Showing papers on "Leaf spot published in 2015"
TL;DR: Results suggest that Si-mediated increase of host defense responses to fungal pathogens in perennial ryegrass has a great potential to be part of an effective integrated disease management strategy against gray leaf spot development.
Abstract: Sustainable integrated disease management for gray leaf spot of perennial ryegrass may involve use of plant defense elicitors with compatible traditional fungicides to reduce disease incidence and severity. Silicon (Si) has previously been identified as a potential inducer or modulator of plant defenses against different fungal pathogens. To this end, perennial ryegrass was inoculated with the causal agent of gray leaf spot, Magnaporthe oryzae, when grown in soil that was nonamended or amended with three different levels of calcium silicate (1, 5, or 10 metric tons [t]/ha). When applied at a rate of 5 t/ha, calcium silicate was found to significantly suppress gray leaf spot in perennial ryegrass, including a significant reduction of disease incidence (39.5%) and disease severity (47.3%). Additional studies observed nonpenetrated papillae or cell-wall appositions harboring callose, phenolic autofluorogens, and lignin-associated polyphenolic compounds in grass grown in the Si-amended soil. Regarding defense...
88 citations
TL;DR: Plants of both cultivars maintained relatively high photosynthetic rates, water-use efficiency, increased growth and yield under elevated [CO2], and the fungal community associated with mycotoxins was not affected by the treatments.
Abstract: Despite the importance of coffee as a globally traded commodity and increasing concerns about risks associated with climate change, there is virtually no information about the effects of rising atmospheric [CO2] on field-grown coffee trees. This study shows the results of the first 2 years of an innovative experiment. Two commercial coffee cultivars (Catuai and Obata) were grown using the first free-air CO2 enrichment (FACE) facility in Latin America (ClimapestFACE). Plants of both cultivars maintained relatively high photosynthetic rates, water-use efficiency, increased growth and yield under elevated [CO2]. Harvestable crop yields increased 14.6 % for Catuai and 12.0 % for Obata. Leaf N content was lower in Obata (5.2 %) grown under elevated [CO2] than under ambient [CO2]; N content was unresponsive to elevated [CO2] in Catuai. Under elevated [CO2] reduced incidence of leaf miners (Leucoptera coffeella) occurred on both coffee cultivars during periods of high infestation. The percentage of leaves with parasitized and predated mines increased when leaf miner infestation was high, but there was no effect of elevated [CO2] on the incidence of natural enemies. The incidence of rust (Hemileia vastatrix) and Cercospora leaf spot (Cercospora coffeicola) was low during the trial, with maximum values of 5.8 and 1 %, respectively, and there was no significant effect of [CO2] treatments on disease incidence. The fungal community associated with mycotoxins was not affected by the treatments.
79 citations
TL;DR: A rich diversity of Cercospora species in northern Iran was revealed and twenty species were identified based on sequence data of five genomic loci, host, cultural and morphological data, and the Consolidated Species Concept was applied.
Abstract: The genus Cercospora includes many important plant pathogenic fungi associated with leaf spot diseases on a wide range of hosts. The mainland of Iran covers various climatic regions with a great biodiversity of vascular plants, and a correspondingly high diversity of cercosporoid fungi. However, most of the cercosporoid species found to date have been identified on the basis of morphological characteristics and there are no cultures that support these identifications. In this study the Consolidated Species Concept was applied to differentiate Cercospora species collected from Iran. A total of 161 Cercospora isolates recovered from 74 host species in northern Iran were studied by molecular phylogenetic analysis. Our results revealed a rich diversity of Cercospora species in northern Iran. Twenty species were identified based on sequence data of five genomic loci (ITS, TEF1-α, actin, calmodulin and histone H3), host, cultural and morphological data. Six novel species, viz. C. convolvulicola, C. conyzae-canadensis, C. cylindracea, C. iranica, C. pseudochenopodii and C. sorghicola, are introduced. The most common taxon was Cercospora cf. flagellaris, which remains an unresolved species complex with a wide host range. New hosts were recorded for previously known Cercospora species, including C. apii, C. armoraciae, C. beticola, C. cf. richardiicola, C. rumicis, Cercospora sp. G and C. zebrina.
