Effect of plant age on temporal progression of common root-rot (Cochliobolus sativus) lesions on subcrown internodes of wheat and barley

The progression of common root-rot lesions on subcrown internodes of Neepawa wheat and Bonanza barley plants inoculated 14, 26, 38 and 50 days after seeding was measured in growth chamber tests. Both in wheat and barley, lesion development was more rapid in older than in younger plants. Variables such as mean daily rates of linear progression of lesions, disease ratings, and proportion of plants becoming severely diseased were higher in older than in younger plants. The possible stress resulting from the removal of the crown roots on more rapid disease development in older than in younger plants is discussed.     

A new technique for monoconidial culture of the most aggressive isolate in a given population of Bipolaris sorokiniana, cause of foliar spot blotch in wheat and barley

We developed a new technique for monoconidial culture of the most aggressive isolate in a given population of Bipolaris sorokiniana, to facilitate the evaluation of spot blotch resistance in wheat and barley. Blotched portions of infected barley leaves were placed on a glass slide in a moist chamber for production of conidia by associated fungal hyphae. Conidia were collected separately and grown on water agar discs. Individual water agar discs having conidium growth were inoculated on barley leaves. The conidium producing the earliest symptom with the largest lesion was considered most aggressive. This lesion was incubated in a moist chamber and the conidial offspring were tested for pathogenicity. When a uniform infection was observed, a small piece of the lesion was cut using a sterilized scalpel, surface sterilized with NaOCl, and inoculated in the centre of Petri dishes containing potato dextrose agar medium. The inoculated Petri dishes were incubated at 25 ± 1 °C to yield monoconidial cultures of the most aggressive isolate. Variability in symptom expression caused by the most aggressive isolate of a given population was much less than variability in symptom expression caused by all isolates collectively. The techniques will be useful for plant pathologists and breeders in screening for spot blotch resistance in wheat and barley.     

Effect of triadimenol,imazalil and nuarimol seed treatment on subcrown internode length,coleoptile-node-tillering and common root rot in spring wheat

Summary The effect of seed treatment with triadimenol at 0.175 and 0.3, imazalil at 0.15 and 0.2, and nuarimol at 0.1 and 0.15 g a.i./kg seed on subcrown internode (SCI) length, occurrence of coleoptile-node-tillers (CNTs), and common root rot severity was studied in two spring wheat cultivars at three locations in Saskatchewan. All three fungicides showed similar effects on both Cypress and Neepawa cultivars. All fungicides significantly reduced severity of common root rot and SCI length, promoted the early development of CNTs and increased (P<0.01) the proportion of CNTs that produced fertile heads of grain.Contribution from Agr. Canada Res. Stn. No. 869.     

Diversity of the <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head and seedling blight on wheat in Slovakia

Species associated with Fusarium head blight are depending on the production and edaphic conditions. The differences are found in the representation of various Fusarium spp. in the diseases, which sporadically occur all over the territory of Slovakia, in all agricultural production types. We identified fifteen Fusarium species during ten years of investigation. Most of the mentioned species F. culmorum (W.G. Smith) Sacc., F. graminearum Schwabe, recently F. cerealis (Cooke) Sacc. (crookwellense Burgess, Nelson & Tousson) and F. sambucinum Fuckel in diseased caryopsis are seed transmitted. The significant differences among species and intra species in cultural and pathogenicity assays in vitro and in vivo were correlated. Some of them are able to produce toxic metabolites — deoxynivalenone, which probably play a role in the aggressiveness of the pathogen and promote disease development and pathogen colonization.     

