Role of seed infection by the Ascochyta blight pathogen of dried pea (Mycosphaerella pinodes) in seedling emergence, early disease development and transmission of the disease to aerial plant parts

The role of infected seed in the epidemiology of Ascochyta blight of pea, caused by Mycosphaerella pinodes, was studied both under growth chamber and field conditions, using healthy seeds, naturally infected seeds and artificially infected seeds. Results suggest that infected seeds caused serious losses, as a result of poor germination and high transmission of the disease, to parts of the plants under soil level. Foot rot symptoms often caused the death of young seedlings. Losses were increased by low temperatures during the early stage of crop development. M. pinodes progressed from seeds to aerial parts of the plants, but no Ascochyta blight symptoms occurred, the disease remaining near to the basal parts of the plants as a foot rot symptom. This suggests that seeds cannot be regarded as a source of contamination in the epidemiology of the disease.     

旱涝胁迫条件下稗草对大豆植株含氮量及蛋白质产量的影响

稗草生长明显降低了大豆籽粒蛋白质产量及氮素向其籽粒中的分配比例,而显著提高了大豆茎、叶、籽含氮量及氮素向其茎、叶中的分配比例。这种影响在座荚期渍涝 鼓粒期干旱条件下最为突出;稗草对大豆籽粒蛋白质生产的危害在幼苗期—开花期的渍涝条件下显著减轻,而在任一时期的干旱条件下均明显加重,且在座荚期的渍涝处理中比在幼苗期—开花期的渍涝处理中大。不同时期、不同旱涝胁迫处理对大豆籽粒蛋白质产量的降低程度不同,其中旱害远大于涝害,后期旱害大于前期旱害,先涝后旱的危害大于先旱后涝的危害,旱涝结合的危害大于只旱或只涝的危害;开花期大豆最不耐涝,鼓粒期最不耐旱。     

干旱与复水对马铃薯块茎膨大期碳氮转运的影响

为探讨干旱及复水对马铃薯块茎膨大期碳氮物质转运影响的生理机制,采用盆栽控水法研究了干旱胁迫、旱后复水过程中马铃薯叶片与块茎中碳水化合物、氮素同化物以及碳氮转运相关酶活性的变化规律。结果表明：干旱胁迫下马铃薯叶片蔗糖磷酸合成酶（SPS）活性显著增强,增幅为54.9%,可溶性糖与蔗糖含量显著增加,分别增加84%、25%;块茎蔗糖与淀粉含量显著下降,分别降低25%、11.8%。复水后叶片可溶性糖含量变化较小,叶片SPS活性仍保持较高水平;块茎中蔗糖合成酶（SS）活性下降6.25%(P＜0.05),蔗糖与淀粉含量分别增加21.8%、29.8%。干旱胁迫下马铃薯叶片中硝酸还原酶（NR）活性下降49.3%,谷氨酰胺合成酶（GS）活性与对照差异不显著,叶片游离氨基酸与可溶性蛋白质含量分别降低29.4%、38.4%,全氮含量降低13%;块茎中游离氨基酸与可溶性蛋白质含量增加16.8%、270.9%。复水后叶片中NR与GS活性高出对照3.5%、12.1%,叶片游离氨基酸、可溶性蛋白质以及全氮含量仍保持较低水平;块茎游离氨基酸、可溶性蛋白含量较高,增幅分别为24.6%、178.4%,全氮含量增加,与对照差异不显著。说明干旱胁迫显著阻碍了马铃薯碳水化合物与氮素同化物的合成与转运,使马铃薯叶片碳水化合物积累,但干旱促进了氮素向块茎转运,块茎中的碳氮比下降;复水后马铃薯植株能够快速修复干旱胁迫造成的损伤,表现为块茎中淀粉含量增多,块茎碳氮比增加。     

Physiological stress responses of Vitis vinifera L. to the fungicides fludioxonil and pyrimethanil

