.45 pg for Malus fusca (diploid) to 2.57 pg for Malus ioensis (triploid). Among diploids, the nuclear (2C) DNA ranges from 1.45 pg for M. fusca to 1.68 pg for Malus transitoria. Among triploids, the nuclear (3C) DNA content ranges from 2.37 pg / 3C for Malus sikkimensis to 2.57 pg / 3C for M. ioensis. Given the complexity of the apple genome and its suggested allopolyploid origin, the results obtained in this study confirm earlier reports that polyploids can easily withstand the loss of a certain amount of DNA, and that there is a slight tendency towards diminished haploid nuclear DNA content with increased polyploidy.Key words: apple, DNA content, flow cytometry, Malus, ploidy.
Identification of proteins induced or upregulated by Fusarium head blight infection in the spikes of hexaploid wheat (Triticum aestivum)
Authors: Zhou Wenchun , Kolb Frederic L , Riechers Dean E
Published: April 2011

Fusarium head blight (FHB) caused by Fusarium graminearum is a destructive disease of wheat and barley. It causes economic losses due to reduction in both yield and quality. Although FHB resistance has been well documented and resistant cultivars have been developed to reduce incidence and severity of FHB, there is a limited understanding of the molecular mechanisms involved in plant resistance against the infection and spread of F. graminearum. In the current study, 2-dimensional displays of proteins extracted from wheat spikelets infected with F. graminearum were compared with those from spikelets inoculated with sterile H2O. Fifteen protein spots were detected that were either induced (qualitatively different) or upregulated (quantitatively increased) following F. graminearum infection of spikelets of 'Ning7840', a resistant cultivar. These proteins were identified by LC-MS/MS analysis. Proteins with an antioxidant function such as superoxide dismutase, dehydroascorbate reductase, and glutathione S-transferases (GSTs) were upregulated or induced 5 d after inoculation with F. graminearum, indicating an oxidative burst of H2O2inside the tissues infected by FHB. An ascorbate-glutathione cycle is likely involved in reduction of H2O2. Expression of proteins with highest similarity to dehydroascorbate reductase and TaGSTF5 (a glutathione S-transferase) differed following FHB infection in susceptible and resistant cultivars. A 14-3-3 protein homolog was also upregulated in FHB-infected spikelets. In addition, a PR-2 protein (β-1, 3 glucanase) was upregulated in FHB-infected spikes, which is in accord with a previous study that analyzed transcript accumulation.Key words: Fusarium head blight, scab, 2-dimensional electrophoresis, LC-MS/MS, protein, wheat, Triticum aestivum.
Linkage mapping of a dominant male sterility geneMs-cd1inBrassica oleracea
Authors: Wang Xiaowu , Lou Ping , Bonnema Guusje , Yang Baojun , He Hangjun , Zhang Yanguo , Fang Zhiyuan
Published: April 2011

The dominant male sterility gene Ms-cd1 (c, cabbage; d, dominant) was identified as a spontaneous mutation in the spring cabbage line 79-399-3. The Ms-cd1 gene is successfully applied in hybrid seed production of several Brassica oleracea cultivars in China. Amplified fragment length polymorphism (AFLP) technology was used to identify markers linked to the Ms-cd1 gene in bulks of male-sterile and male-fertile individuals of a segregating BC3population and in a near-isogenic population of 25 male-sterile plants. Twelve markers within a 20-cM interval proximal to the Ms-cd1 gene were identified, 5 of which can be used to select homozygous male-sterile Ms-cd1/ Ms-cd1 plants. Three AFLP markers and 3 sequence characterized amplified region markers that were linked to MS-cd1 mapped onto linkage group O9, corresponding to chromosome 3 of B. oleracea. This region corresponds to the top of chromosome 5 in Arabidopsis thaliana.Key words: Brassica oleracea, dominant male-sterility gene, bulk segregant analysis, amplified fragment length polymorphism (AFLP), genetic mapping.
Genetic diversity among silkworm (Bombyx moriL., Lep., Bombycidae) germplasms revealed by microsatellites
Authors: Li Muwang , Shen Li , Xu Anying , Miao Xuexia , Hou Chengxiang , Sun Pingjiang , Zhang Yuehua , Huang Yongping
Published: April 2011

