Physiological and genetic mapping study of tolerance to root-knot nematode in rice

The root-knot nematode Meloidogyne graminicola is an obligate biotrophic parasite and a major pest of rice (Oryza sativa) for which resistant varieties are not currently available. Quantitative trait loci (QTLs) for partial resistance to M. graminicola were identified using a mapping population based on two rice varieties, Bala x Azucena. Experiments were carried out to investigate the interactions between M. graminicola and these two varieties in terms of nematode establishment, reproduction and effect on rice yield. Nematode establishment was also assessed in the mapping population. Meloidogyne graminicola consistently caused more galling and had higher reproductive success in Azucena than in Bala. M. graminicola did not significantly reduce yield in Bala, but caused a yield reduction of almost half in Azucena, suggesting that the partial resistance to nematode establishment was related to nematode tolerance. A total of six significant or putative QTLs for nematode tolerance were detected. For two of the QTLs detected, Azucena was the donor of the tolerance alleles, suggesting it may be possible to breed plants with greater tolerance than Bala.     

Analysis of polymorphic microsatellites within the bovine and ovine prion protein (PRNP) genes

Twenty-four microsatellite sites with at least three repeats were found in the bovine prion protein gene (PRNP) and 23 in the ovine PRNP gene. Eight microsatellite sites were polymorphic in cattle and six in sheep with up to 10 alleles per site. In many cases allelic DNA fragments had variants in microsatellite sites and in flanking regions. Distances between microsatellite sites in eight genes from cattle and sheep occurred on average every 0.9 kb. The numerous polymorphic microsatellite sites will improve analysis of phylogenetic origin of different PRNP alleles and trait association studies for bovine spongiform encephalopathy (BSE) and scrapie.     

Growth period QTL-allele constitution of global soybeans and its differential evolution changes in geographic adaptation versus maturity group extension

Soybean (Glycine max (L.) Merr.) has been disseminated globally as a photoperiod/temperature-sensitive crop with extremely diverse days to flowering (DTF) and days to maturity (DTM) values. A population with 371 global varieties covering 13 geographic regions and 13 maturity groups (MGs) was analyzed for its DTF and DTM QTL-allele constitution using restricted two-stage multi-locus genome-wide association study (RTM-GWAS). Genotypes with 20 701 genome-wide SNPLDBs (single-nucleotide polymorphism linkage disequilibrium blocks) containing 55 404 haplotypes were observed, and 52 DTF QTLs and 59 DTM QTLs (including 29 and 21 new ones) with 241 and 246 alleles (two to 13 per locus) were detected, explaining 84.8% and 74.4% of the phenotypic variance, respectively. The QTL-allele matrix characterized with all QTL-allele information of each variety in the global population was established and subsequently separated into geographic and MG set submatrices. Direct comparisons among them revealed that the genetic adaptation from the origin to geographic subpopulations was characterized by new allele/new locus emergence (mutation) but little allele exclusion (selection), while that from the primary MG set to emerged early and late MG sets was characterized by allele exclusion without allele emergence. The evolutionary changes involved mainly 72 DTF and 71 DTM alleles on 28 respective loci, 10–12 loci each with three to six alleles being most active. Further recombination potential for faster maturation (12–21 days) or slower maturation (14–56 days) supported allele convergence (recombination) as a constant genetic factor in addition to migration (inheritance). From the QTLs, 44 DTF and 36 DTM candidate genes were annotated and grouped respectively into nine biological processes, indicating multi-functional DTF/DTM genes are involved in a complex gene network. In summary, we identified QTL-alleles relatively thoroughly using RTM-GWAS for direct matrix comparisons and subsequent analysis.     

Selection on domestication traits and quantitative trait loci in crop–wild sunflower hybrids

