稻茬麦田禾本科杂草防除研究

我县稻茬麦常年占三麦面积的90%以上,以看麦娘、硬草、千金子为主的禾本科杂草是麦田主要恶性杂草,全县发生面积25万亩左右,占三麦面积的39.7%,杂草密度每平方尺200～300株,严重田块超过千株。近几年,冬前化除已达18万亩,但草害造成的损失每年仍在1000万斤左右。1984～1986年,我站对麦田禾本科杂草在免、旋耕田的出草规律及化除技     

汉阴县麦田杂草优势种群及防除

陕西省汉阴县麦田杂草有13科23种,其中分布范围较广、密度较大的有看麦娘、日本看麦娘、菵草、长芒棒头草等单子叶杂草和繁缕、猪殃殃、大巢菜、藜、刺儿菜等双子叶杂草.水稻茬麦田杂草发生危害重于旱地麦田,水稻茬麦田的优势杂草主要有看麦娘、繁缕、日本看麦娘、菵草,旱地麦田优势杂草主要有繁缕、猪殃殃、大巢菜、刺儿菜.针对麦田杂草的发生特点,提出协调农业防除与化学防除的综合治理策略,化学防除要针对麦田的不同杂草优势种群,合理选用除草剂,以达到综合除草效果.     

麦田恶性杂草看麦娘的发生和防治

近几年,我县大面积实行稻麦两熟制,由于三麦播种期显著提早,连茬小麦田增多,导致麦田杂草猖獗发生,其中以看麦娘发生面广量大,危害最重,已成为三麦高产的严重障碍。据1981—84年调查,看麦娘密度平均每平方尺100株以上的(需用药防治的)面积约占总面积的80％左右,一般损失1—2成,严重的3—5成,还有些麦田由于草盖苗严重失收。可见防除麦田杂草对增产潜力很大。几年来我们对麦田主要恶性杂草看麦娘的发生及其     

麦田杂草综合治理应用技术

麦田杂草已发展成为影响我市三麦生产再上新台阶的重大障碍。据1986年春调查，全市麦田主要杂草21科63种。发生面积350万亩左右，其中禾本科杂草80万亩，阔叶杂草270万亩。而且密度很大，硬草、看麦娘等，一般每平方米2700～4500株，高的达9000株以上。每年全市因杂草为害损失小麦7．5万吨以上。为了最大限度地控制麦田草害，我们从1985年起，对麦田杂草综合治理技术进行了研究，总结出了一套行之有效的“精、禁、工。药”麦田杂草综合治理技术措施。“精”：即精选麦种。麦种内含有大量的杂草种子，随麦种调运和播种进行传播。1988年在郊县…     

扬州市邗江区小麦田杂草调查与日本看麦娘的化学防除

2014年对扬州市邗江区的麦田杂草进行了抽样调查,结果表明,小麦田禾本科杂草中优势种类为日本看麦娘、菵草、看麦娘和硬草;阔叶杂草优势种有猪殃殃、野老鹳草、牛繁缕和泥胡菜;日本看麦娘在所有调查田间的发生密度最大、频度最高,且丘陵山区的发生程度重于沿江地区。对日本看麦娘的田间药效试验结果表明,炔草酯、甲基二磺隆对该地区日本看麦娘的防除效果均不理想,7．5％啶磺草胺可湿性粉剂（WP）187．5 g/hm2对麦田日本看麦娘的防除效果较好,且对小麦生长安全,是该地区麦田防除日本看麦娘的理想药剂。     

