Showing papers on "Leaf spot published in 2018"
TL;DR: The experimental results demonstrate that the proposed system can successfully detect and classify four major plant leaves diseases: Bacterial Blight and Cercospora Leaf Spot, Powdery Mildew and Rust.
Abstract: Myanmar is an agricultural country and then crop production is one of the major sources of earning. So, more than half of our population depends on agriculture for livelihood. Due to the factors like diseases, pest attacks and sudden change in the weather condition, the productivity of the crop decreases. Automatic detection of plant diseases is essential to automatically detect the symptoms of diseases as early as they appear on the growing stage. This paper proposed a methodology for the analysis and detection of plant leaf diseases using digital image processing techniques. The experimental results demonstrate that the proposed system can successfully detect and classify four major plant leaves diseases: Bacterial Blight and Cercospora Leaf Spot, Powdery Mildew and Rust.
69 citations
TL;DR: The V76-12 isolate was the most effective treatment tested in reducing leaf spot disease of oil palm seedlings, due to its ability to inhibit mycelial growth in vitro, to reduce disease symptoms in vivo and in natural fields, as well as to enhance PAL, POD and PPO activities in the oil palm.
55 citations
TL;DR: Analysis of the interval sequences has indicated that a major QTL for resistance to late leaf spot anchored by two NBS-LRR resistance genes on chromosome B05 was associated with resistance genes for early leaf spot.
Abstract: Cultivated peanut (Arachis hypogaea L.) is an important oilseed crop that is grown extensively in Africa, Asia and America. The diseases early and late leaf spot severely constrains peanut production worldwide. Because multiple genes control resistance to leaf spot diseases, conventional breeding is a time-consuming approach for pyramiding resistance genes into a single genotype. Marker-assisted selection (MAS) would complement and accelerate conventional breeding once molecular markers tightly associated with the resistance genes are identified. In this study, we have generated a large number of SNPs through genotyping by sequencing (GBS) and constructed a high-resolution map with an average distance of 1.34 cM among 2,753 SNP markers distributed on 20 linkage groups. QTL mapping has revealed that major QTL within a confidence interval could provide an efficient way to detect putative resistance genes. Analysis of the interval sequences has indicated that a major QTL for resistance to late leaf spot anchored by two NBS-LRR resistance genes on chromosome B05. Two major QTLs located on chromosomes A03 and B04 were associated with resistance genes for early leaf spot. Sequences within the confidence interval would facilitate identifying resistance genes and applying marker-assisted selection for resistance.
44 citations
TL;DR: The diversity of 64 Australian isolates of Xanthomonas spp.
Abstract: Several species of Xanthomonas cause bacterial leaf spot, a disease that affects solanaceous crops worldwide. The diversity of 64 Australian isolates of Xanthomonas spp. associated with bacterial leaf spot in tomato, capsicum and chilli crops in eastern Australia was determined using multi-locus sequence analysis of atpD, dnaK, efp and gyrB genes, species-specific PCR assays and biochemical analyses. At least five species of Xanthomonas associated with bacterial leaf spot were identified in Australian tomato, capsicum and chilli crops and their pathogenicity assessed. Phylogenetic and biochemical analyses identified X. euvesicatoria, X. perforans and X. vesicatoria as the most frequently recovered pathogenic species. Non-pathogenic and weakly pathogenic species were also identified. The suitability of the identification methods used and the implications of the detection of these species will be discussed.
40 citations
TL;DR: The results show that C. etunicatum increased plant P uptake and total dry weight and that this beneficial effect was slightly enhanced when in association with the grass endophyte, which has the potential to promote perennial ryegrass growth and resistance to B. sorokiniana leaf spot.
Abstract: Leaf spot of perennial ryegrass (Lolium perenne) caused by Bipolaris sorokiniana is an important disease in temperate regions of the world. We designed this experiment to test for the combined effects of the arbuscular mycorrhizal (AM) fungus Claroideoglomus etunicatum and the grass endophyte fungus Epichloe festucae var. lolii on growth and disease occurrence in perennial ryegrass. The results show that C. etunicatum increased plant P uptake and total dry weight and that this beneficial effect was slightly enhanced when in association with the grass endophyte. The presence in plants of both the endophyte and B. sorokiniana decreased AM fungal colonization. Plants inoculated with B. sorokiniana showed the typical leaf spot symptoms 2 weeks after inoculation and the lowest disease incidence was with plants that were host to both C. etunicatum and E. festucae var. lolii. Plants with these two fungi had much higher activity of peroxidases (POD), superoxide dismutase (SOD) and catalase (CAT) and lower values of malondialdehyde (MDA) and hydrogen peroxide (H2O2). The AM fungus C. etunicatum and the grass endophyte fungus E. festucae var. lolii have the potential to promote perennial ryegrass growth and resistance to B. sorokiniana leaf spot.