The effects of the fungicides fludioxonil and pyrimethanil were evaluated on grapevine leaves using in vitro-grown plantlets, fruiting cuttings, and plants grown in vineyards. In vitro, both water content and osmotic potential decreased in treated leaves. Moreover, carbohydrate accumulated, suggesting that plantlets could react to the stress through an active osmoregulation process by uptaking sugars from the medium. Besides, pyrimethanil stimulated the accumulation of proteins, whereas no significant effect was observed using fludioxonil. The cuttings exhibited similar responses than in vitro though they appeared to be more tolerant since half of the studied parameters recovered 10 days after treatment. In vineyard, both fungicides modified leaf water content and carbohydrate levels, whereas nitrogenous compounds accumulated transiently. These results suggest that in vineyard-grown plants, a strong sugar translocation from mature leaves to sink organs occurs transiently, as well as a protein synthesis and a stimulation of soil nitrogen uptake.     

Seed Development,Oil Accumulation and Fatty Acid Composition of Drought Stressed Rapeseed Plants Affected by Salicylic Acid and Putrescine

Two field experiments were carried out in 2017 and 2018 to evaluate the impacts of salicylic acid (1?mM SA) and putrescine (1?mM Put) on leaf osmolytes, seed reserve and oil accumulation and fatty acid composition of rapeseed (Brassica napus L.) under different watering levels (irrigations after 70 and 150?mm evaporation as normal irrigation and severe drought stress, and 70?→?90?→?110?→?130?→?150 and 70?→?100?→?130→150 as gradual and moderately gradual water deficits, respectively). The experiments were laid out as split plot on the bases of randomized complete block design in three replications. Water stress increased the contents of glycine betaine, proline, soluble sugars, and proteins. Application of SA and Put further enhanced the contents of glycine betaine and soluble sugars, while reduced proline content of leaves. Seed filling duration, seeds per plant, plant biomass and seed yield were decreased with increasing irrigation intervals. Exogenous SA and Put enhanced all of these parameters under different irrigation intervals. Oil accumulation in seeds was diminished as water stress severed. The gradual water deficit considerably reduced the impacts of drought stress on yield related traits and oil content per seed, due to stress acclimation of plants. Oil content of seeds was augmented by SA and Put treatments through prolonging seed filling duration, particularly under limited irrigations. Percentages of palmitic acid and stearic acid (saturated fatty acids) were not affected by water limitation. However, unsaturated fatty acids of linoleic and linolenic acids were reduced, and oleic acid was enhanced due to water shortage. Unsaturation index was improved by SA and Put treatments under severe water stress as a result of decreasing oleic acid and increasing linoleic and linolenic acids contents. The SA spray was the best treatment for improving rapeseed seed and oil production under normal and stressful conditions.

     

水稻抗病性的研究Ⅳ、水稻品种耐肥性与对白叶枯病抗病性的关系

 用人工接种的方法测定水稻品种在不同氮肥水平下的抗病性变化,发现最感染白叶枯病的品种,发病程度一般都随氮肥水平的增加而显著提高;比较抵抗的品种,发病程度虽然亦有所增加,但是幅度要小得多。品种叶片的蛋白质氮的含量,都随着氮肥水平的提高而增加,但是其中游离氨基酸含量则根据品种抗病性的强弱而不同,感病品种一般都随着氮肥水平的提高而增加,而此较抗病的品种则在氮肥水平过高的情况下反而降低,或者始终保持在较低的水平。因此,水稻品种对氮肥水平的生理反应是不同的,其中游离氨基酸的变化可能在一定程度上反应了品种的耐肥性。水稻对胡麻斑病的反应,除品种农垦58以外,发病程度都是随着氮肥水平的提高而降低。与植株蛋白质氮量的高低呈反此,与游离氨基酸含量的变化无一定规律。     

