Red-Light-Induced Resistance in Broad Bean (Vicia faba L.) to Leaf Spot Disease Caused by Alternaria tenuissima

The effect of different light wavelengths on the development of lesions induced by Alternaria tenuissima in broad bean leaves was investigated. Lesion development was completely suppressed in red‐light‐irradiated broad bean leaflets, irrespective of isolate or spore concentration. Pre‐treatment of leaflets with red light for 24 h before inoculation also suppressed lesion development. Alternaria tenuissima failed to produce infection hyphae in red‐light‐irradiated broad bean leaflets. These results indicate that disease suppression in broad bean leaflets is due to light‐induced resistance. Spore germination fluid (SGF) of A. tenuissima allowed non‐pathogenic Alternaria alternata to infect wounded and unwounded broad bean leaflets kept in the dark, results suggesting that SGF induced susceptibility. Red light suppressed susceptibility induced by A. tenuissima SGF; thus, lesion formation and development were suppressed when leaflets inoculated with the spores of A. alternata suspended in A. tenuissima SGF were kept under red light. From these results, we conclude that red light induced resistance in broad bean to leaf spot disease caused by A. tenuissima, and that SGF induced susceptibility of broad bean leaflets to a non‐pathogenic isolate of A. alternata.     

First Report of Black Leaf Spot Caused by Alternaria alternata on Ramie in China

In 2012 and 2013, black leaf spot disease was observed on ramie plants in Hunan and Hubei Provinces, China. In the field, the symptoms of this disease included dark green to black big spots on leaves, often resulting in upwardly curled leaf margins. The pathogen isolates were identified as Alternaria alternata (Fr.) Keissler on the basis of morphology and sequence similarity of 99–100% to the published data for internal transcribed spacer (ITS), and glyceraldehyde‐3‐phosphate dehydrogenase (gdp). To our knowledge, this is the first report of Alternaria leaf spot of ramie in China.     

Corynespora cassiicola leaf spot of pawpaw (Carica papaya L.) in Nigeria

Leaf spot of pawpaw is hereby reported for the first time in Nigeria. The symptom is characterized by a papery center surrounded by a yellow halo. The causal organism is Corynespora cassiicola. Ripe fruits and abaxial surfaces of the leaves were significantly more susceptible to infection than unripe fruits and adaxial surfaces of leaves. Growth and sporulation of the fungus on several media was investigated. The organism grew faster on malt-extract agar (MEA) derived media and slowest on potato-dextrose agar (PDA) supplemented with thiamine. Sporulation was highest on Czapek-dox agar (CDA) plus biotin and lowest on PDA and PDA + thiamine. Reasons for increased susceptibility of ripe fruit are discussed.This revised version was published online in October 2005 with corrections to the Cover Date.     

Target leaf spot of tomato incited by Corynespora cassiicola,an emerging disease in tomato production under Gangetic alluvial region of West Bengal,India

Abstract

Tomato (Lycopersicon esculentum Mill.) is a cosmopolitan vegetable and widely cultivated in almost all the countries of the world including India. Irreversible investment – production ratio for tomato cultivation in recent Indian agricultural systems arise the question, is there any biotic backlogs responsible for such a production loss. Our present investigation is based on this fact. Target leaf spot disease of tomato is caused by Corynespora cassiicola, a serious and emerging disease in India. Prolonged real time surveillance of this disease on tomato from 2010–11 to 2016–17, reflects some remarkable features of pathogenic progress in Gangetic alluvial region of West Bengal. This pathogen is the natural barrier for tomato production with a disease severity ranged between 35% and 58% which ultimately causes tremendous loss of tomato foliage and fruits. C. cassiicola was identified on the basis of morpho-cultural (ITCC Accession No. 7542) and molecular characterization (Genbank Accession No. KJ767193). Homology searching of internal transcribed spacer region of CcHaTom isolate was highly matched with Genbank Accession No. KP666184 (Cynodondactylon/India), AB873045 (Vitex negundo/India) and JN541214 (Malvaviscus concinnus/USA) with 95% similarity. Phylogenetic analysis established that KJ767193 and C. cassiicola retrieved sequences were conspecific from a common ancestral origin, which supports its neighbourhood with this fungal pathogen. Optimum temperature between 24 and 25?°C, coupled with 80–85% relative humidity triggered the disease progress. From the emerging scenario, C. cassiicola infecting tomato is the real threat for indigenous cultivars.     