Fusarium spp. and storage fungi in suboptimally stored wheat: Mycotoxins and influence on wheat gluten proteins

When wheat is stored under suboptimal conditions, a further mycotoxin increase of deoxynivalenol (DON), but especially of mycotoxins produced by storage fungi, e.g. ochratoxin A, is possible, lowering wheat quality and food safety. Different storage trials were conducted under suboptimal storage conditions.Fusarium survival during suboptimal storage was monitored by cultural technique and multiplex-PCR and set into relation to DON contents. Furthermore, XANES spectroscopy was applied on a selected storage trial in order to characterize sulfur speciation in low molecular weight (LMW) subunits of glutenin isolated from suboptimally stored wheat samples highly infected withFusarium and from wheat infected withAspergillus andPenicillium. Distinct changes in sulfur speciation were observed in grains infected with storage fungi, especially a significant increase of higher oxidation states (sulfoxide state, sulfonate state). Presented at the 25^th Mykotoxin Workshop in Giessen, Germany, May 19–21, 2003     

Trends in comparative genetics and their potential impacts on wheat and barley research

We review some general points about comparative mapping, the evolution of gene families and recent advances in the understanding of angiosperm phylogeny. These are considered in relation to studies of large-genome cereals, particularly barley (Hordeum vulgare) and wheat (Triticum aestivum), with reference to methods of gene isolation. The relative merits of direct map-based cloning in barley and wheat, utilization of the smaller genome of rice (Oryza sativa) and gene homology methods that utilize information from model species such as Arabidopsis thaliana are briefly discussed.     

Occurrence and variability of mycotoxigenicFusarium species associated to wheat and maize in the South West of Spain

The contamination of cereals with mycotoxins produced by species ofFusarium is an important risk to human and animal health. The toxigenic profile is different depending on theFusarium species considered and, in some species, differences can also be observed at intraspecific level. Information about the distribution and variability of the mycotoxigenicFusarium species allow prediction of the toxins that may occur and to devise control strategies. In this work, the occurrence of mycotoxigenicFusarium species associated to cereals was analysed in a wide sample of durum wheat fields (Triticum durum Desf.) and maize from the South West of Spain (Andalucía).F. equiseti, F. graminearum andF. culmorum were the most frequentFusarium species detected in wheat fields followed byF. sambucinum andF. avenaceum, whereas in the case of maize,F. verticillioides andF. proliferatum were the onlyFusarium species present. The relationships of the Spanish isolates from theF. equiseti, F. avenaceum andF. sambucinum species were analysed by nucleotide sequence comparison of a partial region of the Elongation Factor 1 alpha (EF-1α) with other sequences available in data bases. The results indicated thatF. avenaceum andF. equiseti showed high variability and that the SpanishF. equiseti isolates seemed to belong toF. equiseti type II. Presented at the EU-USA Bilateral Workshop on Toxigenic Fungi & Mycotoxins, New Orleans, USA, July 5–7, 2005 Financial support: MCYT (AGL2004/07549/C05/5). M. Jurado was supported by pre-doctoral fellowship by the MCYT     

三种草坪草的种带与土传真菌及杀菌剂拌种的防效

以多年生黑麦草(Lolium perenne)、高羊茅(Festuca arundinacea)和草地早熟禾(Poa pratensis)等3种9个草坪草品种为材料,在实验室、温室和田间开展了系列研究.实验室结果表明高羊茅Barlexas品种和草地早熟禾的3个品种,在滤纸苗床发芽率显著高于同样条件下田间土床上的发芽率(P＜0.05).对种带和土传真菌的分离表明,自种子上仅分离获得4种常见种带真菌,而经在田间土壤培养后,分离获得14种真菌,包括早熟禾德氏霉(Drechslera poae)、立枯丝核菌(Rhizoctonia solani)和数种镰刀菌(Fusarium spp.)等.以福美双、甲基硫菌灵和三唑酮对参试品种单独拌种进行温室盆栽试验,播后13～16d,福美双显著提高了多年生黑麦草品种Premier和草地早熟禾品种Platini的出苗率,增幅最高分别为80.6%和45.2%.与对照比,三唑酮拌种显著提高了高羊茅3个品种的出苗率,增幅最高的是Barlexas品种,可达166.7%.福美双、甲基硫菌灵或三唑酮均可提高多年生黑麦草Taya每盆根和茎干重,与对照比,每盆茎干重分别增加47.2%、29.5%和34.7%,福美双和甲基硫菌灵使其根干重分别增加67.7%和97.1%.福美双和三唑酮显著提高了多年生黑麦草Gator Ⅱ每盆茎干重,增幅分别为32.1%和29.6%.甲基硫菌灵拌种使草地早熟禾Platini品种的根与茎干重分别增加230%和100%,参试品种每株幼苗根与茎干重对杀菌剂拌种的反应与每盆重量相似.田间试验结果表明杀菌剂拌种不同程度地提高了草坪草出苗率和田间生物量.经相关与回归分析,参试草坪草在田间与温室盆栽条件下的生物量存在显著的正相关,二者根和茎的相关系数分别为0.81和0.82,回归方程式分别为Y1=13.178+3.5911X1和Y2=0.11803+3.6845X2表示.     

