Competition effects with mixed stands of wheat and kochia (Kochia scoparia) biotypes resistant and susceptible to acetolactase synthase inhibitor herbicides

Abstract

Greenhouse experiments were conducted to compare the competitive ability of sulfonylurea resistant and susceptible kochia (Kochia scoparia L. Schard) compared to wheat. The results of several replacement series experiments indicate that wheat was the dominant competitor, and an average of one wheat plant reduced resistant kochia yield per plant equal to the effect of 4.8 resistant kochia or 5.4 susceptible kochia plants. Intraspeciflc competition was more important than interspecific competition for wheat, whereas the reverse was true for the resistant and susceptible kochia. The results of the niche differentiation index (NDI) indicate that wheat and either resistant or susceptible kochia are only partly limited by the same resources. The resistant and susceptible kochia, however, are limited by the same resources.

The ecological fitness of ALS‐resistant Amaranthus retroflexus and multiple‐resistant Amaranthus blitoides

“…Our data indicate that the trait conferring resistance to ALS inhibitor herbicides in A. retroflexus and A. blitoides is not associated with a growth penalty and did not result in an ecological cost in the field. Similar trends were reported for sulfonylurea resistant K. scoparia biotypes (Christoffoleti & Westra, 1994; Thompson et al ., 1994; Christoffoleti et al ., 1997). Lior (2001) also demonstrated in field experiments that Plantago lagopus L. resistant to sulfonylurea was not less competitive than the susceptible biotype.…”

“…Indeed, greenhouse competition experiments with biotypes resistant to ALS inhibitors in Lactuca serriola L. (Alcocer‐Ruthling et al ., 1992a, b) and Kochia scoparia (L.) Schrad. (Christoffoleti & Westra, 1994; Thompson et al ., 1994), showed no differences in competitiveness between the SuR and SuS biotypes.…”

Wheat Density Alters but Does Not Repress the Expression of a Fluroxypyr-Resistant Kochia (Bassia scoparia) Phenotype

“…Thus, targeting wheat plant densities of 450 plants m −2 could result in an optimal balance of improved crop competitive ability and augmented weed control absent of the potential or perceived yield detriments of ultra-high wheat densities. Further confirmation of these results under variable field conditions is warranted since environmental conditions can be a key driver in the competitive balance among these species [46], and because their ecological niches only partially overlap [47], suggesting that availability of certain resources will drive the competitive balance more than others.…”