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.

中文翻译：

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野生一品红（大戟）抗Imazamox抗性的健身成本

野生一品红（Euphorbia heterophylla L.）是巴西大豆生产中难以控制的杂草，对除草剂（包括乙酰乳酸合酶抑制剂）具有抗性。我们调查了与杂草中给予咪唑莫司抗性的Ser-653-Asn突变相关的潜在适应性成本。F _2的株高，叶和茎干重，单株叶面积和种子产量以及比叶面积，叶面积比，相对生长率和净同化的生长指数将成对的纯合抗性（R）和易感性（S）野生一品红后代进行比较。在大多数研究的性状中，S植物均表现优异。种植后95天（DAP）记录的S和R生物型的株高分别为137和120 cm。在R和S生物型中，叶面积分别为742和1048 cm ²。S植物的叶和茎的干重分别比R植物的高30％和35％。在这两种生物型中，叶片在早期发育阶段的干重份额较大，但从50 DAP起，茎部成为茎干重的主要贡献者。R生物型产生的种子植物为110±4 ^-1，即，每株植物的种子产量比S一（125±7种子植物^-1）少12±3％）。S生物型或两种生物型之间的生长指数叶面积比和比叶面积通常较高；而在R生物型中，相对生长率和净同化率在时间上要好一些。这些结果表明，Ser-653-Asn突变使Imazamox R野生一品红增加了适应性成本。