While Ramularia leaf blight of cotton caused by Ramularia areola is of top most importance for Brazil, information is lacking regarding the survival mechanism of this pathogen during the cotton-free period. The teleom...While Ramularia leaf blight of cotton caused by Ramularia areola is of top most importance for Brazil, information is lacking regarding the survival mechanism of this pathogen during the cotton-free period. The teleomorph of R. areola is expected to belong to the genus Mycosphaerella. In the present study attempts were made to verify occurrence of this teleomorph in the State of Mato Grosso, Brazil. Decaying cotton leaves were collected two months after harvest of 2014 from 44 commercial and experimental fields where aerial fungicidal applications were made or not during the crop cycle to control the Ramularia leaf blight. Examination of the decaying cotton leaves revealed presence of abundant sclerotia, spermagonia and ascoma of Mycosphaerella sp. intermingled with each other during the cotton-free period in most of the leaf samples. Mono-ascospore isolations were obtained from the ascoma and considering their cultural, morphological, pathological and DNA sequence analysis they were identified as Mycosphaerella areola. M. areola and R. areola isolates produced similar symptoms under glasshouse inoculations. Reisolation of the pathogen from the symptoms produced by M. areola isolates yielded R. areola. Some cotton leaves showing such symptoms were kept on the soil surface on plastic trays for two months under natural field condition. After this period the decaying leaves showed abundant perithecia identical to their original M. areola. ITS rDNA sequence analyses revealed identical sequences from M. areola and R. areola isolates. Occurrence and the viability of the perfect stage M. areola during the cotton-free period on the left-over stubble from one season to another were interpreted as the survival mechanism of the pathogen and were considered responsible for the Ramularia blight epidemics in the State of Mato Grosso. Disease management practices for the State of Mato Grosso are discussed. This is the first report about the occurrence of the M. areola in Brazil.展开更多
Geostatistics as a methodology for studying the spatiotemporal dynamics of Ramularia areola in cotton crops. Geostatistics is a tool that has been used to study plant pathology, by modeling the spatiotemporal pattern ...Geostatistics as a methodology for studying the spatiotemporal dynamics of Ramularia areola in cotton crops. Geostatistics is a tool that has been used to study plant pathology, by modeling the spatiotemporal pattern of diseases, generating hypotheses about their epidemiological aspects in order to use tactics and strategies of rational control. The objective of this study was to use geostatistics to study the spatiotemporal dynamics of Ramularia areola in cotton crops. The experiment was conducted at the experimental area of Mato Grosso State University-Tangará da Serra campus, and arranged in a 2 × 3 factorial design, with randomized blocks, with two spaicngs (0.45 and 0.90 cm) and three conditions of soil coverage (no cover, P. glaucum and C. spectabilis). Geostatistical analysis of data was performed using data from temporal and spatial progress of R. areola, obtained through assessments of the incidence and severity of the disease in plants, and spatial dependence, and analyzed using semivariogram fittings. Through the isotropic exponential semivariogram model, it was possible to check the distribution pattern and spatial dependence of Ramularia leaf spot. Spatial dependence was observed for the disease—moderate to strong for most data evaluated. The pathogen spread from the primary source of inoculum, from the center portion towards the edges, forming foci originating from a source of secondary inoculum.展开更多
Spore production ofRamularia areolahas always been a difficult task. Brazilian isolates ofR. areolaproduce spores of variable size and shape. The typical spores are 3 septate, rarely 4 and 5 septate, together with abu...Spore production ofRamularia areolahas always been a difficult task. Brazilian isolates ofR. areolaproduce spores of variable size and shape. The typical spores are 3 septate, rarely 4 and 5 septate, together with abundant single celled oblong to round bodies—a phenomenon not reported earlier forR. areola. Budding of spores is a continuous process as observed in our isolates. By repeated culturing the pathogen either ceases to produce typical spores or loses its pathogenic character. To solve this problem, a technique was developed to produce large quantity of typical spores under laboratory conditions. Sporulating cultures produced on Petri plates containing V8 juice-agar were kept on the laboratory bench till they became dry and then stored at 5°C for reisolation and/or for production of fresh inoculum. In such dried cultures spores remain viable for a period of over 12 months, and hence isolates ofR. areolaoriginatedfrom different geographic regions can be maintained in sporulating form. Results of the present investigation would aid cotton breeders and pathologists in screening germplasm resistant toRamulariaand in other genetical studies under glasshouse conditions.展开更多
Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in ...Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through ERIC- and REP-PCR and ITS1-5.8S-ITS2 rDNA analysis. Difference in virulence spectrum and molecular analysis of some isolates was observed. ERIC- and REP-PCR showed similar results and revealed a high level of diversity among the isolates. A unique profile for both ERIC and REP was obtained for most isolates. On the other hand, the ITS rDNA analysis did not show different PCR-RFLP patterns. While some isolates differed among each other considering genotypic and phenotypic reactions, no clear cut evidence was found about the existence of genetic lineages of R. areola in Brazil. Identification of genetic variability among the R. areola isolates originated from different geographic regions would permit screening of Brazilian germplasm and achieve sources with a wide spectrum of resistance. This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil.展开更多
