QTL controlling partial resistance to Stagonospora nodorum leaf blotch in winter wheat cultivar Alba

Stagonospora nodorum blotch (SNB) is an important foliar and glume disease in cereals. Inheritance of SNB resistance in wheat appears quantitative. The development of partially resistant cultivars seems to be the only effective way to combat the pathogen. Partial resistance components like length of incubation period (INC), disease severity (DIS) and length of latent period (LAT) were evaluated on a population of doubled-haploids derived from a cross between the partially resistant cultivar Alba and the susceptible cultivar Begra. Experiments were conducted in controlled environments and the fifth leaf was examined. Molecular analyses were based on bulked segregant analyses (BSA) and screening with 240 microsatellites DNA markers. The QTL analysis revealed QTL on chromosome 6AL (designated as QSnl.ihar-6A) and putative QTL on chromosome 6D. The QSnl.ihar-6A accounted for 36% of the phenotypic variance for DIS and 14% for INC. The putative QTL accounted for 10% of the variability in INC and 8% of DIS components of SNB resistance.     

Mapping antixenosis genes on chromosome 6A of wheat to greenbug and to a new biotype of Russian wheat aphid

Greenbug and Russian wheat aphid (RWA) are two devastating pests of wheat. The first has a long history of new biotype emergence and recently. RWA resistance has just started to break down. Thus, it is necessary to find new sources of resistance that will broaden the genetic base against these pests in wheat. Seventy‐five doubled haploid recombinant (DHR) lines for chromosome 6A from the F₁ of the cross between “Chinese Spring’ and the “Chinese Spring (Synthetic 6A) (Triticum dicoccoides × Aegilops tauschii)” substitution line were used as a mapping population for testing resistance to greenbug biotype C and to a new strain of RWA that appeared in Argentina in 2003. A quantitative trait locus (QTL) (br antixenosis to greenbug was significantly associated with the marker loci Xgwm1009 and Xgwm1185 located in the centromere region of chromosome 6A. Another QTL which accounted for most of the antixenosis against RWA was associated with the marker loci Xgwm1291 and Xiinni1150. both located on the long arm of chromosome 6A. This is the first report of greenbug and RWA resistance genes located on chromosome 6A. It is also the first report of antixenosis against the new strain of RWA. As most of the RWA resistance genes present in released cultivars have been located in [he D‐ genome, it is highly desirable to find new sources in other genomes to combine the existing resistance genes with new sources.     

Socio-spatial organization reveals paternity and low kinship in the Honduran white bat (Ectophylla alba) in Costa Rica

Ectophylla alba is a tent-making bat that roosts in mixed-sex clusters comprising adults and offspring. Our goal was to determine the genetic identity of individuals belonging to different roosting groups. We tested the hypothesis of kin selection as a major force structuring group composition. We used 9 microsatellites designed for E. alba to determine the genetic identity and probability of parentage of individuals. We analyzed parentage and kinship using the software ML-Relate, GenAIEx, and Cervus. The obtained relationship probabilities (0.5) revealed a clear maternal relationship between female adults and offspring with allele compatibility, and at least 5 relationships between male adults and pups. We found a low degree of relatedness within roosting groups. Between roosting groups at different sites, the mean probability of a half-sibling relationship ranged from 0.214 to 0.244 and, for full-sibling relationship, from 0.383 to 0.553. Genetically, adult individuals were poorly related within clusters, and kinship as an evolutionary force could not explain group membership.     

An investigation of the possible causes for the loss of productivity in genetically improved farmed tilapia strain in Fiji: inbreeding versus wild stock introgression

Four microsatellite markers and a mitochondrial DNA (mtDNA) fragment were used to investigate two possible explanations for a reported decline in productivity of genetically improved farmed tilapia (GIFT) in Fiji: (i) a decline in genetic diversity (GD) and (ii) genetic introgression from feral tilapia populations. Genetic diversity was estimated using θ and allelic richness, while Bayesian clustering was used to assign individuals to genetic groups (K=2 or 3) to test for introgression. Differentiation among groups was estimated using F_ST analysis. Results indicate that genetic diversity had declined compared with a GIFT reference stock from WorldFish Centre, while there was little evidence for introgression from feral tilapia populations. Loss of genetic diversity most probably resulted from practices that have not actively managed genetic resources in the hatchery. While GIFT is considered to be an improved line of Nile tilapia (Oreochromis niloticus), mtDNA analysis here revealed haplotypes assigned previously to three discrete Oreochromis species (O. niloticus, Oreochromis mossambicus and Oreochromis aureus) in both the Fijian strain and the WorldFish Centre strain. Possible sources for the three divergent lineages are discussed. Results have implications for the management and future expansion of the tilapia culture industry in Fiji as well as in other Pacific island nations.     