不同种粒抗性大豆品种感染SMV后可溶性蛋白和游离氨基酸的研究

 采用感斑驳品种合丰25、丰收12,抗斑驳品种东农81-43、铁6915(东农),在隔离网室内进行盆栽试验,于对生真叶期分别接种SMV1号、3号株系,以未接种健株为对照,在鼓半粒期分析种皮游离氨基酸和可溶性蛋白含量。结果表明:抗斑驳品种健株种皮中可溶性蛋白含量显著高于感斑驳品种,说明种皮中可溶性蛋白含量与种粒抗性成正相关,可作为筛选抗斑驳品种的生化指标。感斑驳品种中未检测到甲硫氨酸,抗斑驳品种含有甲硫氨酸,甲硫氨酸能抑制色素的形成。接种SMV后,感斑驳品种种皮中可溶性蛋白含量增加,抗斑驳品种可溶性蛋白含量降低。感斑驳品种种皮中苏、苯丙、异亮、缬氨酸含量增加,抗斑驳品种上述氨基酸含量降低或维持不变。这些氨基酸能促进色素的形成,可能与种皮斑驳的形成有一定关系。     

氮素营养对烤烟抗旱适应性的影响

通过研究在不同氮素营养水平下,烤烟对干旱胁迫的一些反应,包括脯氨酸的积累、丙二醛含量和叶片膜透性的变化,并对不同氮素水平和土壤水分条件下的烤烟叶片水分状况、烤烟生长及其根冠比进行分析.结果表明:干旱胁迫下,烤烟的叶片水势、相对含水量、自由水含量及干物质积累均下降,而脯氨酸、丙二醛、束缚水含量升高,膜透性增大,施氮烤烟与不施氮烤烟之间有明显差异.氮素营养改变了烤烟适应干旱的方式,施氮在一定程度上提高了烤烟的生理耐旱性,促进了根系的发育,增加了干物质积累.     

旱胁迫对啤酒大麦产量及酿造品质的影响

在武威黄羊镇啤酒大麦试验基地进行了干旱胁迫对甘啤6号生育期、农艺性状、籽粒产量、原麦品质、酿造品质的影响试验研究。结果表明:干旱胁迫下甘啤6号各生育期均提前,成活率降低,分蘖减少,株高、穗长、单株穗数、单株粒数、单株粒重、单穗粒重、穗粒数均降低;干旱胁迫使甘啤6号成穗数、穗粒数、千粒重均降低,导致产量降低,其中对成穗数影响最大,其次为穗粒数,对千粒重影响最小;干旱胁迫使大麦蛋白质含量升高,千粒重、淀粉含量和筛选率均降低,千粒重降幅尤其明显;干旱胁迫使麦芽糖化时间、糖化力、粘度、β-葡聚糖、微粉浸出率、粗细粉差降低,粗粉浸出率、a-氨基氮、可溶性氮、蛋白质、库值升高。     

Effect of fungal pathogens on digestibility and chemical composition of Italian ryegrass (Lolium multiflorum) and tall fescue (Festuca arundinacea)

Slight infection by Drechslera siccans or Rhynchosporium spp. significantly reduced in vitro dry matter digestibility, water-soluble carbohydrate and the total amino acid content of Italian ryegrass (Lolium multiflorum) foliage. The concentration of all 15 amino acids detected was reduced, with arginine reduced significantly more than the others. Total nitrogen was either increased or not changed, and the amino acid composition was not altered. Limited work with Drechslera festucae on tall fescue (Festuca arundinacea) gave similar results. Small samples of healthy and diseased grass leaves at three different physiological stages were used to detect these changes.
Limited leaf spotting by D. siccans caused metabolic changes of the same magnitude as extensive leaf blotching by Rhynchosporium. Impaired photosynthesis and growth of the fungi within the leaf tissues are possible causes of these changes. Decreased digestibility and increased dry matter content of diseased grass foliage could be of great practical importance.     