分离自黄瓜的多主棒孢霉不同表型菌株对杀菌剂的敏感性

【目的】通过对分离自黄瓜的多主棒孢霉不同表型菌株适宜生长温度、产孢量等表型特征和对8种杀菌剂的敏感性研究,为多主棒孢霉侵染引起的黄瓜叶斑病和茎疫病的化学防治提供技术支持。【方法】采用温度梯度法测定病菌适宜生长温度;采用PDA培养基25°C黑暗培养5 d和21 d,计测不同表型菌株单位面积产孢量;采用含药平板法测定不同表型菌株对8种杀菌剂的敏感性。【结果】分离自黄瓜的多主棒孢霉不同表型菌株适宜生长温度为25-30°C;在PDA平板25°C黑暗培养5 d,气生菌丝稀少型菌株cu-4、cu-5即大量产孢,产孢量明显多于气生菌丝丰茂型菌株;在试验浓度下,5个试验菌株对8种杀菌剂的敏感性依次为:代森锰锌氟硅唑戊唑醇苯醚甲环唑速克灵百菌清嘧菌酯多菌灵。【结论】分离自黄瓜的多主棒孢霉不同表型菌株在适宜生长温度、菌丝生长速度、产孢量及对杀菌剂的敏感性等方面均存在差异。在试验浓度下,供试菌株对多菌灵和嘧菌酯的敏感性极低(抑制率40%),这2种杀菌剂已失去对该地区黄瓜褐斑病的防控作用。     

Occurrence of Grey Leaf Spot of Sedum erythrostictum Caused by Cercospora cf. pseudokalanchoes in China

Sedum erythrostictum is a perennial herb in the Crassulaceae family, which is a traditional Chinese medicine used for the treatment of hepatitis, dysentery, herpes zoster and swellings. In 2014, a grey leaf spot disease causing significant damage to plants of S. erythrostictum occurred in the Medicinal Herb Garden of Jilin Agricultural University, Jilin Province, China. The fungus mainly infected the leaves. The necrotic lesions on the leaves were circular or elliptical, amphigenous, greyish brown to brown, slightly concave and surrounded by a dark brown distinct margin. The causal agent from symptomatic tissues was identified as Cercospora cf. pseudokalanchoes based on the symptoms, morphological characteristics, molecular identifications and pathogenicity tests. To our knowledge, this is the first formal report of grey leaf spot of S. erythrostictum caused by C. cf. pseudokalanchoes in China.     

Fine Chloroplast Structure in Cucumber and Pea Leaves Developed under Red Light

Photosynthetic activity, the content of various photosynthetic pigments, and the chloroplast ultrastructure were examined in the leaves of cucumber (Cucumis sativus L.) and pea (Pisum sativum L.) plants of different ages grown under red light (600–700 nm, 100 W/m²). In pea leaves tolerant to red-light irradiation, chloroplast ultrastructure did not essentially change. In the first true leaves of cucumber plants susceptible to red-light irradiation, we observed a considerable increase in the number and size of plastoglobules, the appearance of chloroplasts lacking grana or containing only infrequent grana, and stromal thylakoids. In the upper leaves of 22-day-old cucumber plants, the chloroplast structure was essentially similar to that of the control chloroplasts in white light, and we therefore suppose that these plants have acclimated to red light.     

