Surveys of cereal diseases and pests in the Netherlands. 4. Occurrence of powdery mildew and rusts in winter wheat

Results of annual surveys of winter wheat fields from 1974 to 1986 were compiled to describe epidemics of powdery mildew and rusts in relation to weather and cultivar resistance.An average of 29 and 70% of fields were infected by powdery mildew in May and July, respectively. Mildew prevalence in May was positively correlated with average temperature in October and with average temperature over the months December, January, February and March. In addition, it was correlated negatively with the average grade of mildew resistance of the cultivars sown each year. Prevalence of mildew in July did not show consistent correlations with weather characteristics nor with mildew prevalence in May.Yellow rust was usually not detected in May and on average 18% of the fields was infected in July. The occurrence of yellow rust decreased after 1977, when the farmers adopted cultivars resistant or moderately resistant to yellow rust.Brown rust was usually not detected in May, while in July on average 48% of the fields was infected. Brown rust intensity in July was high in years with a high March temperature and high precipitation during April and May.Black rust was rare in the Netherlands, with 3 and 1% of the fields infected in July 1977 and 1981, respectively.     

Nitrogen-induced changes in colony density and spore production of Erysiphe graminis f.sp. hordei on seedlings of six spring barley cultivars

The influence of increasing nitrogen supply (30, 60, 120 and 240 mg N per pot) on susceptibility was studied on seedlings of six cultivars of spring barley inoculated with virulent isolates of powdery mildew. The colony density (CD) measured as colonies per cm² was significantly increased with increasing application of nitrogen on all cultivars, and a significant interaction was found between N and cultivar. The different reactions of the cultivars could not be ascribed to lack of N uptake. In general, increasing N application enhanced the sporulation capacity of colonies (CSC) irrespective of increased CD and the cumulative production of spores per cm² leaf (CSCM) increased strongly with N application in all cultivars. No interaction between N and cultivar was found for the latter component. The increase in CSCM closely corresponded with the increase in N content and fresh weight of uninoculated leaves. No interaction between N treatment and powdery mildew isolates was found for infection efficiency and spore production per colony, when tested on one cultivar. The N-induced changes in infection and sporulation can explain the main part of the increasing effect of N fertilization on powdery mildew development in the field. The results indicate that it may be possible to breed for or select barley cultivars with low N impact on powdery mildew development.     

小麦品种多样性对白粉病及产量和蛋白质的影响

 对品种多样性控制小麦白粉病的效果以及对产量和蛋白质的影响进行了研究,为利用品种多样性控制白粉病提供理论依据和技术支持。采用SSR技术分析5个小麦品种的亲缘关系;2008年和2009年按组合所含品种数为2、3、4和5个进行组合,在田间种植混种组合和单播小区,人工接种白粉菌,比较各小区中小麦白粉病的AUDPC值、产量和蛋白质变化。结果表明,5个品种亲缘关系相对较近;2个品种混合时以抗感搭配较好,随着抗病品种比例增加控病效果增强;2008年混合种植中有防治效果的组合占54.55%,相对防效为10.02%~47.58%,2009年有防治效果的组合占23.08%,相对防效在1.85% 到18.96 % 之间;在适当的组合中,如京冬8号/轮选987、京双16/京411/京冬8号对小麦白粉病有控制效果,混种不会影响产量和蛋白质含量;当有大量能克服本地品种抗性的外来菌源时混合种植的控病效果降低。品种多样性可以用做防治小麦白粉病的一项措施。     

Disease-weather relationships for powdery mildew and yellow rust on winter wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.     

The effect of film-forming anti-transpirants on leaf rust and powdery mildew incidence on wheat

Various film-forming anti-transpirants effectively controlled leaf rust and powdery mildew on wheat in the field. Two applications of anti-transpirant emulsions applied after flag leaf emergence were sufficient to suppress leaf rust and powdery mildew on wheat leaves. When applied before, but not after, inoculation anti-transpirant polymers also reduced leaf rust on seedling plants in a growth room experiment.     

