scholarly journals Temporal Genetic Dynamics of an Experimental, Biparental Field Population of Phytophthora capsici

2016 ◽  
Author(s):  
Maryn O. Carlson ◽  
Elodie Gazave ◽  
Michael A. Gore ◽  
Christine D. Smart
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Haplotype Frequency ◽  
Experimental System ◽  
Experimental Population ◽  
Evolutionary Potential ◽  
Opposite Mating Type ◽  
Generational Shift ◽  
Frequency Changes ◽  
Pathogen Populations

AbstractDefining the contributions of dispersal, reproductive mode, and mating system to the population structure of a pathogenic organism is essential to estimating its evolutionary potential. After introduction of the devastating plant pathogen, Phytophthora capsici, into a grower’s field, a lack of aerial spore dispersal restricts migration. Once established, coexistence of both mating types results in formation of overwintering recombinant oospores, engendering persistent pathogen populations. To mimic these conditions, in 2008, we inoculated a field with two P. capsici isolates of opposite mating type. We analyzed pathogenic isolates collected in 2009-13 from this experimental population, using genome-wide single-nucleotide polymorphism markers. By tracking heterozygosity across years, we show that the population underwent a generational shift; transitioning from exclusively F1 in 2009-10; mixed generational in 2011; and ultimately all inbred in 2012-13. Survival of F1 oospores, characterized by heterozygosity excess, coupled with a low rate of selfing, delayed declines in heterozygosity due to inbreeding and attainment of equilibrium genotypic frequencies. Large allele and haplotype frequency changes in specific genomic regions accompanied the generational shift, representing putative signatures of selection. Finally, we identified an approximately 1.6 Mb region associated with mating type determination, constituting the first detailed genomic analysis of a mating type region (MTR) in Phytophthora. Segregation patterns in the MTR exhibited tropes of sex-linkage, where maintenance of allele frequency differences between isolates of opposite mating type was associated with elevated heterozygosity despite inbreeding. Characterizing the trajectory of this experimental system provides key insights into the processes driving persistent, sexual pathogen populations.

The genetics of pathogenic aggressiveness in three dikaryons of Ustilago hordei

1984 ◽  
Vol 62 (6) ◽  
pp. 1209-1219 ◽  
Author(s):  
C. E. Caten ◽  
C. Person ◽  
J. V. Groth ◽  
S. J. Dhahi
Keyword(s):  
Mating Type ◽  
Opposite Mating Type ◽  
Gene Effects ◽  
Genetic Determination ◽  
Ustilago Hordei ◽  
Number Of Genes ◽  
Polygenic System ◽  
New Races ◽  
Pathogen Populations

The genetic determination of a quantitative component of pathogenicity, aggressiveness, was examined in progeny populations derived from three parent dikaryons of Ustilago hordei. Aggressiveness was assessed as the proportion of smutted plants produced from inoculated seed of a compatible barley cultivar. The parents differed in their origins and cultural histories and this was reflected in the variability of their progenies. A standard race-10 strain appeared to be homozygous for genes affecting aggressiveness, while a dikaryon produced by mating two unrelated sporidia was heterozygous and produced highly variable progeny populations. In these populations, aggressiveness was determined by a polygenic system which involved both additive and dominance gene effects. It was not possible to estimate the number of genes involved, but segregation was apparent in individual tetrads. Furthermore, a difference between opposite mating-type segregants suggested the presence of a factor which affected aggressiveness and was linked to mating type. The dominance effects were ambidirectional suggesting that genotypes giving an intermediate level of aggressiveness are the most fit. The aggressiveness of a pathogen strain is an important factor determining the severity of epidemics on compatible hosts. It is also a major component of fitness and may influence the frequency of virulence factors in pathogen populations and the evolution of new races.

scholarly journals A PCR-based Assay for Distinguishing between A1 and A2 Mating Types of Phytophthora capsici

2017 ◽  
Vol 142 (4) ◽  
pp. 260-264
Author(s):  
Ping Li ◽  
Dong Liu ◽  
Min Guo ◽  
Yuemin Pan ◽  
Fangxin Chen ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Mating Type ◽  
Phytophthora Capsici ◽  
Mating Types ◽  
Sequence Repeat ◽  
Chain Reaction ◽  
Plant Parasite ◽  
Dna Fragment ◽  
Polymerase Chain ◽  
Microsatellite Diversity

Sexual reproduction in the plant parasite Phytophthora capsici Leonian requires the interaction of two distinct mating types, A1 and A2. Co-occurrence of these mating types can enhance the genetic diversity of P. capsici and alter its virulence or resistance characteristics. Using an intersimple sequence repeat (ISSR) screen of microsatellite diversity, we identified, cloned, and sequenced a novel 1121-base pair (bp) fragment specific to the A1 mating type of P. capsici. Primers Pcap-1 and Pcap-2 were designed from this DNA fragment to specifically detect the A1 mating type. Polymerase chain reaction (PCR) using these primers amplified an expected 997-bp fragment from known A1 mating types, but yielded a 508-bp fragment from known A2 mating types. This PCR-based assay could be adapted to accurately and rapidly detect the co-occurrence of A1 and A2 P. capsici mating types from field material.