埋深和播种密度对豚草种子出苗及幼苗生长的影响

豚草是一种全球性的恶性入侵杂草,给我国生物多样性及经济发展造成了巨大威胁。为研究豚草种子出苗和幼苗生长的影响因素,采用盆栽实验分析了种子大小（L、M、S）与埋深（2、4 cm和6 cm）或播种密度（2、4粒/盆和8粒/盆）对豚草（Ambrosia artemisiifolia）种子的出苗和幼苗生长的影响。研究结果表明,埋深对豚草种子出苗的影响高于播种密度及种子大小的影响,较浅的埋深有利于豚草种子出苗;出苗率在不同播种密度下均具有较高水平,达到67.9%-100%,这种高出苗率是豚草在不同生境成功定植的原因之一。豚草的幼苗生长受埋深或播种密度的影响大于种子大小的影响,且小种子更易受埋深或播种密度的影响。种子大小显著影响豚草幼苗的株高和基径（P<0.05）,总体上较大种子的株高和基径高于小种子,此外更小的种子会将生物量更多的分配给根以促进幼苗的生长。幼苗的株高和基径在较浅的埋深下更高,而豚草幼苗的单株生物量、单株地上和地下生物量随埋深的增加而增加。播种密度的增加会加剧豚草幼苗之间对水分、营养、光照等资源的竞争,导致其单株地上、地下及总生物量显著降低（P<0.05）。研究发现豚草在浅埋深、低密度生境中更容易入侵成功,因此可以通过对土壤进行深翻,采取替代控制,种植竞争能力强的本地植物等手段有效管理和防治豚草。     

豚草种带内生真菌及其对种子发芽和幼苗生长的影响

内生真菌是一类共生于植物体内,能够不同程度影响宿主植物生态适应性和竞争能力的微生物。分析内生真菌在豚草种子中的分布、种群结构,以及内生真菌发酵液对种子发芽和幼苗生长的作用。结果显示:发生于6个地区的豚草种子均能分离获得内生真菌,分离率在19%—92.63%之间,不同地区之间差异极显著(P0.01)。内生真菌主要存在于种子的总苞部位,分离率达到65.52%。发生于福建省长乐市松下镇的豚草种带内生真菌种群包含5个属,以链格孢属(Alternaria)真菌为优势菌群,占82.26%;其次为镰孢属(Fusarium)真菌,占9.68%;其它3个属的真菌发生较少,均低于5%。内生真菌主要以水平传播方式在豚草不同世代之间传播。供试的7个内生真菌菌株的发酵液均不同程度地抑制豚草种子发芽,降低幼苗地上部高度、根长度、根数量和总生物量,但不同菌株发酵液之间抑制程度差异明显,显示不同菌株对豚草种子发芽和幼苗生长产生不同的影响。内生真菌发酵液处理后的种子仍然保持较高程度的活力;不同内生真菌发酵液处理后,有活力的种子维持在50%—87.5%之间,均高于(或等于)清水处理的种子,说明内生真菌代谢产物只是抑制种子的发芽,但并不导致种子的腐烂和死亡。这些研究结果初步显示种子携带的内生真菌可能在豚草入侵生物学中发挥重要的作用。     

