Incentive (in)compatibility: Group-based tournaments

Author(s):  
László Csató
Keyword(s):  
Genetics ◽  
2002 ◽  
Vol 161 (2) ◽  
pp. 633-641
Author(s):  
Christina A Muirhead ◽  
N Louise Glass ◽  
Montgomery Slatkin

Abstract Trans-species polymorphism, meaning the presence of alleles in different species that are more similar to each other than they are to alleles in the same species, has been found at loci associated with vegetative incompatibility in filamentous fungi. If individuals differ at one or more of these loci (termed het for heterokaryon), they cannot form stable heterokaryons after vegetative fusion. At the het-c locus in Neurospora crassa and related species there is clear evidence of trans-species polymorphism: three alleles have persisted for ∼30 million years. We analyze a population genetic model of multilocus vegetative incompatibility and find the conditions under which trans-species polymorphism will occur. In the model, several unlinked loci determine the vegetative compatibility group (VCG) of an individual. Individuals of different VCGs fail to form productive heterokaryons, while those of the same VCG form viable heterokaryons. However, viable heterokaryon formation between individuals of the same VCG results in a loss in fitness, presumably via transfer of infectious agents by hyphal fusion or exploitation by aggressive genotypes. The result is a form of balancing selection on all loci affecting an individual's VCG. We analyze this model by making use of a Markov chain/strong selection, weak mutation (SSWM) approximation. We find that trans-species polymorphism of the type that has been found at the het-c locus is expected to occur only when the appearance of new incompatibility alleles is strongly constrained, because the rate of mutation to such alleles is very low, because the number of possible incompatibility alleles at each locus is restricted, or because the number of incompatibility loci is limited.


Plant Disease ◽  
2004 ◽  
Vol 88 (6) ◽  
pp. 645-649 ◽  
Author(s):  
D. J. Vakalounakis ◽  
Z. Wang ◽  
G. A. Fragkiadakis ◽  
G. N. Skaracis ◽  
D.-B. Li

Thirty-four isolates of Fusarium oxysporum, obtained in China from cucumber plants showing either Fusarium wilt (F. oxysporum f. sp. cucumerinum) or root and stem rot (F. oxysporum f. sp. radicis-cucumerinum) symptoms, were characterized by pathogenicity, vegetative compatibility, and random amplified polymorphic DNA (RAPD). Of these, 23 isolates were identified by pathogenicity as F. oxysporum f. sp. cucumerinum, and one as F. oxysporum f. sp. radicis-cucumerinum, while 10 isolates were avirulent on cucumber, melon, sponge gourd, and pumpkin. The Chinese isolates of F. oxysporum f. sp. cucumerinum were assigned to RAPD groups III and XXI and to vegetative compatibility group (VCG) 0183, four new VCGs, 0184 to 0187, and a single-member VCG included in the artificial VCG 018-. The Chinese isolate of F. oxysporum f. sp. radicis-cucumerinum was assigned to RAPD group I and bridging VCG 0260/0261. The occurrence of F. oxysporum f. sp. radicis-cucumerinum on cucumber is reported for the first time in China.


Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 237-240 ◽  
Author(s):  
Matias Pasquali ◽  
Flavia Dematheis ◽  
Giovanna Gilardi ◽  
Maria Lodovica Gullino ◽  
Angelo Garibaldi

Fusarium oxysporum f. sp. lactucae, the causal agent of Fusarium wilt of lettuce, has been reported in three continents in the last 10 years. Forty-seven isolates obtained from infected plants and seed in Italy, the United States, Japan, and Taiwan were evaluated for pathogenicity and vegetative compatibility. Chlorate-resistant, nitrate-nonutilizing mutants were used to determine genetic relatedness among isolates from different locations. Using the vegetative compatibility group (VCG) approach, all Italian and American isolates, type 2 Taiwanese isolates, and a Japanese race 1 were assigned to the major VCG 0300. Taiwanese isolates type 1 were assigned to VCG 0301. The hypothesis that propagules of Fusarium oxysporum f. sp. lactucae that caused epidemics on lettuce in 2001-02 in Italian fields might have spread via import and use of contaminated seeds is discussed.


Author(s):  
Joanna Szczygielska ◽  
Agata Gaca ◽  
Daniel Buczkowski

The classification of explosives in accordance with GHS is based on the system defined in the UN Recommendations on the Transport of Dangerous Goods, Model Regulations. In many cases, classification of explosives depends on certain transport packaging. This approach results in that a number of classified explosives, after removal from the transport packaging, being placed in to another division and compatibility group, what is not communicated by the hazard communication elements appearing on the label. Experts of the GHS Sub-Committee from 2015 have been taking action to change the system of explosives classification, so that the criteria allow for proper assessment of the hazard posed by a specific explosive in a configuration other than for transport.


Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 789-797 ◽  
Author(s):  
R. G. Bhat ◽  
R. F. Smith ◽  
S. T. Koike ◽  
B. M. Wu ◽  
K. V. Subbarao

Epidemics of Verticillium wilt in pepper fields of the central coast of California and isolates of Verticillium dahliae associated with these epidemics were characterized. The mean incidence of wilted plants per field ranged from 6.3 to 97.8% in fields with Anaheim, jalapeno, paprika, or bell peppers. In general, incidence of wilt in jalapeno and bell pepper crops was lower than in crops of other types of pepper. Inoculum density of V. dahliae in the surveyed pepper fields ranged from 2.7 to 66.6 microsclerotia g-1 dry soil, and the correlation between disease incidence and density of microsclerotia was high (r = 0.81, P < 0.01). Distribution of Verticillium wilt was aggregated in a majority of the pepper fields surveyed, but the degree of aggregation varied. Vegetative compatibility group (VCG) characterization of 67 isolates of V. dahliae indicated that 67% belonged to VCG 2, 22% to VCG 4, and 11% to a new group, designated VCG 6. The pathogenicity of isolates of V. dahliae from bell pepper and tomato plants was tested by inoculating 1-month-old bell pepper (cv. Cal Wonder) and tomato (cv. EP 7) seedlings and incubating the inoculated plants in the greenhouse. Seedlings of bell pepper were susceptible only to the isolates of V. dahliae from pepper, whereas seedlings of tomato were susceptible to both pepper and tomato isolates. Pepper isolates belonging to VCG 2, VCG 4, and VCG 6 were highly pathogenic to bell pepper and chili pepper. Temperatures between 15 and 25°C were optimal for mycelial growth of a majority of isolates of V. dahliae. Molecular characterization of pepper isolates of V. dahliae using a polymerase chain reaction (PCR)-based random amplified polymorphic DNA (RAPD) technique revealed minor variation among these isolates, but unique polymorphic banding patterns were observed for isolates belonging to VCG 6. Verticillium wilt of pepper is a major production constraint in the central coast of California. More aggressive isolates of V. dahliae may have been selected in this region as a result of intensive cropping practices.


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