Alteration of photosynthetic performance and source–sink relationships in wheat plants infected by Pyricularia oryzae

Two experiments were carried out to assess the changes associated with photoassimilate production and partitioning in the source–sink relationship of flag leaves and spikes of wheat plants infected with Pyricularia oryzae, the causal agent of blast. Flag leaves and spikes were inoculated at 10 and 20 days after anthesis (daa) with a conidial suspension of P. oryzae. Analysis of chlorophyll a fluorescence using maximal photosystem II quantum efficiency (F_v?F_m), fraction of energy absorbed that is used in photochemistry (YII), quantum yield of non‐regulated energy dissipation (Y(NO)) and quantum yield of regulated energy dissipation (Y(NPQ)), showed an impairment of the photosynthetic performance in both infected flag leaves and spikes, coupled with reduced concentrations of chlorophyll a  + b and carotenoids. Compared to non‐inoculated controls, there was lower capacity for CO₂ fixation by RuBisCO in the infected flag leaves. Similarly, in the infected flag leaves and grains (obtained from infected spikes), there were lower concentrations of soluble sugars, while the hexoses‐to‐sucrose ratio increased in infected flag leaves. Compared to non‐inoculated controls, infected flag leaves showed lower sucrose phosphate synthase (SPS) activity and lower expression of the sucrose synthesis (SuSy) gene, while higher expression and activity of acid invertases also occurred. At the advanced stages of fungal infection, the concentration of starch in grains decreased but remained high for the infected flag leaves. There were reductions in ADP‐glucose pyrophosphorylase activity and the expression of ADP‐glucose pyrophosphorylase genes and a down‐regulation of β‐ and α‐amylase expression at the advanced stages of fungal infection on flag leaves and spikes. In conclusion, the effect of blast on both grain quality and yield can be associated with alterations in both production and partitioning of carbohydrates during the grain filling process.     

Histological investigation of stripe rust (Puccinia striiformis f.sp. tritici) development in resistant and susceptible wheat cultivars

The wheat cultivar Kariega expresses complete adult plant resistance against stripe rust, whereas cv. Avocet S is susceptible. Using confocal laser scanning microscopy, initial fungal penetration into flag leaves was identical in both cultivars, with directional germ-tube growth towards stomata that were penetrated without the formation of an appressorium, followed by differentiation of a substomatal vesicle, infection hyphae, haustorial mother cells and haustoria. During the following 4 days, further fungal development occurred more quickly in the resistant than in the susceptible cultivar. However, by 7 days postinoculation (dpi) the situation changed, with exponential growth of the pathogen occurring only in the susceptible line. Induced cellular lignification, a typical defence reaction of cereals, was observed at 4 dpi in the resistant cultivar, and 2 days later lignified tissue completely surrounded the fungal colonies. In the susceptible cultivar, isolated lignified host cells occurred at 6 dpi, and long, unbranched fungal hyphae outgrowing the resistance reaction were observed.     

Ultrastructural and immunocytochemical investigation of pathogen development and host responses in resistant and susceptible wheat spikes infected by Fusarium culmorum

Pathogen development and host responses in wheat spikes of resistant and susceptible cultivars infected by Fusarium culmorum causing Fusarium head blight (FHB), were investigated by means of electron microscopy as well as immunogold labelling techniques. The studies revealed similarities in the infection process and the initial spreading of the pathogen in wheat spikes between resistant and susceptible cultivars. However, the pathogen’s development was obviously more slow in the resistant cultivars as in comparison to a susceptible one. The structural defence reactions such as the formation of thick layered appositions and large papillae were essentially more pronounced in the infected host tissues of the resistant cultivars, than in the susceptible one. β -1,3-glucan was detected in the appositions and papillae. Furthermore, immunogold labelling of lignin demonstrated that there were no differences in the lignin contents of the wheat spikes between susceptible and resistant cultivars regarding the uninoculated healthy tissue, but densities of lignin in host cell walls of the infected wheat spikes differed distinctly between resistant and susceptible cultivars. The lignin content in the cell walls of the infected tissues of the susceptible wheat cultivar increased slightly, while the lignin accumulated intensely in the host cell walls of the infected wheat spikes of the resistant cultivars. These findings indicate that lignin accumulation in the infected wheat spikes may play an important role in resistance to the spreading of the pathogen in the host tissues. Immunogold labelling of the Fusarium toxin DON in the infected lemma showed the same labelling patterns in the host tissues of resistant and susceptible cultivars. However, there were distinct differences in the toxin concentration between the tissues of the susceptible and resistant cultivars. At the early stage of infection, the labelling densities for DON in resistant cultivars were significantly lower than those in the susceptible one. The present study indicates that the FHB resistant cultivars are able to develop active defence reactions during infection and spreading of the pathogen in the host tissues. The lower accumulation of the toxin DON in the tissues of the infected spikes of resistant cultivars which results from the host’s defence mechanisms may allow more intensive defence responses to the pathogen by the host.     

