马铃薯晚疫病菌对甲霜灵抗性的快速检测方法

为快速检测马铃薯晚疫病菌——致病疫霉Phytophthora infestans对甲霜灵的抗性,基于已知致病疫霉RPA190基因的T1145A变异引起的F382Y氨基酸点突变与甲霜灵抗性有关,通过设计4对特异性引物F382Y-F1/F382Y-R、F382Y-F2/F382Y-R、F382Y-F3/F382Y-R和F382Y-F4/F382Y-R建立等位基因特异性PCR(allele specific-polymerase chain reaction,AS-PCR)快速分子检测法,其中F382Y-R引物在4对引物里保持不变,并分析所建分子检测法的特异性和灵敏度。结果表明,正向特异性引物F382Y-F2、F382Y-F3和F382Y-F4的3''末端在致病疫霉抗甲霜灵菌株原有核苷酸突变位点1145A(对应引物为F382Y-F1)的基础上,再人工引入第1144位的核苷酸突变,将1144T分别突变成1144G、1144C和1144A,并优化退火温度和特异性引物与内参引物ITS1/ITS4比例,最终确定最适退火温度分别为54、60和58℃,特异性引物与内参引物最适浓度比例均为5∶1。以该3条引物对应的3对特异性引物和内参引物ITS1/ITS4组成的3组多重AS-PCR引物对甲霜灵敏感和抗性菌株具有良好的特异性,敏感菌株的扩增产物含1条879bp的内参片段,抗性菌株的扩增产物为1条879bp的内参片段和1条461bp的目的片段。3组AS-PCR检测体系均具有较高的灵敏度,其中引物F382Y-F4/F382Y-R对致病疫霉DNA的检测灵敏度达0.4pg/μL,引物F382Y-F2/F382Y-R和F382YF3/F382Y-R的检测灵敏度达4pg/μL。     

Control of late blight in potato by full and reduced rates of oxadixyl mixtures

The effect of oxadixyl-based fungicidal mixtures on the development of late blight and the buildup of resistance ofPhytophthora infestans to oxadixyl was studied in potato crops (cv. Alpha) grown in plastic houses. Half-rates of SAN 518F (mancozeb + oxadixyl) applied weekly provided better disease control and reduced resistance buildup more effectively than the full rates of the mixture applied biweekly. Mancozeb applied weekly at full rate was less effective than SAN 518F at half-rate. The data suggest that lowering the dosage together with shortening the interval between sprays is an efficient strategy to combat mixed populations — sensitive and resistant to phenylamides — ofP. infestans when phenylamide-based fungicidal sprays are used.     

十一种杀菌剂防治马铃薯晚疫病的适宜施用时期

为了明确当前市场上具有代表性的11种防治马铃薯晚疫病杀菌剂的适宜施用时期,采用人工接种马铃薯叶片的方法,测定了其中5种药剂在接种晚疫病菌前10 d内不同时间施用的预防效果和其中7种药剂在接种后24 h内不同时间施用的治疗效果。结果显示:在保证良好防治效果的前提下,药剂在病原菌接种前保护性施用的适宜时期比在接种后治疗性施用的适宜时期要长。在测试浓度下,接种前5种供试药剂保持100%防治效果的适宜施用时期为接种前3~10 d;而接种后7种供试药剂保持相同防效的适宜施用时期仅为接种后6~12 h,在生产实际中难以操作。研究结果说明,在田间马铃薯晚疫病的化学防治中,为了取得良好防治效果,每次用药均应在病菌侵入之前采用保护性施用,尽量避免在病菌侵入之后进行治疗性施用。     

