scholarly journals Genetic Differentiation of Magnaporthe oryzae Populations from Scouting Plots and Commercial Rice Fields in Korea

2008 ◽  
Vol 98 (4) ◽  
pp. 436-442 ◽  
Author(s):  
S.-Y. Park ◽  
M. G. Milgroom ◽  
S. S. Han ◽  
S. Kang ◽  
Y.-H. Lee
Keyword(s):  
Genetic Differentiation ◽  
Mating Type ◽  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Disease Incidence ◽  
Rice Fields ◽  
Dna Fingerprint ◽  
Group I ◽  
Group Ii ◽  
Set Up

A previous study of the diversity and population structure of the rice blast fungus, Magnaporthe oryzae, over a 20-year period in Korea, found novel fingerprint haplotypes each year, and the authors hypothesized that populations might experience annual bottlenecks. Based on this model, we predicted that M. oryzae populations would have little or no genetic differentiation among geographic regions because rice blast is commonly found throughout Korea each year and M. oryzae would have to disperse from small populations surviving annually between rice crops. To test this hypothesis, we sampled M. oryzae from rice fields in eight provinces in Korea in a single year (1999). In four provinces, we sampled from a set of rice cultivars commonly grown in commercial fields (group I); because of low disease incidence in four other provinces, we could not sample from commercial fields and instead sampled from scouting plots of different cultivars set up for detecting new pathotypes of M. oryzae (group II). All isolates were genotyped with DNA fingerprint probes MGR586 and MAGGY, a telomere-linked gene family member TLH1, the PWL2 host specificity gene and mating type. Fingerprint haplotypes clustered into two distinct lineages corresponding to the two sets of cultivars (groups I and II), with haplotype similarities of 71% between lineages and >76% within lineages. Isolates from the same cultivar within group I were genetically differentiated among locations, and isolates within the same location were differentiated among cultivars. Differentiation for TLH1 and PWL2 was significant (P < 0.03), but not as strong as for fingerprint markers. Similar analyses were not possible among group II isolates because too few isolates were available from any one cultivar. All isolates were in the same mating type, Mat1-1, ruling out sexual reproduction as a source of novel haplotypes. When the 1999 samples were compared with the historical samples from the previous study, haplotypes of group I formed a separate cluster, while those of group II clustered with haplotypes from the historical sample. Altogether, geographic subdivision, monomorphism of mating type, and correlation of haplotypes to sets of cultivars are not consistent with the hypothesis of repeated turnover of haplotypes. Instead, the previous correlations of haplotypes to year might have been caused by inadequate sampling of haplotypes each year, highlighting the need for studies of population genetics to be conducted with systematic samples collected to address specific questions.

LINE-OF-MALE EFFECTS ON LIFETIME PERFORMANCE IN MICE

1985 ◽  
Vol 65 (2) ◽  
pp. 333-340
Author(s):  
J. NAGAI ◽  
A. J. McALLISTER ◽  
J. MASAKI
Keyword(s):  
Total Weight ◽  
Lifetime Data ◽  
Hybrid Male ◽  
Lifetime Performance ◽  
Group I ◽  
Reproductive Life ◽  
Group Ii ◽  
Set Up ◽  
Generation Line ◽  
Synthetic Line

Six straight-bred lines of mice were used both as straight-bred (STR) lines and to set up five crisscross (CC) lines (classes) and five repeat hybrid male cross (RHMC) lines, (classes). Females in each line were pair-mated with either males of the same line (group I) or males from a synthetic line (group II). Pairs were maintained for up to 155 days after mating (lifetime). Data from six generations were analyzed to examine differences between group I and group II in lifetime performance for each line in each generation. Line-of-male effects for the above difference (group I–Group II) expressed as a percentage of the average of group I and group II means were, under CC, RHMC and STR, −11, +5 and −2 for number of parturitions during 155 days, −12, +3, and −7 for total number of young born alive, −12, + 2 and −8 for total weight of young born alive, −12, +3 and −8 for total number of young at weaning, −11, +2 and −8 for total weight of young at weaning and −8, +3 and −1 for actual days of reproductive life, respectively. Lifetime performance of females differed depending on males used for mating, and F1 males were superior to males from the synthetic line which excelled males from straight-bred lines. Key words: Male, lifetime performance, reproduction, mice

scholarly journals Population Structure and Genetic Diversity of Phytophthora nicotianae from Tobacco in Georgia

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1113-1118 ◽  
Author(s):  
Yonggang Li ◽  
Karen Harris-Shultz ◽  
Hongliang Wang ◽  
Phillip A. Wadl ◽  
Pingsheng Ji
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Ssr Markers ◽  
Mating Type ◽  
Geographical Location ◽  
Phytophthora Nicotianae ◽  
Group Method ◽  
Group I ◽  
Tobacco Production ◽  
Group Ii

