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Mature inflorescences of 76 samples of ten genera of native grasses were collected in the Ankara province of Turkey. Microscopic
examination of individual seeds revealed the presence of endophytic fungi in four seed samples, The endophytes were isolated
in pure culture and identified. Seeds were also ground and subjected to ELISA and HPLC analyses to confirm the levels of ergot
alkaloids typically produced by endophytic fungi of grasses. 相似文献
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Cytoplasmic male-sterile winter wheat, grown in the field in England with a limited supply of pollen, set over 80% less seed than fertile wheat. Wheat ears precociously inoculated with ergot ( Claviceps purpurea ) initiated local natural epidemics of disease at flowering and, within 1-5m of primary foci, sclerotial abundance at harvest was correlated inversely with seed set, Sclerotial mass in poorly pollinated male-sterile wheat comprised more than 20% of the threshed grain yield, in contrast to only 0.7% in fertile wheat. 相似文献
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ABSTRACT Sorghum ergot caused by Claviceps africana was observed for the first time in the United States in Southern Texas in 1997. That year there was a widespread ergot epidemic in hybrid seed production fields in the Texas Panhandle. However, occurrence of the disease has been sparse during the past 3 years, easing fears that the hybrid seed industry in the region might be endangered. To determine whether climatic factors were associated with observed variations in prevalence of ergot, weather data (temperature, precipitation, and relative humidity) were collected from seven weather stations in the Texas Panhandle. Sorghum ergot prevalence data for the period 1997 to 2000 were collected from records of seed companies in the Panhandle and related to weather variables. Results showed that, in the southern section of the Panhandle, maximum temperature and precipitation between 1 and 15 August were associated (r(2) = 0.98, P = 0.001 and r(2) = 0.81, P = 0.0193, respectively) with variations in the prevalence of ergot during the 4-year period. In the northern section, only maximum temperature during 16 to 31 July was significantly associated (r(2) = 0.91, P = 0.0111) with disease prevalence. Over all, 1997 was wetter and cooler, during the 1 to 15 August period, than each of the subsequent 3 years. In addition to creating humid conditions for ergot development, precipitation was associated with suppression of maximum temperature, enhancing ergot-favorable temperature conditions. Examination of historic weather data for the region showed that there were many instances in the past where temperature depression was associated with a rise in cumulative precipitation, creating ergot-favorable conditions similar to those in 1997. Cross-spectral analysis was used to determine whether such association is periodic. Weather data from five of the seven locations in the region showed peaks of significant coherency ( alpha< 0.05) at 2 to 4 years and 7 to 10 years or greater, indicating the existence of a periodic cycle in the temperature-precipitation association. The results of the investigation suggested that association of precipitation with temperature depression is a primary factor in development of ergot in the Texas Panhandle, and such association has a periodic cycle. 相似文献
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Kodisch Anna Schmiedchen Brigitta Eifler Jakob Gordillo Andres Siekmann Dörthe Fromme Franz Joachim Oberforster Michael Miedaner Thomas 《European journal of plant pathology / European Foundation for Plant Pathology》2022,163(1):181-191
European Journal of Plant Pathology - Claviceps purpurea causing ergot maintains to be a problem in commercial cytoplasmic male sterile (CMS)-based hybrid rye growing. The fungal spores compete... 相似文献
