Target Leaf Spot Research Articles

Positional cloning of ds1, the target leaf spot resistance gene against Bipolaris sorghicola in sorghum

Target leaf spot is one of the major sorghum diseases in southern Japan and caused by a necrotrophic fungus, Bipolaris sorghicola. Sorghum resistance to target leaf spot is controlled by a single recessive gene (ds1). A high-density genetic map of the ds1 locus was constructed with simple sequence repeat markers using progeny from crosses between a sensitive variety, bmr-6, and a resistant one, SIL-05, which allowed the ds1 gene to be genetically located within a 26-kb region on the short arm of sorghum chromosome 5. The sorghum genome annotation database for BTx623, for which the whole genome sequence was recently published, indicated a candidate gene from the Leucine-Rich Repeat Receptor Kinase family in this region. The candidate protein kinase gene was expressed in susceptible plants but was not expressed or was severely reduced in resistant plants. The expression patterns of ds1 gene and the phenotype of target leaf spot resistance were clearly correlated. Genomic sequences of this region in parental varieties showed a deletion in the promoter region of SIL-05 that could cause reduction of gene expression. We also found two ds1 alleles for resistant phenotypes with a stop codon in the coding region. The results shown here strongly suggest that the loss of function or suppression of the ds1 protein kinase gene leads to resistance to target leaf spot in sorghum.

Patogenicidade de Corynespora cassiicola em soja, limiares térmicos e temperatura ótima para a germinação de conídios em meio de cultura

Ensaios em câmara climatizada e laboratório, foram conduzidos para demonstrar a patogenicidade de Corynespora cassiicola em soja. Para esse estudo, utilizou-se um isolado monosporico obtido de folhas de soja de Primavera do Leste, MT. Os conídios analisados ao mi croscópio ótico a presentaram morfologia semelhante a do gênero Corynespora. A mensuração de 200 conídios desenvolvidos em meio de cultura, obteve-se as seguintes medidas 8-12 x 20 - 280 µm, média de 10 x 150 µm. O isolado foi inoculado no cultivar CD 219 RR para comprovar a sua patogenicidade. Pela comparação dos sintomas com as descrições da literatura e pelo reisolamento do patógeno, seguido de sua caracterização morfológica, confirmou-se à patogenicidade do isolado de C. cassiicola. Para identificar os limiares térmicos inferior (Lti) e superior (Lts) e a temperatura ótima e o limiar térmico superior (Lt s) para a germinação de esporos de C. cassiicola, foi conduzido um ensaio em placas de Petri, com meio de cultur a Czapekága r. Foram testados: ( a ) tempo de exposiçã o de 6 , 1 2 e 24 hora s e (b) temperaturas mínimas de 5, 6, 7, 8, 9 e 10 ºC, intermediárias de 15, 20, 25, 30 e 35ºC e superiores de 36, 37, 38, 39, 40 e 41ºC. Os dados foram submetidos a análise de variância e regressão. Os conídios germinaram em uma ampla gama de tempera tura tendo como valores de Lti 7ºC, ótima de 23ºC e valores de Lts 39ºC.

EST-SSR MARKER LINKED TO CUCUMBER TARGET LEAF SPOT RESISTANCE-RELATED GENE

Cucumber target leaf spot (Corynespora cassiicola (Berk. & Curt.) Wei.), a world wide fungicidal disease of cucumber, was first reported in Europe in 1906. It becomes a serious problem in cucumber protected cultivation in northern part of China recent years. A 241 F 2 population derived from F 1 of Q5 (resistant female) and P57-1 (susceptible male) was used as materials, their resistances to Corynespora cassiicola of cucumber were identified through seedling inoculation. The results indicated that the resistance to Corynespora cassiicola was controlled by a pair of recessive gene, and the susceptible was in the mode of incomplete dominant inheritance. The polymorphism between resistant and susceptible bulk of cucumber target leaf spot were studied using BSA method and SSR, EST-SSR, ISSR techniques. One hundred twelve SSR, 29 EST-SSR and 100 ISSR markers were screened, and a co-dominant EST-SSR marker was obtained. The resistant and susceptible F 2 plants possessed the 203 bp and the 207 bp fragments, respectively, and the mid-plants possessed both two fragments. The EST-SSR marker was closely linked to the cucumber target leaf spot resistance-related gene, and the genetic distance between the marker and the gene was 2.9 cM. The difference of the two fragments lied in the insert or deletion of 4 bases. Resistance of 47 inbred lines through seedling inoculation were compared with their results of marker detection, the coincidence rate was 91.5%.