Effect of bacterial blight (Pseudomonas syringae pv. pisi) on the growth and yield of single pea (Pisum sativum) plants under glasshouse conditions

Single pea ( Pisum sativum ) plants cvs Kelvedon Wonder and Solara, growing in pots in a glasshouse, showed significant reductions in seed yield of 24, 47 or 71% following inoculation with pea bacterial blight ( Pseudomonas syringae pv. pisi ) during reproductive, vegetative or both reproductive and vegetative growth stages, respectively. These yield reductions were seen as reduced numbers of seeds per pod combined with changes in the numbers of pods per plant. Examination of the importance of different disease parameters on yield showed that mean disease on the whole plant was the most important. Equations describing the relationship between seed yield or the natural log of the total weight and mean disease were derived.     

The influence of <Emphasis Type="Italic">Aphanomyces cochlioides</Emphasis> on selected physiological processes in sugar beet leaves and yield parameters

Alterations in some physiological processes in source leaves of sugar beet—such as chlorophyll and carbohydrate concentrations, stomatal conductance, rate of net photosynthesis and transpiration, and activity of the photosynthetic apparatus during root interaction with Aphanomyces cochlioides, were investigated. The influence of time of infection on plant health, yield quality and quantity was also examined. Plants were infected at different times of their growth period: on the sowing day and 4 or 8 weeks after sowing. A variation treatment, with non-pelleted seeds infected on the sowing day, was also analyzed. The experiment showed that development of disease symptoms depends on the time of infection and seed protection. A significant root yield decrease was observed in case of late infection, as compared to the yield of plants infected on the sowing day. The fresh weight of leaves was significantly increased where there was late infection. The infected plants showed a lower content of K⁺, Na⁺ and α-amino-N than did the controls. Infection by A. cochlioides induced chlorophyll degradation mostly in older leaves with the occurrence of natural senescence processes. Chlorophyll fluorescence parameters indicated that the photosynthetic apparatus of younger leaves was more sensitive to pathogen infection, when compared to older ones. The photochemical efficiency of photosystem II was reduced in young leaves mainly due to disturbance of the water-splitting system. In plants grown from non-pelleted seeds a strong impairment of PSII was observed only in those leaves which developed during early pathogen infection. In young leaves of plants infected in the fourth week after sowing, inhibition of the rate of net photosynthesis was correlated with the increase in intercellular CO₂ concentration, indicating some disturbance in the carbon assimilation phase. In mature leaves of late infected plants the reduction of photosynthesis net rate was associated with a decrease of stomatal conductance and an increase of diffusion resistance to CO₂ and H₂O, which was also the cause of the transpiration rate inhibition. When the leaves developed during early infection, an increase of specific leaf weight and accumulation of carbohydrates was observed. In mature leaves of non-protected plants infected on the sowing day, the recovery of all physiological processes was observed together with a diminution of disease symptoms.     

环境与寄主条件对玉米灰斑病菌侵染寄主的影响

利用玉米灰斑病菌株20-47、感病玉米品种(掖单13)和抗病玉米品种(沈单10号),在人工气候室和自然条件下对影响玉米灰斑病菌侵染的环境条件和寄主生育期进行了研究。结果表明:玉米灰斑病是属偏高温高湿类型的病害,在温湿度条件不能得到满足时,病害就难以完成侵染发病;病菌接种侵入的最佳温度为25℃左右,水滴条件下侵染最容易;土壤条件特别是氮、磷肥如果施用不均匀、不足或过多,也都可以对结果产生影响,在通常情况下,增施氮、磷肥能提高玉米对灰斑病的抗性;在一定光照强度范围内,光对鉴定结果的影响不明显,但光暗交替更有利于寄主发病;寄主不同生育期对病原菌侵染寄主的影响不同,11～12叶期(喇叭口期)接种,病菌较易侵染。     

Comparison of visual head blight ratings, seed infection levels, and deoxynivalenol production for assessment of resistance in cereals inoculated with Fusarium culmorum