To determine genetic relationships among strains of silkworm, Bombyx mori L., 31 strains with different origins, number of generations per year, number of molts per generation, and morphological characters were studied using simple sequence repeat (SSR) markers. Twenty-six primer pairs flanking microsatellite sequences in the silkworm genome were assayed. All were polymorphic and unambiguously separated silkworm strains from each other. A total of 188 alleles were detected with a mean value of 7.2 alleles/locus (range 2–17). The average heterozygosity value for each SSR locus ranged from 0 to 0.60, and the highest one was 0.96 (Fl0516 in 4013). The mean polymorphism index content (PIC) was 0.66 (range 0.12–0.89). Unweighted pair group method with arithmetic means (UPGMA) cluster analysis of Nei's genetic distance grouped silkworm strains based on their origin. Seven major ecotypic silkworm groups were analyzed. Principal components analysis (PCA) for SSR data support their UPGMA clustering. The results indicated that SSR markers are an efficient tool for fingerprinting cultivars and conducting genetic-diversity studies in the silkworm.Key words: silkworm, Bombyx mori L., microsatellites, simple sequence repeat (SSR), genetic diversity.
Molecular characterization and mapping ofALMT1, the aluminium-tolerance gene of bread wheat (Triticum aestivumL.)
Authors: Raman Harsh , Zhang Kerong , Cakir Mehmet , Appels Rudi , Garvin David F , Maron Lyza G , Kochian Leon V , Moroni J Sergio , Raman Rosy , Imtiaz Muhammad , Drake-Brockman Fiona , Waters Irene , Martin Peter , Sasaki Takayuki , Yamamoto Yoko , Matsumoto Hideaki , Hebb Diane M , Delhaize Emmanuel , Ryan Peter R
Published: April 2011

The major aluminum (Al) tolerance gene in wheat ALMT1 confers. An Al-activated efflux of malate from root apices. We determined the genomic structure of the ALMT1 gene and found it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified 3 alleles for ALMT1, 1 of which was identical to the ALMT1 gene from an Aegilops tauschii accession. The ALMT1 gene was mapped to chromosome 4DL using 'Chinese Spring' deletion lines, and loss of ALMT1 coincided with the loss of both Al tolerance and Al-activated malate efflux. Aluminium tolerance in each of 5 different doubled-haploid populations was found to be conditioned by a single major gene. When ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and cosegregated with Al tolerance. In 2 populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminium tolerance was not associated with a particular coding allele for ALMT1, but was significantly correlated with the relative level of ALMT1 expression. These findings suggest that the Al tolerance in a diverse range of wheat genotypes is primarily conditioned by ALMT1.Key words: aluminum, tolerance, genetic marker, Triticum aestivum, QTL, deletion mapping.
Variability in Triticum and Aegilops species for seed characteristics
Authors: Waines J. G. , Ehdaie B. , Barnhart D.
Published: April 2011

Seventy-seven accessions of 2x, 4x, and 6x wild, primitive, and modern domesticates of wheat, Aegilops longissima, and Ae. tauschii were assayed for seed weight, protein content, and lysine content. In general, there was more variation between taxa than within taxa in 2x and 4x but not in 6x for seed weight and protein content. Within taxa variation was greater than that between taxa for lysine content. The primitive and wild wheat and Aegilops accessions had significantly lower seed weight than modern 4x and 6x wheats. Mean 1000 seed weight varied from 6.90 to 42.62 g over all accessions. The modern 4x and 6x wheats and Ae. tauschii had lower mean protein and lysine contents than the primitive and wild wheats and Ae. longissima. Mean protein and lysine content for species ranged from 17 to 29% and from 3.9 to 6.2 μg/mg, respectively. Within species variation for lysine content was was highest in T. turgidum var. dicoccoides, T. monococcum var. boeoticum, and T. turgidum var. durum. The lowest mean lysine content belonged to Ae. tauschii, T. aestivum var. aestivum, T. aestivum var. spelta, and T. turgidum var. durum. Correlation between seed weight and protein content was not significant for any species. A significant negative correlation between seed weight and lysine content was found in T. aestivum var. aestivum, T. timopheevii var. araraticum, T. monococcum var. monococcum, and T. monococcum var. boeticum. A significant positive correlation between protein and lysine content was observed in T. aestivum var. aestivum. Lines with high adjusted lysine content/protein were identified in all species except in T. aestivum var. spelta and Ae. tauschii.