ESCAPE FROM MATING-TYPE INCOMPATIBILITY IN BISEXUAL (A + a) NEUROSPORA HETEROKARYONS

1975 ◽  
Vol 17 (3) ◽  
pp. 441-449 ◽  
Author(s):  
A. M. DeLange ◽  
A. J. F. Griffiths
Keyword(s):  
Mating Type ◽  
Loss Of Function ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Heterokaryon Incompatibility ◽  
Recessive Mutant ◽  
Type Rate ◽  
Wild Type Rate ◽  
Incompatibility Locus

In Neurospora crassa, strains of opposite mating type generally do not form stable heterokaryons because the mating type locus acts as a heterokaryon incompatibility locus. However, when one A and one a strain, having complementing auxotrophic mutants, are placed together on minimal medium, growth may occur, although the growth is generally slow. In this study, escape from such slow growth to that at a wild type or near-wild type rate was observed. The escaped cultures are stable heterokaryons, mostly having lost the mating type allele function from one component nucleus, so that the nuclear types are heterokaryon compatible. Either A or a mating type can be lost. This loss of function has been attributed to deletion since only one nuclear type could be recovered in all heterokaryons except one, but deletion spanning adjacent loci has been directly demonstrated in a minority of cases. Alternatively when one component strain is tol and the other tol+ (tol being a recessive mutant suppressing the heterokaryon incompatibility associated with mating type), escape may occur by the deletion or mutation of tol+, also resulting in heterokaryon compatibility. An induction mechanism for escape is speculated upon.

scholarly journals Distribution and Alteration of Mating Type of Phytophthora capsici Population from Red Pepper in Korea

2002 ◽  
Vol 30 (2) ◽  
pp. 152-156 ◽  
Author(s):  
Jeong-Young Song ◽  
Sung-Joon Yoo ◽  
Hong-Gi Kim
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Red Pepper

Pycnial nectar of rust fungi induces cap formation on pycniospores of opposite mating type

Mycologia ◽  
1999 ◽  
Vol 91 (5) ◽  
pp. 858-870 ◽  
Author(s):  
Y. Anikster ◽  
T. Eilam ◽  
L. Mittelman ◽  
L.J. Szabo ◽  
W. R. Bushnell
Keyword(s):  
Mating Type ◽  
Rust Fungi ◽  
Opposite Mating Type

scholarly journals Diversity of Phytophthora capsici in Northwest Spain: Analysis of Virulence, Metalaxyl Response, and Molecular Characterization

Plant Disease ◽  
2006 ◽  
Vol 90 (9) ◽  
pp. 1135-1142 ◽  
Author(s):  
C. Silvar ◽  
F. Merino ◽  
J. Díaz
Keyword(s):  
Mating Type ◽  
Rapd Analysis ◽  
Random Amplified Polymorphic Dna ◽  
Phytophthora Capsici ◽  
Crown Rot ◽  
Group Method ◽  
Pair Group ◽  
Highly Sensitive ◽  
Virulence Assay ◽  
Pepper Cultivar

Phytophthora crown rot, caused by Phytophthora capsici, is potentially the most destructive disease of pepper in Spain. Phenotypic and genetic diversity of 16 P. capsici isolates collected from 11 farms in northwest Spain was characterized based on virulence, mating type, sensitivity to metalaxyl, and genetic analysis using random amplified polymorphic DNA (RAPD) methods. Low variability was observed among the isolates in their metalaxyl response, with 87.5% being highly sensitive. No isolates of the A2 mating type were detected. More variability was found in the virulence assay, and isolates were classified into two groups according to their pathogenicity on a set of four pepper cultivar differentials. Genetic variation examined with eight RAPD primers generated 92 polymorphic bands and revealed the existence of different patterns among isolates. Cluster analysis using the unweighted pair-group method with arithmetic averages (UPGMA) separated the Spanish isolates into three RAPD groups and established a relationship between the Spanish population and a representative worldwide group of isolates. No correlation was found between groups obtained by RAPD analysis and groups defined by virulence or metalaxyl response.