40 citations
TL;DR: The efficacy of Ampelomyces quisqualis against zucchini powdery mildew was found to be improved under higher temperature and CO2 conditions, and changed environmental values on some physiological parameters on the production of mycotoxins as well as on disease management were also considered on selected pathosystems.
Abstract: Increases in carbon dioxide (CO2) and temperature are expected to induce complex effects on plant pathogens. The results of studies on the effects of climate change on a number of pathosystems, such as the downy and powdery mildew of grapevines, and on several pathogens of vegetable crops, such as rocket, basil, beet and zucchini, have been analysed in this review. In the reviewed works, plants were grown in controlled environment facilities (phytotrons) under six different simulated climatic conditions: a standard CO2 concentration (400–450 ppm) with a standard (ranging from 18 to 22/24 °C) and elevated temperature (5 °C higher than standard), and elevated CO2 (800–850 ppm) under a standard and elevated temperature. When the CO2 level and the temperature were increased, an increase was observed of powdery mildew on zucchini, Alternaria leaf spot on rocket salad, black spot and downy mildew on basil, Allophoma tropica on lettuce and Phoma leaf spot on garden beet. Variable effects were instead observed when individual climate parameters were taken into consideration. The effects of changed environmental values on some physiological parameters on the production of mycotoxins as well as on disease management were also considered on selected pathosystems. CO2 concentration and temperature proved to influence disease severity and mycotoxin production in different ways. As far as the application of biocontrol agents is concerned, the efficacy of Ampelomyces quisqualis against zucchini powdery mildew was found to be improved under higher temperature and CO2 conditions. The results obtained with different host/pathogen combinations will allow to develop adaptation strategies for disease management and to provide the seed industry with useful information in order to develop new cultivars that will be more adapted/adaptable to the changing conditions. The usefulness and limitations of studies carried out under controlled environment conditions are critically discussed.
29 citations
TL;DR: The survey proved that the incidence of leaf spot diseases was greatest in Umuahia followed by Okigwe and Ojoto, with a peak at the beginning of the rainy season (February–March), and the importance of the biological control method for rural mango farmers is emphasised.
Abstract: O����� R.N., O������ M.I. (2003): Fungal leaf spot diseases of mango (Mangifera indica L.) in Southeastern Nigeria and biological control with Bacillus subtilis. Plant Protect. Sci., 39: 70–77. The incidence of fungal leaf spot diseases on mango (Mangifera indica) in Southeastern Nigeria and application of a biological control measure was investigated. The survey proved that the incidence of leaf spot diseases was greatest in Umuahia (72%) followed by Okigwe and Ojoto, with a peak at the beginning of the rainy season (February–March). Three pathogenic fungi, Pestalotiopsis mangiferae, Botryodiplodia theobromae and Macrophoma mangiferae, were isolated from leaf spots. Other fungi, Fusariella spp., which are well known saprophytes of dead plant materials, and the fungus Meliola sp., were also isolated from diseased leaves. Pathogenicity tests showed that P. mangiferae, B. theobromae and M. mangiferae were the causal agents of the fungal leaf spot diseases. Symptoms developed 5 weeks after inoculation of healthy leaves. Bacillus subtilis NCIB 3610, isolated from soil under a mango tree, inhibited P. mangiferae, B. theobromae and M. mangiferae by 57%, 61% and 58% respectively on agar plates. Also, in in vivo experiments the symptoms were considerably reduced in the field by the application of the antagonist. The importance of the biological control method for rural mango farmers is emphasised.
26 citations
TL;DR: Diaporthe citri was found associated with shoot blight on Citrus reticulata, which represents a new record for Europe and a new species, Diaporte portugallica sp.