The strength and extent of gene flow from crops into wild populations depends, in part, on the fitness of the crop alleles, as well as that of alleles at linked loci. Interest in crop–wild gene flow has increased with the advent of transgenic plants, but nontransgenic crop–wild hybrids can provide case studies to understand the factors influencing introgression, provided that the genetic architecture and the fitness effects of loci are known. This study used recombinant inbred lines (RILs) generated from a cross between crop and wild sunflowers to assess selection on domestication traits and quantitative trait loci (QTL) in two contrasting environments, in Indiana and Nebraska, USA. Only a small fraction of plants (9%) produced seed in Nebraska, due to adverse weather conditions, while the majority of plants (79%) in Indiana reproduced. Phenotypic selection analysis found that a mixture of crop and wild traits were favoured in Indiana (i.e. had significant selection gradients), including larger leaves, increased floral longevity, larger disk diameter, reduced ray flower size and smaller achene (seed) mass. Selection favouring early flowering was detected in Nebraska. QTLs for fitness were found at the end of linkage groups six (LG6) and nine (LG9) in both field sites, each explaining 11–12% of the total variation. Crop alleles were favoured on LG9, but wild alleles were favoured on LG6. QTLs for numerous domestication traits overlapped with the fitness QTLs, including flowering date, achene mass, head number, and disk diameter. It remains to be seen if these QTL clusters are the product of multiple linked genes, or individual genes with pleiotropic effects. These results indicate that crop trait values and alleles may sometimes be favoured in a noncrop environment and across broad geographical regions.     

Analysis of mechanisms regulating the expression of parental alleles at the GPD locus in mule erythrocytes

Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) was examined by 13% starch gel electrophoresis in 74 mules (42 females and 32 males), 35 donkeys, and ten horses. The quantitative expression of the parental alleles at the Gpd locus varies greatly in female mules from the hemizygous expression of the maternal allele to that of the paternal. The data obtained indicate that the X chromosomes are randomly inactivated in female mules. No selective advantage of a cell population with a maternally (or paternally) derived X active was found in female mule erythrocytes. It is suggested that the phenotypic variability in the expression of the parental Gpd alleles is related to the random proportions established between cells having either a maternal or paternal X active in an initiator (stem) cell group giving rise to erythroid tissue. Initiator cell numbers estimated for erythroid tissue (six or seven) are close to those reported for human females and intergeneric fox hybrids. These numbers may vary depending on the duration of the time of determination and the division rate of initiator cells at determination.     

Characterization of new microsatellite markers in mung bean,Vigna radiata (L.)

The present work reports the isolation and characterization of new polymorphic microsatellites in mung bean (Vigna radiata L.). Of 93 designed primer pairs, seven were found to amplify polymorphic microsatellite loci, which were then characterized using 34 mung bean accessions. The number of alleles ranged from two to five alleles per locus with an average of three alleles. Observed and expected heterozygosity values ranged from 0 to 0.088 and from 0.275 to 0.683, respectively. All seven loci showed significant deviations from Hardy–Weinberg equilibrium, whereas only one pairwise combination (GBssr‐MB77 and GBssr‐MB91) exhibited significant departure from linkage disequilibrium. These newly developed markers are currently being utilized for diversity assessment within the mung bean germplasm collection of the Korean Gene Bank.     

Identification of Hordeum spontaneum QTL alleles improving field performance of barley grown under rainfed conditions

Advanced backcross QTL (AB-QTL) analysis was deployed to identify allelic variation in wild barley (Hordeum vulgare ssp. spontaneum) of value in the improvement of grain yield and other agronomically important traits in barley (Hordeum vulgare ssp. vulgare) grown under conditions of water deficit in Mediterranean countries. A population of 123 double haploid (DH) lines obtained from BC₁F₂ plants derived from a cross between Barke (European two-row cultivar) and HOR11508 (wild barley accession) were tested in replicated field trials, under varying conditions of water availability in Italy, Morocco and Tunisia, for seven quantitative traits. Significant QTL effects at one (P 0.001) or more trial sites (P 0.01) were identified for all traits. At 42 (52%) of the 80 putative QTLs identified, the allele increasing a “traits' value” was contributed by H. spontaneum. For example, though the majority (67%) of QTL alleles increasing grain yield were contributed by H. vulgare, H. spontaneum contributed the alleles increasing grain yield at six regions on chromosomes 2H, 3H, 5H and 7H. Among them, two QTLs (associated to Bmac0093 on chromosome 2H and to Bmac0684 on chromosome 5H) were identified in all three locations and had the highest additive effects. The present study shows the validity of deploying AB-QTL analysis for identifying favourable QTL alleles from wild germplasm and indicates its potential as an enhancement strategy for the genetic improvement of cultivars better adapted to drought-prone environments.     