Key words: seed characteristics, Triticum, Aegilops.
A test for equilocality of supernumerary heterochromatin distribution in grasshoppers
Authors: Cabrero J. , Alché J. D. , Camacho J. P. M.
Published: April 2011

The presence of extra segments in four or more nonhomologous chromosome pairs led us to test the applicability of the principle of the principle of equilocality of heterochromatin distribution to supernumerary heterochromatin. In Chorthippus brunneus, which carries extra segments on all chromosomes except the L3, the 13 heterochromatic variants occupy all possible locations with 3 proximal, 5 interstitial, and 5 distal. This indicates that equilocality does not seem to apply to the supernumerary heterochromatin in this species. On the other hand, the four extra segments found in Chorthippus parallelus and five of the seven extra heterochromatic segments found in Chorthippus binotatus are all located distally on the M5–S8 chromosomes. Thus for these groups of chromosomes the extra heterochromatic segments do appear to show a tendency for an equilocal distribution.

Key words: Chorthippus, heterochromatin.
Genomic rearrangements in maize induced by tissue culture
Authors: Lee Michael , Phillips R. L.
Published: April 2011

Chromosomal instability is a common occurrence in plant tissue cultures and has been documented in plants regenerated from several genotypes of maize (Zea mays L.) tissue cultures. The objective of this research was to evaluate the frequency and types of chromosomal aberrations in regenerated plants of an Oh43–A188 genetic background, which had not been examined previously for chromosome stability in culture. Organogenic callus cultures were intitated from immature embryos of F2 plants for several Oh43 ms isoline × A188 crosses. The chromosome constitution of 267 plants was investigated through meiotic analysis of plants regenerated either 3 to 4 or 8 to 9 months after culture initiation. No abnormalities were detected in 78 plants regenerated during the first period. During the second period, however, 91 of the 189 plants were cytologically abnormal. One hundred and eight aberrations were detected and most (96%) involved changes in chromosome structure such as interchanges (42%), deficiencies (35%), and heteromorphic pairs (19%). All deficiencies were intercalary. Also, most (51%) interchanges involved chromosome 6. An association between male-sterility factors and chromosome instability was not observed. Breakpoints were primarily on chromosome arms containing large blocks of heterochromatin such as knobs. Several abnormal plants from the same culture appeared to contain identical aberrations indicating the aberrations may trace to a single event. A hypothesis for the involvement of heterochromatin in chromosome breakage during in vitro culture is supported.

Key words: Zea mays L., tissue culture, somaclonal variation, chromosome breakage, heterochromatin.
Host–parasite genome relationships in Acridid grasshoppers. II. Patterns of variation in the plasmids of gut bacteria of Caledia captiva and Locusta migratoria
Authors: Colgan D. J. , Willcocks D. A.
Published: April 2011

Plasmid preparations were made from 110 isolates of Enterobacter cloacae taken from the guts of members of the Caledia captiva complex of grasshoppers to ascertain whether a relationship exists between these extrachromosomal elements and taxonomic variation in the grasshoppers themselves. Fifty-two plasmids, distinguishable by mobility or restriction fragment pattern differences, were identified. Thirty-seven of these were similar in size. Five plasmids were nick translated and used to probe Southern blots. Only three instances of cross homology with another plasmid were found, implying a very high level of sequence diversity in the samples. No explanation of the size uniformity and sequence diversity of the plasmids is entirely satisfactory but it appears most likely that the variation is maintained to serve a variety of adaptive functions. No plasmid was found in grasshoppers of more than one taxon of C. captiva. This may be due to geographical limitations on the distribution of plasmids. If this is so, it remains possible that there is an association of one or more plasmids with taxonomic divergence in this grasshopper complex. Plasmid preparations were also made from 68 bacterial isolates (predominantly E. aerogenes) from laboratory-reared Locusta migratoria and from 72 isolates from other acridid grasshoppers. Plasmids of the size general in C. captiva were discovered in most of these isolates. Some smaller plasmids were also found. As judged by restriction endonuclease digests and Southern blotting, plasmid diversity is much less in this sample of L. migratoria bacteria than in the field-collected C. captiva. The plasmids reported in this paper may be considered as possible vectors for use in the genetic control of locusts.