Identification of quantitative trait loci associated with resistance to foliar diseases in sorghum [Sorghum bicolor (L.) Moench

Forage sorghum cultivars grown in India are susceptible to various foliar diseases, of which anthracnose, rust, zonate leaf spot, drechslera leaf blight and target leaf spot cause severe damage. We report here the quantitative trait loci (QTLs) conferring resistance to these foliar diseases. QTL analysis was undertaken using 168 F7 recombinant inbred lines (RILs) of a cross between a female parental line 296B (resistant) and a germplasm accession IS18551 (susceptible). RILs and parents were evaluated in replicated field trials in two environments. A total of twelve QTLs for five foliar diseases on three sorghum linkage groups (SBI-03, SBI-04 and SBI-06) were detected, accounting for 6.9–44.9% phenotypic variance. The morphological marker Plant color (Plcor) was associated with most of the QTL across years and locations. The QTL information generated in this study will aid in the transfer of foliar disease resistance into elite susceptible sorghum breeding lines through marker-assisted selection.

First Report of Target Leaf Spot Caused by Corynespora cassiicola on Balsam Pear in China.

Balsam pear (Momordica charantia L.) is an economically important vegetable in China with increasing interest as a medicinal plant. In December of 2006, a new foliar disease caused by Corynespora cassiicola was observed on balsam pear growing in greenhouses in Shouguang City, Shandong Province, China. The disease occurred on 35% or less of the plants. Leaves of affected plants developed off-white halos surrounding circular lesions that were 1 to 5 mm broad. The lesions became dark brown, necrotic with concentric rings, and up to 15 mm in diameter. Severely affected plants eventually wilted and defoliated. Pieces of tissue from the leading edges of lesions were disinfected in 1% NaOCl for 1 min, rinsed in sterile water, and plated on potato dextrose agar. Colonies of the fungus were gray to dark green. Conidiophores were erect and simple, pale brown to brown, and 100 to 450 μm long and 3 to 8 μm wide. Conidia were obclavate to cylindrical, pale olivaceous brown to dark brown, smooth, 35 to 100 × 8 to 12 μm, and were produced in chains. On the basis of these characteristics, the fungus was identified as Corynespora cassiicola (1). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and deposited in GenBank (Accession No. GQ381292). It was an exact match for a sequence of C. cassiicola previously deposited (Accession No. EU364555). To confirm pathogenicity, 30 1-month-old healthy seedlings of balsam pear were inoculated by spraying a suspension of conidia (1 × 105 conidia per ml) of one isolate of C. cassiicola until runoff. Ten seedlings were sprayed with sterile water as controls. Plants were kept in a humidity chamber at 27°C overnight and then placed in a growth chamber at 27°C. After 7 days, symptoms identical to those described above were observed, while no symptoms developed on the control plants. The pathogen was reisolated from inoculated leaves. C. cassiicola causes foliar diseases on many plants, including tomato, eggplant, soybean, and cucumber (2). There is one report on balsam pear in Korea (3). To our knowledge, this is the first report of target leaf spot caused by C. cassiicola on balsam pear in China.

Extraction of the image of soybean target leaf spot based on improved genetic algorithm

Extraction of the image of soybean target leaf spot based on improved genetic algorithm

Patogenicidade de isolados de Corynespora cassiicola a diferentes espécies de plantas

Corynespora cassiicola, relatado como um patógeno com ampla gama de espécies hospedeiras, tem causado danos em várias culturas de interesse comercial. Neste trabalho avaliou-se, em ambiente de casa-de-vegetação, a patogenicidade de 15 isolados de C. cassiicola originados de diferentes espécies hospedeiras, quando inoculados em 12 diferentes espécies vegetais. Os isolados de pepino foram os mais patogênicos. Além dos híbridos de pepino, estes infectaram outras seis espécies vegetais testadas. Já os isolados de trapoeraba e de alface foram os que apresentaram menor patogenicidade, pois além dos hospedeiros originais infectaram somente uma espécie hospedeira. A maioria dos isolados apresentou elevada inespecificidade. As espécies vegetais testadas reagiram de formas diferentes quando inoculadas com diferentes isolados. O mamoeiro apresentou maior suscetibilidade, sendo infectado por 12 dos 15 isolados. Contrariamente, a trapoeraba e o assa-peixe foram suscetíveis a três e dois isolados, respectivamente.