Effect of fungicide treatment on yield of winter wheat and spring barley cultivars

Analyses of the results of 21 winter wheat and 32 spring barley trials showed that cultivars differed significantly in their yield response to a standard fungicide treatment. Responses were also strongly influenced by differences between sites and between years. Regression analyses showed that responses were significantly related to reductions in foliar disease, particularly that of mildew, although the proportion of variance accounted for was small. Measurements made on seven winter wheat trials indicated that the percentage of leaf area remaining green after anthesis was increased by the fungicide treatment to a greater extent than could be attributed to reduction in foliar disease alone. In one of these trials, yield response was more closely correlated with the increase in leaf area remaining green than with reduction in foliar disease.     

Monitoring für Getreidekrankheiten in Bayern – mehrjährige Auswertungen über die Bedeutung der einzelnen Schaderreger

Since the year 1991, up-to-date data about the actual infestation situations of the most important fungal diseases have been made available to the official advisory service and to the farmers by means of the “Monitoring for cereal diseases”. The classification of infestation is taken according to the scientifically elaborated thresholds of the Wheat Crop System Bayern and the Barley Crop System Bayern, respectively. The extensive data material allowed an evaluation over several years for the various cultivated areas. The least importance in winter wheat had eyespot, brown rust und yellow rust. Most exceedings of the thresholds were caused by Septoria tritici and Drechslera tritici-repentis. On about one third of the examined locations, exceedings of the threshold could already be noted before the growth stage “flag leaf just visible”. According to the infestation situation, in more than half of the cases one treatment would have been appropriate. In the past five years, the net blotch caused by Drechslera teres has turned out to be the most important disease in winter barley. With some difference in importance followed Rhynchosporium leaf blotch, powdery mildew and brown rust. At almost 80% of the locations, threshold exceedings were registered until the growth stage “flag life ligule just visible” (BBCH 39). In the majority of cases, the infestation situation makes a single treatment in winter barley appearing reasonable. In the years 2001–2004 the main pathogen in spring barley had been powdery mildew, followed by Drechslera teres and Rhynchosporium secalis. The exceedings of the thresholds had been spread over a broad range of growth stages. In the past five years the infestation of fungal diseases in triticale has been low. However since 2005 an increase of infestation, especially of powdery mildew, has been registered. The evaluation of the results from the “Monitoring for cereal diseases” over several years allows to estimate the risk of the different fungi in the regions. From that, conclusions about the fungicide intensities required in the average of cases can be drawn.     

The effect of powdery mildew (Erysiphe graminis f. sp. hordei) and leaf rust (Puccinia hordei) on spring barley in New Zealand. I. Epidemic development, green leaf area and yield

Powdery mildew and leaf rust caused large yield losses in spring barley grown near Christchurch, New-Zealand, in two seasons. Disease present during early growth stages was as damaging to yield as disease late in the season. Moderate leaf rust severities after anthesis were most damaging when combined with earlier mildew epidemics. Later growth did not compensate for reduced yield potential induced by early infection. This was attributed, at least in part, to an effect on leaf size, and therefore on green leaf area, at later growth stages. There was a closer relationship, by regression analysis, of yield to green leaf area than to disease severity in three cultivars.
The three cultivars. which differed in yield potential and disease resistance, were not equally sensitive to disease. It is proposed that high yielding cultivars may be the most sensitive to yield constraint by disease.     

Genetics of resistance to wheat leaf rust, stem rust, and powdery mildew in Aegilops sharonensis

Aegilops sharonensis (Sharon goatgrass) is a wild relative of wheat and a rich source of genetic diversity for disease resistance. The objectives of this study were to determine the genetic basis of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis and also the allelic relationships between genes controlling resistance to each disease. Progeny from crosses between resistant and susceptible accessions were evaluated for their disease reaction at the seedling and/or adult plant stage to determine the number and action of genes conferring resistance. Two different genes conferring resistance to leaf rust races THBJ and BBBB were identified in accessions 1644 and 603. For stem rust, the same single gene was found to confer resistance to race TTTT in accessions 1644 and 2229. Resistance to stem rust race TPMK was conferred by two genes in accessions 1644 and 603. A contingency test revealed no association between genes conferring resistance to leaf rust race THBJ and stem rust race TTTT or between genes conferring resistance to stem rust race TTTT and powdery mildew isolate UM06-01, indicating that the respective resistance genes are not linked. Three accessions (1644, 2229, and 1193) were found to carry a single gene for resistance to powdery mildew. Allelism tests revealed that the resistance gene in accession 1644 is different from the respective single genes present in either 2229 or 1193. The simple inheritance of leaf rust, stem rust, and powdery mildew resistance in A. sharonensis should simplify the transfer of resistance to wheat in wide crosses.     