经病原形态、培养性状、致病性测定,本文首次报道了甘肃省夹竹桃和文竹上的2种真菌新病害,夹竹桃叶斑病和文竹叶斑病。其主要致病菌分别为夹竹桃柱隔孢(Ramularia nerii-indiciT.Zhang et M.Y.Gui)和天门冬柱隔孢(Ramularia asparagiZ.Y...经病原形态、培养性状、致病性测定,本文首次报道了甘肃省夹竹桃和文竹上的2种真菌新病害,夹竹桃叶斑病和文竹叶斑病。其主要致病菌分别为夹竹桃柱隔孢(Ramularia nerii-indiciT.Zhang et M.Y.Gui)和天门冬柱隔孢(Ramularia asparagiZ.Y.Zhang et W.Q.Chen),并对每一种病害的症状和病原形态进行了描述。展开更多
文摘While Ramularia leaf blight of cotton caused by Ramularia areola is of top most importance for Brazil, information is lacking regarding the survival mechanism of this pathogen during the cotton-free period. The teleomorph of R. areola is expected to belong to the genus Mycosphaerella. In the present study attempts were made to verify occurrence of this teleomorph in the State of Mato Grosso, Brazil. Decaying cotton leaves were collected two months after harvest of 2014 from 44 commercial and experimental fields where aerial fungicidal applications were made or not during the crop cycle to control the Ramularia leaf blight. Examination of the decaying cotton leaves revealed presence of abundant sclerotia, spermagonia and ascoma of Mycosphaerella sp. intermingled with each other during the cotton-free period in most of the leaf samples. Mono-ascospore isolations were obtained from the ascoma and considering their cultural, morphological, pathological and DNA sequence analysis they were identified as Mycosphaerella areola. M. areola and R. areola isolates produced similar symptoms under glasshouse inoculations. Reisolation of the pathogen from the symptoms produced by M. areola isolates yielded R. areola. Some cotton leaves showing such symptoms were kept on the soil surface on plastic trays for two months under natural field condition. After this period the decaying leaves showed abundant perithecia identical to their original M. areola. ITS rDNA sequence analyses revealed identical sequences from M. areola and R. areola isolates. Occurrence and the viability of the perfect stage M. areola during the cotton-free period on the left-over stubble from one season to another were interpreted as the survival mechanism of the pathogen and were considered responsible for the Ramularia blight epidemics in the State of Mato Grosso. Disease management practices for the State of Mato Grosso are discussed. This is the first report about the occurrence of the M. areola in Brazil.
文摘Geostatistics as a methodology for studying the spatiotemporal dynamics of Ramularia areola in cotton crops. Geostatistics is a tool that has been used to study plant pathology, by modeling the spatiotemporal pattern of diseases, generating hypotheses about their epidemiological aspects in order to use tactics and strategies of rational control. The objective of this study was to use geostatistics to study the spatiotemporal dynamics of Ramularia areola in cotton crops. The experiment was conducted at the experimental area of Mato Grosso State University-Tangará da Serra campus, and arranged in a 2 × 3 factorial design, with randomized blocks, with two spaicngs (0.45 and 0.90 cm) and three conditions of soil coverage (no cover, P. glaucum and C. spectabilis). Geostatistical analysis of data was performed using data from temporal and spatial progress of R. areola, obtained through assessments of the incidence and severity of the disease in plants, and spatial dependence, and analyzed using semivariogram fittings. Through the isotropic exponential semivariogram model, it was possible to check the distribution pattern and spatial dependence of Ramularia leaf spot. Spatial dependence was observed for the disease—moderate to strong for most data evaluated. The pathogen spread from the primary source of inoculum, from the center portion towards the edges, forming foci originating from a source of secondary inoculum.
文摘Spore production ofRamularia areolahas always been a difficult task. Brazilian isolates ofR. areolaproduce spores of variable size and shape. The typical spores are 3 septate, rarely 4 and 5 septate, together with abundant single celled oblong to round bodies—a phenomenon not reported earlier forR. areola. Budding of spores is a continuous process as observed in our isolates. By repeated culturing the pathogen either ceases to produce typical spores or loses its pathogenic character. To solve this problem, a technique was developed to produce large quantity of typical spores under laboratory conditions. Sporulating cultures produced on Petri plates containing V8 juice-agar were kept on the laboratory bench till they became dry and then stored at 5°C for reisolation and/or for production of fresh inoculum. In such dried cultures spores remain viable for a period of over 12 months, and hence isolates ofR. areolaoriginatedfrom different geographic regions can be maintained in sporulating form. Results of the present investigation would aid cotton breeders and pathologists in screening germplasm resistant toRamulariaand in other genetical studies under glasshouse conditions.
基金The present research was conducted under the financial support of IMA,MT,Brazil.
文摘Genotypic and phenotypic variation among 16 isolates of Ramularia areola of Gossypium hirsutum collected from five different geographical regions of Brazil was studied through virulence spectrum on three cultivars in the glasshouse and through ERIC- and REP-PCR and ITS1-5.8S-ITS2 rDNA analysis. Difference in virulence spectrum and molecular analysis of some isolates was observed. ERIC- and REP-PCR showed similar results and revealed a high level of diversity among the isolates. A unique profile for both ERIC and REP was obtained for most isolates. On the other hand, the ITS rDNA analysis did not show different PCR-RFLP patterns. While some isolates differed among each other considering genotypic and phenotypic reactions, no clear cut evidence was found about the existence of genetic lineages of R. areola in Brazil. Identification of genetic variability among the R. areola isolates originated from different geographic regions would permit screening of Brazilian germplasm and achieve sources with a wide spectrum of resistance. This is the first report of the genotypic and phenotypic variability among the R. areola isolates originated from five cotton growing regions of Brazil.
文摘经病原形态、培养性状、致病性测定,本文首次报道了甘肃省夹竹桃和文竹上的2种真菌新病害,夹竹桃叶斑病和文竹叶斑病。其主要致病菌分别为夹竹桃柱隔孢(Ramularia nerii-indiciT.Zhang et M.Y.Gui)和天门冬柱隔孢(Ramularia asparagiZ.Y.Zhang et W.Q.Chen),并对每一种病害的症状和病原形态进行了描述。
