Effects of inoculum concentration, wetness duration and plant age on development of early blight (Alternaria solani) and on shedding of leaves in tomato plants

Effects of inoculum concentration, wetness duration and plant age on the development of tomato early blight were evaluated in relation to host susceptibility under controlled environmental conditions. The main effect of early blight was premature defoliation, which was linearly related to the percentage of leaf area showing symptoms. As ln(inoculum concentration, conidia mL⁻¹) increased from 6·2 to 11·5, the percentages of leaf area affected and of defoliation increased linearly. Four h of leaf wetness after inoculation were sufficient to initiate the disease on plants of hybrid Skala RZ but not on those of cv. Rio Rojo, for which at least 6 h leaf wetness were needed. As wetness duration increased up to 24 h, there was an increase in the percentage leaf area showing symptoms and in the percentage of defoliation, but thereafter there was no significant increase in either parameter. Tomato plants were susceptible to Alternaria solani at all growth stages, but susceptibility increased as plants matured. There were no significant differences in susceptibility between tomato cultivars and hybrids.     

Resistance status of cultivated potatoes to early blight (Alternaria solani) in Denmark

Field experiments were conducted in 2015 and 2016 to classify the resistance level to early blight of the main potato cultivars in Denmark. A total of 38 cultivars were used. The experiment was designed as a randomized complete block design (RCBD) with four replicates. The potatoes were inoculated by spreading barley (Hordeum vulgare) kernels infested with Alternaria solani and A. alternata. Disease assessment was done at weekly intervals starting from the onset of the first symptoms. The disease progress curves (DPC) of early blight on the cultivars were compared to that of Bintje. A multivariate analysis was performed with the apparent infection rate, the relative area under the disease progress curve, the time to reach 50% severity, the daily defoliation, the disease severity in the middle of the epidemic and the duration of the epidemic to classify the resistance level of the cultivars. The analysis of the DPC of the cultivars showed that none of the cultivars was completely resistant to early blight. However, the epidemic development differed between the different cultivars. The resistance levels of the cultivars were thus classified into classes I, II, III and IV interpreted as ‘very susceptible’, ‘susceptible’, ‘moderately slow blighting’ and ‘slow blighting’, respectively. All the late maturity cultivars were classified as class IV, and the earlier maturing cultivars were either class I or class II.     

马铃薯早疫病病菌ISSR-PCR反应体系优化

为了应用ISSR分子标记技术分析马铃薯早疫病病菌遗传多样性,采用单因素水平对影响ISSR反应的Mg~(2+),d NTPs、Taq DNA聚合酶、引物浓度及引物退火温度等条件进行了优化,建立了适宜于早疫病病菌的ISSR最佳反应体系。25μL的反应体系中,Mg~(2+)2.0 mmo1/L,d NTPs 0.15 mmol/L,Taq DNA聚合酶0.75U,引物0.40μmol/L;从30条ISSR引物中筛选出10条多态性较好的ISSR引物,并确定了各条引物的退火温度。结果为应用ISSR分子标记技术研究马铃薯早疫病病菌遗传多样性奠定了基础。     

A study on the synergetic effect of Bacillus amyloliquefaciens and dipotassium phosphate on Alternaria solani causing early blight disease of tomato

European Journal of Plant Pathology - A study of the effect of bioagents and dipotassium phosphate (DPP) and their combination on early blight disease reduction under greenhouse conditions was...     

番茄早疫病研究概述

番茄早疫病是番茄生产中最常见的1种病害.对番茄生产造成较大损失.综述了番茄早疫病病原菌生物学特性、病害发生流行规律和综合防治等方面的内容,为开展研究和生产应用提供参考.     

Tomato early blight (Alternaria solani): the pathogen, genetics, and breeding for resistance

Alternaria solani causes diseases on foliage (early blight), basal stems of seedlings (collar rot), stems of adult plants (stem lesions), and fruits (fruit rot) of tomato. Early blight is the most destructive of these diseases and hence receives considerable attention in breeding. For over 60 years, breeding for early blight resistance has been practiced, but the development of cultivars with high levels of resistance has been hampered by the lack of sources of strong resistance in the cultivated tomato and by the quantitative expression and polygenic inheritance of the resistance. In some accessions of wild species, high levels of early blight resistance have been found, but breeding lines still have unfavorable horticultural traits from the donor parent. Recently, the first linkage maps with loci controlling early blight resistance have been developed based on interspecific crosses. These maps may facilitate marker-assisted selection. This overview presents the current knowledge about the A. solani–tomato complex with respect to its biology, genetics, and breeding.     