江苏省镇江市麦田杂草发生情况调查

为了摸清江苏省镇江市麦田杂草种类、分布状况、出草规律、草相变化、防除情况等,通过倒"W"形九点取样法对镇江市麦田杂草进行了调查。调查结果显示镇江市麦田杂草有29科99种,日本看麦娘、菵草、猪殃殃、看麦娘、稻槎菜、硬草、繁缕、大巢菜、荠菜、涩荠、野老鹳草、牛繁缕、早熟禾为该地区主要危害性杂草,其中菵草、日本看麦娘、猪殃殃为麦田杂草群落优势种。不同地形区域杂草种类和优势种不同。镇江市麦田杂草由20世纪90年代初以看麦娘、日本看麦娘和猪殃殃等为主演变为以菵草、日本看麦娘、猪殃殃为主,稻槎菜、硬草、繁缕等发生较重。出草高峰集中在小麦播后15 d左右,具体到镇江来说11月底至12月上旬为杂草发生高峰期。针对镇江本地杂草发生情况,制定了以土壤封闭和茎叶处理相结合的防控技术方案。     

啶磺草胺水分散粒剂防除冬小麦田杂草试验示范

7.5%啶磺草胺WG 187.5 g/hm2+助剂450 mL/hm2,冬、春用药后60 d除草效果达98%以上,冬用杀草速度快于春用,其药效高峰出现在药后45~60 d。可有效防除麦田看麦娘、硬草、荠菜、繁缕、大巢菜等单、双子叶杂草,并可有效抑制猪殃殃、早熟禾。但在寒潮来临前后使用,会造成小麦叶片发黄,株高受抑制,但药后30 d左右小麦叶色能恢复正常。     

圩区麦田看麦娘的农业防除技术

看麦娘(Alopecurus aequalis)广泛分布于沿江稻茬麦田,其中圩区危害尤为严重,是麦田主要恶性杂草之一。据1986年对未施除草剂的连作麦田调查,其数量占麦田杂草总数的71.56～80％,一般密度在0.17～0.22万株/米~2,多的田块达0.45～0.68万株/米~2,个别甚至超过1万株/米~2。     

骠马防除小麦田杂草技术

近年来,稻麦两熟制地区麦田草害严重,问题突出。本研究以免耕麦田为对象,对新型除草剂骠马的应用技术进行试验研究。结果表明:骠马对以看麦娘、日本看麦娘、(?)草为主的禾本科杂草有极强的杀伤力。骠马与使它隆混用,可兼除猪殃殃等阔叶草,对禾本科杂草有增效作用,使用得当,防除效果一般在90％以上。保产效果显著,对小麦安全。用骠马防除禾本科杂草掌握在11月下旬,麦苗2～3叶,田间看麦娘达出草高峰时,每亩用6.9％骠马50毫升,兑水40千克喷细雾。需要兼除猪殃殃等阔叶杂草的麦田,亩用6.9％骠马40毫升加20％使它隆30毫升,兑水40千克喷细雾,用药时间可推迟到12月上旬。骠马对大元麦有药害,不宜施用。     

冬小麦田大穗看麦娘种群动态及对小麦产量的影响

为明确麦田杂草大穗看麦娘Alopecurus myosuroides的田间种群发生动态规律,采用固定样方和随机样方取样方法于2013—2015年在山东省济南市研究了冬小麦田大穗看麦娘田间种群的萌发和生长动态,并分析了不同密度大穗看麦娘对小麦产量及其构成因素的影响。结果表明:在济南市小麦播后20~40 d为大穗看麦娘出苗高峰期,至11月下旬出苗量占全年出苗总量的97.1%。11月上旬,大穗看麦娘开始出现分蘖,至翌年4月上中旬结束,分蘖数平均每株为6.3个,比小麦多3.1个。3月下旬大穗看麦娘开始拔节,4月中旬平均株高超过小麦,5月下旬平均株高达到75.6 cm,高出小麦2.5 cm。5月上旬大穗看麦娘单茎平均鲜重达到最大为1.7 g,小麦为12.6 g。大穗看麦娘出苗、株高、分蘖和鲜重的变化与小麦变化趋势一致,与时间、温度密切相关。随着大穗看麦娘密度的增加,小麦产量急剧下降,当密度达到420株/m~2时,小麦产量损失率高达65.8%。大穗看麦娘对小麦产量构成因素中的穗密度影响最大,其次是穗粒数,对千粒重影响不显著,当密度为420株/m~2时,小麦穗密度减少55.2%,穗粒数减少26.4%。     

