Fitness competitive ability

This characteristic, however, is not universally found in all triazine-resistant weeds. Gray et al. (1995a, b) found that velvetleaf resistance to atrazine in Wisconsin was not associated with a reduction in fitness, productivity, or intraspecific competitive ability. This triazine-resistant species found in Maryland and Wisconsin does not have D1 level resistance in the chloroplasts, but instead has a more rapid metabolic detoxification of triazines in these biotypes. The extent of the rapid metabolic resistance in other velvetleaf-resistant biotypes is unknown. 

One of the main obstacles for studying the allocation of resources is determining the appropriate currency to measure cost. The different currencies that have been used include (1) the energy stored in chemical bonds,69 (2) biomass allocated to various tissues or materials responsible for different biological functions,70 (3) the amount of limiting resource allocated to different processes, (4) the competitive ability of organisms with different allocation patterns, and (5) some measure of fitness trade-off.71... 

This study also confirms an inferior competitive ability of the resistant strains compared with the wild-type strains [30]. On agar medium, however, the resistant and sensitive isolates did not differ in mycelium growth and sporulation [31]. Because of the lower fitness of resistant strains compared with sensitive strains, the resistant strains disappeared under field conditions in the absence of selection pressure by the antibiotic. Kasugamydn has again been successfully used to control rice blast, either in combination or by alternating application of fungicides displaying different modes of action [13, 19]. 

Baldwin IT, Hamilton W (2000) Jasmonate-induced responses of Nicotiana sylvestris results in fitness costs due to impaired competitive ability for nitrogen. J Chem Ecol 26 915-952. 

These practical approaches are by no means mutually exclusive, and attempts should be made to combine as many of these as possible to improve ones ability to experimentally measure the K-pp of tight binding inhibitors. Thus one should always work at the lowest enzyme concentration possible, and drive the substrate concentration as high as possible, when dealing with competitive inhibitors. A long preincubation step should be used before activity measurements, or the progress curves should be fitted to Equation (6.2) so that accurate determinations of the steady state velocity at each inhibitor concentration can be obtained. Finally, the concentration-response data should be fitted to Morrison s quadratic equation to obtain good estimates of the value of Arfpp. 

The factor / is a reproductive fitness measure that compounds the relative ability of resist nts, compared to susceptibles, in germination, establishment, growth, seed production and survival. Fitness is thus always measured when the resistant and susceptible individuals are in competition with each other in the absence of selection for the mutants. When they are grown separately the resistant individuals are often less productive , and in competitive situations the resistant individuals are more affected (Table I). (See Appendix 1 for exact mathematical definitions.)... 

This equation explicitly depends on the fraction of susceptible (qr(sl) and resistant (qr(, )) seeds that germinate. It also depends on all other aspects, including relative germination ability of resistants in competition with susceptibles. See Eq. A1.20 for the exact definition of the fitness factor /. For simplicity, and in the absence of the detailed information that would permit use of Eq. 2, we shall generally assume that the fraction germinating in a given season is small ( /( ) < 1, < 1) and that resistant and susceptible seeds perish to an... 

Receptor flexibility means that not just one key, but a number of very diverse ones, might actually fit into the same lock the way that four structurally different compounds, efavirenz, nevirapine, Cl-TIBO, and UC-781 (all non-competitive inhibitors. Figure 7.12) bind to the same site on HIV reverse transcriptase. As has been pointed out, this is a nice situation from an IP standpoint," allowing many different chemotypes to be patented for the same target, but it does tend to limit the predictive ability of computer modeling. These days, modeling can allow for a certain amount of receptor flexibility, but correctly anticipating the type of sidechain and/or backbone conformations to expect isn t easy." ... 

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