Effects of foliar- and root-applied silicon on the enhancement of induced resistance to powdery mildew in Cucumis sativus

Two cucumber ( Cucumis sativus ) cultivars differing in their resistance to powdery mildew, Ningfeng No. 3 (susceptible) and Jinchun No. 4 (resistant), were used to study the effects of foliar- and root-applied silicon on resistance to infection by Podosphaera xanthii (syn. Sphaerotheca fuliginea ) and the production of pathogenesis-related proteins (PRs). The results indicated that inoculation with P. xanthii significantly suppressed subsequent infection by powdery mildew compared with noninoculation, regardless of Si application. Root-applied Si significantly suppressed powdery mildew, the disease index being lower in Si-supplied than in Si-deprived plants, regardless of inoculation treatment. The resistant cultivar had a more constant lower disease index than the susceptible cultivar, irrespective of inoculation or Si treatment. Moreover, with root-applied Si, activities of PRs (for example peroxidase, polyphenoloxidase and chitinase) were significantly enhanced in inoculated lower leaves or noninoculated upper leaves in inoculated plants of both cultivars. Root-applied Si significantly decreased the activity of phenylalanine ammonia-lyase in inoculated leaves, but increased it in noninoculated upper leaves. However, Si treatment failed to change significantly the activity of PRs in plants without fungal attack. Compared to the control (no Si), foliar-applied Si had no effects either on the suppression of subsequent infection by P. xanthii or on the activity of PRs, irrespective of inoculation. Based on the findings in this study and previous reports, it was concluded that foliar-applied Si can effectively control infections by P. xanthii only via the physical barrier of Si deposited on leaf surfaces, and/or osmotic effect of the silicate applied, but cannot enhance systemic acquired resistance induced by inoculation, while continuously root-applied Si can enhance defence resistance in response to infection by P. xanthii in cucumber.     

TMV侵染不同抗性番茄品种之后引起的过氧化物酶活性及同工酶的变化

 本文论述了不同抗性番茄品种在接种了TMV之后体内过氧化物酶及其同工酶的变化趋势。不同品种番茄幼苗接种TMV之后30天内病毒含量、过氧化物酶活性及其同工酶的测定结果表明:所有接种的番茄幼苗与健株对照相比均表现酶活性的增强及酶带数目的增多;但不同抗性品种,酶活性交化曲线及同工酶谱带的变化趋势有所不同:感性品种北京早红(+/+)及耐病品种强力米寿接种TMV之后,病毒含量迅速上升,在第15天达到最高峰,同时植株开始显症,其酶活性曲线呈现出1个增值高峰,即酶活性只在显症之后迅速上升于第24天达到最高峰,病株在症状发展过程中产生2条健株所没有的具高迁移率的同工酶谱带A与B。抗性品种Tm-2(Tm-2/+)抑制TMV在体内的增殖,在接种之后30天内植株不表现典型外部症状,其酶活性曲线具有2个增酶高峰,即在接种后第12天达到最高峰,并在第21天有1个新的高峰;在酶活性高峰期,接种植株也产生同工酶谱A与B,与感性品种不同的是谱带A与B形成较早,同时,抗性品种还产生感病品种所没有的1条同工酶谱带F。上述过氧化物酶活性及同工酶的变化趋势可以成为鉴定品种抗性一个有价值的生化指标。     

真菌Sr18代谢产物对根结线虫胁迫下黄瓜叶片保护酶的影响

为探究根结线虫胁迫下丝状真菌Sr18代谢产物对黄瓜的作用机理,采用温室盆栽及人工接种试验,研究了不同浓度的Sr18代谢产物对南方根结线虫胁迫下黄瓜叶片保护酶的影响。结果表明,线虫侵染黄瓜根部以后,黄瓜叶片SOD、POD和CAT活性减弱,PPO和PAL浓度降低。施加不同浓度的Sr18代谢产物,能够使线虫胁迫下的黄瓜叶片SOD、POD和CAT活性增强,使PPO和PAL的含量增加,说明Sr18代谢产物能够提高黄瓜的保护酶活性与含量,增强黄瓜对南方根结线虫的抗性。     