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Trials were conducted in southern Queensland, Australia between March and May 2003, 2004 and 2005 to study patterns of hourly and daily release of the secondary conidia of Claviceps africana and their relationships with weather parameters. Conidia were trapped for at least one hour on most (> 90%) days in 2003 and 2004, but only on 55% of days in 2005. Both the highest daily concentration of conidia, and the highest number of hours per day when conidia were trapped, were recorded 1–3 days after rainfall events. Although the pattern of conidial release was different every day, the highest hourly conidial concentrations occurred between 10·00 hours and 17·00 hours on 73% of all days in the three trials. Hours when conidia were trapped were characterized by higher median values of temperature, windspeed and vapour pressure deficit, lower relative humidity, and leaf wetness values of 0%, than hours when no conidia were recorded. The results indicate that fungicides need to be applied to the highly ergot-susceptible male sterile (A-) lines of sorghum in hybrid seed production blocks and breeders' nurseries as soon as possible after rainfall events to minimize ergot severity. 相似文献
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Batches of glasshouse-grown flowering sorghum plants were placed in circular plots for 24 h at two field sites in southeast Queensland, Australia on 38 occasions in 2003 and 2004, to trap aerial inoculum of Claviceps africana. Plants were located 20–200 m from the centre of the plots. Batches of sorghum plants with secondary conidia of C. africana on inoculated spikelets were placed at the centre of each plot on some dates as a local point source of inoculum. Plants exposed to field inoculum were returned to a glasshouse, incubated at near-100% relative humidity for 48 h and then at ambient relative humidity for another week before counting infected spikelets to estimate pathogen dispersal. Three times as many spikelets became infected when inoculum was present within 200 m of trap plants, but infected spikelets did not decline with increasing distance from local source within the 200 m. Spikelets also became infected on all 10 dates when plants were exposed without a local source of infected plants, indicating that infection can occur from conidia surviving in the atmosphere. In 2005, when trap plants were placed at 14 locations along a 280 km route, infected spikelets diminished with increasing distance from sorghum paddocks and infection was sporadic for distances over 1 km. Multiple regression analysis showed significant influence of moisture related weather variables on inoculum dispersal. Results suggest that sanitation measures can help reduce ergot severity at the local level, but sustainable management will require better understanding of long-distance dispersal of C. africana inoculum. 相似文献
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Ergot, caused by Claviceps africana , has emerged as a serious threat to sorghum hybrid seed production worldwide. In the absence of gene-for-gene-based qualitative resistance in commercial cultivars, varieties with high pollen production that can escape ergot infection are preferred. Recent demonstration of differences in ergot susceptibility among male-sterile lines has indicated the presence of partial resistance. Using chitin-specific fluorescin-isothiocyanate-conjugated wheat germ agglutin and callose-specific aniline blue, this study investigated the process of sorghum ovary colonization by C. africana . Conidia germinated within 24 h after inoculation (a.i.); the pathogen was established in the ovary by 79 h a.i., and at least half of the ovary was converted into sphacelial tissue by 120 h a.i. Changes in fungal cell wall chitin content and strategic callose deposition in the host tissue were associated with penetration and invasion of the ovary. The rate of ovary colonization differed in three male-sterile lines that also differed in ergot susceptibility. This work demonstrates a possible histological basis for partial resistance in male-sterile sorghum lines that could lay the foundation for variety improvement through further breeding and selection. 相似文献
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Ergot disease spread rapidly in Zimbabwe amongst replicated plots of male-sterile sorghum A-lines, from a group of centrally situated and precociously inoculated plants. Prominent secondary conidiation by the pathogen, Claviceps africana , on the surface of exuded honeydew provided airborne spores which were trapped in a Burkard continuous spore trap and showed diurnal peaks of concentration in air close to the primary source of inoculum. The rate of disease spread ( r =0·2; range 0·14–0·58) closely matched that recorded for other plant pathogens such as Phytophthora infestans and Puccinia graminis tritici , and it is concluded that the characteristic secondary conidia of C. africana were the principal epidemiological agents within the experimental area. Ergot spread by windborne secondary conidia has significant epidemiological and economic implications for sorghum hybrid breeding in southern Africa. 相似文献