Seven spring wheat, 13 barley, 14 oats and 20 winter wheat genotypes were inoculated at flowering in 1993 and 1994 with mixed conidial suspensions of 8 isolates of Fusarium culmorum. Four weeks after inoculation, head blight was recorded in the field. After harvest, seed infection was assessed by a Freezing Blotter Test in the laboratory. Seed samples were also analyzed for deoxynivalenol (DON) content. Differences were found in head blight rating, the levels of infected seeds and the DON content between wheat, barley, and oats and between cultivars. Highly significant correlations were found between the percentage of heavily infected seed and the DON content. The weighted mean value of infected seeds and DON content were also significantly correlated. No significant correlation was found between head blight rating in the field and DON content. The level of infected seeds, as determined by the Freezing Blotter Test, was a better indication of the DON content in the seeds than the head blight rating. This visual assessment of levels of infected seeds gives a reliable estimate of resistance to Fusarium.     

外源一氧化氮对Na_2CO_3胁迫下南瓜幼苗碳氮代谢的影响

为探讨外源NO对Na_2CO_3胁迫下南瓜幼苗碳氮代谢过程的影响,以银辉2号南瓜品种为材料,采用盆栽法研究了80μmol·L-1SNP对60 mmol·L-1Na_2CO_3胁迫下南瓜幼苗生长、叶绿体色素含量、碳氮代谢相关酶活性及代谢产物量的变化规律。结果表明:Na_2CO_3胁迫12 d,南瓜幼苗地上和地下部分干重、相对生长量、根冠比、Rubisco羧化活力、光合色素含量和氮代谢相关酶活性均不同程度下降;Rubisco氧化活力、游离氨基酸总量和蛋白水解酶活性显著上升。80μmol·L-1SNP外源处理能明显缓解Na_2CO_3胁迫对南瓜幼苗生长及光合作用的抑制,增加了干物质的积累和光合色素的含量。与Na_2CO_3胁迫处理相比,干物质积累量、相对生长量、叶绿素和类胡萝卜素(caro)含量、硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、Rubisco羧化酶、淀粉酶(AMY)活性和可溶性蛋白含量分别提高了26.72%、30.45%、17.69%、46.15%、46.43%、30.70%、38.75%、70.0%、65.37%;Rubisco加氧酶、蛋白水解酶活性和游离氨基酸总量分别降低了18.29%、31.76%、28.57%。外源NO通过促进淀粉酶和Rubisco羧化活性的提高和氧化活性的下降,维持了可溶性总糖含量的稳定;通过增强NR、GS和谷氨酸合酶(GOGAT)活性、抑制蛋白水解酶和谷氨酸脱氢酶(GDH)活性,降低叶片中游离氨基酸含量,增加了蛋白质的积累。本研究结论:碱性盐胁迫下,80μmol·L-1的SNP通过增强南瓜幼苗的光合碳代谢,促进了酮酸转化为氨基酸。通过提高氮代谢相关酶NR、GS、GOGAT活性,促使碳流由光合碳代谢转向氮代谢,维持了盐害下南瓜幼苗碳氮代谢的正常进行,增强了南瓜幼苗抵御Na_2CO_3胁迫的能力。     

Epiphytotics of chickpea Ascochyta blight in Turkey as influenced by climatic factors

Journal of Plant Diseases and Protection - Chickpea Ascochyta blight caused by Didymella rabiei is one of the most important fungal diseases affecting yield and seed quality negatively in Turkey....     