Soybean seedling emergence at high temperatures

Bragg and Cobb soybean [Glycine max (L.) Merr.] seeds were germinated in sand at temperatures ranging from 25 to 40°C. Emergence decreased with increasing temperature above 37°C, with virtually no emergence at 40°C. Emergence of 12 other cultivars at 38°C ranged from 25 to 95%. Foster and Coker 338 were more sensitive to high temperature than the other cultivars.     

A survey of the natural occurrence ofFusarium toxins in wheat grown ina southwestern area of Germany

Wheat for feed use (84 samples) was collected after harvest from 79 farms in a southwestern part of Germany (Baden-Wuerttemberg). The 1987 crop year was characterized by heavy rainfall in the summer months. The internal mycoflora of wheat samples was primarily fusaria, and storage fungi were rarely present. TheFusarium toxins, zearalenone (ZON), - and -zearalenol (,-ZOL), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), nivalenol (NIV), T-2 Toxin (T-2), HT-2 toxin (HT-2) and diacetoxyscirpenol (DAS) were analysed by gas chromatography with mass selective detection (detection limit: 1–3 µg/kg). Each of the samples contained at least one of theFusarium toxins examined except DAS. DON, ZON, 3-AcDON, NIV, T-2, HT-2 and -ZOL were detected in 96%, 80%, 59%, 26%, 26%, 7% and 5% of samples, with an average of 1632, 178, 7, 9, 82, 10 and 23 µg/kg, and a maximum of 20538, 8036, 18, 32, 249, 20 and 71 µg/kg, respectively. -ZOL (12 µg/kg) was found in one sample with -ZOL (71 µg/kg). One, two, three, four, five and sixFusarium toxins were detected in 6%, 27%, 37%, 23%, 4%, and 4% of total samples, respectively. The most frequent combination was that of ZON with DON and 3-AcDON, followed by the combinations ZON/DON and ZON/DON/3-AcDON/NIV in 22, 20, and 11% of total samples, respectively.Abbreviations 3-AcDON 3-Acetyldeoxynivalenol - DAS Diacetoxyscirpenol - DON Deoxynivalenol - HT-2 HT-2 toxin - NIV Nivalenol - T-2 T-2 toxin - -ZOL -Zearalenol - -ZOL -Zearalenol - ZON Zearalenone     

Production of trichothecene mycotoxins byFusarium graminearum andFusarium culmorum on barley and wheat

Wheat cultivars (Stoa, MN87150, SuMai-3, YMI-6, Wheaton) and barley cultivars (Robust, Excel, Chevron, M69) were inoculated in the field with isolates ofFusarium graminearum andF. culmorum. The diseased (Fusarium head blight) kernels were analyzed for deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-ADON) and nivalenol (NIV).F. culmorum produced all three trichothecenes on all cultivars tested whereasF. graminearum only produced DON and 15-ADON. There was no well defined correlation between DON production in the host and resistance although the data tended to favor SuMai-3 as having definitive resistance to bothF. graminearum andF. culmorum.Minnesota Agricultural Experiment Station, Paper No. 20 279.     

Temperature and seedling age affect susceptibility of perennial ryegrass seedlings to pathogenic fungi

Summary Effects of temperature and seedling age on survival of perennial ryegrass (Lolium perenne L.) seedlings grown on sand-wheat wholemeal cultures of different isolates ofFusarium spp. (9 isolates),Pythium spp. (9 isolates), andChaetomium spp. (1 isolate) are reported. Some isolates were virulent over the whole range of temperatures tested (7.5–27.5°C). The virulence of others depended on temperature. Most isolates were less virulent at intermediate temperatures (12.5–22.5°C) than at higher or lower temperatures. At 25°C ryegrass seedlings were susceptible to fungal attack for only a limited period after germination commenced. This period differed for different fungi, but for most isolates tested, seedlings were resistant after 2–3 days.     

