Amplified Fragment Length Polymorphism Analysis Research Articles

AFLP and MSAP Analysis on Genetic Variation in Early Generations of Artificially Synthesized Brassica napus

In order to reveal pattern of genetic and epigenetic changes following allopolyploidization of A and C genomes in Brassica,AFLP(amplified fragment length polymorphism) was utilized to detect level of genome changes for S0 plants of cross A(Qinghai Dahuang×Zhonghua Jielan) and S0,S1 plants of cross B(Qinghai Dahuang×Zhongchi Jielan).Moreover,MSAP(me-thylation sensitive amplification polymorphism) was utilized to detect level of methylation changes for S0 plants of cross B.Five hundred and twenty three bands were amplified in S0 plants of cross A with 16 pairs of primer,nine out of these bands amplified showed significant differences between S0 and parents plants,mainly including deletion of seven parental restriction fragments and gain of two new fragments,accounting for 1.33% and 0.38% of total fragments,respectively.One thousand and ninety three bands were amplified in parental plants of B cross with 45 pairs of primer,only one from C genome out of these fragments lost in all S0 plants,accounting for 0.09% of total bands.In 16 S1 plants from the B9 plant,10 out of 1092 bands amplified showed varia-tions,consisting of the deletion of nine fragments from C genome and the gain of one new fragment.By MSAP approach,three loci with cytosine methylation changes were founded on A genome of S0 plants of B cross,which accounted for 1.37% of loci detected.In addition,a plant with flower color mutation in S0 generation of B cross was observed;we speculated that the flower color mutation was probably caused by genetic changes on C genome.This study provided theoretical informations for innovation of rapeseed germplasm by resynthesizing Brassica napus.

Yersinia enterocoliticaof Porcine Origin: Carriage of Virulence Genes and Genotypic Diversity

Yersinia enterocolitica is an important foodborne pathogen, and pigs are recognized as a major reservoir and potential source of pathogenic strains to humans. A total of 172 Y. enterocolitica recovered from conventional and antimicrobial-free pig production systems from different geographic regions (North Carolina, Ohio, Michigan, Wisconsin, and Iowa) were investigated to determine their pathogenic significance to humans. Phenotypic and genotypic diversity of the isolates was assessed using antibiogram, serogrouping, and amplified fragment length polymorphism (AFLP). Carriage of chromosomal and plasmid-borne virulence genes were investigated using polymerase chain reaction. A total of 12 antimicrobial resistance patterns were identified. More than two-thirds (67.4%) of Y. enterocolitica were pan-susceptible, and 27.9% were resistant against β-lactams. The most predominant serogroup was O:3 (43%), followed by O:5 (25.6%) and O:9 (4.1%). Twenty-two of 172 (12.8%) isolates were found to carry Yersinia adhesion A (yadA), a virulence gene encoded on the Yersinia virulence plasmid. Sixty-nine (40.1%) isolates were found to carry ail gene. The ystA and ystB genes were detected in 77% and 26.2% of the strains, respectively. AFLP genotyping of isolates showed wide genotypic diversity and were grouped into nine clades with an overall genotypic similarity of 66.8-99.3%. AFLP analysis revealed that isolates from the same production system showed clonal relatedness, while more than one genotype of Y. enterocolitica circulates within a farm.

Evaluation of the genetic relationship between Fritillaria species from Turkey’s flora using fluorescent-based AFLP

In this study, the genetic relationships among 12 Fritillaria taxa collected from different regions of Turkey were investigated using the amplified fragment length polymorphism (AFLP) technique. Seven primer pair combinations were used for the analysis. The neighbor-joining and principal coordinate analysis methods were implemented to identify the taxonomy of the species. The analyses generated congruent results with each other and with the previous studies. The neighbor-joining analysis clustered the species into 3 groups, while the principal coordinates analysis did not support separation of the third group. The subgenera Fritillaria and Petilium diverged from each other with strong support in all analyses. The neighbor-joining tree further divided the members of subgenus Fritillaria into 2 subgroups. Statistical analysis of the data set using NTSYS 2.1 showed a very good fit between the data matrix and the cophenetic matrix for the AFLP data with an r-value of 0.91. Generating a high polymorphic band profile, this analysis presented the feasibility of using AFLP for a genetic relationship analysis of Fritillaria. This primary report on AFLP analysis of Fritillaria species could facilitate achieving a deeper understanding of genetic relationships between the species.