葡萄对霜霉病抗性机理初探

经田间自然鉴定、接种鉴定及室内离体接种鉴定结果表明：葡萄对霜霉病抗性与品种叶内的含水量、可滴定酸、还原糖、淀粉、水解氨基酸、游离氨基酸含量无显著相关，与叶背气孔密度、气孔开闭程度也无相关，而外施高浓度蔗糖及邻苯二酚却显著降低霜霉菌的致病力。     

Effects of sowing date on severity of blight caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> and yield components of five chickpea cultivars grown under two climatic conditions in Tunisia

Five chickpea cultivars, Chitoui, Neyer, Kasseb, Beja 1 and Bouchra, were planted on three sowing dates at two Experimental Stations in Tunisia: Bou Salem in the north and the more southerly Mornag, where the climate is drier. Severity of blight, caused by Ascochyta rabiei, was measured on a 1–9 scale (defined) on vegetative parts and on pods as percent infected and percent infected that were empty. At both locations, disease was essentially absent on plants sown on the third dates but present on plants sown on the two earlier dates. At Bou Salem, disease severity was highest for the second sowing date whereas at Mornag it was highest for the first sowing date; but for each sowing date, disease severity was lower at Mornag than at Bou Salem. Yield components were measured as number of pods per plant, number of seeds per plant, number of seeds per 100 pods, 100 seed weight and weight of seeds per plant. Both disease severity and yield differed significantly among sowing dates (differently at each location) and also among cultivars for each sowing date, these differences depending both on sowing date and location. A lower yield was always associated with a higher disease severity, although the quantitative relationship differed between cultivars and locations. Cultivar Beja 1 had the lowest vegetative disease scores at both locations and both sowing dates 1 and 2. Beja 1 also scored well for all yield components. Plants sown on the third (latest) date gave the highest yields for all cultivars at both locations (except for an unusually high yield of Neyer at Mornag on sowing date 2), in some instances being more than double those from the earlier sowing dates. Thus, in contrast to other studies, late sowing did not result in yield loss.     

Management of bakanae and bacterial seedling blight diseases in nurseries by irradiating rice seeds with atmospheric plasma

The control of seedborne rice seedling diseases in the seed beds is important to avoid epidemics in rice nurseries and paddies, which may result in severe yield loss. Recently, irradiation with plasma containing electrons, creating positive or negative ions and neutral species, has been shown to have an antimicrobial effect, probably via generation of reactive oxygen species. This study examines whether two seedborne rice seedling diseases, bakanae disease caused by the fungal pathogen Fusarium fujikuroi, and bacterial seedling blight caused by Burkholderia plantarii, are suppressed by irradiation of infected rice seeds with atmospheric plasma. Seed germination and seedling growth were not inhibited in plasma‐treated healthy seeds. When F. fujikuroi‐infected rice seeds were irradiated with plasma after being immersed in sterile distilled water, bakanae disease severity index and the percentage of plants with symptoms were reduced to 18.1% and 7.8% of non‐irradiated control, respectively, depending on the duration of plasma irradiation. The bacterial seedling blight disease index was also reduced by plasma irradiation in vacuum‐inoculated seeds to 38.6% of the non‐irradiated control, and in infected seeds harvested from spray‐inoculated heads of rice plants to 40.1% of the control. Therefore, plasma irradiation seems to be effective in controlling two independent seedborne rice seedling diseases.     

Ascochyta blight of chickpea in Australia: identification, pathogenicity and mating type

The aetiology of blight of chickpea in South Australia was studied following sporadic disease outbreaks over several years that had been tentatively identified as Phoma blight. Nine fungal isolates from diseased chickpeas were tested for pathogenicity in the glasshouse, of which two caused symptoms resembling those of Ascochyta blight. The two aggressive isolates were identified as Ascochyta rabiei based on morphological characteristics of cultures and RAPD analysis. This was further confirmed by successful mating to international standard isolates, which showed that the two Australian isolates were MAT1-1. These isolates are accessioned as DAR 71767 and DAR 71768, New South Wales Agriculture, Australia. This is the first time that A. rabiei has been positively identified in commercial chickpeas in the southern hemisphere. The pathogen was found (in 1992) in only one of 59 seed samples harvested throughout Australia between 1992 and 1996 and tested using International Seed Testing Association methods. The teleomorph has not been found in Australia and results to date suggest that only one mating type is present. This suggests that quarantine restrictions on imported chickpea seed should be retained to prevent the introduction of the opposite mating type.