Genetic variability of six indigenous goat breeds using major histocompatibility complex-associated microsatellite markers

The present study aimed at analyzing the genetic variability of indigenous goat breeds (Capra hircus) using the MHC-associated microsatellite markers BF1, BM1818, BM1258, DYMS1, and SMHCC1. The following breeds were included: Chinese Xuhuai, Indian Changthangi and Pashmina, Kenyan Small East African (SEA) and Galla, and Albanian Vendi. To examine genetic variability, the levels of heterozigosity, degrees of inbreeding, and genetic differences among the breeds were analyzed. The mean number of alleles ranged from nine in the Galla to 14.5 in the Vendi breed. The mean observed heterozygosity and mean expected heterozygosity varied from 0.483 in the Vendi to 0.577 in the Galla breed, and from 0.767 in the SEA to 0.879 in the Vendi breed, respectively. Significant loss of heterozygosity (p < 0.01) indicated that these loci were not in Hardy-Weinberg equilibrium. The mean F_IS values ranged from 0.3299 in the SEA to 0.4605 in the Vendi breed with a mean value of 0.3623 in all breeds (p < 0.001). Analysis of molecular variance indicated that 7.14% and 4.74% genetic variation existed among the different breeds and geographic groups, whereas 92.86% and 95.26% existed in the breeds and the geographic groups, respectively (p < 0.001). The microsatellite marker analysis disclosed a high degree of genetic polymorphism. Loss of heterozygosity could be due to genetic drift and endogamy. The genetic variation among populations and geographic groups does not indicate a correlation of genetic differences with geographic distance.     

Application of microsatellites from maize to teosinte and other relatives of maize

Teosinte comprises different Zea species (Zea mays, Zea diploperennis, Zea perennis, Zea luxurians) that can be crossed with cultivated maize (Z. mays ssp. mays). Nine microsatellites from maize were applied to different teosinte species in order to evaluate their usefulness in markerbased exploitation of these genetic resources. The same microsatellites were tested with rye, barley, and sorghum as potential molecular markers for these species. Almost all microsatellite × teosinte combinations yielded polymerase chain reaction (PCR) fragments in the range of cultivated maize. Using an F₂ population of a cross between maize inbred A188 and an individual of Zea mays ssp. mexicana, amplification products for maize and teosinte originated from the same genomic location for each of nine microsatellites investigated. PCR fragments of reduced intensity were generally obtained by applying maize microsatellites to rye, barley and sorghum. Polymorphisms among accessions within teosinte (sub)species occurred frequently. In contrast, no polymorphisms were obtained within rye, barley, and sorghum. Hence, application of maize microsatellites to teosinte for fingerprinting or marker-assisted introgression of genomic regions from teosinte into cultivated maize appears promising.     

Assessment of genetic diversity of cultivated chickpea using microsatellite-derived RFLP markers: Implications for origin

Restriction fragment length polymorphism (RFLP) analysis was performed on 30 accessions of cultivated chickpea (Cicer arietinum L.) collected from 11 different countries representing the Near East, Central Asian and Hindustani regions. A synthetic digoxygenated oligonucleotide (GATA)₄ complementary to a microsatellite DNA sequence was used as a probe. The results revealed that simple repetitive sequences are abundant and polymorphic in the chickpea genome. The fragments detected were used lo estimate the genetic diversity within accessions and a similarity index between the genotypes of the accessions. The genetic distance data were used to construct a dendrogram depicting genetic relationships among the different accessions. The results indicate that the greatest genetic diversity occurs in Pakistan, Iraq, Afghanistan, south-east Russia, Turkey and Lebanon. Lower genetic diversity was found in Iran, India, Syria, Jordan and Palestine, Based on DNA markers, it is concluded that there are three centres of diversity for chickpea: Pakistan-Afghanistan. Iraq Turkey and Lebanon. India, which was previously considered as a secondary center of diversity for chickpea, showed lower diversity than the above regions.     

家猪1号染色体微卫星标记与背膘厚的相关性

为了定位家猪背膘厚在1号染色体上的数量性状位点（QTL），检测和分析了一个复杂家猪系1号染色体上8个微卫星位点的基因型及其与背膘厚的相关性，结果表明，S0113与背膘厚的相关极显著，SW974与背膘厚的相关程度也达到极显著水准，说明两上相邻的标记区域可能存在显著影响背膘厚的大效基因，其余6个微卫星标记位点与背膘厚的相关均不显著。     

Heritability of juvenile growth traits in red drum (Sciaenops ocellatus L.)

Heritability of juvenile growth rate was estimated for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐eight families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring were individually tagged with Passive Integrated Transponder (PIT) tags and mixed for grow‐out in replicate ‘common‐garden’ tanks. Juvenile growth was followed from 166.4±18.6 to 254.0±27.0 mm (total length). Offspring were assigned a posteriori to individual brood fish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability (h²) of a thermal growth coefficient was estimated using an animal‐additive model and a restricted maximum‐likelihood algorithm. Estimates of h² were 0.33±0.08 and 0.31±0.08 for thermal growth coefficient based on length and weight respectively. These results indicate a significant genetic component in juvenile growth rate in red drum. Estimates of h² for condition coefficient (K) at various measurement dates averaged 0.38, suggesting a genetic component to shape in juvenile red drum.