黄瓜感染霜霉病菌叶片中一些酶活性的变化

 黄瓜抗病组合受霜霉病菌侵染的部位周围的叶组织内多酚氧化酶(PPO)活性的增加高于中抗和感病组合,而中抗组合又高于感病组合;抗性和中抗组合的过氧化物酶(PO)活性的增加高于感病组合;抗性组合苯丙氨酸解氨酶(PAL)活性的增加高于中抗和感病组合。抗性组合受侵后产生两条新的PPO同功酶带和两条新的PO同功酶带;中抗组合产生一条新的PPO同功酶带和一条新的PO同功酶带;感病组合只产生一条新的PO同功酶带,没有新的PPO同功酶带出现。     

土壤水分和氮素对春小麦叶片抗氧化系统的影响

植物的抗逆性与其清除活性氧(ROS)的能力相关,提高抗氧化代谢水平是增强植物胁迫耐性的有效途径.以抗旱性不同的3个品种为材料,研究土壤水分和氮素水平及其耦合效应对春小麦叶片抗氧化系统的影响,以探讨水、氮对春小麦抗氧化系统的影响规律及抗氧化系统与抗旱性间的关系.结果表明:干旱胁迫使春小麦叶片丙二醛(MDA)含量升高,膜质...     

Nucleoside/nucleotide pools in wheat leaves naturally infected with Erysiphe graminis. I. Changes in the flag leaf

Nucleoside and nucleotide contents of the flag leaves of wheat plants, naturally infected with the powdery mildew fungus Erysiphe graminis were analysed in a field experiment. Fungicide treated plants were used as controls. Only low levels of infection occurred during the experiment (1% to 4% of the leaf area), but they resulted in higher leaf dry weight, and lower levels of chlorophyll, inorganic phosphate and NADP compared with the control plants. Although the total adenine nucleotide pools were the same in the flag leaves of infected and control plants, the energy charge values were slightly larger in the infected flag leaves. The total nucleoside content was higher in the infected flag leaves than the control; while the adenosine pool decreased, that of uridine increased strongly. Although the level of UDP-glucose was similar in the flag leaves of infected and control plants only decreasing slightly with time, UDP-N-acetylglucosamine, a precursor for fungal chitin biosynthesis, showed very different behaviour. The amounts of UDP-N-acetylglucosamine were very low in the control plants but increased greatly in the infected flag leaves to very high values (900nmol g⁻¹ d.wt) obviously reflecting exploitation of the hosts metabolism by the fungus for precursors for chitin biosynthesis. The size of the uridine pools was also correlated with the degree of infection and probably reflected recycling of the UDP moiety.     

Changes in phenylalanine ammonia-lyase and peroxidase activities in wheat cultivars expressing resistance to the leaf-rust fungus

Phenylalanine ammonia-lyase (PAL) and peroxidase activities increased slightly during pre-haustorial stages of development of the leaf-rust fungus ( Puccinia recondita f. sp. tritici ) in each combination of rust strain and wheat line used. Activity of both enzymes greatly increased during the formation of the first haustoria by avirulent and virulent strains in an Lr28-bearing line but not in an Lr20 -bearing line. PAL increased markedly in activity at the time when an avirulent strain was known to cause hypersensitivity in the Lr28 -bearing line and when another avirulent strain was known to cause cellular changes that preceded the expression of resistance in the Lr20 -bearing line. PAL increased less markedly and not at all at corresponding times when virulent strains developed in the Lr28 and Lr20 lines, respectively. Increases in peroxidase activity occurred after the increases in PAL activity and were greater during resistance expression than in leaves infected with virulent strains. Cytochemical tests revealed enhancements of peroxidase activity in epidermal and guard cells in response to avirulent and virulent strains and in mesophyll cells that were becoming necrotic in response to avirulent strains only. The implications of the changes are that aromatic and phenylpropanoid synthesis and peroxidations may be enhanced in wheat by infection and particularly during resistance expression. The products of these processes may play roles in both Lr28- and Lr20 -based expression of resistance.     