Genetic diversity and species delimitation in the cultivated and wild Guinea yams (Dioscorea spp.) from Southwest Ethiopia as determined by AFLP (amplified fragment length polymorphism) markers

Yams (Dioscorea spp.) rank as the fourth most important root and tuber crop after potatoes, cassava and sweet potatoes. They are an economic crop in most of the tropics especially in West Africa, which produces over 95 % of the world output. Despite their cultural and economic importance there is taxonomic confusion regarding Guinea yams. The currently used classification scheme, which relies on vegetative and inflorescence characters, does not consistently delimit species boundaries between members of Guinea yams (D. cayenensis Lam.–D. rotundata Poir. complex), their wild relatives (D. abyssinica Kunth and D. praehensilis Benth.,) and D. sagittifolia Pax. Establishing the taxonomic identity of the germplasm and understanding the systematic relationships among crops is vital to the management of genetic resources and the utilization of accessions. In this study, amplified fragment length polymorphism (AFLP) genetic fingerprinting was used to evaluate and characterize 43 individual plants, belonging to different populations of wild and cultivated Guinea yams. The three primer combinations used in the AFLP analyses generated 158 scorable bands, with an overall polymorphism of 78 %. Ordination and cluster analyses of AFLP data failed to produce any clear species boundary between either the Guinea yam accessions or between them and their wild relatives. The average genetic similarity between the study individuals of Guinea yams and their wild relatives ranged from 60 to 100 %. The first, second and third principal coordinates axes cumulatively account for 77.45 % of the total variation. AFLP analyses also revealed a higher genetic divergence among cultivated Guinea yam accessions of the Sheko cultivars. Ordination and cluster analysis using UPGMA revealed no clear species boundaries between members of the complex. Thus, the taxonomy of these “species” needs to be revisited using other markers.

Genetic diversity of Phytophthora colocasiae isolates in India based on AFLP analysis.

Phytophthora colocasiae that causes taro leaf blight is one of the most devastating diseases of taro which is widely distributed in India. Inter and intra-specific genetic diversity among P. colocasiae isolates collected from same field was assessed using amplified fragment length polymorphism (AFLP) marker. Seven primer pairs produced 431 markers, of which 428 (99.2 %) were polymorphic. Considerable genetic variability was displayed by the isolates. The average value of the number of observed alleles, the number of effective alleles, mean Nei’s genetic diversity, and Shannon’s information index were 1.993, 1.385, 0.261, and 0.420, respectively. Analysis of molecular variance (AMOVA) showed that the majority (85 %) of the diversity were present within populations of P. colocasiae. Dendrogram based on AFLP molecular data using the unweighted pair group method with arithmetic mean (UPGMA) classified the P. colocasiae isolates into two major clusters irrespective of their geographical origin. Clustering was further supported by principle coordinate analysis. Cophenetic correlation coefficient between dendrogram and original similarity matrix was significant (r = 0.816). The results of this study displayed a high level of genetic variation among the isolates irrespective of the geographical origin. The possible mechanisms and implications of this genetic variation are discussed.