马铃薯早疫病菌分生孢子萌发条件的研究

为了明确马铃薯早疫病菌分生孢子萌发的条件,研究了温度、湿度、pH、光照、营养条件等对马铃薯早疫病菌分生孢子萌发的影响。结果表明,分生孢子在水滴中于30℃1 h即可萌发,8 h后达到萌发高峰,萌发率为98.4%;萌发的最适温度为30℃;相对湿度85%以上均可萌发,水滴中萌发率最高;pH6~10的条件利于分生孢子萌发;紫外线对分生孢子萌发有抑制作用;无机氮源中的铵态氮和尿素对孢子萌发有抑制作用,有机氮源中半胱氨酸和谷氨酸对孢子萌发有抑制作用;山梨糖不利于分生孢子萌发;光照对分生孢子萌发也有抑制作用;分生孢子致死温度是57℃。     

马铃薯早疫病菌室内杀菌剂筛选及配比试验

采用生长速率法,对18种杀菌剂及药剂配比进行室内毒力测定,结果表明,杀菌剂苯醚甲环唑、嘧菌酯、腐霉利和异菌脲对马铃薯早疫病菌抑制效果好,有效中浓度（EC50）小于1 μg/mL;代森锰锌与嘧菌酯混配,配比为 4∶6、5∶5、6∶4、7∶3、8∶2、9∶1 均有增效作用,其中配比9∶1 增效作用最好,其次是配比6∶4。     

Effect of nutrients and plant extracts on Alternaria blight of tomato caused by Alternaria Alternata

Journal of Plant Diseases and Protection - Studies with nutrients and phyto-extracts were performed in vitro and in vivo to assess their potential in controlling Alternaria blight of tomato...     

Physiological and histopathological assessments of the susceptibility of different tomato (Solanum lycopersicum) cultivars to early blight disease

European Journal of Plant Pathology - The current research aims to evaluate the susceptibility of the tomato of the tomato (Solanum lycopersicum) cultivars 65,015 (CV1), Basma (CV2), Dalia (CV3),...     

Correction to: Physiological and histopathological assessments of the susceptibility of different tomato (Solanum lycopersicum) cultivars to early blight disease

European Journal of Plant Pathology - A Correction to this paper has been published: https://doi.org/10.1007/s10658-021-02275-y     

Differential responses of resistant and susceptible tomato varieties to inoculation with Alternaria solani

In spite of numerous studies on host pathogen interaction, very few address the differences in response in a resistance and a susceptible host. This study investigates the defense responses of resistant versus susceptible variety of tomato against the necrotrophic pathogen Alternaria solani. Various histochemical, biochemical and molecular methods were employed to compare the production and localization of phenolics, hydrogen peroxide, superoxide dismutase, polyphenol oxidases and protein cross-linking. Comet assays showed different rates of apoptosis in the hosts. A. solani transformed with green fluorescent protein gene under a constitutive promoter was used to compare progress of infection in the two varieties. The differential expression profiles of TPK1b gene were obtained over time in the two hosts. The implication of the findings, in the context of mechanism of resistance in plants, is discussed.     

Correction to: Effects of some biological agents on the growth and biochemical parameters of tomato plants infected with Alternaria solani (Ellis & Martin) Sorauer

European Journal of Plant Pathology -     

Biochemical and molecular studies of early blight disease in tomato

Tomato early blight occurs worldwide and it is prevalent wherever tomatoes are grown. Alternaria solani Sorauer, the causal agent, has been recognized as a serious foliar pathogen of tomato and there are very few cultivars which possess resistance against early blight. Alternaric acid is the major toxin of A. solani. In this study, alternaric acid and fungal culture filtrate were used as an elicitor in NDT-96 (tolerant) and GP-5 (susceptible) tomato varieties in order to study and compare their abilities to induce defense-related enzymes, viz., catalase, peroxidase, β-1,3 glucanase, phenylalanine-ammonia-lyase (PAL), chitinase and polyphenol-oxidase (PPO) along with total phenols, and total soluble proteins. NDT-96 showed a rapid induction of all these pathogenesis-related enzymes except catalase along with total phenols as compared to GP-5 with both the treatments. Differential expression of total soluble proteins revealed higher protein content in NDT-96 as compared with GP-5. A 49.48 kDa protein was observed to be absent in GP-5. In addition, 25 microsatellite markers (SSR) were screened for polymorphisms among the above mentioned two tomato varieties. Of these, SSR 286 revealed a significant polymorphic band of 108 bp in NDT-96.     