Abstract: Species of Diaporthe are important plant pathogens, saprobes, and endophytes on a wide range of plant hosts. Species such as D . citri are well-known on Citrus , as agents of pre- or post-harvest infections, causing dieback, melanose and stem-end rot on fruit. In this study we explored the occurrence and diversity of Diaporthe associated with tropical and sub-tropical plants. In particular, species of Camellia and Citrus were sampled. Surveys were carried out during 2017 in the Azores Islands, Portugal. Ten Diaporthe strains were isolated from symptomatic twigs and leaves. Five representative isolates were subjected to morphological characterization and multi-locus phylogeny based on five genomic loci (ITS, tef1 , cal , his3 and tub2 ). Diaporthe citri was found associated with shoot blight on Citrus reticulata , which represents a new record for Europe. A new species, Diaporthe portugallica sp. nov. was isolated and described from leaf spots on Camellia sinensis .
25 citations
University of Illinois at Urbana–Champaign1, Mississippi State University2, Southern Illinois University Carbondale3, Ohio State University4, Ohio Agricultural Research and Development Center5, University of Arkansas6, University of Nebraska–Lincoln7, University of Kentucky8, Louisiana State University Agricultural Center9, University of Tennessee10, University of Delaware11, North Carolina State University12, Virginia Tech13, Iowa State University14, Auburn University15, University of Georgia16, Purdue University17
TL;DR: Management of frogeye leaf spot should focus on integrated management practices such as planting resistant soybean cultivars, rotating with nonhost crops, and tilling to speed up decomposition of infested soybean residue.
Abstract: Isolates of Cercospora sojina, causal agent of frogeye leaf spot of soybean (Glycine max), were collected across Alabama, Arkansas, Delaware, Illinois, Indiana, Iowa, Kentucky, Louisiana, Mississip...
24 citations
TL;DR: The endophytic strains CB361-80 (Ochrobactrum sp.) and CC372-83 (Pantoea sp.) successfully colonized the cucumber tissues and the populations of the two isolates in the root and shoot tissues did not decrease following the inoculation of the pathogenic bacterium.
Abstract: Endophytic bacteria (EB) isolated from healthy cucumber plant tissues (e.g., root, stem, leaves) were evaluated as possible biological control of Pseudomonas syringae pv. lachrymans, the causative agent of angular leaf spot disease in cucumber. In this study, 24 endophytic bacteria were selected for tests based on biocontrol traits such as indole-3-acetic acid and siderophore production, solubilization of phosphate, and inhibition growth of P. syringae pv. lachrymans in vitro. Some of the selected endophytes successfully inhibited the pathogen were tested in pots. In the pot experiment, two isolates (CB361-80) and (CC372-83) were selected as the most promising biocontrol agents tested against the pathogen. According to the identification carried out by using 16S rRNA primers and sequence analysis, the two selected endophyte isolates (CB361-80) and (CC372-83) showed 99% similarity to Ochrobactrum pseudintermedium and Pantoea agglomerans, respectively. Two EB isolates colonized seeds at the rate of 3 × 106–7.1 × 107 CFU/g 1 day after seed bacterization. The population of the two EB isolates in cucumber tissues were found to be about 2 × 104–7.5 × 104 CFU/g in roots and 3.8 × 104–2.2 × 105 CFU/g in shoots 45 days after seed bacterization. The populations of the two isolates in the root and shoot tissues did not decrease following the inoculation of the pathogenic bacterium. The endophytic strains CB361-80 (Ochrobactrum sp.) and CC372-83 (Pantoea sp.) successfully colonized the cucumber tissues.
23 citations
TL;DR: During the summer of 2017, corn in production areas throughout Louisiana exhibited symptoms similar to eyespot, caused by Kabatiella zeae, which is the first report of the disease in Louisiana and the United States.
Abstract: During the summer of 2017, corn (Zea mays L.) in production areas throughout Louisiana exhibited symptoms similar to eyespot, caused by Kabatiella zeae (Narita & Y. Hirats). Symptoms included round...
TL;DR: F foliar application of J. mimosifolia leaf extract with very low dose of chemical fungicide is a promising approach for the management of leaf blight and spot blotch in wheat.