Aspergillus flavus colonization and aflatoxin B1 formation in barley grain during interaction with other fungi

Colonization of barley grain by Aspergillus flavus and formation of aflatoxin B₁ in the presence of Penicillium verrucosum, Fusarium sporotrichioides, and Hyphopichia burtonii were studied over a three-week period in all combinations of 20 or 30 °C and 0.97, 0.95 or 0.90 a_w. Grain colonization was assessed initially by observing hyphal extension on the grain surface, using scanning electron microscopy, and then from the proportion of seeds infected and numbers of colony forming units (cfu) formed. Aflatoxin b¹ concentrations were determined by enzyme linked immunosorbent assay using a monoclonal antibody. These studies showed that interaction between A. flavus and other fungi in paired culture had different effects on both colonization and aflatoxin formation depending on the species involved and environmental conditions. Germination of A. flavus spores was unaffected by the presence of other species on the grain surface. Subsequently, three principal patterns of A. flavus colonization of barley grain were observed through the incubation period in the presence of other fungal species: (a) colonization unaffected by the presence of other species; (b) colonization initially slower in the presence of other species but later differing little from pure cultures; and (c) colonization adversely affected by the presence of other species. Five main patterns of aflatoxin B₁ production were observed relative to pure culture but with no consistent relationship with species, a_w, temperature or incubation period; (a) little changed; (b) increased slowly; (c) decreased; (d) enhanced; and (e, f) increased initially but later decreased to (e) the same level as in pure culture or (f) to less than in pure culture. Generally, production of aflatoxin B₁ by A. flavus was less than in pure culture but sometimes was changed only slightly by the presence of P. verrucosum, F. sporotrichioides or H. burtonii or was temporarily enhanced.     

Effect of tetcyclacis and chlormequat applied to seed on seedling growth of triticale cv. Lasko

The growth of triticale seedlings from seeds treated with three concentrations of the plant growth regulators (PGRs), tetcyclacis and chlormequat, with or without drying after soaking was studied. Both tetcyclacis and chlormequat inhibited shoot growth. They reduced shoot:root ratios, first by restricting shoot growth (one week after treatment) and later by boosting root growth (eight weeks after transplanting). At the concentrations used tetcyclacis was a more active PGR than chlormequat and promoted tiller production. Drying, after soaking, promoted root growth, retarded the elongation growth of seedlings and enhanced some of the effects of the PGRs. Analyses of regressions between those growth characteristics significantly influenced by PGRs and the concentration revealed a quadratic relationship.     

砂生槐根瘤内生菌对青稞种子萌发及幼苗的促生作用

该文以接种不同砂生槐根瘤内生菌的黑青稞种子和不接种菌株的黑青稞种子为研究材料,采用培养皿作为基质,观察黑青稞种子萌发及幼苗生长情况,测定接种不同根瘤内生菌后的黑青稞发芽率、发芽势、发芽指数、株高、根长、须根数、根冠比、植株全株干/鲜重的生理性状,并对各不同处理进行隶属函数综合评价.结果表明:菌株R7和R17的发芽率均达...     