59 citations
TL;DR: A fine-mapping approach of a major quantitative trait locus (QTL) ALS4.1GS, UC for ALS resistance in a mapping population derived from the resistant genotype G5686 and the susceptible cultivar Sprite was reported on.
Abstract: Key message
A major QTL for angular leaf spot resistance in the common bean accession G5686 was fine-mapped to a region containing 36 candidate genes. Markers have been developed for marker-assisted selection.
58 citations
DOI•
30 Dec 2015
TL;DR: In this paper, a literature review was carried out to explore major maize diseases and their management in Nepal, and the major and economically important maize diseases reported are Gray leaf spot, Northern leaf blight, Southern leaf Blight, Banded leaf and sheath blight, Ear rot, Stalk rot, Head smut, Common rust, Downy mildew and Brown spot.
Abstract: In Nepal, maize ranks second after rice both in area and production. In recent years, maize area and production has shown a steady increase, but productivity has been low (2.46 t/ha). The major maize producing regions in Nepal are mid hill (72.85%), terai (17.36%) and high hill (9.79%) respectively. A literature review was carried out to explore major maize diseases and their management in Nepal. The omnipresent incidence of diseases at the pre harvest stage has been an important bottleneck in increasing production. Till now, a total of 78 (75 fungal and 3 bacterial) species are pathogenic to maize crop in Nepal. The major and economically important maize diseases reported are Gray leaf spot, Northern leaf blight, Southern leaf Blight, Banded leaf and sheath blight, Ear rot, Stalk rot, Head smut, Common rust, Downy mildew and Brown spot. Information on bacterial and virus diseases, nematodes and yield loss assessment is also given. Description of the major maize diseases, their causal organisms, distribution, time and intensity of disease incidence, symptoms, survival, spreads, environmental factors for disease development, yield losses and various disease management strategies corresponded to important maize diseases of Nepal are gathered and compiled thoroughly from the available publications. Concerted efforts of NARC commodity programs, divisions, ARS and RARS involving research on maize pathology and their important outcomes are mentioned. The use of disease management methods focused on host resistance has also been highlighted.Journal of Maize Research and Development (2015) 1(1):28-52DOI: http://dx.doi.org/10.5281/zenodo.34292
40 citations
TL;DR: It is demonstrated, for the first time, that photosynthesis in the leaves of maize plants is dramatically affected during the infection process of S. macrospora, and impacts are primarily associated with limitations of a diffusive and biochemical nature.
Abstract: This study investigated the effect of macrospora leaf spot (MLS), caused by Stenocarpella macrospora, on photosynthetic gas exchange parameters and chlorophyll a fluorescence parameters determined in leaves of plants from two maize cultivars ('ECVSCS155' and 'HIB 32R48H') susceptible and highly susceptible, respectively, to S. macrospora. MLS severity was significantly lower in the leaves of plants from ECVSCS155 relative to the leaves of plants from HIB 32R48H. In both cultivars, net CO2 assimilation rate, stomatal conductance, and transpiration rate significantly decreased, while the internal to ambient CO2 concentration ratio increased in inoculated plants relative to noninoculated plants. The initial fluorescence and nonphotochemical quenching significantly increased in inoculated plants of ECVSCS155 and HIB 32R48H, respectively, relative to noninoculated plants. The maximum fluorescence, maximum PSII quantum efficiency, coefficient for photochemical quenching, and electron transport rate significantly decreased in inoculated plants relative to noninoculated plants. For both cultivars, concentrations of total chlorophyll (Chl) (a+b) and carotenoids and the Chl a/b ratio significantly decreased in inoculated plants relative to noninoculated plants. In conclusion, the results from the present study demonstrate, for the first time, that photosynthesis in the leaves of maize plants is dramatically affected during the infection process of S. macrospora, and impacts are primarily associated with limitations of a diffusive and biochemical nature.
34 citations
TL;DR: Results suggest susceptibility to disease and prevailing environment are important drivers of observed differences and yield increases as a result of the physiological benefits of plant health benefits under low disease were not consistent.
