Identification of AFLP markers linked to one recessive genic male sterility gene in oilseed rape, Brassica napus

The commercial utilization of heterosis in seed yield by means of hybrid varieties is of great importance for increasing oilseed rape production in China. This requires a functional system for the production of hybrid seed. The Brassica napus oilseed rape line 9012AB is a recessive epistatic genic male sterility (GMS) two‐type line, in which the sterility is controlled by two pairs of recessive duplicate sterile genes (ms1 and ms2) interacting with one pair of a recessive epistatic inhibitor gene (rf). Homozygosity at the rf locus (rfrf) inhibits the expression of the recessive male sterility trait in homozygous ms1ms1ms2ms2 plants. This study was conducted to identify molecular markers for one of the male fertility/sterility loci in the B. napus male sterility line 9012AB. Sterile bulk (BS) and fertile bulk (BF) DNA samples prepared from male sterile and male fertile plants of the homozygous two‐type line 9012AB were subjected to amplified fragment length polymorphic (AFLP) analysis. A total of 256 primer combinations were used and seven markers tightly linked to one recessive genic male sterile gene (ms) were identified. Among them, six fragments co‐segregated with the target gene in the tested population, and the other one had a genetic distance of 4.3 cM. The markers identified in this study will greatly enhance the utilization of recessive GMS for the production of hybrid seed in B. napus oilseed rape in China.     

Purity control of F1-hybrid tomato cultivars by RAPD markers

Randomly amplified polymorphic DNA (RAPD) markers were applied in purity control of hybrid seed production of tomato (Lycopersicon esculentum Mill.). DNA from three commercial F₁-hybrid cultivars and their parental lines was subjected to RAPD screening with 50 primers. Two of four primers which detected polymorphism between the parents tested, generated paternal-specific RAPDs, enabling a clear distinction to be made between hybrids and their maternal parents. In addition, combination of the polymorphic DNA products generated by these primers exhibited hybrid-specific patterns, enabling each cultivar to be identified. This result indicates the practical usefulness of RAPD markers in hybrid-tomato-seed purity-control tests and cultivar identification. The approach is advantageous in its rapidity and simplicity, particularly as an alternative for those cultivars for which lengthy and costly phenotypic tests are currently used.     

Genetic diversity of hexaploid wheat cultivars estimated by RAPD markers, morphological traits and coefficients of parentage

Estimates of genetic diversity can be based on different types of data. The aim of this research were to study genetic diversity among Croatian wheat cultivars by random amplified polymorphic DNA (RAPD) markers, morphological traits and pedigree records; to analyse differences between wheat cultivars from two breeding centres; and to evaluate usability of RAPD markers for estimation of genetic diversity among wheat cultivars in comparison with morphological traits and pedigree record data. Studies were conducted on 14 wheat cultivars and breeding lines from two breeding centres in Croatia. For the RAPD analysis 36 primers were screened and the 14 most polymorphic ones yielded 341 polymorphic bands. Twelve morphological traits were used for morphological analysis. Pedigrees were composed of seven generations of ancestors. RAPD markers showed a high level of polymorphism among the cultivars examined and the breeding lines. No significant correlations were observed among the methods tested.     

Random amplified polymorphic DNA analysis of Australian rice (Oryza sativa L.) varieties

Summary The genetic relationships between rice varieties were analysed by using the polymerase chain reaction (PCR), with arbitrary oligonucleotide primers in the random amplified polymorphic DNA (RAPD) method. PCR with 22 arbitrary primers applied to 37 varieties produced 144 useful markers, of which 67% were polymorphic. Thus, with selected primers sufficient polymorphism could be detected to allow identification of individual varieties. Visual examination of electrophoresis gels and analysis of banding patterns confirmed that commercial Australian and USA lines and their relatives were very closely related, with similarity indices of 88–97%. Three varieties originating from more distant geographical centres were easily distinguished, producing variety-specific amplification profiles and expressing a lower similarity index of 80% to all other varieties tested. PCR offers a potentially simple, rapid and reliable method for rice genotype identification and recognition of lines that could contribute genetic diversity to new commercial varieties.Abbreviations PCR Polymerase Chain Reaction - RAPD Random Amplified Polymorphic DNA     

Characterization of natural orchardgrass (Dactylis glomerata L.) populations of the Thrace Region of Turkey based on ploidy and DNA polymorphisms

Determining the ploidy and geneticdiversity of a germplasm is necessarybefore initiating breeding or geneticstudies. This study was conducted tocharacterize the ploidy level of 57 naturalpopulations of orchardgrass (Dactylisglomerata L.) collected from the ranges ofThrace region of Turkey and the diversityamong populations based on RAPD (RandomAmplified Polymorphic DNA) markers. Flowcytometry was used to determine nuclear DNAcontent (pg 2C^-1 = DNA content of adiploid somatic nucleus) of 6 plants foreach population. Nuclear DNA contents werecorrelated to ploidy level with root tipchromosome counts on selected plants. Onthe basis of this study, mean nuclear DNAcontent of orchardgrass was determined as9.57 ± 0.33 (with 95% confidenceinterval) while all the plants used inchromosome counting were determined to betetraploid, with 2n = 28 mitoticchromosomes, suggesting that diploidorchardgrass plants are likely very rare orabsent in ranges of Thrace region ofTurkey. In the RAPD assay, over 40polymorphic fragments were generated whichallowed some populations to bedistinguished from the rest by uniquemarkers. A cluster analysis was performedusing Nei's (1972) genetic distance indexwith an unweighted pair group method witharitmetic mean (UPGMA). The clusteranalysis indicated that there is a highlevel of gene flow among naturalorchardgrass populations and thereforegenes distributed quite homogeneouslythrough out the region. The results of thisstudy can be useful in the development ofDactylis germ plasm collectionstrategies in Thrace region for breedingpurpose.     