四种化合物诱导马铃薯抗晚疫病的效果及其相关防御基因表达分析

为探究水杨酸、壳聚糖、麦角甾醇和纤维二糖4种化合物诱导马铃薯抗晚疫病的效果及其作用机理,采用整株喷雾法、挑战接种法、菌丝生长速率法分析4种化合物对马铃薯晚疫病的预防作用及对其病原菌致病疫霉Phytophthora infestans的离体抑制效果,利用实时荧光定量PCR技术测定4种化合物诱导后马铃薯病程相关蛋白和防御酶基因的调控表达情况。结果显示,水杨酸、壳聚糖、纤维二糖和麦角甾醇分别处理马铃薯植株24 h后接种致病疫霉,在多个浓度下对晚疫病均有不同程度的诱导抗性,其中在1 000 μmol/L浓度（壳聚糖浓度为1 000 mg/L）时诱导抗性最好,较对照显著提高,诱抗效果分别为54.73%、61.99%、59.73%和48.59%。壳聚糖对马铃薯晚疫病的诱抗效果高于其它3种化合物,且只有壳聚糖能显著抑制致病疫霉的菌丝生长和孢子囊形成,说明壳聚糖除了能诱导作物产生抗病性外,还具有直接抑菌作用。4种化合物诱导后马铃薯病程相关蛋白基因PR1、过氧化物酶基因POD和多酚氧化酶基因PPO的表达量在施用早期均显著升高。表明这些化合物能诱导马铃薯对晚疫病产生抗性,可能与马铃薯体内过氧化物酶、多酚氧化酶的活性和抗病信号传导途径关键基因PR1的表达有关。     

Control of late blight in organic potato production: evaluation of copper-free preparations under field,growth chamber and laboratory conditions

In order to replace copper fungicides in organic potato production, 53 copper-free preparations (CFPs) based on natural compounds, including plant extracts and microorganisms, and five copper preparations were evaluated for their potential to control Phytophthora infestans, the pathogen that causes late blight of potatoes. In in vitro assays, 30% of the CFPs inhibited indirect germination of sporangia, 26% mycelial growth and in growth chamber experiments, 21% efficiently reduced foliar blight of tomato plants. In micro-plot field trials with applications twice a week, the copper preparations were the most effective and reduced foliar blight by 99%. Of the CFPs tested, Oekofluid P, Mycosin and other sulphuric clays, and C-2000 reduced late blight the most, from 63% to 37%. In small-plot trials in 2001, 2002 and 2004, 27 CFPs with different formulations and four copper preparations were examined. In 2004, copper preparations at full and reduced rates and sulphuric clays were applied either weekly or according to the decision support system Bio-PhytoPRE. With Bio-PhytoPRE, copper preparations reduced foliar blight of potatoes by 23–77% and increased tuber yield by 2–28%, depending on the copper rate applied and year. With CFPs, maximal efficacy was 17% and no effect on tuber yield was observed. In vitro and in vivo trials showed that the rainfastness and the persistence of CFPs was low compared with copper preparations. This indicates that the failure of CFPs under field conditions is probably due to a lack of stability under prevailing environmental conditions and not to a lack of efficacy. Until stable formulations for CFPs are developed, an optimised and restricted use of copper fungicides using a decision support system could help to control late blight in organic potato production and to reduce copper input into the environment.     

Mycorrhiza induced resistance in potato plantlets challenged by Phytophthora infestans

Biological control of soil-borne pathogens by arbuscular mycorrhizal (AM) fungi has been repeatedly demonstrated. However, their role in the control of above-ground hemibiotrophic pathogens is less conclusive. Here, we investigated in vitro the impact of an AM fungus on Phytophthora infestans in potato plants. The leaf infection index was decreased in mycorrhizal potato plants. Real-Time Quantitative PCR revealed the induction of two pathogenesis related genes (PR1 and PR2) in the leaves of mycorrhizal plants shortly after infection with P. infestans. These results suggested a systemic resistance in mycorrhizal plants, related to the priming of the two PR genes in potato.     