‘Marketmore 97’: A Monoecious Slicing Cucumber Inbred with Multiple Disease and Insect Resistances

‘Marketmore 97’ is the most recent addition to a series of disease-resistant slicing cucumbers developed in the Cornell University Department of Plant Breeding. The fruit have green skin with white spines and an average length and diameter of 18.8 cm and 4.8 cm, respectively. Broad resistance to a number of destructive diseases and insects makes this cultivar well-suited to low-input agricultural systems at the scale of the home gardener or the commercial grower. In addition to the cucumber mosaic virus (CMV), cucumber scab (Cladosporium cucumerinum Ell. & Arth.), downy mildew (Pseudoperonospora cubensis Berk & Curtis), and powdery mildew (Sphaerotheca fuliginea Schl. ex Fr.) resistances of ‘Marketmore 76’, ‘Marketmore 97’ contains resistance to alternaria leaf spot [Alternaria alternata (Fr.) Keis.], Ulocladium leaf spot (Ulocladium cucurbitae Let. & Roum.), target leaf spot (Corynespora cassiicola Berk. & Curt.), watermelon mosaic virus, papaya ringspot virus, and zucchini yellow mosaic virus. Furthermore, the bitterfree character of this cultivar is responsible for nonpreference of the striped cucumber beetle (Acalymma vittatum Fab.) and spotted cucumber beetle (Diabrotica undecimpunctata howardi Barber). Finally, a near isogenic line of ‘Marketmore 97’ is available that is gynoecious. A replicated trial of ‘Marketmore 97’ conducted in New York in 2006 confirmed comparable yield and quality to other Marketmore cultivars.

Reação de híbridos de pepino para cultivo protegido a isolados de Corynespora cassiicola

Corynespora cassiicola causa mancha alvo em folhas de diversas espécies de plantas, entre elas as cucurbitáceas. Este trabalho objetivou analisar a patogenicidade de 15 isolados de C. cassiicola originados de diferentes espécies hospedeiras a híbridos de pepino (Cucumis sativus) tipo 'japonês', assim como avaliar a severidade da doença em condições de casa-de-vegetação. Verificou-se que somente três isolados originados de pepino e um isolado de abóbora foram capazes de infectar os quatro híbridos de pepino. Os híbridos Natsubayashi e Tsuyataro também foram infectados pelos dois isolados originados de soja e um originado de tomateiro. Quanto à severidade, os isolados de C. cassiicola originados de pepino mostraram-se significativamente mais agressivos. Além disso, Tsuyataro mostrou-se mais suscetível dentre os híbridos testados. As diferenças na agressividade dos isolados de C. cassiicola sugerem maior adaptação dos isolados originados de pepino para os quatro híbridos, uma vez que estes foram significativamente mais agressivos do que os demais isolados.

시설하우스에서 Corynespora cassiicola에 의해 발생하는 오이 갈색무늬병

2000년도와 2001년도에 남부지방(구례, 별교, 영암)의 시설 내 오이재배지에서 갈색무늬병에 피해가 심하였다. 잎에서 전형적인 수침상 병반이 생기고 초기에 황색 halo를 지닌 갈색반점이 생긴 후 점차 불규칙하고 큰 병반으로 진전되어 때때로 낙엽을 유발하였다. 감염잎으로부터 분리한 병원균은 분생자경에 연쇄상 혹은 단일 분생포자를 형성하였고 분생포자는 거의 무색에서 올리브 갈색 내지는 갈색을 띠었으며 모양은 7-11개의 위격벽을 지닌 원통형,역곤봉형, 직립형, 만곡형 등이었다. 또한 분리 병원균의 ITS영역의 염기서열은 Corynespora cassciicola와 일치하였다. 형태적, ITS영역 분석을 기초로 분리된 병원균은 C. cassiicola로 동정하였다. 병원균의 생육은 3<TEX>$0^{\circ}C$</TEX> Czapek Solution Agar 배지에서 가장 좋았으며, 발병환경 조사 결과 3<TEX>$0^{\circ}C$</TEX>에서 18시간 이상 습전시간이 유지될 때 발병이 높아, 고온과 식물의 긴 습전기간이 발병량의 증가를 가져오는 요인이었다. 또한 국내 품종들을 대상으로 오이갈색무늬병에 대한 감수성과 저항성 품종들을 선발하였다. An epidemic of target leaf spot of cucumber (Cucumis sativus) occurred in commercial greenhouses in Korea in 2000/2001. The early symptoms on the leaves were small brown spots with yellow halos. These lesions became irregular enlarging in diameter and eventually defoliation resulted. The causal agent was a fungus with morphological characteristics matching Corynespora cassiicola. The sequence of the ITS region of C. cassiicola CM2000-1 was identical to that of an authentic strain of Corynespora cassiicola. Optimal germination of spores and mycelial growth on plate was at 3<TEX>$0^{\circ}C$</TEX>. A long dew period on the leaf surface and high temperatures were the main contributing factors for disease development and the greenhouse epidemic. Artificial inoculation of the Korean isolate of C. cassiicola revealed resistance in some Korean cucumber cultivars.