Glacial cycles as an allopatric speciation pump in north‐easternAmerican freshwater fishes

Allopatric speciation may be the principal mechanism generating new species. Yet, it remains difficult to judge the generality of this process because few studies have provided evidence that geographic isolation has triggered the development of reproductive isolation over multiple species of a regional fauna. Here, we first combine results from new empirical data sets (7 taxa) and published literature (9 taxa) to show that the eastern Great Lakes drainage represents a multispecies suture zone for glacial lineages of freshwater fishes with variable levels of genetic divergence. Second, we performed amplified fragment length polymorphism analyses among four pairs of lineages. Results indicate that lineages with relatively deep levels of mtDNA 5' COI (barcode) sequence divergence (>2%) developed strong reproductive barriers, while lineages with lower levels of divergence show weaker reproductive isolation when found in sympatry. This suggests that a threshold of 2% sequence divergence at mtDNA could be used as a first step to flag cryptic species in North American freshwater fishes. By describing different levels of divergence and reproductive isolation in different co-occurring fishes, we offer strong evidence that allopatric speciation has contributed significantly to the diversification of north-eastern American freshwater fishes and confirm that Pleistocene glacial cycles can be viewed as a 'speciation pump' that played a predominant role in generating biodiversity.

Determination of the minimum population size for ex situ conservation of water-shield (Brasenia schreberi J.F. Gmelin) inferred from AFLP analysis

Determination of the minimum population size is an important component for the ex situ conservation of an endangered species. Here, we present the identification of collection strategies that most efficiently captured the genetic diversity of Brasenia schreberi J.F. Gmelin (water-shield) in natural populations from the mainland (MGC) and Jeju Island (JNS) of South Korea, using amplified fragment length polymorphism (AFLP) markers. A total of 313 and 383 polymorphic bands were detected in the MGC and JNS populations, respectively. All of the 140 sampled ramets were distinguishable by the presence of distinct AFLP phenotypes. According to the simulation of the individual sampling by maximization sampling, 25 and 28 individuals captured all of the genetic diversity in the MGC population (mainland of South Korea) and the JNS population (Jeju Island), respectively. The level of genetic diversity of the core collections was similar to the entire collection, indicating that the core collections very well represent the diversity of the entire collection. We therefore suggest a management unit of B. schreberi based on the genetic information for assessing the minimum population size for its ex situ conservation.

Characterization of the rescued “Voghera” sweet pepper landrace grown in northern Italy

A traditional Italian sweet pepper landrace, ‘Peperone di Voghera’, which faced the risk of extinction, was analyzed for its genetic, phenological, morphological, agronomic and biochemical traits. An extant population was compared with cultivars ‘Quadrato d’Asti’, ‘Cuneo’, and ‘Giallo d’Asti’, cultivated in the same area, in order to evaluate the chance of the landrace recovery. Amplified fragment length polymorphism (AFLP) analysis demonstrated that Voghera landrace is distinct with respect to reference cultivars, thus excluding extensive genetic contamination and providing a molecular basis of both phenological and biochemical differences. Leaf chlorophyll content is lower, fruits start ripening earlier than controls, and yield (1100-1300 g plant-1) does not significantly differ. Sensitivity to root pathogens, the main factor that led to the decline in the past, does not seem to compromise the future chance of recovery. Vitamin C concentration is high (200-240 mg/100 g) and preserved by cold storage; more than 25% of vitamin C is also kept in pickled fruits. ‘Voghera’ landrace has nutritional and gastronomic properties that can be appreciated by consumers. The high internal genetic variability shown by AFLP analysis indicates that future selection work is necessary to fully maintain the original traits of the landrace and to improve it.

AFLP analysis shows high incongruence between genetic differentiation and morphology-based taxonomy in a widely distributed tortoise

