【目的】明确我国水稻田发生危害的稗属(Echinocloa spp.)杂草种类分布特点。【方法】2015年至2018年间的9月至11月,在东北、华东、华南、西北、西南水稻产区依据《中国植物志》英文修订版的分类鉴定标准,于水稻收割前采用七级目测法调查了73个地点共525块稻田稗属杂草的发生情况。【结果】共发现8种稗属杂草,其中无芒稗(E. crusgalli var. mitis)的发生频度最大(55.43%),其次是硬稃稗(E. glabrescens, 47.28%)、稗原变种(E. crusgalli var. crusgalli,40.40%)、西来稗(E. crusgalli var. zelayensis,24.09%);长芒稗(E. caudate)、水田稗(E. oryzoides)、孔雀稗(E. cruspavonis)、光头稗(E. colona)的频度较低。东北地区稻田稗属杂草以水田稗为单优势种;华东地区稻田稗属杂草呈现共优势的格局,硬稃稗、无芒稗危害最重,西来稗、稗原变种发生量也较大;华南地区稻田以稗原变种为单优势种;西北地区稻田无芒稗和稗原变种为优势种;西南地区稻田无芒稗占优势,稗原变种危害频繁。在这8种水稻田常见稗属杂草中,无芒稗的生态位宽度值最大(35.2),其次是硬稃稗(23.6)、西来稗(18.2)和稗原变种(16.3)。无芒稗、硬稃稗、西来稗相互之间的生态位重叠值较高,稗原变种与孔雀稗、光头稗、长芒稗的重叠值也较高。【结论】我国不同地区具有不同的稻田稗属杂草种类分布格局,其背后的机理亟待研究阐明。

Resistance to the acetyl-coenzyme A carboxylase (ACCase)- and acetolactate synthase (ALS)- inhibiting herbicides in shortawn foxtail (Alopecurus aequalis) has been reported in wheat fields of eastern China. To better understand the distribution of the resistant populations and the occurrence of the target-site mutations, 74 populations collected from Anhui, Jiangsu and Shandong province were surveyed, and the ACCase and ALS gene fragments, encompassing all the documented mutant codon positions, were amplified and sequenced. Plants from 37 and 34 populations survived fenoxaprop-P-ethyl and mesosulfuron-methyl treatment at 62.1 g a.i. ha and 9 g a.i. ha respectively, with different survival rates. Twenty-seven populations exhibited multiple resistance to fenoxaprop-P-ethyl and mesosulfuron-methyl. Whole-plant dose-response experiments showed that the resistance index ranged from 6.2 to 167.8 for fenoxaprop-P-ethyl, and from 7.8 to 139.5 for mesosulfuron-methyl. Four ACCase (I1781L, I2041N, I2041T and D2078G) and four ALS (P197R, P197S, P197T and W574 L) resistance mutations were detected respectively. Individuals containing two amino acid substitutions were also found. D2078G and W574 L were predominant ACCase and ALS gene mutations respectively. This study has shown that fenoxaprop-P-ethyl and mesosulfuron-methyl resistance was prevalent in A. aequalis in eastern China, and target site mutations in the ACCase and ALS gene were one of the most common mechanisms.Copyright © 2018 Elsevier Inc. All rights reserved.

Target-site-based resistance to acetyl-CoA carboxylase (ACCase) inhibitors in Alopecurus myosuroides Huds. is essentially due to five substitutions (Isoleucine-1781-Leucine, Tryptophan-2027-Cysteine, Isoleucine-2041-Asparagine, Aspartate-2078-Glycine, Glycine-2096-Alanine). Recent studies suggested that cross-resistance patterns associated with each mutation using a seed-based bioassay may not accurately reflect field resistance. The authors aimed to connect the presence of mutant ACCase isoform(s) in A. myosuroides with resistance to five ACCase inhibitors (fenoxaprop, clodinafop, haloxyfop, cycloxydim, clethodim) sprayed at the recommended field rate.Results from spraying experiments and from seed-based bioassays were consistent for all mutant isoforms except the most widespread, Leucine-1781. In spraying experiments, Leucine-1781 ACCase conferred resistance to clodinafop and haloxyfop. Some plants containing Leucine-1781 or Alanine-2096 ACCase, but not all, were also resistant to clethodim.Leucine-1781, Cysteine-2027, Asparagine-2041 and Alanine-2096 ACCases confer resistance to fenoxaprop, clodinafop and haloxyfop at field rates. Leucine-1781 ACCase also confers resistance to cycloxydim at field rate. Glycine-2078 ACCase confers resistance to all five herbicides at field rates. Only Glycine-2078 ACCase confers clethodim resistance under optimal application conditions. It may be that Leucine-1781 and Alanine-2096 ACCases may also confer resistance to clethodim in the field if the conditions are not optimal for herbicide efficacy, or at reduced clethodim field rates.Copyright (c) 2008 Society of Chemical Industry.