Abstract: Two experiments (pot and field experiments) were conducted in two consecutive years to evaluate the protective effects of botanical-chemical formulations on physiological, biochemical performance and grain yield of wheat inoculated with Bipolaris sorokiniana. We compared different formulations comprising Calotropis procera, Jacaranda mimosifolia, Thevetia peruviana extracts, chemical fungicide (mefenoxam) and salicylic acid to modulate the defense system of wheat host plants. Among the selected plant species J. mimosifolia aqueous and methanolic leaf extracts (1.2% w/v) resulted in 96 to 97% inhibition against B. sorokiniana. Both in pot and field experiments, among all the formulations of selected plant extracts the combined formulation of JAF2 (J. mimosifolia 0.6%)+MFF2 (mefenoxam 0.1%) lowered the dose of chemical fungicide required to reduce the leaf spot blotch disease. The same formulation induced resistance in wheat apparently through the accumulation of peroxidase, polyphenol oxidase, protease, acid invertase, chitinase and phenylalanine ammonia lyase. This formulation also stimulated the defense-related gene expression of PR-proteins. The same treatment gave even more increase (48%, 12% and 22%) in no. of grains/spike, grains weight and grain yield, than the MFF1 (mefenoxam 0.2%). We conclude that foliar application of J. mimosifolia leaf extract with very low dose of chemical fungicide (J. mimosifolia 0.6%+mefenoxam 0.1%) is a promising approach for the management of leaf blight and spot blotch in wheat.
TL;DR: Three gene models linked to the associated single nucleotide polymorphism were expressed at flowering time and tissue related with gray leaf spot infection, explaining a considerable proportion of the phenotypic variance.
Abstract: Gray leaf spot is a maize foliar disease with worldwide distribution and can drastically reduce the production in susceptible genotypes. Published works indicate that resistance to gray leaf spot is a complex trait controlled by multiple genes, with additive effect and influenced by environment. The aim of this study was to identify genomic regions, including putative genes, associated with resistance to gray leaf spot under natural conditions of disease occurrence. A genome wide association study was conducted with 355,972 single nucleotide polymorphism markers on a phenotypic data composed by 157 tropical maize inbred lines, evaluated at Maringa -Brazil. Seven single nucleotide polymorphisms were significantly associated with gray leaf spot, some of which were localized to previously reported quantitative trait loci regions. Three gene models linked to the associated single nucleotide polymorphism were expressed at flowering time and tissue related with gray leaf spot infection, explaining a considerable proportion of the phenotypic variance, ranging from 0.34 to 0.38. The gene model GRMZM2G073465 (bin 10.07) encodes a cysteine protease3 protein, gene model GRMZM2G007188 (bin 1.02) expresses a rybosylation factor-like protein and the gene model GRMZM2G476902 (bin 4.08) encodes an armadillo repeat protein. These three proteins are related with plant defense pathway. Once these genes are validated in next studies, they will be useful for marker-assisted selection and can help improve the understanding of maize resistance to gray leaf spot.
TL;DR: Conidia were first detected in early May in RT both years and PC in 2015, and in mid-June in PC 2014, providing evidence of a diurnal effect for airborne C. beticola conidia, and the presence of conidia was not a limiting factor for disease development.
Abstract: Cercospora beticola is the most important pathogen of sugar beet in temperate climates and is the causal agent of Cercospora leaf spot (CLS). The relationships among weather variables, disease se...
TL;DR: The study shows that several species of Alternaria are associated with leaf spot in date palm and wheat in Oman, with some isolates having the ability to cause infection in both hosts.
Abstract: This study was conducted to investigate the Alternaria species associated with leaf spot of date palm and wheat in Oman. Out of 98 date palm leaf samples and 146 wheat leaf samples, Alternaria was isolated from 27 and 23% of the samples developing leaf spot symptoms, respectively. Identification of Alternaria isolates using sequences of the internal transcribed spacer region of the ribosomal RNA (ITS rRNA), glyceraldehyde-3-phosphate dehydrogenase (GPDH), translation elongation factor (TEF) and RNA polymerase II subunit (RPB2) genes, showed that the isolates belong to seven Alternaria species or species complexes. A. burnsii - A. tomato and A. arborescens species complexes (58 and 4%, respectively) and A. alternata (38%) were the species recovered from the symptomatic date palm leaves. A. alternata (67%), A. burnsii - A. tomato species complex (15%), A. jacinthicola (3%), A. ventricosa (3%), A. slovaca (6%) and Alternaria caespitosa (6%) were isolated from wheat. Pathogenicity test showed that tested isolates of A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31), A. jacinthicola (WBR4) and A. slovaca (WDK9, WDK7) were pathogenic on date palm, while A. alternata (DPM19, WDK12), A. burnsii - A. tomato species complex (DPM31, WDK11) and A. slovaca (WDK9, WDK7) were pathogenic on wheat. This is the first report of date palm and wheat as new hosts for A. burnsii - A. tomato species complex and the first reports of A. burnsii - A. tomato species complex, A. caespitosa A. slovaca, and A. ventricosa in Oman. The study shows that several species of Alternaria are associated with leaf spot in date palm and wheat in Oman, with some isolates having the ability to cause infection in both hosts.