Morphology has traditionally been used to diagnose the taxa of various taxonomic ranks. However, there is growing evidence that morphology is not always able to reveal cryptic taxa, and that pronounced morphological variation could reflect phenotypic plasticity rather than evolutionary divergence. Spur-thighed tortoises (the Testudo graeca complex), distributed in the western Palaearctic region, are characterized by high morphological variability and complicated taxonomy, which are under debate. Previous molecular studies using mainly mitochondrial DNA (mtDNA) sequences have revealed incongruence between genetic differentiation and morphology-based taxonomy, suggesting that morphological variability is the result of phenotypic plasticity and stabilizing selection, which masks the true genealogies. In the present study, we used a range-wide sampling and nuclear Amplified fragment length polymorphism (AFLP) markers to investigate genetic differentiation within the T. graeca complex. We found that spur-thighed tortoises are differentiated into four geographically well-defined AFLP groups: Balkans–Middle Eastern, western Mediterranean, Caucasian and central-eastern Iranian. Compared with the distribution of mtDNA lineages, the groups are largely concordant, although the AFLP markers are less sensitive and distinguish fewer groups than do mtDNA sequences. The AFLP groups show an allopatric or parapatric distribution. The AFLP differentiation conflicts with the previously proposed morphology-based taxonomy of the complex, suggesting that local adaptation to different environmental conditions may have led to the great extent of morphological variation within the same lineages. We propose a re-evaluation of the taxa that were confirmed genetically using a thorough morphological analysis corrected for phenotypic plasticity. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●●, ●●–●●.

Variation in genetics and performance of Dutch western flower thrips populations.

Invasion of pests may result in local adaptation and the development of biotypes specialized in different hosts. In this study, we investigated western flower thrips, Frankliniella occidentalis (Pergande), an invasive pest in Europe. Thrips from different commercial glasshouse crops within the Dutch Westland and a lab culture kept on chrysanthemum were compared. Genetic barcoding was applied for the identification of potential western flower thrips cryptic species in the Netherlands revealing that all western flower thrips populations studied belonged to the "glasshouse" strain reported in California as the only existing species in the Netherlands. Feeding and reproduction parameters in leaf disc and whole plant bioassays were scored. We detected significant differences in thrips feeding among host plants and thrips origin. Host plants differed in average thrips damage while thrips from different origins caused similar amounts of damage across host plants. In contrast, reproductive success of thrips on all plant species depended strongly on thrips origin. The thrips lab culture maintained on chrysanthemum obtained the highest levels of reproduction on chrysanthemum. Differences among the other thrips populations were relatively small. Amplified fragment length polymorphisms analyses were used to study genetic differences between western flower thrips populations and confirmed that the lab culture population was also genetically the most different of all studied populations. The results of the amplified fragment length polymorphisms analyses together with the better reproductive performance of thrips on the host plant on which they were maintained demonstrate the evolution of a lab biotype specialized in a particular host. This finding has potential relevance for future crop control and breeding programs.

Exploration of amplified fragment length polymorphism analysis as an effective tool for discriminating pathogenic strains of bacteria

Exploration of amplified fragment length polymorphism analysis as an effective tool for discriminating pathogenic strains of bacteria K Weinbrecht,1 A Taylor,2 C Beaumann,3 RW Allen11Department of Forensic Sciences, Center for Health Sciences, Oklahoma State University, Tulsa, OK; 2Centers for Disease Control, Atlanta, GA; 3PharmaNet-i3, Indianapolis, IN, USABackground: The detrimental effect pathogens used as bioweapons could have on the US is sufficient to warrant extensive efforts to establish preparedness to prevent, and, if necessary, respond to such an event. The objective of this research was to adapt and refine amplified fragment length polymorphism (AFLP) analysis for DNA profiling of microbial strains for use in forensic and clinical case work.Methods: Included in this study were multiple strains of Pseudomonas syringae that were restricted in their respective host ranges (ie, the pathovars maculicola and tomato), Pseudomonas aeruginosa, Serratia marcescens, and Staphylococcus aureus. AFLP profiles were reduced to numeric haplotype codes that conveyed the size characteristics of the profiles.Results: The AFLP assay exhibited over 97% reproducibility and every analyzed strain produced a unique haplotype code. Conserved areas of similarity were identified in haplotype codes of closely related strains of the same species, indicating that AFLP may also be a useful species identification tool, a possibility supported by cluster analysis of AFLP codesConclusion: The results of this study demonstrate that AFLP technology is sufficiently reproducible, powerful, and reliable for use as a broadly effective molecular screening tool in microbial forensics.Keywords: amplified fragment length polymorphism, pathogenic strains, bacteria