Abstract: Foliar fungicide use in the U.S. Corn Belt increased in the last decade; however, questions persist pertaining to its value and sustainability. Multistate field trials were established from 2010 to 2012 in Illinois, Iowa, Ohio, and Wisconsin to examine how hybrid and foliar fungicide influenced disease intensity and yield. The experimental design was in a split-split plot with main plots consisting of hybrids varying in resistance to gray leaf spot (caused by Cercospora zeae-maydis) and northern corn leaf blight (caused by Setosphaera turcica), subplots corresponding to four application timings of the fungicide pyraclostrobin, and sub-subplots represented by inoculations with either C. zeae-maydis, S. turcica, or both at two vegetative growth stages. Fungicide application (VT/R1) significantly reduced total disease severity relative to the control in five of eight site-years (P < 0.05). Disease was reduced by approximately 30% at Wisconsin in 2011, 20% at Illinois in 2010, 29% at Iowa in 2010, and 32 and ...
27 citations
TL;DR: This paper presents the results of a two-year study of mycology and Plant Pathology at the undergraduate and post-graduate levels at Banaras Hindu University, Varanasi on the basis of a probabilistic method called “ Crimean-Celtic method”.
Abstract: Ramesh Chand*, Chhattar Pal, Vineeta Singh, Manoj Kumar, Vinay Kumar Singh and Pallem Chowdappa Department of Mycology and Plant Pathology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221 005, India Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 005, India Centre for Bioinformatics, School of Biotechnology, Banaras Hindu University, Varanasi 221 005, India ICAR-Central Plantation Crops Research Institute, Kudlu, P.O. Kasargod 671 124, India
26 citations
TL;DR: Evaluated fungal resistance under field conditions of 43 wild accessions and three interspecific hybrids of the genus Arachis, as well as six A. hypogaea genotypes to find accessions with as good as or better resistance than A. Hypogaea.
Abstract: Peanut, Arachis hypogaea L., is a protein-rich species consumed worldwide. A key improvement to peanut culture involves the development of cultivars that resist fungal diseases such as rust, leaf spot and scab. Over three years, we evaluated fungal resistance under field conditions of 43 wild accessions and three interspecific hybrids of the genus Arachis, as well as six A. hypogaea genotypes. In the first year, we evaluated resistance to early and late leaf spot, rust and scab. In the second and third years, we evaluated the 18 wild species with the best resistance scores and control cultivar IAC Caiapo for resistance to leaf spot and rust. All wild accessions displayed greater resistance than A. hypogaea but differed in their degree of resistance, even within the same species. We found accessions with as good as or better resistance than A. cardenasii, including: A. stenosperma (V15076 and Sv 3712), A. kuhlmannii (V 6413), A. kempff-mercadoi (V 13250), A. hoehnei (KG 30006), and A. helodes (V 6325). Amphidiploids and hybrids of A. hypogaea behaved similarly to wild species. An additional four accessions deserve further evaluation: A. magna (V 13751 and KG 30097) and A. gregoryi (V 14767 and V 14957). Although they did not display as strong resistance as the accessions cited above, they belong to the B genome type that is crucial to resistance gene introgression and pyramidization in A. hypogaea.
26 citations
TL;DR: Xanthomonad-like isolates were obtained from affected weed leaf samples and each was able to artificially infect and cause symptoms on the three weed species and tomato plants.
Abstract: Plants of Nicandra physaloides, Solanum americanum and Euphorbia heterophylla with leaf lesions have been found naturally grown among tomato plants in commercial fields in Brazil. Tomato bacterial spot was occurring in these fields. Xanthomonad-like isolates were obtained from affected weed leaf samples. These isolates were species identified using BOX-PCR and specific primers. Isolates from N. physaloides and S. americanum were identified as Xanthomonas perforans and that of E. heterophylla were identified as X. gardneri. Each of them was able to artificially infect and cause symptoms on the three weed species and tomato plants.
23 citations
Journal Article•
TL;DR: Under in vitro conditions, all the four species of Trichoderma (10 isolates) proved 100% potential inhibition against rice blast pathogen Pyracularia oryzae.