Developmental consequences of mutations in the 84B alpha-tubulin gene of Drosophila melanogaster

Developmental effects of six mutations in the gene encoding the majority of alpha-tubulin in all tissues at all stages of Drosophila melanogaster development have been examined. All six alleles produce at least partially stable alpha 84B protein. In genetic assays, two of these alleles approximate the null condition. The other four alleles appear to form a graded series of hypomorphs. The two most severe alleles produce a semidominant maternal-effect polyphasic lethality, plus a predominantly larval recessive zygotic lethality. Clonal analysis of one of these alleles suggests it is a cell lethal. Worsening of the lethal phenotype (negative complementation) occurs in most interallelic heterozygotes involving these two mutations. As hemizygotes, the other four alleles are predominantly larval/pupal lethals. Partial complementation is achieved by most interallelic heterozygotes involving these four alleles. Phenotypic defects associated with the six tubulin mutation include disrupted embryos, pseudopupae, pharate adults with defects in various cuticular pattern elements, pharate adults with retarded head development, adults with leg tremors and extremely short life spans, and viable but sterile adults with bristle defects.     

COMPLEMENTARY SEX DETERMINATION IN HYMENOPTERAN PARASITOIDS AND ITS IMPLICATIONS FOR BIOLOGICAL CONTROL

Abstract In haplodiploid Hymenoptera, unfertilized eggs produce haploid males while fertilized eggs lead to diploid females under most circumstances. Diploid males can also be produced from fertilization under a system of sex determination known as complementary sex determination (CSD). Under single-locus CSD, sex is determined by multiple alleles at a single sex locus. Individuals heterozygous at the sex locus are female while hemizygous and homozygous individuals develop as haploid and diploid males, respectively. In multiple-locus CSD, two or more loci, each with two or more alleles, determine sex. Diploid individuals are female if one or more sex loci are heterozygous, while a diploid is male only if homozygous at all sex loci. Diploid males are known to occur in 43 hymenopteran species and single-locus CSD has been demonstrated in 22 of these species. Diploid males are either developmentally inviable or sterile, so their production constitutes a genetic load. Because diploid male production is more likely under inbreeding, CSD is a form of inbreeding depression. It is crucial to preserve the diversity of sex alleles and reduce the loss of genetic variation in biological control. In the parasitoid species with single-locus CSD, certain precautionary procedures can prevent negative effects of single-locus CSD on biological control.     

蜜蜂（Apis）苹果酸脱氢酶同工酶的研究进展

苹果酸脱氢酶（MDH）是糖代谢中重要的酶。在西方蜜蜂（Apis mellifera L.）中,MDH分为3个区带MDHⅠ、MDHⅡ和MDH Ⅲ。不同级型和不同发育阶段,MDHⅠ和MDH Ⅲ变化不大;MDHⅡ呈现多态现象,由a、b、c3个等位基因编码。东方蜜蜂（A.cerana F.）的MDH由S、F两个等位基因编码,也有报道它是单态性的。MDH在西方蜜蜂研究中应用较多,主要有处女王交配次数;蜂群中的劳动分工;蜜蜂种群遗传组成分析等。MDH和分子生物学的结合研究势必将推动蜜蜂研究的深入和发展。 Research Progress in Malate Dehydrogenase(MDH) of Honeybees LIU Yan-he1,ZHANG Chuan-xi1,XU Bao-hua2,3,CHEN Sheng-lu1 1.Institute of Applied Entomology,Zhejiang University,Hangzhou 310029,China; 2.College of Animal Science,Zhejiang University,Hangzhou 310029,China; 3.College of Animal Sciences,Shandong Agricaltural University,Taian 271018,China Abstract:Malate dehydrogenase(MDH) is an important enzyme in glycometabolism.MDH of Apis mellifera showed three enzyme active zones,MDHⅠ,MDHⅡand MDHⅢ.MDHⅠand MDHⅢ maintained relative stability in different castes and developmental phases,but MDHⅡwas polymorphic,and controlled by three alleles,a,b and c.MDH of Apis cerana was coded by S and F alleles,but some authors reported it is monomorphic.MDH was applied to the studies of A.mellifera,which included several aspects as follows:the number of queen matings,labor division in honeybee societies,the analysis of genetic constitution in honeybee populations and so on.The combination of both MDH and molecular biology will certainly promote honeybee studies. Key words：honeybees;malate dehydrogenase(MDH)     

Breed differences in frequency of BoLA specificities*

A total of 675 cattle of five purebred and one crossbred group were tested for lymphocyte antigens. The purebred animals represented progeny of 107 sires. Lymphocytotoxicity sera obtained from parous cows were used to detect six antigens which are controlled by codominant alleles at the BoLA-TxA locus. Gene frequencies for the six alleles varied within breeds and large differences were observed between breeds for a given allele.     

