Molecular evidence of biased inheritance of trifluralin herbicide resistance in foxtail millet

Inheritance of trifluralin herbicide resistance was investigated for phenotype and genotype (molecular identification) in 12 segregating populations derived from crosses between resistant green foxtail (Setaria viridis) and foxtail millet cultivars (S. italica). Combining a herbicide bioassay and a bidirectional allele‐specific polymerase chain reaction (PCR) assay, the trifluralin resistance in foxtail millet was proved to be conferred by a recessive α2‐tubulin gene mutation at Ile‐239, the allele transferred by green foxtail. However, a distorted segregation ratio in F₂ populations was confirmed, with 16.9% resistant plants on average instead of the 25% expected for a single gene recessive mutation. This was not due to non‐germinating seed and the distortion was also observed in the next generations, indicating a heritable phenomenon. After further crosses and self‐fertilization, however, more advanced generations did not show the same pattern of skewed inheritance as in the early generations. These results suggest the possibility of linkage between the α2‐tubulin gene and a modifier gene to explain the distorted segregation, which might be broken by crossing over.     

氟乐灵除草肥在胡麻田的试验研究

试验采用完全随机的方法,就氟乐灵除草剂与肥料混用在胡麻田中的药效及安全性作了盆栽试验,对不同氟乐灵除草肥浓度下胡麻及其模拟杂草的出苗、株高、鲜重等形态指标及胡麻的叶绿素、硝酸还原酶、POD、可溶性糖等生理指标进行了测定分析。结果表明:氟乐灵(2.25L/hm2)与肥料混用对胡麻田安全性较高,对胡麻田模拟禾本科杂草谷子及模拟阔叶杂草油菜的防除效果较好,可作为胡麻田良好的除草肥。     

Antimicrotubule herbicides for in vitro chromosome doubling in Beta vulgaris L. ovule culture

In vitro chromosome doubling during ovule culture of sugar and fodder beets (Beta vulgaris L.) was studied with four anti-microtubule herbicides: amiprophos-methyl (APM), oryzalin, pronamide, and trifluralin at concentrations of 0–300 μM. Best chromosome doubling results were obtained by treatment of the ovules with 100 μM APM which produced 4.7 diploid plants per 100 ovules. Highest chromosome doubling was found with oryzalin using 1 μM, with trifluralin at 10 μM, and with pronamide at 10 μM producing 2.8, 2.0, and 2.0 diploid plants per 100 ovules, respectively. The APM treatments showed relatively low toxicity on embryo formation which in combination with a high chromosome doubling effect, resulted in up to 89 diploids per 100 plants regenerated. Oryzalin and trifluralin had more severe toxic effects, which reduced embryo formation, thereby lower percentages of chromosome doubled plants were obtained from these treatments. Pronamide had no significant toxic effect but it induced chromosome doubling at lower frequencies. Compared to colchicine, APM seems to be as efficient for chromosome doubling during beet ovule culture, but at molar concentrations 100 times lower than those used for chromosome doubling with colchicine. This revised version was published online in July 2006 with corrections to the Cover Date.     

玉米抗腐霉菌茎腐病超微结构的研究

超微结构观察表明,抗茎腐病玉米品种冀丰５８号幼苗根组织被肿吓腐霉菌侵染后,细胞迅速出现严重的质壁分离,质膜消失、各种细胞器紊乱破碎。侵入根组织的肿囊腐霉菌数量少,幼嫩且形态异常,菌丝外周或整个菌丝中出理一些电子致密物质,可能与发生过敏性坏死反应有关。感颈腐病品种掖单１３号幼苗根组织被侵染细胞的壁完整,但细胞质凝聚或细胞器发生解体。根组织内在大量胞间及胞内生长菌丝,菌丝较成熟、粗壮,含大量的泡囊及线粒体,结构正常。氟乐灵浸种后再接种肿囊腐霉,玉米根系的超微结构较单独接种肿囊霉处理有明显的不同,抗病品种的ＨＲ反应更加剧烈、迅速,甚至感病品种也被诱导产生了ＨＲ反应,尤其是被侵染细胞及其临近细胞有大量近球形的电子致密物质沉积,该物质可能与抗性有关。这些电子致密物质在抗感品种上均有出现,在单独接种肿囊腐霉处理中出现很少。     

Phytotoxicity of trifluoromethyl- and methyl-substituted dinitroaniline herbicides on resistant and susceptible populations of black-grass (Alopecurus myosuroides)

A Petri-dish assay was used to determine the phytotoxicities of the dinitroaniline herbicides pendimethalin, trifluralin, benfluralin and ethalfluralin, and the methyl-substituted analogues of the last three herbicides, on susceptible (Rothamsted) and multiple-herbicide resistant (Peldon) populations of blackgrass Alopecurus myosuroides Huds. The Peldon population showed a high degree of resistance to pendimethalin, which possesses a 3,4-dimethyl substitution. The two populations were equally sensitive to trifluralin, benfluralin and ethalfluralin which do not possess ring-methyl groups but contain a 4-trifluoromethyl group. Substitution of the 4-trifluoromethyl with a methyl group, as demonstrated by the analogues, reduced phytotoxicity, but to a much greater degree in Peldon than in the Rothamsted population. The study indicates that resistance to pendimethalin in the Peldon population is attributable to an oxidative degradation of the 4-methyl group, analogous to that which occurs with resistance to chlorotoluron. The lack of cross-resistance to the other dinitroaniline herbicides appears to be due to the absence of ring-methyl or other groups which are vulnerable to oxidative degradation, trifluoromethyl groups being particularly resistant to this form of reaction.     