TL;DR: It is found that cultivar resistance to lower leaf damage correlated significantly with the abundance of endophytic fungal species, suggesting that endophytics fungi can promote leaf spot resistance in apple cultivars.
TL;DR: The tested AM fungus Funneliformis mosseae and rhizobium have the potential to reduce damage and yield loss in lucerne from spring black stem and leaf spot caused by P. medicaginis and this beneficial effect was enhanced when in association with S. medicae.
Abstract: Spring black stem and leaf spot of lucerne (alfalfa, Medicago sativa L.), caused by Phoma medicaginis, is an important disease in temperate regions of the world. It is now a serious disease threatening global lucerne production. This experiment was designed to test the combined effects of the arbuscular mycorrhizal (AM) fungus Funneliformis mosseae and the rhizobium Sinorhizobium medicae on growth, nutrient uptake and disease severity in lucerne. The results showed that F. mosseae increased plant phosphorus and nitrogen uptake and plant dry weight, and this beneficial effect was enhanced when in association with S. medicae. Rhizobial and AM fungal effects were mutually promoting; inoculation with AM fungus significantly increased the formation of root nodules, and inoculation with rhizobium increased the percentage of root length colonised by AM fungus (P < 0.05). After infection with P. medicaginis, typical leaf spot symptoms with the lowest disease incidence and disease index occurred on plants that were host to both F. mosseae and S. medicae. Plants with both symbiotic microorganisms had higher activities (concentrations) of phenylalanine ammonia-lyase, chitinase, β-1,3-glucanase, lignin, hydroxyproline-rich glycoprotein and jasmonic acid. Therefore, the tested AM fungus (F. mosseae) and rhizobium (S. medicae) have the potential to reduce damage and yield loss in lucerne from spring black stem and leaf spot caused by P. medicaginis.
TL;DR: In conclusion, saplings treated with the dip method and sprayed 4 times with a spore suspension of biocontrol agents such as T. asperellum, T. viride and T. harzianum are suggested for the ecofriendly management of this epidemic leaf spot disease of Aloe vera in agricultural fields.
Abstract: Aloe vera (L.) Burm.f. is a highly important and extensively cultivated medicinal plant and that is also extensively used in the cosmetic industry. It has been frequently reported to suffer from Alternaria leaf spot disease in various parts of the world. Various fungicides used to combat this disease, have deleterious effects on the environment and on pharmacologically important constituents of Aloe vera. To avoid the harmful effects of fungicides an ecofriendly approach has been adopted here. A weekly survey was conducted during 2013-2015 in and around North 24 Parganas (West Bengal) to obtain the percentage of disease index (PDI). For biological control of the disease, screening of the antagonistic efficacy of biocontrol agents was carried out through the in vitro dual-culture-plate method and scanning electron microscopy (SEM) was used to study the mechanism. The in vitro effects of fungicides on the radial growth of the pathogen were evaluated through the poison food method and were compared with potent antagonistic fungi. Field application of potent antagonistic fungi was conducted through the dip-and-spray method. The results showed that, the PDI peaked during the hot and humid conditions of May to September (76.57%-98.57%) but decreased during the winter, December-January (35.71-46.66%). Trichoderma asperellum exerted the greatest inhibition of the radial growth of A. brassicae acting through non volatile (70.39%) and volatile metabolites (72.17%). A SEM study confirmed the hyperparasitic nature of T. asperellum through hyphal coiling-T. asperellum was similar to 2% blitox-50 (73.92%) and better than 2% bavistin (59.77%) (in vitro). In agricultural field trials (2013-15), Trichoderma application restricted the disease to the smallest area (PDI 24.00-29.33%) in comparison to untreated plots (73.33%). In conclusion, saplings treated with the dip method (108 spores / mL) and sprayed 4 times with a spore suspension of biocontrol agents such as T. asperellum, T. viride and T. harzianum, standardized at a rate of 2.5 L / plot (36 sq ft) (108 spores/ mL) are suggested for the ecofriendly management of this epidemic leaf spot disease of Aloe vera in agricultural fields.