Key words: host–parasite, plasmids, grasshoppers, Enterobacter.
Permanent odd polyploidy in a grass (Andropogon ternatus)
Authors: Norrmann Guillermo A. , Quarín Camilo L.
Published: April 2011

Andropogon ternatus is a triploid species (2n = 3x = 30) with a striking process of microsporogenesis that leads to the formation of two kinds of pollen grains. One-half of the grains carry only one 10-chromosome genome and the other half carry two genomes. After the first meiotic division in the megaspore mother cell, the micropylar daughter cell always has two nuclei, each with 10 chromosomes (genomes S and T); the chalazal daugher cell has one 10-chromosome set (genome S) and undergoes the second meiotic division giving rise to two megaspores; the one closer to the chalaza is the functional megaspore, while the other degenerates. The two-nucleate micropylar daughter cell remains undivided and then degenerates. Thus, the embryo sac always develops from a megaspore with 10 chromosomes (genome S). The results of interspecific crosses with a taxonomically related diploid species (A. selloanus) as well as the study of pollen grain development suggest that the grains carrying nuclei with 20 chromosomes (genomes ST) are functional in the fertilization process, while those with 10-chromosome nuclei seem to be ineffective. Therefore, A. ternatus is a sexual triploid that accomplishes the stability of its odd polyploid level by transmitting one genome through the egg cell and two genomes through the sperm nucleus. This is the first report of permanent odd polyploidy for a species of the monocotyledons.

Key words: Gramineae, Andropogon ternatus, odd polyploidy, female meiosis, breeding systems.
Genetic study of glutamate oxaloacetic transaminase in soybean
Authors: Kiang Y. T. , Chiang Y. C. , Bult C. J.
Published: April 2011

A four-band electrophoretic zymogram for glutamate oxaloacetic transaminase (GOT, EC 2.6.1.1) is observed in mature soybean (Glycine max (L.) Merr.) seed. The zymogram pattern has a cluster of three bands (Rf's of 0.26, 0.29, and 0.32) and a single band. No variation was observed in the cluster of three bands. The fourth band has three variants that are controlled by a single locus, Got, with three alleles. They are designated as Got-a (Rf = 0.52), Got-b (Rf = 0.54), and Got-c (Rf = 0.57), respectively. In the wild soybean, G. soja (Sieb. & Zucc), the Got-a allele was found in four accessions from South Korea (PI 407.194, PI 407.269, PI 407.270, and PI 504.286; frequency 4/187). The Got-c allele also was found in four G. soja accessions from South Korea (PI 407.184, PI 407.207, PI 407.222, and PI 407.225; frequency 4/187). All other G. soja accessions examined carry the Got-b allele (frequency 179/187). All the G. max cultivars and accessions examined are homozygous for the Got-b allele (frequency 320/321) except for cv. Hardee, in which two seeds were homozygous for the Got-c allele. Linkage tests show that the Got locus segregates independently of the Ap, Dia1, Dia2, Idh1, Pgd2, and W1 loci. No linkage was detected when isozyme loci other than Got were tested (Am3–W1, Ap–W1, Dia1–W1, Pgd–W1, Dia1–Idh1, Pgd2–Idh1, and Ap–Idh2).

Key words: soybean, glutamate oxaloacetic transaminase, GOT, electrophoresis, isozymes.
Genetic linkage of the Adh1 and W1 loci in soybeans
Authors: Kiang Y. T. , Chiang Y. C.
Published: April 2011

Four crosses were made among seven soybean cultivars for determining possible linkage between Adh1 and W1 loci. An examination of F2 seed indicated that these loci are linked with a recombination value of 20.6 ± 1.2%. These loci are located in linkage group 8.

Key words: soybean linkage, isozymes, alcohol dehydrogenase (Adh1), color locus (W1), Glycine max.
Chromosome instability in wheat plants regenerated from suspension culture
Authors: Fedak George , Armstrong K. C. , Handyside R. J.
Published: April 2011

Plants of Triticum aestivum cv. Chinese Spring were regenerated from 30 calli obtained from suspension cultures. All four plants showed abnormal meiotic chromosome behaviour relative to the control. The average meiotic configuration over all plants was 1.55 I + 18.16 II + 0.30 III + 0.82 IV. In addition, an isochromosome was frequently observed in cells of all plants, which was indicative of centromeric breaks.