The effect of silicon on antioxidant metabolism of wheat leaves infected by Pyricularia oryzae

This study investigated whether the increase in wheat resistance to blast, caused by Pyricularia oryzae, potentiated by silicon (Si) is linked to changes in the activity of antioxidative enzymes. Wheat plants (cv. BR 18) were grown in hydroponic culture with either 0 (–Si) or 2 mm (+Si) Si and half of the plants in each group were inoculated with P. oryzae. Blast severity in the +Si plants was 70% lower compared to the ?Si plants at 96 h after inoculation (hai). Superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione‐S‐transferase (GST) activities were higher in the leaves of the ?Si plants compared with the +Si plants at 96 hai. This indicates that other mechanisms may have limited P. oryzae infection in the +Si plants restricting the generation of reactive oxygen species, obviating the need for increased antioxidative enzyme activity. In contrast, glutathione reductase (GR) activity at 96 hai was higher in the +Si plants than in the ?Si plants. Although the inoculated plants showed significantly higher concentration of malondialdehyde (MDA) than the non‐inoculated plants, lower MDA concentrations were observed in the +Si plants compared with the ?Si plants. The lower MDA concentration associated with decreased activities of SOD, CAT, POX, APX and GST, suggest that the amount of reactive oxygen species was lower in the +Si plants. However, GR appears to play a pivotal role in limiting oxidative stress caused by P. oryzae infection in +Si plants.     

Effects of blast on components of wheat physiology and grain yield as influenced by fungicide treatment and host resistance

Two field experiments (Exp. 1 and Exp. 2) were carried out to assess the physiological performance and grain yield of wheat cultivars BR‐18 (moderately resistant) and Guamirim (susceptible) inoculated with Pyricularia oryzae in plots treated or untreated with Ópera (fungicide 13.3% epoxiconazole + 5% pyraclostrobin). Results from regression analyses indicated that spike and leaf blast severity at 10–14 days after inoculation (dai) were associated with greater yield losses (highest negative slope) than severity at 18–22 dai. Relative to untreated Guamirim, there were 0.3% and 16% increases in Exp. 1 and 2, respectively, for untreated BR‐18 (resistance alone). For fungicide treatment alone, the mean yield of Guamirim increased by 20% and 61% in Exp. 1 and 2, respectively, relative to the untreated fungicide control, whereas for the fungicide treated BR‐18, the mean yield increased by 26% and 83% in Exp. 1 and 2, respectively. Fungicide application and cultivar resistance resulted in higher measures of leaf health and photosynthetic performance in both spikes and leaves than in the untreated susceptible reference treatment. The results from this study may be useful in future efforts to develop crop loss models and management guidelines for wheat blast.     

Wheat leaf resistance to Pyrenophora tritici‐repentis induced by silicon activation of phenylpropanoid metabolism

Tan spot caused by Pyrenophora tritici‐repentis is a disease present in all wheat‐producing countries and silicon (Si) treatment of wheat plants has been shown to increase plant resistance to tan spot. In this study, the effect of phenylpropanoid metabolism on resistance to tan spot was evaluated and some phenolic compounds that accumulated in response to P. tritici‐repentis attack were identified. Furthermore, the effect of Si on phenylalanine ammonia‐lyase (PAL) activity and phenolic compound accumulation were determined in situ. Antifungal activity of differentially accumulated phenolic compounds was also evaluated in in vitro tests. Results showed that the increase in concentration of phenolic compounds was greatest at the onset of infection, and that some compounds showed fungitoxic effects including fungal tip swelling, granulation of germ tube and hyphae, and hyphal hyperbranching. Silicon‐induced reduction in both lesion size and tan spot disease progression were associated with activation of phenylpropanoid metabolism. PAL activity and accumulation of antifungal phenolic compounds were greater in pathogen‐inoculated plants supplied with Si. In these plants, fluorescence indicative of accumulation of phenolic compounds occurred early in epidermal cells and its intensity increased during the evaluation period, showing higher numbers of fluorescent cells around infected cells. Thus, the combined responses of cell fluorescence at sites of infection, increased PAL activity and accumulation of phenols indicate that Si strengthened wheat defence responses to infection by P. tritici‐repentis, reducing the severity of tan spot.     