Joint effects of biotic and abiotic stressors on winter wheat suppression of Bromus tectorum

In winter wheat systems in the Northern Great Plains of the United States, Bromus tectorum and wheat streak mosaic virus (WSMV) commonly co‐occur. While independent effects of these pests on wheat yields have been well documented, to our knowledge, no study has investigated whether WSMV modifies interactions between wheat and B. tectorum. Furthermore, the impact that environmental stressors such as nutrient availability have on these interactions has not been addressed. We conducted a randomised split‐plot field study over 2 years to investigate the effects of WSMV and nitrate (N) availability on winter wheat suppression of Bromus tectorum. The study included four N treatments (10–19, 20–31, 31–84, and 85–207 kg ha^?1) and two WSMV treatments (mechanically inoculated or control). Increasing soil N increased the susceptibility of wheat to WSMV infection. In 2009, wheat in the lowest and highest N levels had 24% and 65% of plants infected respectively. However, regression analysis indicated that interactive effects of wheat competition, N and WSMV did not play a consistent role in B. tectorum growth. Specifically, the effect of both wheat density and distance from row on B. tectorum biomass remained constant across inoculation treatments, suggesting that wheat inoculated with WSMV suppressed B. tectorum as effectively as healthy wheat. Furthermore, wheat had a greater impact on B. tectorum growth in higher N environments, even though incidence of WSMV infection in wheat was highest. Overall, our results suggest that WSMV infection may not change the ability of wheat to suppress B. tectorum.     

A unique race of the wheat stem rust pathogen with virulence on Sr31 identified in Spain and reaction of wheat and durum cultivars to this race

Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is a re-emerging disease, posing a threat to wheat production. In Spain, stem rust has been rarely detected since the 1970s, but infection was observed in wheat fields in 2018. We analysed six stem rust samples collected in Rota, Cádiz province and one from Monteagudo del Castillo, Teruel province. All the samples from Rota were typed as race TKTTF, whereas the sample from Monteagudo del Castillo, collected in a wheat field adjacent to barberry bushes, was typed as race TKHBK. This race has a unique and significant virulence combination that includes virulence to Sr31, Sr33, Sr53 and Sr59, and is avirulent to Rusty, a durum line developed for universal susceptibility to the wheat stem rust pathogen. TKHBK is the first race outside the Ug99 race group with virulence to Sr31 and the first known race with virulence to Sr59. Genotyping studies indicate that race TKHBK does not belong to the Ug99 or TKTTF race groups and constitutes a previously unknown lineage. Two hundred bread and durum wheat cultivars and breeding lines from Spain were evaluated against TKHBK, TKTTF, and six additional races. Resistance was observed to all the races evaluated. Molecular markers confirmed the presence of Sr7a, Sr24, Sr31, Sr38 and Sr57 in bread wheat, and Sr13 in durum wheat. The re-emergence of wheat stem rust in Spain and the occurrence of unique virulences underscore the need to continue surveying and monitoring this disease.     

中国不同春麦区小麦地方种质抗条锈病评价及抗性基因分析

为明确中国不同春麦区小麦地方种质对当前小麦生产上流行的条锈病菌Puccinia striiformis f.sp.tritic的抗性水平及其所含抗性基因,利用条锈病菌生理小种条中32（CYR32）和条中34（CYR34）及混合生理小种（致病类群）对来自5个春麦区的196份小麦地方种质进行苗期、成株期抗性鉴定,并通过6个已知条锈病抗性基因Yr9、Yr18、Yr26、Yr48、Yr65和Yr67对其所含重要抗性基因进行分子标记检测。结果显示,在苗期,有11份小麦地方种质对CYR32表现出抗性,有12份对CYR34表现出抗性,分别占供试种质总数的5.61%和6.12%;有6份对CYR32和CYR34均表现出抗性;在成株期,有59份小麦地方种质在5个田间诱导环境下表现出稳定的抗性。有119份小麦地方种质检测到含抗性基因,其中有3份携带Yr9,有50份携带Yr18,有43份携带Yr48,有54份携带Yr65,所有供试种质均未检测到Yr26和Yr67,抗性基因的组合分析发现,共有31份小麦地方种质携带4种抗性基因组合类型Yr9+Yr18、Yr18+Yr48、Yr18+Yr65和Yr48+Yr65。表明来自中国5个春麦区的小麦地方种质条锈病抗性表型呈多样性,且携带目前在小麦抗病育种和生产上有效的条锈病抗性基因（组合）,建议加大对小麦地方种质的保护和应用力度。     