POOR FRUITERS AND BARRAGE MUTANTS IN GELASINOSPORA

1956 ◽  
Vol 34 (2) ◽  
pp. 231-240 ◽  
Author(s):  
E. Silver Dowding ◽  
A. Bakerspigel
Keyword(s):  
Growth Rate ◽  
Mating Type ◽  
Opposite Mating Type ◽  
Nutritional Factors ◽  
Wild Strains ◽  
Hyphal Tip

Anomalous sterility and slow fruiting occur among the following types of cultures: (1) mated homokaryotic mycelia grown from dwarf ascospores; (2) heterokaryotic mycelia grown from normal-sized ascospores; (3) hyphal-tip cultures from heterokaryotic mycelia. Such behavior may be caused by a mutant nucleus whose nutritional factors do not complement those in the nuclei of opposite mating type. Among the sterile and slow-fruiting strains were found 'barrage' mutants. They differ in texture and growth rate from wild strains. When grown in pairs, their hyphac, as they approach each other, exhibit aversion or barrage. Progeny of mated barrage strains are likewise barrage strains.

Evidence for mitochondrial gene control of mating types in Phytophthora

2005 ◽  
Vol 51 (11) ◽  
pp. 934-940 ◽  
Author(s):  
Yu-Huan Gu ◽  
Wen-Hsiung Ko
Keyword(s):  
Mating Type ◽  
Mitochondrial Gene ◽  
Phytophthora Capsici ◽  
Nuclear Genes ◽  
Gene Control ◽  
Mating Types ◽  
Phytophthora Parasitica ◽  
Decisive Effect ◽  
Mating Type Genes ◽  
Fusion Products

When protoplasts carrying metalaxyl-resistant (Mr) nuclei from the A1 isolate of Phytophthora parasitica were fused with protoplasts carrying chloroneb-resistant (Cnr) nuclei from the A2 isolate of the same species, fusion products carrying Mr nuclei were either the A2 or A1A2 type, while those carrying Cnr nuclei were the A1, A2, or A1A2 type. Fusion products carrying Mr and Cnr nuclei also behaved as the A1, A2, or A1A2 type. The result refutes the hypothesis that mating types in Phytophthora are controlled by nuclear genes. When nuclei from the A1 isolate of P. parasitica were fused with protoplasts from the A2 isolate of the same species and vice versa, all of the nuclear hybrids expressed the mating type characteristics of the protoplast parent. The same was true when the nuclei from the A1 isolate of P. parasitica were fused with the protoplasts from the A0 isolate of Phytophthora capsici and vice versa. These results confirm the observation that mating type genes are not located in the nuclei and suggest the presence of mating type genes in the cytoplasms of the recipient protoplasts. When mitochondria from the A1 isolate of P. parasitica were fused with protoplasts from the A2 isolate of the same species, the mating type of three out of five regenerated protoplasts was changed to the A1 type. The result demonstrated the decisive effect of mitochondrial donor sexuality on mating type characteristics of mitochondrial hybrids and suggested the presence of mating type genes in mitochondria. All of the mitochondrial hybrids resulting from the transfer of mitochondria from the A0 isolate of P. capsici into protoplasts from the A1 isolate of P. parasitica were all of the A0 type. The result supports the hypothesis of the presence of mating type genes in mitochondria in Phytophthora.Key words: mating type, mitochondrial gene, Phytophthora parasitica, Phytophthora capsici.

scholarly journals Isolation and genetic analysis of Saccharomyces cerevisiae mutants supersensitive to G1 arrest by a factor and alpha factor pheromones.

1982 ◽  
Vol 2 (1) ◽  
pp. 11-20 ◽  
Author(s):  
R K Chan ◽  
C A Otte
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Solid Medium ◽  
G1 Arrest ◽  
Alpha Cells ◽  
Opposite Mating Type ◽  
Alpha Factor ◽  
Complementation Groups ◽  
Chromosome Iii ◽  
The Right

Eight independently isolated mutants which are supersensitive (Sst-) to the G1 arrest induced by the tridecapeptide pheromone alpha factor were identified by screening mutagenized Saccharomyces cerevisiae MATa cells on solid medium for increased growth inhibition by alpha factor. These mutants carried lesions in two complementation groups, sst1 and sst2. Mutations at the sst1 locus were mating type specific: MATa sst1 cells were supersensitive to alpha factor, but MAT alpha sst1 cells were not supersensitive to a factor. In contrast, mutations at the sst2 locus conferred supersensitivity to the pheromones of the opposite mating type on both MATa and MAT alpha cells. Even in the absence of added alpha pheromone, about 10% of the cells in exponentially growing cultures of MATa strains carrying any of three different alleles of sst2 (including the ochre mutation sst2-4) had the aberrant morphology ("shmoo" shape) that normally develops only after MATa cells are exposed to alpha factor. This "self-shmooing" phenotype was genetically linked to the sst2 mutations, although the leakiest allele isolated (sst2-3) did not display this characteristic. Normal MATa/MAT alpha diploids do not respond to pheromones; diploids homozygous for an sst2 mutation (MATa/MAT alpha sst2-1/sst2-1) were still insensitive to alpha factor. The sst1 gene was mapped to within 6.9 centimorgans of his6 on chromosome IX. The sst2 gene was unlinked to sst1, was not centromere linked, and was shown to be neither linked to nor centromere distal to MAT on the right arm of chromosome III.

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