AFLP에 의한 한국산 새우난초속 식물과 그의 수종 돌연변이에 대한 분류학적 연구

Five Korean Calanthe species, C. discolor, C. bicolor, C. sieboldii, C. reflexa, and C. aristulifera, were studied using amplified fragment length polymorphism (AFLP) to assess their taxonomic and genetic rela- tionships. Sixteen accessions belonging to five native Calanthe spp. and mutants with yellow tepal and white lip (YW mutants) were studied. We identified 50 putative markers using AFLP analysis. The results of AMOVA showed that genetic variance was higher between species than within species. Genetic dissimilarity when com- pared with the rest of the species was the lowest for individuals of the YW mutants and the highest for indi- viduals of C. reflexa. The mutants clustered outside the major group. Calanthe bicolor clustered with C. discolor, suggesting that its genetic composition is closer to that of C. discolor. Though it is suggested to have originated as a result of natural hybridization between C. sieboldii and C. discolor, introgression is likely to have occurred in the direction of C. discolor based on the data of molecular marker, clustering and genetic dissim- ilarity. Calanthe reflexa and C. aristulifera were genetically the most diverse of the species studied. In conclu- sion, the results showed that there is genetic diversity in Korean Calanthe species, that C. bicolor introgressed in the direction of C. discolor and that the YW mutants are genetically closer to C. sieboldii.

Creation of novel interspecific-interploid Hylocereus hybrids (Cactaceae) via embryo rescue

In this study we developed a technique for rescuing embryos at a very early developmental stage following interspecific-interploid crosses between Hylocereus sp. Controlled hand pollinations were performed between the tetraploid H. megalanthus (Vaup.) Bauer as the female parent and either diploid H. monacanthus (Lem.) Britton et Rose or H. undatus (Haw.) Britton et Rose as the male parent. The fertilized ovules were excised from ovaries 10 or 30 days after pollination (DAP). Pollinated ovules containing the funiculi and placental tissue and immature embryos were placed on half-strength basal Murashige and Skoog (MS) medium containing 680 μM glutamine, 0.54 μM α-naphthaleneacetic acid, and 0.45 μM thidiazuron and supplemented with 0.00, 0.09, 0.17 or 0.26 M sucrose concentrations. The best ovule response was recorded at 30 DAP, and the most prolific callus formation was observed at 10 DAP. Callus formation was observed in most of the treatments using whole ovules but not in the isolated immature embryos. The calli were mucilaginous or compact, transparent and friable, but they did not form embryogenic structures. Embryo development was significantly affected by the sucrose concentration, and the best results were obtained with 0.17 M sucrose. More than 70 % of the obtained hybrids were successfully hardened off and transplanted in soil where they grew normally. Ploidy level analyses of 77 putative hybrids exposed diploid, triploid, tetraploid, and higher than tetraploid levels. Among those hybrids studied, 22 progenies were randomly chosen for amplified fragment length polymorphism analysis, and all were identified as genuine hybrids. The technology described here is an additional stage in the breeding program for Hylocereus species resulting in novel, interspecific hybrids obtained using the embryo rescue technique.

Probing the Molecular Mechanisms for Pristinamycin Yield Enhancement in Streptomyces pristinaespiralis

The mechanisms for the enhancement of pristinamycin production in the high-yielding recombinants of Streptomyces pristinaespiralis obtained by genome shuffling were investigated by quantitative real-time PCR (Q-PCR) and amplified fragment length polymorphism (AFLP) techniques. Q-PCR analysis showed that snaB and snbA involved, respectively, in the biosynthesis of pristinamycins II and I component had more extended high expression in the recombinant than that in the ancestor during fermentation process, indicating their expression changes might be key factors during the biosynthesis of the antibiotic. In addition, the antecedent establishment of the high self-resistance to pristinamycin, because ptr resistance gene started high-level expression ahead of the onset of the antibiotic production in the recombinant, might also lead to the increase of the antibiotics yield. AFLP analysis of these recombinants revealed genome variation of two novel genes, the homologs of AfsR regulatory gene and transposase gene, indicating these two gene variations were probably responsible for yield improvement of pristinamycin. This study provided several potential molecular clues for pristinamycin yield enhancement.