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Susceptibility to ergot in Zimbabwe of sorghums that remained uninfected in their native climates in Ethiopia and Rwanda 总被引：1，自引：0，他引：1
Forty-four local Ethiopian and Rwandan sorghums ( Sorghum bicolor ) were observed to remain free of ergot, or had only low incidence, in their natural equatorial latitudes and were potentially of interest, in the design of male-sterile lines for F1 hybrid breeding, if they possessed a physiologically based resistance mechanism. These sorghums were therefore also investigated under natural and artificial disease pressures in Zimbabwe where unadapted development and inappropriate long daylength prevented flowering in 18 accessions. Of the remaining 16 Ethiopian and 10 Rwandan accessions which flowered, only one from each country remained free of ergot. The susceptibility expressed was ascribed to observed asynchrony of stigma exsertion with anthesis. In the Rwandan accession that persistently remained free of ergot in Zimbabwe, histology of ovules showed pollination before floret gaping, so that a general principle of disease escape due to efficient pollination is proposed for the Ethiopian and Rwandan sorghums in their native climates. The findings emphasize that cleistogamy is a desirable character for avoiding ergot infection in self-fertile sorghums and suggest that the Ethiopian and Rwandan sorghums may not generally be useful for breeding ergot-resistant male-sterile female lines. However, a few accessions deserve more detailed study as a potential genetic resource, before a firm conclusion that all apparent resistance is disease escape owing to efficient pollination. 相似文献
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民勤沙区不同稳定性沙丘植被生境条件研究 总被引：12，自引：3，他引：9
固定、半固定和流动沙丘生境条件测定结果表明：固定沙丘优势种均生长不良,枯梢、死亡普遍,其伴生植物的种类和密度均很小;沙丘水分条件决定了其生境条件,固定沙丘水分条件最差亦即生境条件最差;固定沙丘和半固定沙丘表面易形成粘粒、粉粒结皮,其表土层田间持水量大,影响降水下渗;固定沙丘表面田间持水量大是影响降水下渗的关键,其沙丘表土层粘粒、粉粒含量高是导致其田间持水量大的关键。其伴生草本植物密度并不随表土层田间持水量大而增加的原因,主要是由于当地降水少、气候干燥、表土层土壤水分易蒸发损耗所致。 相似文献
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塔里木河中下游农户能流分析及生态经济分形特征 总被引：3，自引：1，他引：2
能流分析和分形理论是农业生态经济系统定性研究和定量分析的重要手段之一。把农户作为“分形元” ,以尉犁县兴平乡达西村 4 0个农户为研究对象 ,在绿洲农业生态系统能流分析基础上 ,对不同经营类型农户的生态经济特征进行分形研究 ,结果表明 :(1) 5类农户从总体上都显现生产经营结构单调 ,能量利用和转化链条短 ;牲畜养殖是唯一的次级生产系统 ,能量转化率低 ,增效不明显。 (2 )农田亚系统是农户生产力的主体 ,棉花生产现在和今后若干年内仍将是农户的支柱产业。 (3)基于农户分析的生态效益和经济效益之间没有相关关系 ;生态效益高 ,并不意味着经济效益也高 ,反之亦然。农户生产系统总体的生态经济协调发展水平不高。 相似文献
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从新疆巩留县往西的察布查尔县境内,约2 000 km2的伊犁河南岸荒漠是未来灌区项目建设的所在地。2002年8月,对该地及其南缘和北缘地带的昆虫区系进行了调查,查明计有291种昆虫,隶属于15目87科239属,并对未来灌区建设对昆虫区系的影响进行了预测。 相似文献
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塔里木河下游绿色走廊特点及衰败成因分析 总被引：43，自引：7，他引：43
近50年来塔木河上中游的水土开发活动，使得下游地区的来水骤减并中断有近30年的历史，从而引发了下游绿色走廓的逐步走向衰败、土地荒漠化趋势加剧等生态环境恶化问题。本文在前人研究成果基础上，综合分析了塔河下游绿色走廓发生、发展的特殊性和特点，认为绿色走廓衰败主要有5个主要因素：绿色走廓自然生命过程的衰退；新生幼林发生和发育原生机制的中断；土壤盐分的累积和增加；水分条件持续恶化；人类开垦荒地、滥伐、滥控等行为。通过成因分析认为，只有充分考虑到下游绿色走廓的特点及其衰败的原因，才能从根本上解决下游绿色走廓衰败的问题。 相似文献
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为筛选能有效防除云南麦田入侵杂草小籽虉草Phalaris minor的除草剂, 采用温室盆栽法分别测定了麦田常用7种茎叶处理剂各7个梯度剂量对小籽虉草的毒力?结果表明, 在推荐剂量下, 50%异丙隆WP?5%唑啉草酯EC?15%炔草酯WP?69 g/L精噁唑禾草灵EW?7.5%啶磺草胺WG?30 g/L甲基二磺隆OD和70%氟唑磺隆WG对小籽虉草药后30 d的株防效分别为99.34%?99.43%?87.50%?75.00%?34.50%?37.50%, 54.17%, 药后30 d的鲜重防效分别为87.92%?92.66%?56.09%?74.43%?57.17%?45.61%?44.67%?所有除草剂中, 唑啉草酯的GR90接近推荐使用剂量的90%?异丙隆的GR90略高于推荐剂量, 其他除草剂的GR90远高于麦田推荐使用剂量?以上结果表明, 防治麦田杂草小籽虉草的首选除草剂为唑啉草酯, 备选除草剂种类少? 相似文献
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宁夏近40多年积温及不同积温期降水量变化研究 总被引：4，自引：0，他引：4
选取宁夏22个地面气象站1961~2005年逐日平均气温、逐日降水量资料,统计计算日平均气温稳定通过0℃和10℃期间的积温,结果表明:随着气候的变暖,宁夏各地≥0℃和≥10℃积温呈明显增加趋势,近19 a增加显著;≥10℃积温不同等值线明显向地势较高地区移动,喜温作物面积扩大;积温持续日数明显增加,有利于作物的成熟;≥0℃和≥10℃积温期间降水量主要在部分干旱地带增加,这有利于干旱地带农牧业生产和植被恢复。 相似文献
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环境条件变化下汾河水库沉积物中重金属形态分布特征及潜在生态风险评价 总被引：9，自引：0，他引：9
对汾河水库沉积物中重金属的污染特征和潜在生态风险评价结果表明:汾河水库沉积物中Cd含量为11.42±2.84mg/kg,高于中国湖泊底泥重金属含量背景值。沉积物中Cd的单项潜在生态风险系数远大于其它重金属,高达2346.57,具有极强的生态危害性;而Zn、Cr和Cu只显示出轻微的生态危害性,故Cd是导致汾河水库沉积物中重金属的潜在生态风险增强的主要贡献者。室内模拟沉积物经历好氧和厌氧等环境条件下,并用EDTA铵盐溶液单一提取法和BCR连续提取法分别研究了汾河水库沉积物中Cd、Zn、Cr和Cu等重金属的形态分布特征;结果表明:在好氧条件下,Cd的形态分布特征变化最为明显,具有潜在环境效应的Cd含量所占总量的比例上升至52.15%;用EDTA单一提取法测定结果表明:生物有效态Cd含量占总量的比例(B/T)在好氧处置后最高,达30.37%;上述试验结果进一步证明了沉积物中Cd具有强烈的潜在生态风险和较高的生物有效性。 相似文献