Abstract: Different isolates of Trichoderma were isolated from soil samples which were collected from different part of India. These isolates were grouped into four Trichoderma species viz., Trichoderma asperellum (Ta), T. harzianum (Th), T. pseudokoningii (Tp) and T. longibrachiatum (Tl) based on their morphological characters. Identification of the above isolates was also confirmed through ITS region analysis. These Trichoderma isolates were tested for in vitro biological control of Alternaria solani, Bipolaris oryzae, Pyricularia oryzae and Sclerotinia scierotiorum which cause serious diseases like early blight (target spot) of tomato and potato, brown leaf spot disease in rice, rice blast disease, and white mold disease in different plants. Under in vitro conditions, all the four species of Trichoderma (10 isolates) proved 100% potential inhibition against rice blast pathogen Pyracularia oryzae. T. harzianum (Th-01) and T. asperellum (Ta-10) were effective with 86.6% and 97.7%, growth inhibition of B. oryzae, respectively. Among others, T. pseudokoningii (Tp-08) and T. Iongibrachiatum (Tl-09) species were particularly efficient in inhibiting growth of S. sclerotiorum by 97.8% and 93.3%. T. Iongibrachiatum (TI-06 and TI-07) inhibited maximum mycelial growth of A. solani by 87.6% and 84.75. However, all the T. harzianum isolates showed significantly higher inhibition against S. sclerotiorum (CD value 9.430), causing white mold disease. This study led to the selection of potential Trichoderma isolates against rice blast, early blight, brown leaf spot in rice and white mold disease in different crops.
TL;DR: MAX can be used to analyze the composition and distribution of nutrients in plant tissues and, if associated with mineral nutrition, it may help understand host-pathogen relationships and plant disease management.
Abstract: Knowing the structure and distribution of nutrients in plant tissues can clarify some mechanisms of pathogen attack in plants and plant defense against infection, thus helping management strategies. The aim of this study was verify differences in distribution of mineral nutrients in coffee leaf tissues around foliar lesions of bacterial blight of coffee, blister spot, cercospora leaf, phoma leaf spot and coffee leaf rust. Fragments of leaf tissue surrounding the lesions were dehydrated in silica gel, carbon covered and subjected to X-ray microanalysis (MAX). Thirty-three chemical elements were detected in leaf tissue; however, there was variation in potassium and calcium contents surrounding the lesions. The highest potassium content was found in asymptomatic tissues surrounding the lesions, decreasing toward the transition zone and reaching minimum content in symptomatic tissues. The highest calcium content was found in symptomatic tissues, decreasing toward the transition zone and reaching minimum content in asymptomatic tissues. Therefore, MAX can be used to analyze the composition and distribution of nutrients in plant tissues and, if associated with mineral nutrition, it may help understand host-pathogen relationships and plant disease management.
TL;DR: Climate room trials with isolates obtained from infested sugar beet leaves showed that Stemphylium sp.
Abstract: During the summer of 2007, a distinctive type of yellow leaf spot was observed for the first time in sugar beet (Beta vulgaris L.) in the Netherlands. In the following years a rapid spread over all regions of the Netherlands was reported. The infestation appears in June-August on the leaves of sugar beet and starts with small, irregular, yellow spots. Subsequently the yellow spots become necrotic from the centre of the lesion outward, with the tissue becoming brown (or brownish). The spots spread over the leaves and infest all the leaves of the plant. Due to the loss of leaves the size of the canopy declines and yield loss occurs. Research was conducted to identify the causal agent. Climate room trials with isolates obtained from infested sugar beet leaves showed that Stemphylium sp. was able to infest leaves of healthy growing sugar beet plants with brown spots, similar to the necrotic spots seen in the field. From the leaf spots in the climate room trials, Stemphylium sp. was re-isolated, according to Koch’s postulates. Thus, it was confirmed that this Stemphylium sp. is a primary pathogen for sugar beet. In field trials of fungicide efficacy a sugar yield loss of up to 42 % (a financial yield loss of 51 %) was found. Field trials show that it is hard to control this Stemphylium sp. with the fungicides registered for sugar beet in the Netherlands and efficacy of control of Stemphylium sp. differs between fungicides with active ingredients belonging to the same chemical class. In addition to sugar beet, potato (Solanum tuberosum L.), white mustard (Sinapsis alba L.), red beet (Beta vulgaris L.), spinach (Spinacia oleracea L.) and fat hen (Chenopodium album L.) were identified as hosts in an assay of plants grown and inoculated in climate rooms.