TL;DR: Field experiments were conducted to develop an integrated method for the management of LLS and RR of groundnut using the best performing PGPR, SAR inducer and plant extract in combinations, which resulted in significant reductions in the area under the disease progress curve (AUDPC) for LLS compared with that of untreated control.
Abstract: Greenhouse experiments were conducted to study the efficacy of plant growth-promoting rhizobacteria (PGPR) for control of root rot (RR) in groundnut (Arachis hypogaea L.) caused by Macrophomina phaseolina and to test the ability of plant systemic acquired resistance (SAR) inducers and plant extracts to protect groundnut plants from late leaf spot (LLS) caused by Phaeoisariopsis personata. Seed treatment and soil application of a talc-based formulation of B. subtilis strain G1 significantly reduced the incidence of root rot under greenhouse conditions. In experiments with SAR inducers, foliar application of salicylic acid (SA) (7 mM) on 45 days after sowing significantly reduced LLS incidence and increased the pod yield. Foliar application of aqueous extract (10%) from leaves of Adhatoda vasica and zimmu (Allium sativum x A. cepa) on 45 days after sowing significantly decreased the LLS incidence and increased the pod yield compared with the untreated control. Field experiments were conducted to develop an integrated method for the management of LLS and RR of groundnut using the best performing PGPR, SAR inducer and plant extract in combinations. Combined application of B. subtilis strain G1 through seed (10 g/kg) and soil (2.5 kg/ha) followed by foliar application of A. vasica extract (10%) on 30, 45 and 60 days after sowing significantly reduced LLS and RR diseases in groundnut and increased the pod yield under field conditions. The above treatment resulted in significant reductions in the area under the disease progress curve (AUDPC) for LLS compared with that of untreated control.
TL;DR: In 2017, leaf spots were found on lettuce growing in fields in Songkhla Province, southern Thailand and the fungus isolated from the spot lesions on the leaves was identified as Curvularia aeria, the first report of C. aeria causing leaf spot on lettuce.
Abstract: In 2017, leaf spots were found on lettuce growing in fields in Songkhla Province, southern Thailand. The fungus isolated from the spot lesions on the leaves was identified as Curvularia aeria (Bat., J.A.Lima and C.T.Vasconc.) Tsuda based on morphological characteristics and DNA sequences of the ITS region of the rRNA gene. After a conidial suspension of the isolate was sprayed on lettuce seedlings, the leaf spots developed on lettuce seedlings, and the fungus was reisolated; leaves of plants inoculated with water did not develop spots. This is the first report of C. aeria causing leaf spot on lettuce.
29 Jun 2018
TL;DR: A total of 28 isolates obtained from the main potato-growing regions of Iran, including the Ardebil, Hamedan, Isfahan, and Fars provinces were analyzed to investigate the virulence and genetic variability of Iranian A. alternata isolates and showed high variability in terms of virulence.
Abstract: Leaf spot disease in potato is caused by Alternaria alternata (Fr.) Keissler, an opportunistic pathogen that infests many agricultural crops worldwide in the field and during postharvest storage of vegetables and fruits. Alternaria alternata is associated with leaf spot disease in potato in Iran. Thus, there is a need to investigate the virulence and genetic variability of Iranian A. alternata isolates to facilitate the development of appropriate management strategies. In the present study, we analyzed a total of 28 isolates obtained from the main potato-growing regions of Iran, including the Ardebil, Hamedan, Isfahan, and Fars provinces. The pathogens were characterized based on sequence analysis of the genes encoding glyceraldehyde-3-phosphate dehydrogenase ( gpd ), plasma membrane ATPase, Alternaria allergen a 1 (Alt a1), calmodulin, and actin. In addition, random amplified polymorphic DNA (RAPD), intersimple sequence repeat (ISSR), and virulence studies were performed. Phylogenetic analysis of the combined dataset indicated that the five representative isolates were grouped with the subcluster comprising A. alternata . RAPD and ISSR analyses clustered the 28 A. alternata isolates into different groups with no correlation with their corresponding geographical origins. Results of the pathogenicity assay indicated that all A. alternata isolates were pathogenic against potato. However, the A. alternata isolates showed high variability in terms of virulence.
TL;DR: Cultivar selection and fungicide use under environments conducive to disease are beneficial components of an integrated leaf spot disease management program for winter wheat in western Canada.
Abstract: A complex of leaf-spotting diseases—tan spot, the Septoria complex, spot blotch, and powdery mildew—are frequently observed on winter wheat in western Canada; however, there are few studies indicat...