Gene expression analysis in cucumber leaves primed by root colonization with Pseudomonas chlororaphis O6 upon challenge-inoculation with Corynespora cassiicola.

Root colonization by Pseudomonas chlororaphis O6, a non-pathogenic rhizobacterium, induced systemic resistance in cucumber against target leaf spot caused by Corynespora cassiicola. A cDNA library was constructed using mRNA extracted from cucumber leaves 12 h after inoculation with C. cassiicola, using plants colonized by O6. To identify genes involved in O6-mediated induced systemic resistance (ISR), we employed a subtractive hybridization method using mRNAs extracted from pathogen-challenged cucumber leaves of plants lacking colonization. Differential screening of the cDNA library led to the isolation of six distinct genes encoding a GTP binding protein, a 60S ribosomal protein, a hypersensitive-induced reaction protein, a ubiquitin extension protein, a pyridine nucleotide-disulfide oxidoreductase, and a signal recognition particle receptor. Expression of these genes was not induced by O6 colonization alone. Rather, transcript accumulation of these genes increased significantly faster and stronger in the O6 colonized than in non-colonized plants after challenge infection. Therefore, O6-mediated ISR may be associated with an enhanced capacity for the rapid and effective activation of cellular defence responses after challenge inoculation.

Occurrence of target leaf spot disease caused by Corynespora cassicola on cucumber in Korea

., 1993).A survey of commercial fields conducted between 2000and 2001 in Chonnam province revealed severe damageon a Japanese cucumber variety, Baeksung 3, but not onKorean varieties. However, by 2002 these varieties wereseverely affected by target leaf spot in fields in Chonnamand Gyeongnam provinces. Leaf symptoms began assmall brown spots with yellow halos, enlarging andbecoming irregularly shaped before defoliation occurred.The morphology of the fungus consistently obtained fromthese symptoms matched the description of

The Formation of Test Arrays and a Core Collection in Cucumber Using Phenotypic and Molecular Marker Data

Genetic relationships among 970 cucumber (Cucumis sativus L.) plant introductions (PIs) in the U.S. National Plant Germplasm System (NPGS) were assessed by observing variation at 15 isozyme loci. Allozyme frequency data for these PIs were compared to allozyme variation in heirloom and modern (H&amp;M) cultivars released from 1846-1985 (H&amp;M cultivars; 178 accessions), and experimental commercial (EC) germplasm (EC germplasm; 82 accessions) in use after 1985. Multivariate analysis defined four distinct groups of accessions (Groups A-D), where Group A consisted of PIs received by the NPGS before 1992, Group B contained PIs from India and China obtained by NPGS after 1992, Group C consisted of EC germplasm, and Group D contained H&amp;M cultivars. Morphological, abiotic stress (water and heat stress tolerance) and disease resistance evaluation data from the Germplasm Resources Information Network (GRIN) for the PIs examined were used in conjunction with estimates of population variation and genetic distance estimates to construct test arrays and a core collection for cucumber. Disease resistance data included the evaluation of angular leafspot [Pseudomonas lachrymans (E.F. Smith) Holland], anthracnose [Colletotrichum lagenarium (Ross.) Ellis &amp; Halst], downy mildew [Pseudoperonospora cubensis (Berk. &amp; Curt) Rostow], rhizoctonia fruit rot (Rhizoctonia solani Kuhn), and target leafspot [Corynespora cassiicola (Berk. &amp; Curt) Wei] pathogenicity. The test arrays for resistance-tolerance to angular leafspot, anthracnose, downy mildew, rhizoctonia fruit rot, target leafspot, and water and heat stress consisted of 17, 16, 17, 16, 17, 16, and 16 accessions, respectively. The core collection consisted of accessions in these test arrays (115) and additional 32 accessions that helped circumscribe the genetic diversity of the NPGS collection. The core collection of 147 accessions (115 + 32) represents ≈11% of the total collection's size (1352). Given estimates of genetic diversity and theoretical retention of diversity after sampling, this core collection could increase curatorial effectiveness and the efficiency of end-users as they attempt to identify potentially useful germplasm.

