The occurrence of "arms race" or "trench warfare" dynamics has been studied in controlled laboratory experiments with bacterium-phage systems and theoretical predictions have been tested [ 4- 10].
Thus, the occurrence of host races [ 6, 10, 56] cannot at present be explained by limited phenotypic plasticity or by strong genetic trade-offs in adaptation to different host plants.
The study clearly highlighted the occurrence of multiple/new races of Foc in India and suggests the continuous monitoring of changes in Foc population to check the susceptibility of widely grown resistant cultivars against these races.
Mathematical models of predator-prey or parasitoid-host coevolution predict that environmental factors influencing the fecundity, density-dependent factors limiting population dynamics, and the costs of defensive traits of victims determine the occurrence of arms races or the levels of coevolutionary escalation ([ 77- 79]; N. Iseki, H. Toju and A. Sasaki, unpubl).
Occurrence of this new race of Foc in India mainly appeared to be a recent introduction through seed transmission and pathogen genetic variability from accumulation of mutations over the time.
Compelling evidence of such intrinsic limits to host range within a single species stems from the occurrence of sympatric host races [ 1- 8].
First, both non-government, community-driven initiatives follow occurrences of deadly race-related violence that have caused deep hurt, confusion and division within American communities.
Lycopadiene (46) is considered a biomarker for race L strains of B. braunii as there are no reports for the occurrence of this compound in race B strains [ 90].
In the present study, although the AST and LDH levels did not significantly change in either group, the CK level was elevated equally in both groups upon racing, indicating the occurrence of muscular damage during horse racing (Table 1).
This simple model has been extended to multilocus models [4], [5], where costs can prevent the occurrence of generalist parasites ('super-races') that infect all host genotypes, resulting in the occurrence of sustained, potentially chaotic fluctuations in host and parasite genotypes [5].