A RAPD-derived STS marker is linked to a bacterial wilt (Burkholderia caryophylli) resistance gene in carnation

Bacterial wilt caused by Burkholderia caryophylli is one of the most important and damaging diseases of carnations (Dianthus caryophyllus) in Japan. We aimed to identify random amplified polymorphic DNA (RAPD) markers associated with the genes controlling bacterial wilt resistance in a resistance-segregating population of 134 progeny plants derived from a cross between Carnation Nou No. 1 (a carnation breeding line resistant to bacterial wilt) and Pretty Favvare (a susceptible cultivar). We screened a total of 505 primers to obtain RAPD markers useful for selecting resistant carnation lines: 8 RAPD markers identified by bulked segregant analysis were linked to a major resistance gene; of these, WG44-1050 had the greatest effect on resistance to bacterial wilt. A locus with large effect on bacterial resistance was mapped around WG44-1050 through QTL analysis. The RAPD marker WG44-1050 was successfully converted to a sequence-tagged site (STS) marker suitable for marker-assisted selection (MAS). Five combinations of primers were designed for specific amplification of WG44-1050. In addition, the STS marker we developed was useful and reliable as a selection marker for breeding for resistance to bacterial wilt, using a highly resistant wild species, D. capitatus ssp. andrzejowskianus and a resistant line, Carnation Nou No. 1, as breeding materials.     

Molecular markers for yellow stem borer Scirpophaga incertulas (Walker) resistance in rice

Breeding for yellow stem borer resistance in rice is difficult owing to the complex genetics of the trait and inherent difficulties in screening. Identification of molecular markers linked to the trait would enhance phenotypic evaluation for the trait. An F₂ population was developed using parents contrasting in their reaction to yellow stem borer resistance. Random Amplified Polymorphic DNA (RAPD) analysis,in conjunction with bulked segregant analysis, enabled us to identify four phenotype-specific RAPD markers. The markers C1₃₂₀ and K6₆₉₅ were linked with resistance and AH5₆₆₀ and C4₁₃₀₀ with susceptibility. The markers K6₆₉₅ and AH5₆₆₀ were linked to the gene(s) at distances of 12.8 cM and 14.9 cM, respectively. Scoring of these markers in a set of germplasm confirmed their reproducibility and their association with the trait. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hand pulling of Striga hermonthica in pearl millet∗

Abstract

Before 1960, Panama disease (fusarium wilt) was the most important disease in the banana export trades. Although the importance of Panama disease decreased after the Cavendish cultivars replaced Gros Michel, recent outbreaks have renewed interest in this problem. Race 4 affects cultivars of the Cavendish subgroup in the subtropics, as well as race 1 and race 2 suscepts. It has caused concern in the tropically based export trades which depend almost entirely on the Cavendish clones. Attention is also drawn to affected non‐exported bananas which are important cash crops or staple foods. Although they are not as well documented as those on the Cavendish subgroup, epidemics of the disease on non‐exported bananas are far more important.     

Pharmacokinetics and Safety of Oral Administration of Meloxicam to Foals

Background

The pharmacokinetics, efficacy, and safety of meloxicam have been evaluated in adult horses, but not foals. Physiologic differences between neonates and adults might alter drug pharmacokinetics and therapeutic index.

Hypotheses

The pharmacokinetics of meloxicam will be different in foals compared with adult horses, and foals could be at increased risk for adverse drug effects.

Animals

Twenty lightbreed foals less than 6 weeks of age at commencement of the study.

Methods

Single and repeated oral dose pharmacokinetics were determined for meloxicam (0.6 mg/kg) in 10 foals. The safety of the drug was further evaluated in a 2nd group of 10 foals in a randomized blinded prospective study.

Results

Plasma concentrations after a single oral dose of meloxicam (0.6 mg/kg) and time to maximum plasma concentration were similar to adult horses. However, drug clearance was much more rapid in foals (elimination half‐life 2.48 ± 0.25 hours). Administration of 0.6 mg/kg every 12 hours was well tolerated by foals for up to 3 weeks, with no evidence of drug accumulation in plasma. Adverse effects observed in adult horses at higher dose rates were not observed in foals given 1.8 mg/kg twice daily for 7 days.

Conclusions and clinical importance

Meloxicam at an oral dose rate of 0.6 mg/kg every 12 hours provided plasma concentrations likely to be therapeutic. In contrast to findings for other NSAIDs, foals appeared more resilient to the adverse effects of this drug than was observed in adult horses.