Genetic variation among natural isolates of the ectomycorrhizal hypogenous fungus, Rhizopogon roseolus from Japanese pine forests inferred using AFLP markers

Genetic variation among 45 Rhizopogon roseolus isolates from 21 different regions of Japan were inferred using amplified fragment length polymorphism (AFLP) markers. Using three primer pair combinations, AFLP analysis reproducibly produced a total of 223 DNA fragments, 74.4% of which were polymorphic. Pairwise dissimilarity of AFLP patterns between isolates ranged from 0.043 to 0.228. Cluster analysis and principal coordinate analysis of AFLP data generally showed four major clusters from geographically distinct areas. The findings suggested that the Japanese populations of R. roseolus from different geographical regions can be distinguished based on AFLP characters.

Phylogenetic relationships and species delimitation of New Zealand bluebells (Wahlenbergia, Campanulaceae) based on analyses of AFLP data

Phylogenetic and phenetic analyses of amplified fragment length polymorphism (AFLP) data were used to compare 38 individuals of 17 species of Australasian Wahlenbergia, with a focus on the New Zealand representatives. Overall, support values were slightly higher in the AFLP analyses than in previously published DNA sequence analyses, indicating the marginally better phylogenetic resolution of this technique. However, higher support was generally found towards the tips of the branches, whereas deeper relationships were equally poorly supported using either AFLPs or DNA sequence data. AFLP analyses are useful for species delimitation in New Zealand Wahlenbergia. The four members of the lowland radicate Wahlenbergia gracilis complex may all belong to the same species. We also present evidence that Wahlenbergia vernicosa should not be considered a subspecies of the Australian Wahlenbergia littoricola. The morphologically distinctive Wahlenbergia matthewsii and Wahlenbergia congesta subsp. haastii were recovered as being distinct using AFLP analyses, but members of the alpine rhizomatous Wahlenbergia albomarginata/ Wahlenbergia pygmaea complex could not be distinguished from each other.

Population Genetics of the Western Bean Cutworm (Lepidoptera: Noctuidae) Across the United States

AbstractThe western bean cutworm, Striacosta albicosta (Smith), is a secondary pest of maize (Zea mays L.) and dry beans (Phaseolus vulgaris L.) in the western United States. Recently, this insect has undergone a major territory expansion into the eastern United States and has become a pest throughout much of the Corn Belt. This study was instigated to examine the population genetics of this pest to facilitate control and resistance management, as well as to shed light on the current habitat expansion. S. albicosta individuals were collected from 24 different locations across the traditional and expanded range and amplified fragment length polymorphism analysis was conducted to assess genetic variability. In total, 90 markers were analyzed, encompassing >90% of genetic variation. Gst across all locations was moderately high (Gst = 0.5032). AMOVA analysis revealed that the majority of genetic variation was within locations (54%) and among locations within groups (45%) indicating genetic differentiation of subpopulations. The Mantel test revealed no correlation between geographic and genetic distance (n = 548; r = 0.0045; P = 0.4350). Locations sampled in the eastern United States did not exhibit any reduction in genetic variation in comparison to locations sampled in the western United States, so we conclude that no bottleneck event has occurred with this territory expansion.