黄瓜褐斑病菌毒素对抗、感黄瓜品种的作用

在黄瓜褐斑病菌毒素的作用下,黄瓜品种的根数、根长、芽长受到了抑制,根的电导值及叶片的苯丙氨酸解氨酶(PAL)活性升高。抗病品种的根数、根长、芽长受毒素的影响较感病品种小,即感病品种对毒素敏感,且抗、感品种的电导值差异达显著水平。抗病品种的PAL活性增加幅度较感病品种大。     

First Report of Leaf Spot Disease in Angelica dahurica Caused by Phoma bellidis in China

Angelica dahurica is a perennial herb belonging to the Umbelliferae family that has been used as a valuable traditional Chinese medicine. In August 2013, leaf spot disease in A. dahurica was first observed at the Medicinal Herb Garden in Shenyang Agricultural University, Shenyang, Liaoning, China. Morphological assessment, evaluation of culture characteristics, internal transcribed spacer and beta‐tubulin sequence analysis and pathogenicity identified the causal agent as Phoma bellidis. To our knowledge, this is the first report of leaf spot disease in A. dahurica that was caused by P. bellidis.     

Transformation of Corynespora cassiicola by Agrobacterium tumefaciens

The fungus causing target spot disease, Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei, poses an increasing threat to watermelon (Citrullus lanatus), muskmelon (Cucumis melo), and cucumber (Cucumis sativus); the most economically important cucurbit crops grown in China. An understanding of the molecular mechanisms underlying the pathogenicity of C. cassiicola is essential for the development of new strategies to control this disease-causing fungus. Agrobacterium tumefaciens-mediated transformation (ATMT) might be useful to obtain transformants of C. cassiicola, for the ultimate identification of genes involved in pathogenicity. In the present work, we established and optimized an ATMT protocol using A. tumefaciens strain AGL-1 carrying the vector pATMT1 for C. cassiicola. Efficiency of ATMT was 102–148 transformants per 10⁶ conidia and successive subculturing of transformants on non-selective and selective media demonstrated that the integrated transfer (T)-DNA was stably inherited in C. cassiicola transformants. The integration of the hygromycin B phosphotransferase (hph) gene into C. cassiicola was validated by PCR and Southern blot analyses, which revealed that nearly 90 % of the transformants contained single-copy T-DNA. The transformants with altered phenotypes were characterized. Three of these transformants completely lost pathogenicity and other three showed strongly impaired pathogenicity relative to the Cc-GX strain on muskmelon leaves. These results strongly suggest that ATMT may be used as a molecular tool for identifying genes relevant to pathogenicity in the fungus C. cassiicola, an emerging threat to several agronomically important plants in China.     

Red Light Increases Suppression of Downy Mildew in Basil by Chemical and Organic Products

Basil is an economically important herb in the United States and in the world. Recent epidemics of basil downy mildew, caused by Peronospora belbahrii, have significantly affected basil production in the United States. ProPhyt (potassium phosphite), Actigard (acibenzolar‐S‐methyl) and Organocide (sesame oil) were evaluated in the greenhouse in the presence or absence of red light for their effects on the severity of downy mildew and sporangial production by P. belbahrii. Red light at intensity of 12 μmol photons/m²/s significantly (P < 0.05) reduced severity of downy mildew in basil. ProPhyt‐treated basil plants had the lowest disease severity irrespective of red light exposure. Basil plants treated with Actigard and Organocide under red light had significantly lower disease severity compared to plants under dark conditions with the same fungicide treatments 14 and 13 days after inoculation (DAI) in experiments 1 and 2, respectively. Red light significantly reduced AUDPC in the treatments of Actigard and Organocide in both experiments. Basil plants treated with Actigard and Organocide under red light had significantly reduced number of P. belbahrii sporangia than those under dark conditions receiving the same fungicide treatments. This is the first report demonstrating red light in combination with Actigard and Organocide for improved management of downy mildew in greenhouse‐grown basil.     