Photosynthesis is not impaired in healthy tissue of blighted potato plants

The net photosynthetic rates of green leaf tissue of potato plants of different cultivars were measured in the field and in a controlled environment after infection of the plants byPhytophthora infestans.Infection had no significant effect on the net photosynthetic rate at light saturation, the efficiency of light use at low light intensities, or dark respiration. The reported effect ofP. infestans on tuber yield seems to be caused solely by a reduction in the green leaf area. Therefore, a high rate of photosynthesis in green leaf tissue of infected plants is not a good selection criterion for potato genotypes.Samenvatting Bepalingen van netto fotosynthesesnelheden, bij verschillende aardappelrassen, werden uitgevoerd in het veld en onder geconditioneerde omstandigheden. De metingen werden gedaan aan groen blad van planten die in verschillende mate waren aangetast doorPhytophthora infestans.Infectie had geen significante invloed op de netto fotosynthesesnelheid bij lichtverzadiging, de efficiëntie van lichtbenutting bij lage lichtintensiteit, of de donkerademhaling. Het effect vanP. infestans op de knolopbrengst van aardappelrassen lijkt uitsluitend veroorzaakt te zijn door een vermindering van groen bladoppervlak. Daarom is selectie van aardappelgenotypen met superieure handhaving van fotosynthetische activiteit bij aantasting, geen kansrijk veredelingsdoel.     

Exploiting host resistance to reduce the use of fungicides to control potato late blight

Field trials in 1996, 1997 and 1998 with six potato cultivars differing in levels of foliar and tuber race-nonspecific resistance to late blight were treated with 100, 50 and 33% of the recommended dose of the fungicide fluazinam at application intervals of 7, 14 and 21 days. Using a mixed inoculum of six or seven indigenous isolates of Phytophthora infestans small potato plots were inoculated via infector plants. A foliar blight model for the relationship between the effects of resistance, fungicide application and disease pressure was developed using multiple regression analysis. Cultivars with a high level of quantitative resistance offered the greatest potential for fungicide reduction. The model showed that the effect of resistance on integrated control increased exponentially with increasing cultivar resistance. Reducing fungicide input by lowering the dose resulted in less foliar disease than extending application intervals. The higher the disease pressure, the greater the risk associated with reducing fungicide input by extension of application intervals. The field resistance of cultivars to tuber blight mainly determined the frequency of tuber infection. Exploiting high foliar resistance to reduce fungicide input carried a high risk when cultivar resistance to tuber blight was low. When field resistance to tuber blight was high, a medium level of resistance in the foliage could be exploited to reduce fungicide dose to c . 50%, provided application was at the right time. At a high level of field resistance to both foliar and tuber blight, application intervals could be extended.     

Occurrence of the R1 allele conferring resistance to late blight in potato R-gene differentials and commercial cultivars

A total of 23 Scottish and 14 Dutch potato R-gene differentials as well as five Austrian, two Dutch and two German commercial potato cultivars were screened for the R1 allele conferring resistance to Phytophthora infestans carrying Avr1 , via PCR amplification and sequencing. A single 1400 bp fragment with complete sequence identity to the corresponding part of the R1 allele, was obtained from genomic DNA of all potato R-gene differential clones whose denomination indicates R1 or a combination of R1 and other major resistance factors. The R1 allele was detected, as expected, in all these clones. This fragment also occurred in one Austrian and one German cultivar. Unexpectedly, the same R1 allele also was detected within all R5, R6 and R9 differentials.     

马铃薯晚疫病CARAH预警模型在我国的应用及评价

CARAH预警模型引入我国后,在马铃薯晚疫病监测预警中发挥了重要作用。本文对目前各地CARAH模型的应用情况进行了综合分析,总结了模型在马铃薯晚疫病中心病株出现时间预测、发生程度风险评估、防治效果等方面的作用,分析了品种抗性、区域气候特征等因素对模型应用的影响,提出了进一步研究和完善建议。     