TL;DR: The effects of Bacillus subtilis, Aspergillus awamori and Pseudomonas fluorescens on the wilt–leaf spot disease complex of tomato caused by Meloidogyne javanica, Ralstonia solanacearum and Xanthomonas campestris pv were observed.
Abstract: The effects of Bacillus subtilis, Aspergillus awamori and Pseudomonas fluorescens on the wilt–leaf spot disease complex of tomato caused by Meloidogyne javanica, Ralstonia solanacearum and Xanthomonas campestris pv. vesicatoria were observed. Inoculation of B. subtilis, A. awamori and P. fluorescens caused a significant increase in plant growth and chlorophyll contents of pathogen-inoculated plants. Inoculation of P. fluorescens caused a greater increase in plant growth and chlorophyll contents of pathogen-inoculated plants than that caused by A. awamori. Application of P. fluorescens with B. subtilis caused a greater increase in plant growth and chlorophyll contents of pathogen-inoculated plants, but the maximum increase was observed when all the three biocontrol agents were inoculated together. P. fluorescens colonized tomato roots more than colonization by B. subtilis. Root colonization by P. fluorescens and B. subtilis was reduced when pathogens were inoculated with rhizobacteria. Inoculation of P. fluorescens caused a greater reduction in galling and nematode reproduction, followed by B. subtilis and A. awamori. Maximum reduction in galling, nematode reproduction, wilt and leaf spot disease indices was observed when all three biocontrol agents were used together.
TL;DR: The morphology of the algae were examined and found to consistently match the species Cephaleuros virescens, which was found to be the causal organism of a leaf spot disease on Para rubber.
Abstract: In this study Cephaleuros virescens was found to be the causal organism of a leaf spot disease on Para rubber (Hevea brasiliensis). The algae caused circular orange to dark brown lesions on both leaf surfaces. The morphology of the algae (thallus, filamentous cells, sporangiophore, sporangia, gametangia and zoospore) were examined and found to con- sistently match the species Cephaleuros virescens.
TL;DR: Cordana leaf spot of banana is shown to be associated with several species of a new genus described here as Neocordana gen. nov, which belongs to Pyriculariaceae rather than Cordanaceae where the type species of Cordana, C. pauciseptata resides.
Abstract: Cordana leaf spot of banana is shown to be associated with several species of a new genus described here as Neocordana gen. nov. Furthermore, Neocordana belongs to Pyriculariaceae (Magnaporthales) rather than Cordanaceae where the type species of Cordana, C. pauciseptata resides. Neocordana is established to accommodate Cordana musae, C. johnstonii, C. versicolor, and a previously undescribed species, N. musicola, which is morphologically and phylogenetically distinct. Neocordana species are found to be associated with leaves of Musa spp. (Musaceae) and Canna denudata (Cannaceae). Based on these results, Cordanaceae is best recognized in a separate order, established here as Cordanales ord. nov.
TL;DR: Based on the pathogenicity test accompanied by completion of Koch's postulates, sequence analysis, and bacteriological tests, the strains were identified as P. coriandricola ICMP12471 deposited in the Plant Associated and Environmental Microbes Database ( http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl ).