Magnaporthe oryzae conidia on basal wheat leaves as a potential source of wheat blast inoculum

Wheat blast caused by Magnaporthe oryzae Triticum causes significant losses on wheat during outbreak years in several South American countries. Despite reports of wheat blast leaf lesions on some wheat cultivars, the importance of inoculum originating from leaves in severely affected commercial fields is disputed. It is generally considered that leaf lesions and/or sporulation on leaves do not usually appear before the occurrence of spike blast in wheat. The purpose of this study was to (i) determine the occurrence of wheat blast on basal leaves, (ii) estimate the number of conidia produced on these leaves, and (iii) determine the impact of current fungicide application practices on inoculum produced from sporulating lesions on basal wheat leaves. Inoculations at the three‐leaf stage showed that certain cultivar and isolate combinations caused more disease on old wheat leaves than young expanding leaves. Under optimum conditions, M. oryzae had the potential to produce tens to hundreds of thousands of conidia on small amounts of wheat basal leaves. A mean of 1 669 000 conidia were produced on 1 g dry basal leaves of a highly susceptible cultivar under optimum conditions for sporulation. Conidia production on leaves coincided with spike emergence under both greenhouse and field conditions. When field studies were conducted under natural epidemic conditions, foliar fungicide applications reduced the amount of M. oryzae conidia on basal leaves by 62–77% compared to non‐sprayed controls. An earlier application of foliar fungicides might reduce inoculum if conidia from basal leaves contribute to wheat spike blast development.     

Tracing seed to seedling transmission of the wheat blast pathogen Magnaporthe oryzae pathotype Triticum

Wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT), initially restricted to South America, is a global threat for wheat after spreading to Asia in 2016 by the introduction of contaminated seeds, raising the question about transmission of the pathogen from seeds to seedlings, a process so far not well understood. We therefore studied the relationship between seed infection and disease symptoms on seedlings and adult plants. To accomplish this objective, we inoculated spikes of wheat cv. Apogee with a transgenic isolate (MoT-DsRed, with the addition of being resistant to hygromycin). We identified MoT-DsRed in experiments using hygromycin resistance for selection or by observation of DsRed fluorescence. The seeds from infected plants looked either apparently healthy or shrivelled. To evaluate the transmission, two experimental designs were chosen (blotter test and greenhouse) and MoT-DsRed was recovered from both. This revealed that MoT is able to colonize wheat seedlings from infected seeds under the ground. The favourable conditions of temperature and humidity allowed a high recovery rate of MoT from wheat shoots when grown in artificial media. Around 42 days after germination of infected seeds, MoT-DsRed could not be reisolated, indicating that fungal progression, at this time point, did not proceed systemically/endophytically. We hypothesize that spike infection might occur via spore dispersal from infected leaves rather than within the plant. Because MoT-DsRed was not only successfully reisolated from seed coats and germinating seeds with symptoms, but also from apparently healthy seeds, urgent attention is needed to minimize the risks of inadvertent dispersal of inoculum.     

Tolerance to paraquat-mediated oxidative and environmental stresses in squash (Cucurbita spp.) leaves of various ages

Paraquat is labeled for row-middle application on cucurbits, but drift to crop foliage is inevitable. Experiments were conducted to determine whether differential tolerance to paraquat existed among leaves of various ages in Cucurbita spp. (squash) and other plants, and to examine whether leaves tolerant to paraquat are also tolerant to other herbicides and abiotic stresses. Physiological responses to paraquat, including antioxidant activity, were investigated in squash leaves to identify mechanisms of paraquat tolerance. Although the level of paraquat tolerance differed by leaf age, cultivar, and species, the level of paraquat injury was lower in younger leaves than in older leaves in 14 of 18 squash cultivars and 5 of 12 other species tested. Cellular leakage and lipid peroxidation were consistently lower in the youngest leaf (leaf 4) than in the older leaves. Quantum yield and relative chlorophyll content were the same in all leaves of nontreated plants. Epicuticular wax content was higher in the youngest leaf than in leaves 1, 2, and 3 of cv. ‘Joongangaehobak’ and ‘Wonbiaehobak’. However, leaf cuticle content was not consistent with leaf ages. Differential leaf response to paraquat was partially correlated with the change in catalase, peroxidase, ascorbate peroxidase (APX), and glutathione reductase activities in nontreated and treated leaves. The APX activity in the youngest leaf was generally 2 times higher than in leaves 1-3 in both nontreated and treated plants. Ascorbate antioxidant levels were also higher in the youngest leaf than those in leaves 1-3. Leaves tolerant to paraquat were also tolerant to diquat and to abiotic stresses, low temperature and drought. However, tolerance to oxyfluorfen, which has a different mode of action than paraquat and diquat, was higher in older than in younger leaves. Higher tolerance to paraquat-mediated oxidative and abiotic stresses in young leaves of most squash cultivars might contribute to the differential prevention of oxidative damage in leaves of various ages.     