AFLP analysis of genetic variation in wild populations of five Rhododendron species in Qinling Mountain in China

The genetic diversity in 22 populations of 5 wild Rhododendron species in Qinling Mountain in China was evaluated using amplified fragment length polymorphism (AFLP). Four AFLP selective primer combinations generated a total of 135 bands with their sizes ranging from 67 kb to 501 kb, among which 123 bands were found to be polymorphic, accounting for 92.04% variations. POPGENE analysis indicated that all the five species had high levels of genetic diversity, with percentage of polymorphic loci (PPL) ranging from 87.2 to 99.8% and effective number of alleles (ne) varying from 1.4205 to 1.9957. Shannon’s Information Index (I) differed from 0.4286 to 0.6921, while Nei’s gene diversity (H) varied from 0.2711 to 0.4989. The 5 species showed similar levels of genetic variations, with Hs and Ht ranging from 0.2253 to 0.4041 and from 0.2400 to 0.4994, respectively. The coefficient of gene differentiation among 22 populations (Gst) was 0.0923, accounting for 90.8% genetic diversity and only 9.2% genetic variations among the populations tested. The differences among populations were low in comparison with the previous studies on other species using the same technique. Low level of the genetic differences among Rhododendron populations investigated in the present study might be due to their outcrossing reproductive system. The analysis of molecular variance (AMOVA) also showed that variations among the species and populations were low, mainly due to a high variation within the populations. Based on unbiased genetic distances determined by an unweighted pair group method using arithmetic mean (UPGMA) phenogram, all populations could be grouped into Rhododendron species.

Screening of Lactobacillus rhamnosus strains mutated by microwave irradiation for increased lactic acid production

The present study focused on using microwave radiation to produce mutant strains ofLactobacillus rhamnosus with increased lactic acid production. At microwave radiation frequency 2450-MHz and irradiation time 3 min, an L (+)-lactic acid high-yield mutant, W4-3-9, was obtained. With glucose as the sole carbon source, production of lactic acid and L-(+)-lactic acid by the W4-3-9 strain was 1.5-fold greater than that of the parent strain. The mutant was stable for increased L-lactic acid production for at least 9 generations. Results of amplified fragment length polymorphism analysis suggest that mutations of malate/lactate dehydrogenase and pyruvate kinase genes are the possible cause of the increased production of lactic acid in W4-3-9. We believe that microwave irradiation could be an efficient method for inducing microbial mutagenesis. Key words: Lactobacillus casei subsp. rhamnosus CICC 6013, mutation, L-lactic acid, microwave irradiation, amplified fragment length polymorphism.

Population Structure and Management of Podosphaera pannosaAssociated with Peach Powdery Mildew in Oman

AbstractIn 2004, severe powdery mildew infection on peach occurred in Al‐Jabal Al‐Akdhar, Oman, and resulted in substantial yield losses to growers. This study was conducted to investigate occurrence, causal agents, genetic diversity and efficacy of azoxystrobin in management of this disease. Powdery mildew was observed on all farms and peach trees in Al‐Jabal Al‐Akdhar. Disease symptoms were first observed on shoots in April, followed by appearance on fruits. Disease severity reached its peak between May and June. Morphological and molecular identification of 22 powdery mildew isolates indicated that all belong to Podosphaera pannosa. Podosphaera pannosa reproduced the same symptoms upon inoculation on peach leaves. Amplified fragment length polymorphisms analysis of 35 isolates of P. pannosa from five different villages using four primer pair combinations produced 688 polymorphic loci and 35 different genotypes. Populations of P. pannosa were found to have low levels of gene diversity (H = 0.1858), which suggests that P. pannosa has been recently introduced into Al‐Jabal Al‐Akdhar. Analysis of molecular variance showed low levels of genetic differentiation among populations from the different villages, implying the introduction of P. pannosa into the different villages via common sources as well as frequent movement of pathogen inoculum among the different villages. Evaluating the efficacy of azoxystrobin showed that azoxystrobin is as efficacious as thiophanate‐methyl in managing the disease, with sulphur being the least efficacious. The study is the first to report the presence of P. pannosa in Oman. Also reported are its genetic diversity and its management under commercial conditions.