Effects of plant age on disease development and virulence of Clavibacter michiganensis subsp. michiganensis on tomato

The effect of plant age at the time of inoculation on the severity of bacterial wilt and canker disease caused by Clavibacter michiganensis subsp. michiganensis (Cmm) was examined in six greenhouse experiments. The period during which inoculations led to wilt and death of tomato plants was defined. This period, designated ‘window of vulnerability’, ranged from transplanting to the 17‐ to 18‐leaf stage. Plants inoculated after this period expressed disease symptoms but did not wilt or die. No significant changes in disease incidence were observed when leaves of different ages were inoculated. Yield accumulation was significantly reduced in plants inoculated within the window of vulnerability compared with those inoculated after this period. Expression of virulence genes, viz. celA, encoding a secreted cellulase, and the serine protease‐encoding pat‐1, chpC and ppaA, was induced during the early stages after inoculation in plants inoculated within the window of vulnerability. Differences in Cmm population between plants inoculated within and outside of this period were insignificant after the first week post‐inoculation, indicating that differences in disease severity, yield loss and expression of virulence determinants are not correlated with Cmm population level. Results suggest that implementation of precautionary measures during the window of vulnerability to avoid secondary spread of Cmm will have a season‐long effect on plant mortality and may minimize, or even prevent, yield losses.     

Evaluation of virulence and pathogenicity of Alternaria patula on French marigold (Tagetes patula)

Alternaria patula, the cause of French marigold leaf black spot and flower blight, was first isolated from seeds of French marigold cv. Queen Sophia. It is described as a new species of Alternaria and has a considerable morphological variation with a preferential pathogenicity to Asteraceae, Solanaceae and Cucurbitaceae plants. Alternaria patula produces an array of pectin depolymerases that can break 1,4-α-glycosidic bonds either by hydrolysis of polygalacturonases (PG, E.C. 3.2.1.15) or via trans-elimination of pectate lyases (PL, E.C. 4.2.2.2) and pectin lyases (PNL, E.C. 4.2.2.10). This study is the first to emphasize the variability and significance to pathogenesis of the pectinolytic enzymes of A. patula that target various pectic polymers structures during host tissue invasion. Alternaria patula also produced zinniol derivatives as non-host-specific toxins (nHSTs), albeit without phytotoxic symptoms in French marigold. The management of Alternaria blight caused by A. patula via the application of pyrifenox and antagonistic Bacillus amyloliquefaciens effectively reduced disease severity, without adverse effects on French marigold in both in vitro and in vivo bioassays.     

Assessment of early blight (<Emphasis Type="Italic">Alternaria solani</Emphasis>) resistance in tomato using a droplet inoculation method

A droplet inoculation method was used for evaluation of tomato resistance to early blight, a destructive foliar disease of tomato caused by Alternaria solani (Ellis and Martin) Sorauer. In this test method, leaflets are inoculated with small droplets of a spore suspension in either water or a 0.1% agar solution. Early blight resistance was evaluated based on lesion size. The droplet method better discriminated the level of resistance (P < 0.001) for a range of spore densities in comparison with the more commonly used spray inoculation method. Lesions generated by droplet inoculation at 7 days after inoculation ranged from small flecks to almost complete blight with an exponential-like distribution of lesion sizes. Significant correlations (r = 0.52, 0.58, and 0.63, P < 0.001) were observed across three glasshouse tests of 54 accessions including wild species using the droplet method. The most resistant accessions included wild species: one accession of Solanum arcanum, three accessions of Solanum peruvianum, one accession of Solanum neorickii, and one of Solanum chilense. Solanum pennellii and Solanum pimpinellifolium accessions were susceptible, whereas Solanum habrochaites and Solanum lycopersicum accessions ranged from susceptible to moderately resistant. The droplet test method is simple to apply, offers a fine discrimination of early blight resistance levels, and allows objective evaluation.