Associations between marker genotypes, halothane reaction, CC activity and meat quality characters in a sample of German Landrace pigs

Routine blood typing of German Landrace pedigree populations and an earlier study revealed very low frequencies of the favourable alleles at the marker loci Phi, Pgd and H . The hypothesis was that in this population the whole linkage group of favourable alleles at the halothane and neighbouring marker loci may have been lost as a consequence of intense selection for leanness and type. The present study of 1050 German Landrace pigs at the Relliehausen experimental station, where some effort has been made to maintain a higher frequency of the favourable alleles Phi^A (0.48), H- (0.43) and Pgd^A (0.70) gave quite different results.
The frequency of halothane-positive pigs found by using a severe test was only 30 %. Only 5.4 %, 8.8 %, 13.4 % and 13.9 7% of animals with Phi^AIA, H^-I-, Pgd^A/A and Phi^A/B genotypes respectively were halothane-positive. Forty to sixty per cent of pigs with these marker genotypes could therefore be expected to be homozygous halothane-negative ( N/N ) animals. Creatine kinase activity and three selected meat quality characters showed highly significant differences between the A/A and the B/B genotypes for the marker loci Phi and Pgd , with the heterozygotes being intermediate. These differences are greater than those observed between halothane-negative and halothane-positive phenotypes. The only other consistently superior marker genotype in this population was the H blood group genotype H -^I- . In contrast to findings from Sweden and Switzerland, the postalbumin locus Po2 and the suppressor locus S for the A-O blood groups did not exhibit useful marker qualities.
It is concluded that in the German Landrace the marker loci Phi, Pgd and H could also be helpful in breeding homozygous halothane-negative pigs with distinctly better meat quality characteristics.     

Trinucleotide repeat microsatellite markers for black poplar (Populus nigra L.)

Using an enrichment procedure, we have cloned microsatellite repeats from black poplar (Populus nigra L.) and developed primers for microsatellite marker analysis. Ten primer pairs, mostly for trinucleotide repeats, produced polymorphic fragments in P. nigra. Some of them also showed amplification in other poplar species. (P. deltoides, P. tricocarpa, P. tremula, P. tremuloides, P. candicans, P. lasiocarpa). The best six loci were tested on 23 P. nigra genotypes collected across Europe. The microsatellites produced up to 12 alleles per locus in this set, with observed heterozygosity between 0.32 and 0.91.     

The locus encoding an oligomorphic family of <Emphasis Type="Italic">MHC-A</Emphasis> alleles (<Emphasis Type="Italic">Mane-A</Emphasis>*06/<Emphasis Type="Italic">Mamu-A</Emphasis>*05) is present at high frequency in several macaque species

Several macaques species are used for HIV pathogenesis and vaccine studies, and the characterization of their major histocompatibility complex (MHC) class I genes is required to rigorously evaluate the cellular immune responses induced after immunization and/or infection. In this study, we demonstrate that the gene expressing the Mane-A*06 allele of pig-tailed macaques is an orthologue of the locus encoding the Mamu-A*05 allele family in rhesus macaques. Analysis of the distribution of this locus in a cohort of 63 pig-tailed macaques revealed that it encodes an oligomorphic family of alleles, highly prevalent (90%) in the pig-tailed macaque population. Similarly, this locus was very frequently found (62%) in a cohort of 80 Indian rhesus macaques. An orthologous gene was also detected in cynomolgus monkeys originating from four different geographical locations, but was absent in two African monkey species. Expression analysis in pig-tailed macaques revealed that the Mane-A*06 alleles encoded by this locus are transcribed at 10- to 20-fold lower levels than other MHC-A alleles (Mane-A*03 or Mane-A*10). Despite their conservation and high prevalence among Asian macaque species, the alleles of the Mane-A*06 family and, by extension their orthologues in rhesus and cynomolgus monkeys, may only modestly contribute to cellular immune responses in macaques because of their low level of expression.     

Breed differences in frequency of BoLA specificities

A total of 675 cattle of five purebred and one crossbred group were tested for lymphocyte antigens. The purebred animals represented progeny of 107 sires. Lymphocytotoxicity sera obtained from parous cows were used to detect six antigens which are controlled by codominant alleles at the BoLA-TxA locus. Gene frequencies for the six alleles varied within breeds and large differences were observed between breeds for a given allele.