Black shank, caused by Phytophthora nicotianae, occurs worldwide and is responsible for significant yield loss in tobacco production in Georgia. Management of the disease has primarily relied on utilization of tobacco cultivars with resistance to race 0 of the pathogen and application of the fungicide mefenoxam. Races of P. nicotianae currently prevalent in tobacco production in Georgia, their sensitivity to mefenoxam, and genetic diversity of the pathogen are largely unknown. To determine population structure and genetic diversity of the pathogen, simple sequence repeat (SSR) markers were used. Three races of P. nicotianae (races 0, 1, and 3) were isolated from infected tobacco plants, with race 3 identified in Georgia for the first time. The majority of isolates were identified as A2 mating type and all isolates were sensitive or intermediately sensitive to mefenoxam at 1 or 10 μg/ml, with effective concentration of mefenoxam for 50% mycelial growth reduction values ranging from <0.01 to 0.12 μg/ml. Bayesian and unweighted pair group method with arithmetic means analyses of 59 isolates using SSR markers grouped the isolates in two major groups. Group I contained 20 isolates, of which 19 isolates were collected from Berrien County. Group II contained 39 isolates collected from Bacon, Cook, Tift, and Toombs Counties as well as one sample from Berrien County. Genetic diversity of the isolates was associated with geographical location of collection, and isolates in group I were primarily (75%) race 1, whereas isolates in group II were primarily (69%) race 0. The presence of a single pathogen mating type at most of the locations implies low probability of sexual recombination that may have contributed to the low genetic diversity at a particular geographical location. Sensitivity of the isolates to mefenoxam indicates that the fungicide remains to be a potent tool for growers to combat the disease. Information generated in the study advances our knowledge about diversity and population structure of P. nicotianae, which facilitates development and implementation of effective disease management programs.

Repetitive monosynaptic activation of motoneurones

1951 ◽  
Vol 138 (893) ◽  
pp. 475-498 ◽  
Keyword(s):  
Repetitive Stimulation ◽  
Monosynaptic Reflex ◽  
Synaptic Potential ◽  
Group I ◽  
Excitatory Action ◽  
Extensor Motoneurones ◽  
Group Ii ◽  
Set Up ◽  
Reflex Discharge ◽  
Stimulation Of

Repetitive monosynaptic activation of motoneurones has been set up by maximum repetitive stimulation of the group I afferent fibres of the nerves to various muscles. By studying the effects produced by stimuli of varying strengths and also by comparing the responses of flexor and extensor motoneurones, it has been possible to allow for complications arising from concomitant stimulation of group II and III fibres in these nerves. Motoneurone responses have been recorded either as impulses discharged along the ventral root or as synaptic potentials electrotonically transmitted thereto. The repetitive synaptic potential conforms to a standard pattern for both flexor and extensor motoneurones. With frequencies over 100/sec. there is a brief initial phase of summation, then decline to a plateau at about the height of the initial single potential. On cessation of stimulation there is an immediate decline to a positive after-potential which bears a close resemblance to that observed after repetitive stimulation of peripheral nerve. The repetitive potential is com­pounded of ‘diphasic’ potentials generated by each successive volley, an initial negative synaptic potential and a later positive after-potential. At high frequencies of stimulation the successive potentials show an initial rapid decline in size to a low value, e. g. to 50% at 400/sec., which is only in part attributable to a decline in the size of the volleys entering the spinal cord. Focal recording has permitted simultaneous comparison of these two declines. The excitability of the motoneurones during and after repetitive activation was tested heterosynaptically. During the synaptic potential plateau the excitability is raised, with periodic variations in phase with the successive volleys, while depression is observed during the positive after-potential. With extensor muscles the reflex discharge of impulses conforms in general with the repetitive synaptic potential curve, the initial summation giving monosynaptic reflex dis­charges to the first two or three volleys at high frequency. It is probable that a motoneurone fires only once in this initial burst. Subsequently, the combination of autogenetic inhibitory action of group II fibres (which may however be negligible), diminished synaptic excitatory action, and depressant action of the accumulated positive after-potentials (subsynaptic depression) may prevent all further discharge. Alternatively, after a brief quiescent interval, a small irregular discharge may be set up monosynaptically by subsequent volleys. With low frequencies of stimulation the second and subsequent volleys may all evoke reflex discharges, but they are always smaller than the initial discharge. Repetitive activation of flexor moto­-neurones differs from extensors in that the autogenetic excitatory action of group II afferent fibres makes both the initial and later bursts of reflex discharge larger and more sustained.

scholarly journals Evidence of Genetic Exchange by Parasexual Recombination and Genetic Analysis of Pathogenicity and Mating Type of Parasexual Recombinants in Rice Blast Fungus, Magnaporthe oryzae