Dehydro-alpha-lapachone isolated from Catalpa ovata stems: activity against plant pathogenic fungi

The methanol extract of stems of Catalpa ovata G Don exhibits potent in vivo antifungal activity against Magnaporthe grisea (Hebert) Barr (rice blast) on rice plants, Botrytis cinerea Pers ex Fr (tomato grey mould) and Phytophthora infestans (Mont) de Bary (tomato late blight) on tomato plants, Puccinia recondita Rob ex Desm (wheat leaf rust) on wheat plants and Blumeria graminis (DC) Speer f. sp. hordei Marchal (barley powdery mildew) on barley plants. An antifungal substance was isolated and identified as dehydro-alpha-lapachone from mass and nuclear magnetic resonance spectral data. It completely inhibited the mycelial growth of B. cinerea, Colletotrichum acutatum Simmonds, Colletotrichum gloeosporioides Simmonds, M. grisea and Pythium ultimum Trow over a range of 0.4-33.3 mg litre(-1). It also controlled the development of rice blast, tomato late blight, wheat leaf rust, barley powdery mildew and red pepper anthracnose (Colletotrichum coccodes (Wallr) S Hughes). The chemical was particularly effective in suppressing red pepper anthracnose by 95% at a concentration of 125 mg litre(-1).     

小麦品种混种对白粉病的调控及其对部分产量性状及蛋白质含量的影响

对品种混合种植控制小麦白粉病的效果以及对小麦穗重、千粒重、蛋白质等指标的影响进行了研究,为混合种植控制白粉病提供理论依据和品种组合。在对37个小麦品种进行SSR多样性分析的基础上,选用8个生产品种（后备品种）,按品种数3、4、5、6、8进行组合,在田间以随机区组设计种植混播组合和单播小区,人工接种白粉菌,比较各小区中小麦白粉病的AUDPC值、穗重、千粒重和粗蛋白差异。结果表明,8个品种亲缘关系较远;4品种混种时AUDPC最小,穗重最重。26个品种混种组合中有防治效果的组合占到73.08%,相对防效为1.23%~56.65%;混种未对穗重和粗蛋白含量造成负面影响。品种多样性种植可以用做调控小麦白粉病的一项措施。     

Laboratory and greenhouse evaluation of a new systemic fungicide,N,N'-bis-(1-formamido-2,2,2-trichloroethyl)-piperazine (CELA W 524)

The new systemic fungicide N,N'-bis-(1-formamido-2,2,2-trichloroethyl)-piperazine (CELA W 524) was shown to display a moderate to distinct fungitoxic activity in vitro towards several pathogenic and non-pathogenic fungi. Depending on the inert ingredients present², the available formulations proved to be either rather phytotoxic or virtually non-phytotoxic. Pre-infectional spraying with the non-phytotoxic formulation provided complete protection of barley, bean, cucumber, pea and tomato plants against barley powdery mildew, bean rust, cucumber powdery mildew and cucumber scab, pea powdery mildew and tomato leaf mould, respectively. some suppression of disease symptoms —although only at high concentrations of CELA W 524 — was observed in the case of leaf spot in pea plants. Upon post-infectional treatment disease control was less pronounced, although powdery mildew diseases and tomato leaf mould were effectively suppressed. When applied via the roots CELA W 524 proved to be systemically active, successfully protecting barley plants against powdery mildew, and cucumber plants against powdery mildew and cucumber scab.Samenvatting Het nieuwe systemische fungicide CELA W 524 (C. H. Boehringer Sohn, Ingelheim am Rhein, Duitsland) bleek een matige tot duidelijke fungitoxische werking in vitro te vertonen tegenover verschillende pathogene en niet-pathogene schimmels. Eén van de beschikbare formuleringen bleek vrij sterk fytotoxisch, de andere was nagenoeg niet fytotoxisch. Bespuiting vóór inoculatie met de niet-fytotoxische formulering resulteerde in volledige bescherming van gerst, bonen, komkommers, erwten en tomaten tegen respectievelijk gerstemeeldauw, boneroest, komkommermeeldauw en vruchtvuur, erwtemeeldauw en bladvlekkenziekte bij tomaat. Enige onderdrukking van ziektesymptomen trad ook op bij erwten, geïnoculeerd metAscochyta pisi, tenminste, wanneer hoge concentraties van CELA W 524 werden gebruikt. Bij bespuiting na inoculatie was het effect geringer, hoewel meeldauwziekten en bladvlekkenziekte bij tomaat toch doeltreffend bestreden werden. Toegediend via de wortels bleek CELA W 524 systemisch actief; het beschermde aldus gerst tegen meeldauw en komkommers tegen meeldauw en vruchtvuur.     