TL;DR: The occurrence of Fusarium spp.
TL;DR: Pathogenicity testing showed that watermelon, cantaloupe, and squash seedlings were susceptible to a majority of these strains, and the distribution of one haplotype in 9 of 10 Florida and Georgia counties sampled indicated that these epidemics were associated with the recent introduction of a novel clonal P. syringae lineage throughout major watermelon production areas in Florida.
Abstract: From 2013 to 2014, bacterial leaf spot epidemics incited by P. syringae pv. syringae affected an estimated 3,000 hectares of watermelon and squash in Florida, and caused foliar blighting and transplant losses in severely affected fields. To investigate the diversity of the causal agent, we isolated 28 P. syringae strains from diseased plants grown in ten Florida and Georgia counties over the course of 2 years. Strains were confirmed as P. syringae through sequence analysis of the 16S rRNA and LOPAT profiling, however 20 displayed an atypical phenotype by exhibiting non-fluorescent activity on KB and being negative for ice-nucleating activity. Multilocus sequence analysis and BOX-PCR revealed the presence of two haplotypes among the collected strains, that grouped into two distinct clades within P. syringae phylogroup 2. Pathogenicity testing showed that watermelon, cantaloupe, and squash seedlings were susceptible to a majority of these strains. While both haplotypes were equally virulent on cantaloupe, t...
TL;DR: Exposure to abiotic stress increased symptom development in all susceptible and most partially resistant barley varieties, in association with greater hydrogen peroxide levels in leaves, implying that in seedlings the pathogenic transition of the normally endophytic fungus R. collo-cygni does not result from senescence as such, but rather is promoted by factors that result in changes to host reactive oxygen species.
Journal Article•
TL;DR: Sesame phyllody is the most destructive disease in India and among the fungal diseases, Alternaria leaf blights, Phytophthora leaf spot, Cercospora leaf spot Macrophomina root /stem rot, Powdery Mildew, Bacterial leaf spot and Bacterial blight are important diseases of sesame.
Abstract: Sesame phyllody is the most destructive disease in India. Among the fungal diseases, Alternaria leaf blights, Phytophthora leaf spot, Cercospora leaf spot Macrophomina root /stem rot, Powdery Mildew, Bacterial leaf spot and Bacterial blight are important diseases of sesame. The incidence of important diseases varies from state to state based on agro climatic situations. Seed treatment with Thiram (0.2%) +Carbendazim 50WP (0.1%) and foliar spray should be done with Wettable sulphur (0.2%) was most effective to minimize the incidence of powdery mildew. For bacterial diseases Streptocycline (250-300ppm) may be used for seed treatment. Seed treatment with Thiram (0.2%) + Carbendazim 50WP (0.1%) and two foliar sprays of (Mancozeb 2%+ Carbindazim1%) was effective in reducing the Alternaria and Cercospora disease and highest yield. Seed treatment with Imidacloprid (@ 5 ml/kg seed) followed by foliar spray of Thiomethaxam @ 0.2 g/l was found effective in reducing the vector population and phyllody incidence. Seed treatment with Trichoderma viride (5g/kg seed and soil application of T. viride @ 2.5 kg/ha was found effective and economical for the management of Macrophomina root /stem rot of sesame.
TL;DR: The work aimed to identify gene resources suitable for developing new breeding lines of winter barley with improved resistance by evaluating response to natural RLS infection in 19 winter barley cultivars registered in the Czech Republic.
Abstract: The fungus Ramularia collo-cygni is increasingly important as the causal agent of Ramularia leaf spot (RLS), a novel leaf spot disease of barley. The work aimed to identify gene resources suitable for developing new breeding lines of winter barley with improved resistance. During the first experimental period (2001-2005), RLS incidence was monitored in 711 cultivars and advanced breeding lines. Differences were detected in the intensity of symptomatic expression, but no material showed high resistance. During the second experimental period (2006-2009), response to natural RLS infection was evaluated in 19 winter barley cultivars (12 six-row and 7 two-row) registered in the Czech Republic. Highest susceptibility was detected in 6-row cvs. Luran, Laverda and Wendy while cvs Breunskylie (2-row), Merlot and Highlight (both 6-row) showed relatively lower disease incidence. High resistance was not detected. On average, 2-row cultivars showed lower intensity than 6-row cultivars and significant variation was observed among years.