2006 ◽  
Vol 96 (7) ◽  
pp. 746-750 ◽  
Author(s):  
M. T. Noguchi ◽  
N. Yasuda ◽  
Y. Fujita
Keyword(s):  
Mating Type ◽  
Magnaporthe Oryzae ◽  
Genomic Dna ◽  
Rice Blast ◽  
Southern Blot Analysis ◽  
Selectable Marker ◽  
Marker Gene ◽  
Rice Blast Fungus ◽  
Selectable Marker Gene ◽  
Sexual Cross

A selectable marker gene conferring resistance to bialaphos (BI) was introduced into rice blast isolate Y90-71BI and another conferring resistance to blasticidin S (BS) into isolate 3514-R-2BS of Magnaporthe oryzae to demonstrate exchange of DNA. Colonies obtained from co-cultures of these two isolates were resistant to both BI and BS and had both resistance genes as shown by Southern blot analysis of their genomic DNA. Conidia from these BI-BS-resistant isolates had only one nucleus per cell after staining with 4′,6-diamidino-2-phenylindole (DAPI). Using flow cytometry, however, these BI-BS-resistant isolates were found to be haploid. Segregation of BI-BS-resistant isolates for pathogenicity (avirulence to virulence) on rice line K59-1 was consistent with a 1:1 ratio, as was segregation for mating type. These BI-BS-resistant isolates were thus apparently derived from parasexual exchange of DNA and the segregation of pathogenicity and of mating type of the parasexual recombinants might correspond to that of the progeny of the offspring of the sexual cross.

scholarly journals Population Structure, Pathogenicity, and Mating Type Distribution of Magnaporthe oryzae Isolates from East Africa

2015 ◽  
Vol 105 (8) ◽  
pp. 1137-1145 ◽  
Author(s):  
Geoffrey Onaga ◽  
Kerstin Wydra ◽  
Birger Koopmann ◽  
Yakouba Séré ◽  
Andreas von Tiedemann
Keyword(s):  
Population Structure ◽  
Gene Flow ◽  
Genetic Differentiation ◽  
East Africa ◽  
Mating Type ◽  
Magnaporthe Oryzae ◽  
Geographic Origin ◽  
The Philippines ◽  
Genetic Population ◽  
Principal Coordinates

Rice blast, caused by Magnaporthe oryzae, is one of the emergent threats to rice production in East Africa (EA), where little is known about the population genetics and pathogenicity of this pathogen. We investigated the genetic diversity and mating type (MAT) distribution of 88 isolates of M. oryzae from EA and representative isolates from West Africa (WA) and the Philippines (Asia) using amplified fragment length polymorphism markers and mating-type-specific primer sets. In addition, the aggressiveness of each isolate was evaluated by inoculating on the susceptible Oryza sativa indica ‘Co39’, scoring the disease severity and calculating the disease progress. Hierarchical analysis of molecular variance revealed a low level of genetic differentiation at two levels (FST 0.12 and FCT 0.11). No evidence of population structure was found among the 65 isolates from EA, and gene flow among EA populations was high. Moreover, pairwise population differentiation (GST) in EA populations ranged from 0.03 to 0.04, suggesting that >96% of genetic variation is derived from within populations. However, the populations from Asia and WA were moderately differentiated from EA ones. The spatial analysis of principal coordinates and STRUCTURE revealed overlapping between individual M. oryzae isolates from EA, with limited distinctness according to the geographic origin. All the populations were clonal, given the positive and significant index of association (IA) and standardized index of association (rd), which indicates a significant (P < 0.001) departure from panmixia (IA and rd = 0). Both MAT1-1 and MAT1-2 were detected. However, MAT1-1 was more prevalent than MAT1-2. Pathogenicity analysis revealed variability in aggressiveness, suggesting a potential existence of different races. Our data suggest that either M. oryzae populations from EA could be distributed as a single genetic population or gene flow is exerting a significant influence, effectively swamping the action of selection. This is the first study of genetic differentiation of rice-infecting M. oryzae strains from EA, and may guide further studies on the pathogen as well as resistance breeding efforts.

scholarly journals Genetic Structure of the Rice Blast Pathogen (Magnaporthe oryzae) over a Decade in North Central California Rice Fields

2017 ◽  
Vol 75 (2) ◽  
pp. 310-317 ◽  
Author(s):  
Deborah Pagliaccia ◽  
Ryan Z. Urak ◽  
Frank Wong ◽  
LeAnn I. Douhan ◽  
Christopher A. Greer ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Rice Fields ◽  
North Central ◽  
Central California

scholarly journals Control of Magnaporthe oryzae and Rice Growth Promotion by Bacillus subtilis JN005

2021 ◽  
Author(s):  
Huajun Zhu ◽  
Hu Zhou ◽  
Zuohua Ren ◽  
Erming Liu
Keyword(s):  
Bacillus Subtilis ◽  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Growth Promotion ◽  
Biological Control Agent ◽  
Disease Incidence ◽  
Control Treatment ◽  
Bacterial Suspension ◽  
Sterile Water ◽  
Rice Leaves