Application of real-time and multiplex polymerase chain reaction assays to study leaf blotch epidemics in barley

ABSTRACT Leaf blotch, caused by Rhynchosporium secalis, was studied in a range of winter barley cultivars using a combination of traditional plant pathological techniques and newly developed multiplex and real-time polymerase chain reaction (PCR) assays. Using PCR, symptomless leaf blotch colonization was shown to occur throughout the growing season in the resistant winter barley cv. Leonie. The dynamics of colonization throughout the growing season were similar in both Leonie and Vertige, a susceptible cultivar. However, pathogen DNA levels were approximately 10-fold higher in the susceptible cultivar, which expressed symptoms throughout the growing season. Visual assessments and PCR also were used to determine levels of R. secalis colonization and infection in samples from a field experiment used to test a range of winter barley cultivars with different levels of leaf blotch resistance. The correlation between the PCR and visual assessment data was better at higher infection levels (R(2) = 0.81 for leaf samples with >0.3% disease). Although resistance ratings did not correlate well with levels of disease for all cultivars tested, low levels of infection were observed in the cultivar with the highest resistance rating and high levels of infection in the cultivar with the lowest resistance rating.     

The combined effects of multiple diseases and climatic conditions on thousand kernel weight losses in winter wheat

Thousand kernel weight (TKW) is a yield component associated with grain quality. It is reported in the literature that TKW is significantly influenced by varieties, agro-ecological conditions and disease indices, but the influence of their interactions on TKW loss has rarely been taken into consideration. The main objective of this study was to examine the combined effects of multiple diseases and climatic conditions on TKW losses in winter wheat. Leaf rust, powdery mildew, and Septoria tritici blotch were considered biotic predictor variables in regression models explaining TKW losses. Monthly averages of temperature, relative humidity and total rainfall in May and June in the 2006–2013 growing seasons were used as abiotic predictor variables. The results of this study indicated a significant low positive correlation between yield loss and TKW loss in the two varieties. TKW losses were less influenced by leaf rust, powdery mildew, and Septoria tritici blotch than yield losses. The significant influence of the interaction between variety and the environmental conditions on TKW loss was confirmed from the general linear model function. The results of this study indicated that factors influencing yield and yield component losses are part of the complex environment, and the relationship between them should be investigated with respect to their interactions.     

Cellular characteristics of temporary partial breakdown of mlo- resistance in barley to powdery mildew

When water-stress is relieved, powdery mildew (Erysiphe graminis f.sp. hordei) infection increases on both Mlo -susceptible and mlo -resistant spring barley cultivars. The breakdown is temporary and is determined by the genetic background rather than the specific resistance allele. The relief of water-stress time-point for maximum mildew infection frequency on mlo -resistant barley is approximately 7 h post-inoculation. The degree of breakdown varies with epidermal cell type; increased infection frequency is greatest on short followed by long and adjacent epidermal cell types, rather than on the stomatal subsidiary cells with which occasional colonies are typically associated. Infection frequency on the short cells of mlo -resistant cv. Atem increases from less than 1% under a non-stressed watering regime to more than 10% after a relief of water-stress at 7 h post-inoculation. Following haustorium formation, colonies develop and reach sporulation within 7 days post-inoculation. In host epidermal cells, the extent of cross-linked protein at interaction sites is reduced under conditions of water-stress or stress-relief. Cross-linked protein is reduced in terms of the frequency of occurrence at primary germ tube interaction sites 7 h post-inoculation and the deposition size at appressorial germ tube interaction sites 24 h post-inoculation. This indicates a delayed or reduced defence response during the recovery period. These data demonstrate a differential cellular response to powdery mildew in barley genotypes prone to resistance expression breakdown following relief of water-stress.     