Genotype and fungicide effects on late-season root growth of winter wheat

The aim of this work was to investigate differences among genotypes in post-anthesis root growth and distribution of modern UK winter wheat cultivars, and the effects of fungicide applications. Post-anthesis root growth of up to six cultivars of winter wheat (Triticum aestivum L.), given either one or three applications of fungicide, was studied in field experiments during two seasons. Total root mass remained unchanged between GS63 (anthesis) and GS85, but root length increased significantly from 14.7 to 31.4 km m⁻² in one season. Overall, there was no evidence for a decline in either root mass or length during grain filling. Root mass as a proportion of total plant mass was about 0.05 at GS85. There were significant differences among cultivars in root length and mass especially below 30 cm. Malacca had the smallest root length and Savannah the largest, and Shamrock had a significantly larger root system below 40 cm in both seasons. Fungicide applied at ear emergence had no significant effect on root mass in either season but increased root length (P<0.01) in the more disease-prone season. By maintaining a green canopy for longer, fungicide applied at flag leaf emergence may have resulted in delayed senescence of the root system and contributed to the post-anthesis maintenance of root mass and length. Section Editor: R. W. Bell     

Biological control of maize seed pathogenic fungi by use of actinomycetes

The effectiveness of twoStreptomyces spp. strains to controlpathogenic fungi was studied in stored maizegrain. The treatments included seeddisinfection and inoculation withStreptomyces spp. strains previously isolatedfrom maize rhizosphere. Actinomycete inoculumconsisted of filtered suspension and totalsuspension of fermentor-producedStreptomyces spp. strains biomass. Treatmentswith Streptomyces spp. strains aloneeffectively suppressed the development ofAspergillus spp., Curvularia lunata, andDrechslera maydis and significantly(p < 0,05) reduced the incidence ofFusarium subglutinans and Cephalosporiumacremonium. Among the inoculation treatments,nondisinfested seed inoculated with filteredsuspension was the only treatment that did notsuppress the development of Penicilliumspp. Maize seed inoculation with totalsuspension of strains was the most effectivetreatment to control the incidence of seedpathogenic fungi. The development of theDiplodia maydis was only suppressed by thecombination of seed disinfection andinoculation with total suspension of strains.Although, the strain DAUFPE 11470 showed thegreatest effectiveness for controlling thefungi pathogenic to seed, root and shootdevelopment was reduced by treatment with thisstrain.The results indicate thatStreptomyces spp. strains reduce the incidenceof seed pathogenic fungi and have potential asa biological control agent. However, an efficient methodof seed treatment with the biological controlagent must be developed before it can become anagricultural practice.     

沙埋与水分对科尔沁沙地主要固沙植物出苗的影响

蒿属半灌木乌丹蒿(Artemisia wudanica)、白沙蒿(A. sphaerocephala)、差不嘎蒿(A. halodendron)是科尔沁沙地的主要固沙植物。其中乌丹蒿和差不嘎蒿是科尔沁沙地的本土植物,白沙蒿为来自于库布齐沙漠、毛乌素沙地的飞播植物。设置了 5个沙埋深度(0.5、1.0、1.5、2.0和3.0 cm)和 4个水分梯度(86、171、257和 342 mL,分别模拟每月25、50、75和100 mm的降雨量),以探讨3种植物幼苗出土对沙埋和水分的响应。结果表明,沙埋与水分均显著影响着3种蒿属植物的幼苗出土(P < 0.001)。3种植物最适沙埋深度在0.5-1.5 cm范围内,萌发出土时适宜水量要高于当地种子萌发期的平均降水量(50 mm/月)。两种固沙先锋植物乌丹蒿和白沙蒿的种子出苗率均显著高于差不嘎蒿,乌丹蒿较白沙蒿也明显为高,尤其在水分缺乏时,表现出两种先锋植物种子出苗对干旱有更好的适应性。协方差分析表明,乌丹蒿幼苗死亡率显著高于白沙蒿和差不嘎蒿(P < 0.05),在达到75 mm/月降水量时,3种植物的出苗较好,但不能满足乌丹蒿幼苗生长对水分的需求,而实际种子萌发期的降水量平均只有50 mm/月。因而降水的缺乏导致乌丹蒿种群更新出现问题,加之飞播植物的竞争,使得近几年科尔沁沙地较多乌丹蒿种群出现衰退。