Association of the Production of Phenylpropanoid Compounds at the Infection Sites of Corynespora cassiicola with Soybean Resistance against Target Spot

This study investigated, at the microscopic level, whether the differential defence responses of soybean cultivars that are resistant (Fundacep 59) and susceptible (TMG 132) to target spot, caused by Corynespora cassiicola, could be associated with an increase in the production of phenolics, flavonoids and lignin at the infection sites. Many larger necrotic lesions with yellow halos were noticed on the leaves of plants from cultivar TMG 132, in contrast to the leaves of plants from cultivar Fundacep 59. Necrotic lesions also developed on the petioles of leaves of plants from cultivar TMG 132, while on the petioles and veins of leaves of plants from cultivar Fundacep 59, the lesions were of purple colour. The growth of fungal hyphae was reduced on the leaves of plants from cultivar Fundacep 59, and an apparently high density of trichomes was found in comparison with the leaves of plants from cultivar TMG 132. An appressorium‐like structure was produced at one or both extremities of the conidium of C. cassiicola, preferentially at the major and minor veins on the adaxial leaf surface of plants from both cultivars. Most cells on the leaves of plants from cultivar Fundacep 59 reacted against C. cassiicola infection by accumulating phenolic‐like compounds, which contributed to the death of many fungal hyphae and a greater maintenance of cell integrity. In contrast, fungal hyphae grew without any impedance in the leaf cells of plants from cultivar TMG 132, which was associated with signs of intense leaf tissue disorganization. Stronger autofluorescence and deposition of lignin and flavonoids were found in the cells of leaves of plants from cultivar Fundacep 59, in contrast to cultivar TMG 132. It can be concluded that soybean resistance to target spot is probably dependent on the activation of the phenylpropanoid pathway.     

Subcutaneous Fungal Infection Caused by a Non-sporulating Strain of Corynespora cassiicola Successfully Treated with Terbinafine

Mycopathologia - Corynespora cassiicola is a common plant pathogen, but C. cassiicola infection in human hosts is extremely rare. In this report, we present an 84-year-old male with long-term use...     

玉米弯孢叶斑病菌的形态学分类与RAPD分析

对16个供试弯孢分离株根据其分生孢子的形态进行分类,其中12个为新月弯孢(Curvularia luna-ta),其余4个是画眉草弯孢(C.eragrostidis)。对这些分离株基因组DNA进行RAPD分析发现,一些分属于两种不同弯孢菌的分离株间比同种弯孢的分离株间具有更近的遗传距离,即具有更近的亲缘关系。因此,根据弯孢菌的形态分类和利用RAPD标记的分类结果存在不一致现象。     

玉米灰斑病的抗性机理研究进展

玉米灰斑病(gray leaf spot of maize, GLS)是重要的玉米叶部病害,严重时可导致整株玉米枯死,已成为玉米生产上的主要病害之一。本文在前人研究的基础上系统地阐述了国内外对玉米抗灰斑病抗性生理及遗传QTL定位的最新的研究进展,并且对如何加快玉米灰斑病的研究和抗病品种的选育进行了探讨。     

Red‐Light‐Induced Resistance to Brown Spot Disease Caused by Bipolaris oryzae in Rice

In this study, the protective effect of red light against the brown spot disease caused by the fungus Bipolaris oryzae in rice was investigated. Lesion formation was significantly inhibited on detached leaves that were inoculated with B. oryzae and kept under red for 48 h, but it was not inhibited when the leaves were kept under natural light or in the dark. The protective effect was also observed in intact rice plants inoculated with B. oryzae; the plants survived under red light, but most of them were killed by infection under natural light or dark condition. Red light did not affect fungal infection in onion epidermis cells or heat‐shocked leaves of rice, and it did not affect cellulose digestion ability; this suggested that the protective effect is due to red‐light‐induced resistance. In addition, the degree of protection increased as the red light dosage increased, regardless of the order of the red light and natural light period, indicating that red‐light‐induced resistance is time dependent. Feeding of detached leaves with a tryptophan decarboxylase inhibitor, s‐α‐fluoromethyltryptophan (0.1 mm ), for 24 h inhibited the development of resistance in response to red light irradiation. Suppression of resistance was also observed in leaves treated with a phenylalanine ammonia‐lyase inhibitor, α‐aminooxy acetic acid (0.5 mm ). These results suggest that the tryptophan and phenylpropanoid pathways are involved in the red‐light‐induced resistance of rice to B. oryzae.     

