Fitness Cost of Imazamox Resistance in Wild Poinsettia (Euphorbia heterophylla L.)

Abstract

Wild poinsettia (Euphorbia heterophylla L.) is a difficult-to-control weed in soybean production in Brazil that has developed resistance to herbicides, including acetolactate synthase inhibitors. We investigated the potential fitness cost associated to the Ser-653-Asn mutation that confers imazamox resistance in this weed. Plant height, leaf and stem dry weight, leaf area and seed production per plant as well as the growth indices of specific leaf area, leaf area ratio, relative growth rate and net assimilation in F2 homozygous resistant (R) and susceptible (S) wild poinsettia progenies were pairwise compared. S plants were superior in most of the traits studied. Plant heights for S and R biotypes, recorded at 95 days after planting (DAP), were 137 and 120 cm, respectively. Leaf areas were 742 and 1048 cm2 in the R and S biotypes, respectively. The dry weights of leaves and stems in the S plants were 30 and 35%, respectively, higher than in the R plants. In both biotypes, the leaves had a greater share in dry weight at early development stages, but from 50 DAP, the stem became the main contributor to the dry weight of the shoots. The R biotype produced 110 ± 4 seed plant−1, i.e., 12 ± 3% less seeds per plant than that of the S one (125 ± 7 seed plant−1). The growth indices leaf area ratio and specific leaf area were generally higher in the S biotype or similar between both biotypes; while the relative growth rate and net assimilation rate were punctually superior in the R biotype. These results demonstrate that the Ser-653-Asn mutation imposed a fitness cost in imazamox R wild poinsettia.

Performance of ACCase-Resistant and ACCase-Susceptible Phenotypes of Sterile Oat Avena sterilis subsp. ludoviciana (Durieu) Nyman under Drought Conditions in the Greenhouse

“…Therefore, lower seed numbers produced by the ACCase-resistant phenotype would cause a reduced frequency of the resistance alleles in the absence of herbicide selection [37]. Hassanpour-Bourkheili et al (2020) found increased seed production of imazamox-susceptible than resistant biotypes of wild poinsettia (Euphorbia heterophylla L.), suggesting a fitness penalty for the resistant phenotype [38]. However, investigating the germination response of ACCase-resistant and ACCase-susceptible sterile oat under different environmental conditions, Hassanpour-Bourkheili et al (2021) reported no fitness cost for seed output [20].…”

Herbicide Resistance in Phalaris Species: A Review

“…The fitness cost imposed by herbicide resistance may be quantified by measuring various characteristics of the species, including germination [83], phenology, vegetative characteristics, fecundity, and yield [90]. Conversely, herbicide resistance may impose no fitness cost on the species [91,92]. Furthermore, the mutation responsible for resistance may even lead to positive [93] effects on the growth and reproduction of the species.…”