AbstractIt is quite important to develop the microorganism resources with biocontrol capacity for rice blast. This study evaluated Bacillus subtilis JN005 for growth promotion and biocontrol efficacy against Magnaporthe oryzae. Results showed that rice seeds treated with 1 × 107 cfu/mL suspension of B. subtilis JN005 had 16% germination energy, 14% germination rate, 15% germination index, and 270% vigor index compared to those treated with sterile water (control). In pot experiments, the JN005 strain-treated rice plants exhibited notable increase in plant height, root length, stem circumference, and fresh weight, as well as higher concentration of chlorophyll a, chlorophyll b, and total chlorophyll in rice leaves. Rice leaves inoculated with the JN005 strain resulted in increased activities of defense-related enzymes, including peroxidase (POD), phenylalanine ammonialyase (PAL), superoxide dismutase (SOD), and catalase (CAT) compared to the water and the M. oryzae-inoculated treatments. In vitro inoculated rice leaves with 1 × 107 cfu/mL bacterial suspension compared to sterile water or control treatment exhibited lower disease incidence in the curative and preventive groups by 79% and 76%, respectively. Field experiment showed that after spraying with 1 × 107 cfu/mL bacterial suspension, efficacy rates on controlling rice blast on plants were (56.82 ± 1.12)% and (58.39 ± 3.05)% at seedling and maturity stages, respectively, and that rice production yield was (524.40 ± 17.88) g/m2. Therefore, B. subtilis JN005 could be a promising biological control agent for rice blast, thereby warranting further investigation of its efficacy.

scholarly journals Rice Blast Disease (Magnaporthe oryzae): A Menace to Rice Production and Humanity

2020 ◽  
pp. 32-39
Author(s):  
G. O. Agbowuro ◽  
M. S. Afolabi ◽  
E. F. Olamiriki ◽  
S. O. Awoyemi
Keyword(s):  
Food Security ◽  
Magnaporthe Oryzae ◽  
Rice Blast ◽  
Disease Incidence ◽  
Rice Production ◽  
Rice Blast Disease ◽  
Control Measures ◽  
Blast Disease ◽  
Economic Losses ◽  
Rice Grain

Rice blast disease is one of the major constraints to rice production, threatening food security globally. Rice grain production losses due to the disease leads economic losses to the farmers, and to an increase in global rice price as a result of the supply that is far below the consumer demand. The losses from the disease annually was estimated to feed over 60 million individual. The disease has been studied comprehensively by researchers due to the importance attached to rice and its vast spread and destructiveness across the globe. A good understanding of the pathogen causing the disease, its life cycle and development, epidemiology, symptoms, management strategy will offer a good insight into the disease incidence and give an appropriate and effective decision-making in its management. Different control measures have been adopted managing the disease, including the use of resistant varieties. Integrated disease management strategies coupled with good agronomy practices are required for successful control of rice blast for food security. This review, therefore, examined the fundamentals of rice blast disease (Magnaporthe oryzae) and offered strategies to minimize the disease activities to ensure proper production and increase the supply of rice grains.

scholarly journals Use of Chlorhexidine on Umbilicus in Prevention of Neonatal Sepsis

2021 ◽  
pp. 434-438
Author(s):  
Rimsha Mohsin ◽  
Palwasha Khan ◽  
Maryum Naveed
Keyword(s):  
Neonatal Sepsis ◽  
Mode Of Delivery ◽  
Sampling Technique ◽  
Cross Sectional Study ◽  
Cord Care ◽  
Cross Sectional ◽  
Group I ◽  
Umbilical Cord Care ◽  
Group Ii ◽  
Set Up

Objectives: The main objective of the study is to analyse the use of chlorhexidine on umbilicus in prevention of neonatal sepsis. Materials and Methods: This cross sectional study was conducted in Sheikh Zaid hospital Rahim Yaar Khan during March 2020 till September 2020. The data was collected through non-probability consecutive sampling technique. The data was collected from 100 infants. Arrangements with a grouping of 4.0% free chlorhexidine were set up by weakening 20% chlorhexidine digluconate to the proper fixation with cleaned water. Results: The data was collected from 100 neonates. All the demographic values which include age, gender, gestational age and mode of delivery were calculated. According to baseline values the birth weight of chlorhexidine group was 1.87 ± 0.463 kg and dry cord group was 1.69 ± 0.421 kg. Umbilical sepsis is observed in only 1 patient in group I and in 3 patients in group II. Only single mortality was observed in group I and in 6 neonates in group II.   Conclusion: It is concluded that chlorhexidine umbilical cord care is more appropriate than the currently WHO recommended dry cord care.

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