The Effect of Light and Temperature on Competition between Atrazine Susceptible and ResistantBrassica rapa

Abstract

Biotypes of Brassica rapa susceptible (S) and resistant (R) to atrazine were grown in competitive replacement series in all possible combinations of two light levels and three temperature regimes in controlled growth cabinets. Photosystem II function was investigated in all conditions by fluorescence-induction techniques. There were no significant differences in the dry weight of the two biotypes when grown in pure stands. In pure stands both biotypes produced more biomass under the high light level. Under high light both biotypes yielded more biomass at high temperature ; in low light they did so at medium temperature. Under high light conditions at high and medium temperatures the susceptible biotype had a greater photon yield and relative competitive ability than the resistant due to the greater vulnerability of triazine-resistant biotypes to photoinhibition. However, surprisingly, the resistant biotype was the better competitor, and had a higher photon yield, in the high light\low temperature regime. In low light no photoinhibition was expected and indeed there were no significant differences in any fluorescence parameters between the resistant and susceptible biotypes. Nevertheless, there were differences in the whole plant performance ; the susceptible biotype was a better competitor at low and medium temperatures, but the resistant biotype was better at high temperature. Relatively small variations in both light and temperature, well within the range encountered during British summer time, can have large effects on the relative competitiveness of triazine R and S biotypes in this species with implications for the spread of resistance genes through semi-natural communities. In light of predicted climate changes, interactions between climate and resistance should be studied across a wider range of herbicide types and weed species.# 1997 Annals of Botany Company

The Biology of Canadian Weeds. 137. Brassica napus L. and B. rapa L.

“…An interaction between temperature and light levels in the competitive outcome between triazine-tolerant and triazine-susceptible rapid-cycling domesticated B. rapa was observed. At low light and high temperatures, the resistant biotype was a better competitor than the susceptible biotype (Plowman and Richards 1997). Friesen et al (2003) examined 27 commercially available certified seedlots of conventional B. napus for contamination with herbicide-resistant seed.…”

The effect of low growth temperature on Hill reaction and Photosystem 1 activities in three biotypes of Kochia scoparia (L.) Schrad. with different sensitivity to atrazine and ALS-inhibiting herbicides

“…It is now widely accepted that the resistance of plants to triazines, caused by the specific mutation(s) at the Q B site of the D1 protein, is associated not only with the lowered efficiency of photosynthetic electron transport but also with the increased sensitivity of plants to photoinhibition and the decreased efficiency of some protective processes (e.g. the light-induced formation of zeaxanthin) (Darko et al 1996, Plowman and Richards 1997, Devine and Shukla 2000, Kumata et al 2001, Szigeti and Lehoczki 2003, Varadi et al 2003. The triazinesusceptible biotypes are therefore usually better adapted to the growth under high light conditions compared to the resistant ones.…”

“…The triazinesusceptible biotypes are therefore usually better adapted to the growth under high light conditions compared to the resistant ones. Plowman and Richards (1997), who examined the effect of high and low light and three temperature regimes on atrazine-susceptible and -resistant Brassica rapa, have found that under high light conditions the susceptible biotype showed a greater photon yield and relative competitive ability than the resistant biotype when grown at high or medium temperatures, but at low temperature the situation was reverse. Under low light conditions, the chlorophyll fluorescence parameters of both biotypes did not differ in either temperature regime examined, which agrees well with our results.…”

“…Amaranthus sp., Conyza canadensis, Senecio vulgaris, Solanum nigrum) it seems that the biotypes resistant to triazines are better adapted to low temperatures and worse adapted to heat and high light intensity compared to the sensitive ones (McCloskey and Holt 1991, Dekker 1993, Plowman and Richards 1997, Kremer and Lotz 1998, Dulai et al 1999, Szigeti and Lehoczki 2003. Kochia is a plant with C4 type of photosynthesis and as such normally prefers warmer temperatures to cold (Nord et al 1999, Fischer et al 2000.…”

An Investigation of Tradeoffs in Herbicide Resistant <i>Brassica rapa</i>: Effects on Pollen and Ovule Production, Biomass and Development

“…For example, Plowman and Richards (1997) conducted a study comparing competitive ability between resistant and susceptible biotypes of Brassica rapa. Their study consisted of two light levels and three temperature treatments.…”