A single polymerase chain reaction-based assay for simultaneous detection of two mutations conferring resistance to tubulin-binding herbicides in Setaria viridis

A simple method based upon polymerase chain reaction (PCR) was developed to detect mutant alleles of the gene encoding α2-tubulin, which confers recessive resistance to tubulin-binding herbicides in Setaria viridis. Multiplex, bidirectional allele-specific PCR (Mbi-PASA) was shown to specifically and reliably detect the presence of all sensitive (Leu₁₃₆, Thr₂₃₉) and resistant (Phe₁₃₆, Ile₂₃₉) α2-tubulin alleles in a single reaction. Double-blind analysis of 2000 S. viridis seedlings using seed bioassay and Mbi-PASA confirmed that the presence of two mutant α2-tubulin alleles in a seedling was always associated with cross-resistance to dinitroaniline and benzoic acid herbicides, sensitivity to a benzamide herbicide, and hypersensitivity to carbamate herbicides. No other resistance mechanism was detected in the S. viridis populations screened. Successful Mbi-PASA genotyping was achieved with fresh and dried plant fragments from the field. Compared with bioassays, Mbi-PASA is faster and more robust, removing the need for live plant material. It is the only way of detecting recessive resistance before resistant plants occur in a field. Mbi-PASA can be performed with basic molecular biology laboratory equipment, and is suitable for high-throughput genotyping adaptation. It is the tool of choice for resistance diagnosis in such cases where only a few recessive, target-derived, genes control resistance to herbicides.     

不同抗有丝分裂剂诱导植物多倍体的成效对比

多倍体具有提高作物环境耐受性以及生物量的优势,因而人工诱导多倍体为作物育种和开发提供了新思路。使用抗有丝分裂剂获得多倍体,其效果取决于抗有丝分裂剂的种类、浓度和处理时间。本文对比了不同抗有丝分裂剂的作用原理及其诱导多倍体的处理条件和效果,以期帮助科研工作者选择合适的试剂,提高植物多倍体的诱导效率。     

Measurement and modelling of glyphosate fate compared with that of herbicides replaced as a result of the introduction of glyphosate-resistant oilseed rape

BACKGROUND: Crops resistant to glyphosate may mitigate the increasing contamination of the environment by herbicides, since their weeding requires smaller amounts of herbicides and fewer active ingredients. However, there are few published data comparing the fate of glyphosate with that of substitute herbicides under similar soil and climatic conditions. The objectives of the work reported here were (i) to evaluate and compare the fate in soil in field conditions of glyphosate, as used on glyphosate-resistant oilseed rape, with that of two herbicides frequently used for weed control on the same crop, albeit non-resistant: trifluralin and metazachlor, and (ii) to compare field results with predictions of the pesticide root zone model (PRZM), parameterized with laboratory data. Dissipation and vertical distribution in the soil profile of glyphosate, trifluralin and metazachlor were monitored in an experimental site located in Eastern France for 1 year. RESULTS: Herbicide persistence in the field increased as follows: metazachlor < glyphosate < trifluralin, contrary to laboratory results showing glyphosate to be least persistent. The main metabolite of glyphosate-aminomethylphosphonic acid (AMPA)-was more persistent than glyphosate. AMPA and trifluralin had the largest vertical mobility, followed by metazachlor and glyphosate. PRZM underestimated the dissipation rate of glyphosate in the field and the formation of AMPA, but its predictions for trifluralin and metazachlor were correct. The simulation of herbicides and AMPA distribution in the soil profile was satisfactory, but the mobility of trifluralin and metazachlor was slightly underestimated, probably because PRZM ignores preferential flow. In general, data from the laboratory allowed an acceptable parameterization of the model, as indicated by goodness-of-fit indices. CONCLUSION: Because of the detection of AMPA in the deep soil layer, the replacement of both trifluralin and metazachlor with glyphosate might not contribute to decreasing environmental contamination by herbicides. PRZM may be used to evaluate and to compare other weed control strategies for herbicide-resistant as well as non-resistant crops.     

氟乐灵微囊的制备、表征及其光稳定性研究

为增强氟乐灵的光稳定性,提高其有效利用率,以壳聚糖(CS)和甲基丙烯酸甲酯(MMA)为壁材,采用原位聚合法制备了氟乐灵微囊,并测定了其外观形态、粒径及其分布、包封率和载药量,同时研究了其释放特性及其在土壤和水中的光稳定性。结果表明:所制备的氟乐灵微囊呈规则球形;粒径在3~10μm之间,平均粒径为6.5μm;包封率和载药量分别为79%和45%;该微囊具有良好的缓释性能,释放以Fick扩散为主;与氟乐灵乳油相比,氟乐灵微囊的光稳定性显著增强,在试验条件下,其在土壤表面和水中的光解半衰期分别为22 d和173 min。