Phosphite compounds reduce disease severity in potato seed tubers and foliage

Phosphites (Phi) are alkali metal salts of phosphorous acid, with the ability to protect plants against different pathogens. In this research, the effect of Phi applied to potato plants on severity of three important potato diseases in Argentina was assessed. Seed tubers and foliage of potato cvs Shepody and Kennebec were treated with Phi to assess effects on resistance against Phytophthora infestans, Fusarium solani and Rhizoctonia solani. Protection resulting from Phi treatment in seed tubers was high against P. infestans, intermediate against F. solani, and low against R. solani. In addition, seed tubers treated with calcium or potassium phosphites (CaPhi and KPhi, respectively) at 1% of commercial product emerged earlier than untreated ones. When Phi were foliarly applied two or four times at different doses, high levels of protection against P. infestans were achieved in both cultivars. Higher protection was observed in Kennebec when CaPhi was applied, while in Shepody this was true for KPhi. Expression of β-1,3-glucanases was induced at different times after treatment but no correlation between β-1,3-glucanases expression and foliar protection level was found. On the other hand, Phi positive protection effects did not produce negative effects in plant growth. Leaves from CaPhi-treated plants showed a darker green colour than leaves from control plants; also an increase in Rubisco protein and a delay in crop senescence was observed.     

Evaluation and analysis of reduction of late blight disease in a diploid potato progeny

The rate of late blight disease was analysed for individuals of a diploid Solanum phureja – Solanum tuberosum dihaploid hybrid population (PD), using three different assessment techniques, in the laboratory, screenhouse, and field. These hybrids expressed low disease rates in the field, comparable to resistance based on intact R genes. However, none of the parents of PD expressed any R genes and the pattern of segregation within the PD population was not indicative of R-gene inheritance. The foliage (or leaflet) area diseased had the largest broad-sense heritability of all criteria analysed, in all tests performed. In the field evaluations, the PD population showed intermediate levels of broad-sense heritability for foliage area diseased, relative to the much larger heritability detected for the group of controls possessing R genes. Resistance in the field of the PD hybrids had very little genotype-environment (G × E) interaction, indicating stability of its expression. All genotypes without R genes exhibited heritable, reduced rates of late blight disease in the field, but they were susceptible with low heritability in screenhouse and laboratory tests. This differential expression of disease indicates that the plants' indirect response to unknown environmental stress in the field may have been measured. The value of the PD hybrids for breeding of late blight resistant potato and the use of the disease rate data for detection of the underlying quantitative trait loci are discussed.     

Sources of resistance to ascochyta blight in wild Cicer species

Ascochyta blight [Ascochyta rabiei (Pass.) Lab.] is the major foliar disease of chickpea (Cicer arietinum L.). In search of better sources of resistance to ascochyta blight, 201 accessions of 8 annual wildCicer species were evaluated in field and greenhouse for 3 years (1988 to 1991) at Tel Hadya, Syria. One accession each ofC. judaicum Boiss (ILWC 165) andC. pinnatifidum Jaub. & Spach. (ILWC 159) were consistently rated resistant in both field and greenhouse evaluations. Another three accessions ofC. judaicum (ILWC 61, ILWC 154, ILWC 199) and six accessions ofC. pinnatifidum (ILWC 78, ILWC 88, ILWC 155, ILWC 160, ILWC 162, ILWC 203) were resistant or moderately resistant. The blight-resistant accessions ofC. judaicum originated from Jordan, Lebanon, Syria, and Turkey; and those ofC. pinnatifidum from Syria and Turkey. None of the accessions ofC. bijugum, C. chorassanicum, C. cuneatum, C. echinospermum, C. reticulatum andC. yamashitae were resistant to blight.     

近几年我国马铃薯晚疫病流行特点分析与监测建议

马铃薯晚疫病是马铃薯上的重要病害,是影响马铃薯产业发展的主要制约因素。本文系统总结了2008-2014年我国马铃薯晚疫病的发生概况及特点,分析了其影响因素。该病害年度间、地区间、品种间发生不平衡,北方产区受气候因素影响大,西南及中原产区常年偏重发生。2012年、2013年马铃薯晚疫病在全国范围内偏重发生,局部大发生,发生范围广、流行扩展速度快、危害重。在气候、菌源量、品种抗性及防治因素中,气候是影响马铃薯晚疫病发生流行的最重要因素。     