Blue Light Reception in Phycomyces: Red Light Sensitization in madC Mutants

Sporangiophores of the zygomycete fungus Phycomyces blakesleeanus are sensitive to near UV and blue light. The quantum effectiveness of yellow and red light is more than 6 orders of magnitude below that of near UV or blue light. Phototropism mutants with a defect in the gene madC are about 10⁶ times less sensitive to blue light than the wild type. These mutants respond, however, to yellow and red light when the long wavelength light is given simultaneously with actinic blue light. In the presence of yellow or red light the photogravitropic threshold of madC mutants is lowered about 100-fold though the yellow and the red light alone are phototropically ineffective. A step-up of the fluence rate of broad-band red light (> 600 nm) from 6 × 10^?3 to 6W m^?2 elicits, in mutant C 148 madC, a transient deceleration of the growth rate. The growth rate of the wild type is not affected by the same treatment. The results are interpreted in terms of a red light absorbing intermediate of the blue light photoreceptor of Phycomyces. The intermediate should be short-lived in the wild type and should accumulate in madC mutants.     

美洲黑杨抗黑斑病基因的RAPD标记筛选和连锁分析

以美洲黑杨（Populus deltoides Bartr.cv.“Lux”(I-69/55)）为母本,欧美杨（P.euramericana cv.I-45）为父本得到的F1为材料,其中I-69对黑斑病表现为高度抗病,I-45为高度感病。利用分离群体混合分析（bulked segregrants analysis,BSA）技术建立两个DNA池（感病池和抗病池）,筛选出了与抗黑斑病性状基因相连锁的RAPD标记:OPAI17―1550、OPAI13―900。利用选择性基因型分析法进行标记―抗黑斑病基因连锁分析,两标记与抗黑斑病基因遗传距离分别为29.9cM和37.4cM。 Identification of Markers Linked to Resistance Locus of Marssonina Leaf Spot in Poplars by Bulked Segregant Analysis(BSA) ZHANG Bo1,HUANG Min-ren1,ZHUGE Qiang1,HAN Zheng-min1,YIN Tong-ming1,PAN Hui-xin1,ZHU Li-huang2,WU Rong-ling3,WANG ming-xiu１ 1.The Key Laboratory of Forest Tree Genetic Engineering,Nanjing Forestry University,Nanjing,210037,China; 2.The Institute of Genetics and Developmental Biology,Chinese Academy of Science,Beijing 100101,China; 3.Department of Statistics,University of Florida,Gainesville,Florida 32611,USA Abstract:DNA markers linked to resistance locus of Marssonina leaf spot in poplars were found by bulked segregant analysis(BSA).The bulks consisted of individual with a extreme phenotype taken from a population of 91 F1 clones,which is a progeny of Populus deltoides Bartr.cv.“Lux”(I-69/55)(Resistance) and P.euramericana cv.I-45(Susceptible).Out of 114 RAPD primers,four markers showed polymorphisms between the resistance-bulk and the susceptible-bulk.By using selective genotype linkage analysis,OPAI17-1550 and OPAI13-900 were found linked to the resistance locus.The genetic distances between the two markers and the resistance locus were 29.9cM and 37.4cM,respectively. Key words：BSA; RAPD; selective genotype analysis; Marssonina leaf spot