感染花生条纹病毒(PStV)后花生生理生化性状变化的研究

 研究表明,花生接种条纹病毒发病后叶片的光合强度、叶绿素含量及超氧化物歧化酶(SOD)活性明显下降,而过氧化物酶(POD)活性却显著提高。高感花生品种白沙1016上述指标的变化幅度较大,发病植株叶片中POD同功酶出现了4条健株中没有的新带,迁移率分别为0.67、0.73、0.80和0.89,而原有的迁移率为0.38的1条谱带变弱消失,发病后SOD同功酶谱带数没有显著变化。     

Indian peanut clump virus (IPCV) infection on wheat and barley: symptoms, yield loss and transmission through seed

Wheat and barley crops were shown to be susceptible to Indian peanut clump virus (IPCV) under field conditions. In wheat, the Hyderabad isolate of IPCV (IPCV-H) induced symptoms resembling the rosette caused by soil-borne wheat mosaic virus, and these were apparent only three weeks after emergence. Early-infected plants were severely stunted and dark green, with chlorotic streaks on the youngest leaves, which turned necrotic as the plants aged; most of these plants died. Late-infected plants were also stunted and were conspicuous in the field because of their dark green appearance as a result of delayed maturity. The virus was detected by ELISA and nucleic acid hybridization in all plants with symptoms. These plants usually produced fewer tillers than healthy ones. Spikes were malformed, often did not emerge from the flag leaf, and they contained few, shrivelled seeds. Grain yield was decreased, on average, by 58%. In barley, IPCV-H caused severe stunting and general leaf chlorosis. As the plants aged, the leaves became necrotic and the few infected plants that reached maturity produced small spikes. IPCV-H antigens were detected by ELISA in every wheat seed from infected plants and the virus was transmitted through wheat seed at a frequency of 0.5–1.3%. Storage at 4°C for more than a year did not affect seed transmission frequency. The virus was detected in leaves and roots of seed-transmitted plants. Seed transmission was not detected in barley. The Durgapura isolate (IPCV-D) was detected in wheat crops (cv. RR-21) at 3 different locations in Rajasthan State, India. Infected plants showed reduced growth without any overt symptoms.     

Towards the Development of a Novel In Vitro Strategy for Early Screening of Fusarium Ear Blight Resistance in Adult Winter Wheat Plants

A novel in vitro bioassay is described for screening Fusarium ear blight (FEB) resistance in adult winter wheat plants. Seven winter wheat cultivars were assessed for components of partial disease resistance as 28 day-old detached leaf segments in the laboratory using isolates of Microdochium nivale var. nivale and M. nivale var. majus. Results were compared with disease data obtained at anthesis using the same cultivars as whole plants and the same isolates under glasshouse conditions. Significant cultivar differences were observed using detached leaves, with cv. Avalon (a Fusarium culmorum ear susceptible cultivar) having the shortest leaf incubation period, greatest leaf lesion development and shortest leaf latent period compared to cv. Spark (a Fusarium culmorum ear resistant cultivar), which had the longest leaf incubation period, least leaf lesion development and longest leaf latent period. Using whole plants, cv. Avalon had the shortest ear incubation period and greatest ear disease severity, whilst cv. Spark had the longest incubation period and least ear disease severity. Overall, cultivars of intermediate F. culmorum ear resistance expressed intermediate responses to M. nivale isolates, using both detached leaves and whole plants. Significant correlations were found with ear disease severity and ear incubation period in whole plants and components of partial disease resistance in detached leaves, with significant correlations obtained between leaf incubation period and ear disease parameters using the M. nivale var. nivale isolate. In addition, leaf latent period and leaf lesion size showed significant correlations with whole plant reactions using M. nivale var. nivale and var. majus isolates. The in vitro screening of cultivars as detached leaves using M. nivale isolates may offer a real possibility of a rapid bioassay for the early screening of FEB resistance in wheat and other cereals.