Crop damage caused by powdery mildew on hop and its relationship to late season management

Powdery mildew of hop (Podosphaera macularis) may cause economic loss due to reductions in cone yield and quality. Quantitative estimates of crop damage from powdery mildew remain poorly characterized, especially the effect of late season disease management on crop yield and quality. Field studies in Washington State evaluated cone yield, bittering acid content and quality factors when fungicide applications were ceased at different stages of cone development. The incidence of cones with powdery mildew was linearly correlated with yield of cones, bittering acids and accelerated cone maturation. In cultivar Galena, the cumulative effect of every 1% increase in cones powdery mildew incidence was to reduce alpha‐acid yield by 0·33%, which was due to direct effects on cone yield but also indirect effects mediated by dry matter. In the more susceptible cultivar Zeus, alpha‐acid yield was increased 20% by controlling powdery mildew through the transition of bloom to early cone development compared to ceasing fungicide applications at bloom: additional applications provided only modest improvements in alpha‐acid yield. In both cultivars, the impact of powdery mildew on aroma characteristics and bittering acid content were less substantial than cone yield. The damage caused by powdery mildew to cone colour and alpha‐acid yield, as well as the effectiveness of fungicide applications made to manage the disease, appears inseparably linked to dry matter content of cones at harvest. Realising achievable yield potential in these cultivars requires control of the disease through early stages of cone development and harvest before maturity exceeds c. 25% dry matter.     

小麦叶锈病、白粉病和条锈病普遍率与严重度间的关系

 在田间接种条件下,详细地观察了小麦叶锈病、白粉病和条锈病普遍率与严重度之间的关系(I-S关系)。结果表明供试三种病害的I-S关系均可用指数函数描述;在普遍率小于70%左右时,用直线方程拟合效果更好;普遍率大于90%时,对严重度的预测效果较差。分别建立了各病的I-S关系式。小麦生育阶段(拔节期、抽穗开花期、灌浆期)对叶锈病和白粉病I-S关系没有明显的影响,而条锈病的I-S关系在不同生育阶段有一定的差异。文章最后对I-S关系的使用进行了讨论。     

83份西农系小麦品种（系）抗性鉴定及抗病基因分子检测

为西北农林科技大学小麦新育成品种（系）在黄淮麦区的大面积推广,该研究对83份西农新育成的小麦品种（系）进行苗期抗条锈病和白粉病鉴定,成株期抗条锈病、白粉病、叶锈病和赤霉病鉴定,并在田间自然环境下对其抗性进行鉴定及对相关抗病基因进行分子检测。结果显示,在苗期人工接种鉴定中,有63、29和16份小麦品种（系）分别对条锈菌Puccinia striiformis f.sp.tritici生理小种CYR32、CYR33和CYR34表现出抗性,9份小麦品种（系）对3个条锈菌生理小种均表现出抗性;有10、3和0份小麦品种（系）分别对白粉菌Blumeria graminis f.sp.tritici生理小种E15、E09和A13表现出抗性。在成株期人工接种鉴定中,有23、15、28和62份小麦品种（系）分别对条锈病、白粉病、叶锈病和赤霉病表现出抗性。在83份小麦品种（系）中有6份在苗期和成株期均对小麦条锈病表现出抗性。在田间抗性鉴定中,有57、6、65和40份小麦品种（系）分别对条锈病、白粉病、赤霉病及叶锈病表现出抗性。在83份小麦品种（系）中,3份含有Yr5基因,22份含有Yr9基因,3份含有Yr17基因,2份含有Pm24基因,14份含有Lr1基因,所占比例分别为3.6%、26.5%、3.6%、2.4%和16.8%。     

三唑酮(粉锈宁)拌种控制小麦条锈病流行的初步研究

四年试验结果表明,用三唑酮拌种对防治小麦秋苗条锈病,压低田间菌量都有显著作用。这对控制越夏区(包括传播桥梁地带)的菌量保护广大麦区具有实际意义;对翌春条锈病有控制流行的作用,可推迟暴发期8～15天,保产效果为6～15.6％。试验结果还说明,拌种对翌春条锈病的控制作用,是在于压低初始菌量。因此拌种方法,适用于春季菌源以当地为主的地区,适用于春季流行的关键因素是越冬菌量的地区,并且处理的范围越大,越彻底,效果越好。还讨论了用拌种防治秋苗叶锈病和白粉病的作用。