Efficacy of the R2 resistance gene as a component for the durable management of potato late blight in France

Many race-specific resistance genes to potato late blight are overcome in France, but the disease appears later on genotypes carrying the R2 gene. This study examined whether R2 could contribute to durable late-blight control in France, and analysed the conditions of its performance. Plants grown from tubers of different physiological ages showed no difference in R2 expression in field and climate-chamber experiments, demonstrating that the delay in epidemic onset provided by R2 was not the result of gene inactivation in old plants. Among isolates collected at one site, those virulent on R2 were classified into three AFLP profiles. AFLP-VII comprised exclusively isolates virulent to R2 , whereas AFLP-IV and AFLP-V included both virulent and avirulent isolates. No significant aggressiveness differences were observed between virulent and avirulent isolates from AFLP-V; however, isolates from AFLP-VII were significantly less aggressive than virulent isolates from AFLP-V. These results indicate that: (i) the delayed onset of epidemics on R2 cultivars is the result of the breakdown of R2 by virulent isolates; (ii) aggressiveness of isolates virulent to R2 depends primarily on the genetic background of the pathogen where the mutation to virulence occurs; and (iii) this mutation does not lead per se to lower pathogenic fitness. It is suggested that R2 is unlikely to make a lasting contribution to late-blight control in France, and that diversification strategies such as cultivar mixtures might not considerably increase its durability.     

The oligopeptide elicitor Pep-13 induces salicylic acid-dependent and -independent defense reactions in potato

The Phytophthora-derived oligopeptide elicitor, Pep-13, originally identified as an inducer of plant defense in the nonhost–pathogen interaction of parsley and Phytophthora sojae, triggers defense responses in potato. In cultured potato cells, Pep-13 treatment results in an oxidative burst and activation of defense genes. Infiltration of Pep-13 into leaves of potato plants induces the accumulation of hydrogen peroxide, defense gene expression and the accumulation of jasmonic and salicylic acids. Derivatives of Pep-13 show similar elicitor activity in parsley and potato, suggesting a receptor-mediated induction of defense response in potato similar to that observed in parsley. However, unlike in parsley, infiltration of Pep-13 into leaves leads to the development of hypersensitive response-like cell death in potato. Interestingly, Pep-13-induced necrosis formation, hydrogen peroxide formation and accumulation of jasmonic acid, but not activation of a subset of defense genes, is dependent on salicylic acid, as shown by infiltration of Pep-13 into leaves of potato plants unable to accumulate salicylic acid. Thus, in a host plant of Phytophthora infestans, Pep-13 is able to elicit salicylic acid-dependent and -independent defense responses.     

Integrated control of potato late blight: predicting the combined efficacy of host resistance and fungicides

Integrating cultivars that are partially resistant with reduced fungicide doses offers growers an opportunity to decrease fungicide input but still maintain disease control. To use integrated control strategies in practice requires a method to determine the combined effectiveness of particular cultivar and fungicide dose combinations. Simple models, such as additive dose models (ADM) and multiplicative survival models (MSM), have been used previously to determine the joint action of two or more pesticides. This study tests whether a model based on multiplicative survival principles can predict the joint action of fungicide doses combined with cultivars of differing partial host resistance. Data from eight field experiments on potato late blight (Phytophthora infestans) were used to test the model; the severity of foliar blight was assessed and scores used to calculate the area under the disease progress curve (AUDPC). A subset of data, derived from the most susceptible cultivar, King Edward, was used to produce dose–response curves from which parameter values were estimated, quantifying fungicide efficacy. These values, along with the untreated values for the more resistant cultivars, Cara and Sarpo Mira, were used to predict the combined efficacy of the remaining cultivar by fungicide dose combinations. Predicted efficacy was compared against observations from an independent subset of treatments from the field experiments. The analysis demonstrated that multiplicative survival principles can be applied to describe the joint efficacy of host resistance and fungicide dose combinations.