Journal Article•
TL;DR: Results suggest that susceptible maize varieties may give higher yield with the optimisation of the time of application of the fungicides and higher economic and environmental gains can be achieved with judicious use of fungicides.
Abstract: Maize is an important food security crop along with rice and wheat globally. Losses caused by biotic stresses in maize are substantial and Curvularia leaf spot is important among them. Further management of Curvularia leaf spot is done primarily through chemicals, therefore an attempt was made to evaluate the efficacy of com- monly used systemic and non-systemic fungicides against the pathogen, and most susceptible growth stage for disease development was identified. In vitro evaluation of four systemic and four non-systemic fungicides was done at different concentrations, for checking the growth of pathogen. The data revealed that Carboxin (at 25 ppm) completely inhibited growth of pathogen. Further among non-systemic fungicides treatment of Mancozeb showed maximum growth inhibition (98. 24% at 200 ppm). Under glass house conditions mancozeb was found to be more effective than Carboxin for controlling the disease severity. Further to determine the time of application of fungicides, developmental stage most susceptible to Curvularia lunata was studied. Three growth stages (Knee height stage, Silking stage and Tasseling stage) were compared. Maximum disease index and severity was found at Silking stage (47% and 53.75%, respectively) followed by Tasseling stage (42.5% and 18.4%, respectively) and Knee height stage (37% and 30%, respectively), indicating that the disease progresses with the maturity of the plant and is maximum at the Silking stage. Results suggest that susceptible maize varieties may give higher yield with the optimisation of the time of application of the fungicides and higher economic and environmental gains can be achieved with judicious use of fungicides.
TL;DR: A study to characterize the pathotype and virulence variability among 39 P. griseola isolates, ALS pathogen, occurring in Ethiopia revealed the presence of high and diverse pathogenic variability of the pathogen.
Abstract: Angular leaf spot (ALS) caused by the fungus Pseudocercospora griseola is one of the most economically important disease affecting common bean production in Ethiopia. Until now, no information has been generated regarding the pathotype and pathogenic variability and its distribution in Ethiopia. A study was undertaken to characterize the pathotype and virulence variability among 39 P. griseola isolates, ALS pathogen, occurring in Ethiopia. A total of 21 pathotypes (63:63, 63:59, 63:23, 61:51, 56:36, 55:39, 49:7, 48:60, 42:59, 41:10, 34:53, 23:61, 19:33, 17:45, 8:18, 8:0, 4:16, 1:24, 1:10, 16:18. and 4:37) were determined using 12 sets of ALS common bean differentials cultivars. These results revealed the presence of high and diverse pathogenic variability of the pathogen. Among the determined pathotypes 63:59 and 19:33 were the most frequently appeared. And the occurrence of three pathotypes (63:63, 63:59 and 63:23) were confirmed as well as the previous reports in central America and Argentina. This will be the first comprehensive report of P. griseola pathotypes existing in the common bean growing areas of Ethiopia. Except pathotype 8:0 that were compatible with Andean common bean groups, most of the isolates were pathogenic to both Andean and Mesoamerican common bean gene pools. Based on that, the isolates were classified as Mesoamerican origin pathotypes. This specific study provided major information about the pathogenic diversity and determined the pathotype of P. griseola from common bean in Ethiopia.
TL;DR: Based on morphological and phylogenetic analysis, the fungus was shown to be distinct, and is described here as Calonectria fragariae sp.
Abstract: A major problem in the strawberry production chain is the occurrence of fruit rot caused by fungi, thus, accurate identification of the pathogens associated with these rots is important for suitable management of diseases. During an assessment of postharvest diseases of strawberry plants, a rot caused by Calonectria was found. The surface of the infected fruits showed a slight leakage of liquid and the presence of mycelium with clearly defined hyphae containing a mass of conidiophores and conidia. Morphological examination was performed on isolates derived from single germinated conidium cultures, and phylogenetic analyses of four DNA loci (β-tubulin, histone H3, elongation factor and calmodulin) was undertaken. In order to confirm the pathogenicity, strawberry fruits and plants were dipped or sprayed with a conidial suspension. Strawberry fruits showed rot symptoms similar to those initially observed, and the plants developed leaf spot symptoms. The fungus was successfully reisolated from the infected tissues. Based on morphological and phylogenetic analysis, the fungus was shown to be distinct, and is described here as Calonectria fragariae sp. nov. This finding provides additional information for the better understanding of strawberry diseases in Brazil, enabling the development of more effective strategies of management of these diseases.