Mancha areolada causada por Thanatephorus cucumeris em mogno africano

O mogno africano (Khaya ivorensis) foi introduzido no Brasil para substituir o mogno brasileiro (Swietenia macrophylla) devido a sua alta resistência ao microlepidóptero Hypsiphyla grandella, a principal praga do mogno brasileiro. Em 1999, observou-se alta incidência da mancha areolada, causada por Thanatephorus cucumeris em viveiros e áreas de plantios definitivos de mogno africano nos Estados do Amazonas e Pará, causando lesões em folhas maduras e 100% de queda das folhas jovens. Nas folhas jovens surgem pequenas lesões marrons circundadas por uma margem púrpura e em folhas maduras as manchas são marrom-claras, exibindo anéis concêntricos.

First Report of Bipolaris sorghicola on Johnsongrass in Argentina.

Target leaf spot was found on johnsongrass (Sorghum halepense (L.) Pers.) in La Plata, Argentina (34°54'S, 58°30'W). Up to 80% disease severity was observed in adult plants. In most diseased plants, spots were well defined, delimited by leaf veins, and elongated. Individual lesions ranged in size from small spots (2 to 3 mm) to large lesions (10 to 15 mm). Lesions sometimes coalesced to produce extensive areas of necrosis. Isolates identified as Bipolaris sorghicola (Lefebre & Scherwin) Alcorn (1) grew slowly on potato dextrose agar medium, producing a compact dark brown mycelium. Conidia were 40 to 80 μm long, slightly curved and golden brown, with three to seven pseudosepta. Although germination of conidia was mainly bipolar, lateral germination sometimes was observed. Twenty monoconidial isolates were inoculated at 105 conidia per cm3 on johnsongrass at the 4-leaf stage to confirm the pathogenicity of B. sorghicola. After inoculation, plants were placed in a high-humidity chamber for 24 h; thereafter, they were kept at 25°C day and 18°C night temperatures. Typical lesions developed after 10 days. The pathogen was reisolated from lesions after 15 days. Johnsongrass is one of the most noxious weeds in the world. Due to its potential as a biocontrol agent, further studies are needed to determine the effect of B. sorghicola on johnsongrass. Reference: (1) J. L. Alcorn. Mycotaxon 27:1, 1983.

九州・沖縄地域における薬剤耐性キュウリ褐斑病菌の発生実態

九州・沖縄地域における薬剤耐性キュウリ褐斑病菌の発生実態

The natural occurrence of Thanatephorus cucumeris leaf spot on Hevea brasiliensis in Sri Lanka

Thanatephorus cucumeris. the causal agent of target leaf spot disease of Hevea, is recorded in Sri Lanka for the first time on Hevea brasiliensis.

Occurrence of Target Leaf Spot (Bipolaris sorghicola) on Sorghum in Mississippi

Occurrence of Target Leaf Spot (Bipolaris sorghicola) on Sorghum in Mississippi

Pathogenicity ofDrechslera sorghicolaIsolates on Sorghum in Venezuela

Drechslera sorghicola was identified as the causal organism of target leaf spot of sorghum. The fungus produces well-defined and elongated spots, which vary in size and color according to the sorghum genotype. The disease may be of economic importance in regions where high humidity and favorable temperatures occur during the growing season

Drechslera sorghicola . [Descriptions of Fungi and Bacteria

Abstract A description is provided for Drechslera sorghicola . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Sorghum , causing at first small reddish purple or tan spots, later zonate target spots. DISEASE: Target leaf spot of Sorghum spp. The leaf spots are well defined, round-elliptical with narrow tan brown borders, varying in size from minute specks to lesions up to 2-6 × 20 mm which may coalesce to form extensive patches of dead tissue. Colour varies with the host. The larger spots become delimited by the veins and hence elongated. Other lesions show the characteristic light and dark zonate patterns. Spots may be uniformly purplish with or without straw coloured centres and without the zonate pattern. GEOGRAPHICAL DISTRIBUTION: Reported from Africa, Asia, Australia and N. America; probably widespread with the crop. TRANSMISSION: No studies reported.