The development of a PCR-based method for detecting <Emphasis Type="Italic">Puccinia striiformis</Emphasis> latent infections in wheat leaves

Stripe rust of wheat caused by Puccinia striiformis f. sp. tritici is one of the most important diseases on wheat worldwide, especially in temperate regions with cool moist weather conditions. A rapid and reliable detection of the pathogen in latent infected wheat leaves during overwintering of the fungus in the dormant stage will contribute to determine the initial inoculum potential and thus to predict early outbreak and to improve effective management of the disease. To achieve this aim, a PCR-based method was developed for specific and sensitive detection of P. striiformis. Specific primers were designed according to a genome-specific sequence of P. striiformis. To evaluate the specificity of the primers, seven different isolates and races of P. striiformis as well as six other pathogens of wheat were tested. All isolates of P. striiformis yielded a distinct band of a fragment of 470 bp, while using DNA of the other wheat pathogens as a template no amplification product was detected. The sensitivity of the primers was tested using serial dilutions of total DNA from P. striiformis; the limit of detection was 10 pg of DNA. Using extracts from P. striiformis-infected wheat leaves, the fungus could be determined in the leaves before symptoms appeared. The stripe rust could also be detected in the dormant stage by the PCR assay in samples of wheat leaves taken during the winter season. The application of the PCR assay may be useful for rapid and reliable detection of P. striiformis in latent infected leaves of overwintering wheat plants.     

Natural hybridization between wheat (Triticum aestivum L.) and its wild relatives Aegilops geniculata Roth and Aegilops triuncialis L.

BACKGROUND

Cultivated bread wheat (Triticum aestivum L.) spontaneously hybridizes with wild/weedy related Aegilops populations, but little is known about the actual rates at which this hybridization occurs under field conditions. It is very important to provide reliable empirical data on this phenomenon in order to assess the potential crop–wild introgression, especially in the context of conducting risk assessments for the commercialization of genetically modified (GM) wheat, as gene flow from wheat to Aegilops species could transfer into the wild species genes coding for traits such as resistance to herbicides, insects, diseases or environmental stresses.

RESULTS

The spontaneous hybridization rates between wheat and A. geniculata and A. triuncialis, which are very abundant in the Mediterranean area, have been estimated for the first time in the northern part of the Meseta Central, the great central plateau which includes the largest area of wheat cultivation in Spain. Hybridization rates averaged 0.12% and 0.008% for A. geniculata and A. triuncialis, respectively. Hybrids were found in 26% of A. geniculata and 5% of A. triuncialis populations, at rates that can be ≤3.6% for A. geniculata and 0.24% for A. triuncialis.

CONCLUSION

The detection of Aegilops spp.–wheat hybrids in Aegilops populations indicates that gene flow can occur, although wheat is considered a crop with a low-to-medium risk for transgene escape. These data on field hybridization rates are essential for GM wheat risk assessment purposes. © 2023 Society of Chemical Industry.     