Many herbicide-resistant weed species are polyploids, but far too little about the evolution of resistance mutations in polyploids is understood. Hexaploid wild oat (Avena fatua) is a global crop weed and many populations have evolved herbicide resistance. We studied plastidic acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide resistance in hexaploid wild oat and revealed that resistant individuals can express one, two or three different plastidic ACCase gene resistance mutations (Ile-1781-Leu, Asp-2078-Gly and Cys-2088-Arg). Using ACCase resistance mutations as molecular markers, combined with genetic, molecular and biochemical approaches, we found in individual resistant wild-oat plants that (1) up to three unlinked ACCase gene loci assort independently following Mendelian laws for disomic inheritance, (2) all three of these homoeologous ACCase genes were transcribed, with each able to carry its own mutation and (3) in a hexaploid background, each individual ACCase resistance mutation confers relatively low-level herbicide resistance, in contrast to high-level resistance conferred by the same mutations in unrelated diploid weed species of the Poaceae (grass) family. Low resistance conferred by individual ACCase resistance mutations is likely due to a dilution effect by susceptible ACCase expressed by homoeologs in hexaploid wild oat and/or differential expression of homoeologous ACCase gene copies. Thus, polyploidy in hexaploid wild oat may slow resistance evolution. Evidence of coexisting non-target-site resistance mechanisms among wild-oat populations was also revealed. In all, these results demonstrate that herbicide resistance and its evolution can be more complex in hexaploid wild oat than in unrelated diploid grass weeds. Our data provide a starting point for the daunting task of understanding resistance evolution in polyploids.

本研究旨在评估江苏稻田中稗草对四种不同除草剂的抗药性。通过2019—2022年从江苏省稻田采集稗草种子，并采用茎叶喷雾法分别测定了不同稗草种群对噁唑酰草胺、氰氟草酯、五氟磺草胺和二氯喹啉酸的抗药性。采集到的100个稗草种群用鉴别剂量法筛选出对不同除草剂的疑似抗性种群，再用不同除草剂的系列浓度药液测定这些疑似抗性种群对相应除草剂的抗性指数。测定结果表明，对噁唑酰草胺表现低抗性种群、中抗性种群和高抗性种群分别为10、8、1个；对氰氟草酯表现低抗、中抗种群各5个种群；对五氟磺草胺表现低抗、中抗和高抗种群分别为3、9、1个种群；对二氯喹啉酸表现低抗、中抗和高抗种群分别为1、7、1个种群。所测稗草种群在江苏地区13个地级市中除常州市外，均有抗性种群分布，部分地区的稗草种群表现出多抗性。

随着水稻栽培技术的持续优化，近十年我国稻谷产量均保持在2.1亿t左右的高位。直播稻作为一种高效、轻简的栽培技术，受到了广大种植户的青睐。但实际生产中，直播稻较移栽稻在我国的应用仍存在一些争议。为此，本文采用荟萃分析（meta-analysis）方法量化了直播稻和移栽稻对产量、经济效益、稻米品质、倒伏性状及温室气体排放的影响差异。总体来讲，与移栽稻相比，直播稻产量显著下降了6.3%，主要原因是群体总颖花量（-3.8%）和结实率（-1.8%）显著降低。我国不同种植制度下直播稻的产量均显著下降，其中单季稻（-10.9%）和双季晚稻（-13.1%）产量下降的幅度显著高于中稻（-4.8%）和双季早稻（-4.4%）；吉林、辽宁、新疆、宁夏、山东、江苏和浙江直播稻产量的降幅达10%—20%，黑龙江和江西直播稻产量的降幅为5%—10%，其他省份直播稻产量较移栽稻差异不显著。从经济效应来看，种植直播稻能获得与移栽稻相当的净收益（P>0.05）。直播稻显著降低了精米率（-3.1%）和胶稠度（-3.5%），改善了外观品质（垩白粒率和垩白度分别下降了25.3%和22.5%），对营养品质和食味值的影响均不显著。直播稻显著提高了茎秆基部第1节间（+12.4%）和第3节间（+10.3%）的倒伏指数，对第2节间倒伏指数的影响不显著，这表明种植直播稻会增加倒伏的风险。从温室气体排放来看，与移栽稻田相比，直播稻田甲烷排放（-42.8%）、全球增温潜势（-36.2%）和温室气体排放强度（-41.1%）均显著下降，但提高了氧化亚氮排放（+29.1%）。此外，笔者在氮素利用与损失、水分利用效率、能量利用效率和草害发生对直播稻和移栽稻的响应进行了简要综述和比较分析。最后，分别在品种筛选、栽培技术优化、种植区域布局和政策服务方面提出了未来直播稻发展的建议，以期为我国直播稻栽培技术创新与区域化应用提供数据支撑和科学依据。