Key words: culture (suspension), wheat, chromosome instability.
Phylogenetic relationships in the evolution of Solanum scabrum
Authors: Ganapathi A. , Rao G. R.
Published: April 2011

Several cross-pollinations were made between Solanum scabrum (2n = 6x = 72) and S. nigrum (2n = 6x = 72), S. americanum (2n = 2x = 24), and a C3 amphiploid of the cross S. villosum (2n = 4x = 48) × S. americanum (2n = 2x = 24) with a view to determine their phyletic relationship. It was found that the crosses between S. nigrum and S. scabrum, and S. scabrum and a "big-fruited form" were accomplished easily, whereas the cross S. scabrum × S. americanum was successful only when S. scabrum, the higher chromosomal form, was used as the maternal parent. The hybrids (F1) exhibited moderate pollen fertility and vigorous growth, and set fruits and seeds abundantly, even though meiotic abnormalities were encountered in most of the pollen mother cells. From the chromosome pairing behaviour in the hybrids, it is concluded that S. americanum is the diploid ancestor of hexaploid S. scabrum and S. nigrum. The latter two species might have evolved from the sterile triploid hybrids of S. villosum × S. americanum by spontaneous amphiploidy.

Key words: Solanum, phylogenetics. polyploidy.
Genetics and cytogenetics of resistance to Puccinia graminis tritici in three South African wheats
Authors: Singh R. P. , McIntosh R. A.
Published: April 2011

Resistance to Puccinia graminis tritici pathotype 34-1, 2, 3, 4, 5, 6, 7 in a South African wheat, W3757, was attributed to a dominant gene located in an alien (possibly Agropyron elongatum) chromosome that had substituted with wheat chromosome 6D. This gene, designated SrB, and present in two additional South African wheats, W3758 and W3759, conferred a high level of adult plant resistance to pathotypes used for field assessments. Because SrB is apparently different from other genes transferred from A. elongatum to wheat, its possible exploitation following translocation to a wheat chromosome seems warranted.

Key words: Puccinia graminis tritici, Triticum aestivum, wheat cytogenetics, rust resistance, alien substitution line.
Idiograms of horse chromosomes at prometaphase, early metaphase, and midmetaphase after R-banding by BrdU incorporation followed by the fluorochrome–photolysis–Giemsa technique
Authors: Romagnano April , Drouin Régen , Richer Claude-Lise
Published: April 2011

We present three idiograms of equine chromosomes, R-banded after BrdU incorporation and stained by the fluorochrome–photolysis–Giemsa technique. The haploid set of prometaphasic chromosomes shows 591 bands (range 7–38 per chromosome), the early metaphasic set 404 (range 5–26), and the midmetaphasic set 272 (range 3–18). Following cell synchronization with thymidine, more than twice as many R-bands were revealed on the resulting prometaphasic chromosomes, making possible the establishment of a very accurate and characteristic representation of this banding pattern in the domestic horse.

Key words: chromosome banding, horse, R-bands, prometaphase.
Somatic immunoglobulin sequence divergence and its implications for studies of evolutionary divergence
Authors: Golding G. Brian
Published: April 2011

The divergence of immunoglobulin genes due to somatic mutation provides a natural example of DNA sequence divergence. This divergence was examined to gain insight into the processes of evolution and the determinants of the variance-to-mean ratio of sequence divergence. Normally, this ratio is found to be larger than expected (1.0 under Poisson assumptions) for the evolutionary divergence or most genes. Although not significantly less than one, all seven groups of immunoglobulin amino acid sequences have ratios smaller than expected, contrary to the evolutionary pattern generally observed. The substitutions in the immunoglobulin genes appear to be highly nonrandom and an excess of parallel changes (the major nonrandom feature of these mutations) is shown to cause smaller ratios. Because convergent or parallel mutations are often observed in the evolutionary divergence of genes, this suggests that forces causing the large observed ratios may actually have to be more powerful than previously expected. Further, since selection is one of the likely causes of parallel mutations, it should be noted that selection could significantly decrease the variance-to-mean ratio. The high frequency of parallel mutations and their resulting effects, as observed in the immunoglobulin genes, suggest that only poor inferences of sequence divergence can be made without actual knowledge of the ancestral sequence.Key words: molecular evolution, parallel mutations, neutral allele theory, sequence divergence, immunoglobulin, somatic mutations.