Sources of inoculum and reappearance of spot blotch of wheat in rice–wheat cropping

A study was undertaken to examine the main source of inoculum of Bipolaris sorokiniana responsible for its reappearance in rice–wheat cropping regions of eastern India. Soil samples were collected at monthly intervals during April–October in the years 2000 and 2001 from fields having rice–wheat cropping. Bipolaris sorokiniana conidia were isolated and their viability was found to decline sharply with the onset of flooding in the month of August. In contrast to 82% in April, viability was 4% and <1% in August and September, respectively. Viable conidia were multiplied in the laboratory and inoculated on to susceptible cv. Sonalika under controlled conditions for test of pathogenicity. Appearance of symptoms typical to spot blotch were recorded after 7 days. Twenty-two different species (weeds and grasses) normally found to be associated with rice–wheat fields were tested for the presence of B. sorokiniana to evaluate their possible role as alternative hosts. Only three species, i.e. Setaria glauca, Echinochloa colonum and Pennisetum typhoids, were found to naturally harbour B. sorokiniana. Isolates from these hosts were tested for pathogenicity and also for their possible spread to wheat. When reisolated from these hosts, the pathogen did not infect wheat. Seeds of 25 different wheat genotypes were tested for B. sorokiniana infection. All genotypes were infected and the incidence of infection varied from 26% to 86%. Five isolates of wheat and one isolate from each of the three species (S. glauca, E. colonum and P. typhoids) were subjected to RAPD analysis. Two broad clusters were formed, suggesting that the wheat isolates were different from the isolates originating from other hosts. The results indicate that seeds are the most important source of inoculum for the reappearance of spot blotch of wheat in rice-wheat cropping systems in eastern India.     

The allelopathic effect of three Amaranthus spp. (pigweeds) on wheat (Triticum durum)

The allelopathic effect of Amaranthus retroflexus L., Amaranthus blitoides S. Wats, and Amaranthus gracilis Desf. on wheat Triticum durum L. was investigated under laboratory, glasshouse and field conditions. Laboratory experiments showed that fresh shoot or root extract of the three weed species reduced germination, coleoptile length, root length and root dry weight of wheat seedlings. The inhibitory effects were rate dependent, with low concentrations of shoot extract promoting shoot growth of wheat. Fresh plant extracts were more phytotoxic than dried plant extracts and shoot extracts had higher detrimental effects than root extracts. In pot experiments, dried shoot extract of A. gracilis increased shoot and root dry weights of wheat seedlings. For A retroflexus and A. blitoides the extracts of these and dried shoots (8 g kg^?1), which had been added to soil mixtures significantly reduced ger-mination and growth of wheat seedlings. Addition of up to 16 g kg^?1 of A. gracilis residues promoted shoot growth of wheat and had no significant harmful effect on root growth. Roots appeared more sensitive to allelopathic effect than shoots. Under field conditions, incorporation of A. retroflexus or A. blitoides residues in the soil reduced height, grain and straw yield of wheat, whereas A. gracilis residues stimulated plant height and increased yield.     

Aubian wheat mosaic virus, a new soil-borne wheat virus emerging in France

The properties of Aubian wheat mosaic virus (AWMV), a new soil-borne wheat virus in France, were investigated. Symptoms include foliar mosaic and severe stunting of winter wheat. The vector of the disease is unknown but the plants infected carry Polymyxa graminis in the roots. AWMV was transmitted mechanically to wheat and to two dicotyledoneous species: Lactuca sativa and Vicia faba. This virus was transmitted by seed to three winter wheat cultivars tested. Purified preparations contained rod-shaped particles with a variable length of 150–700 nm. Certain particles are very long and appear flexible. Antiserum raised against AWMV reacted specifically with AWMV in both indirect and direct enzyme-linked immunosorbent assays (ELISA). The incidence of AWMV in 26 winter wheat cultivars was investigated in the field during the growing season of 1999–2000. AWMV was detected in roots and shoots of all cultivars regardless of the symptoms. Twelve virus species belonging to the genera Benyvirus, Bymovirus, Furovirus, Pecluvirus and Pomovirus did not react with the AWMV antisera. A new tubular virus described in winter wheat in Bedfordshire in England reacted strongly with AWMV in ELISA. It is concluded that AWMV and probably the Bedford-virus constitute a previously undescribed tubular virus biologically and serologically distinct from other soil-borne viruses of wheat.