Abstract: During the spring of 2014, a severe leaf spot disease was observed on carrot (Daucus carota), parsley (Petroselinum crispum), and parsnip (Pastinaca sativa) on a 0.5-ha vegetable farm in Vojvodina Province, Serbia. The disease appeared under wet and cool conditions with 5 to 25% of plants infected for each of the three crops. Symptoms were characterized as brown angular leaf spots, ~2 mm in diameter, often limited by veins. Collected symptomatic leaves were rinsed and dried at room temperature, and leaf sections taken from the margin of necrotic tissue were macerated in sterile phosphate buffer and streaked onto nutrient agar with 5% (w/v) sucrose (NAS). After isolation, whitish, circular, dome-shaped, Levan-positive colonies consistently formed. Five strains from each host (carrot, parsley, and parsnip) were used for further study. Strains were gram-negative, aerobic, and positive for catalase and tobacco hypersensitive reaction but negative for oxidase, rot of potato slices, and arginine dihydrolase. These reactions corresponded to LOPAT group Ia, which includes Pseudomonas syringae pathovars (3). Repetitive extragenic palindromic sequence (Rep)-PCR fingerprint profiles using the REP, ERIC, and BOX primers (4) were identical for all strains. Sequence typing of the housekeeping genes gyrB and rpoD (1) was performed for three representative strains (one from each host). Sequences were deposited in the NCBI GenBank database as accessions KM979434 to KM979436 (strains from carrot, parsnip, and parsley, respectively) for the gyrB gene and KM979437 to KM979439 (strains from parsnip, parsley and carrot, respectively) for the rpoD gene. Sequences were compared with pathotype strain Pseudomonas syringae pv. coriandricola ICMP12471 deposited in the Plant Associated and Environmental Microbes Database ( http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl ). BLAST analysis revealed 100% homology for gyrB and 99% homology for rpoD. Pathogenicity was tested with five representative strains from each host on four-week-old plants of carrot (cv. Nantes), parsley (cv. NS Molski), and parsnip (cv. Dugi beli glatki) using two methods: spraying the bacterial suspension (108 CFU ml-1) on the leaves until runoff (5) and injecting the bacterial suspension into leaves with a hypodermic syringe (2). Four plants were used per strain and method. Sterile distilled water was applied as a negative control treatment for each plant species. All plants were kept in a mist room with 100% humidity for 4 h, then transferred to a greenhouse at 25°C and 80% relative humidity and examined for symptom development over a period of three weeks. For all strains, inoculated leaves first developed water-soaked lesions on the leaves 5 to 7 days after inoculation (DAI); 14 DAI lesions became dark brown, often surrounded by haloes. No symptoms were observed on control plants inoculated with sterile distilled water. For fulfillment of Koch's postulates, re-isolations were done onto NAS. Re-isolated bacteria were obtained from each inoculated host and confirmed to be identical to the original isolates using the LOPAT tests and Rep-PCR fingerprinting profiles. Based on the pathogenicity test accompanied by completion of Koch's postulates, sequence analysis, and bacteriological tests, the strains were identified as P. s. pv. coriandricola. To our knowledge, this is the first report of bacterial leaf spot of carrot, parsley, and parsnip in Serbia. It may present a threat to production due to quality requirements for fresh market. References: (1) P. Ferrente and M. Scortichini. Plant Pathol. 59:954, 2010. (2) M. Gupta et al. Plant Dis. 97:418, 2013. (3) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (4) F. J. Louws et al. Appl. Environ. Microb. 60:2286, 1994. (5) X. Xu and S. A. Miller. Plant Dis. 97:988, 2013.
TL;DR: During summer-autumn 2014, extensive necroses were observed on Salvia leucantha plants growing in a private garden near Biella (northern Italy, ca 45°39’N 8°00’E) and the fungus was consistently isolated on potato dextrose agar (PDA), consistent with Alternaria sp.
Abstract: During summer-autumn 2014, extensive necroses were observed on Salvia leucantha plants growing in a private garden near Biella (northern Italy, ca 45°39’N 8°00’E). A high proportion (70%) of about 100 plants was diseased. Pale-brown, small, irregular lesions were present on the leaves, which were followed by extensive chlorosis and, eventually, leaf drop. A fungus was consistently isolated on potato dextrose agar (PDA) which on potato carrot agar (PCA), produced a greenish mycelium, with brown, septate, ovoid or obclavate conidia with both transverse and longitudinal septa and a prominent tapered beak, measuring 14.3- 42.3×5.4-12.6 μm (average: 22.8×9.1 μm). These morphometric traits were consistent with those of Alternaria sp. (Simmons, 2007). DNA was extracted using the Nucleospin plant kit (Macherey Nagel, Germany) and PCR carried out using ITS1/ITS4 primers. A 483 bp PCR product was amplified and sequenced (GenBank accession No KP280314) and a BLASTn search (Altschul et al., 1997) confirmed that the sequence corresponded to Alternaria sp. In pathogenicity tests, leaves of three healthy plants of S. leucantha were inoculated by spraying with a spore and mycelium suspension (1×105 CFU/ml) of the fungus grown on PDA. Plants inoculated only with sterile PDA fragments suspended in water served as control. Inoculated plants were covered with plastic bags and maintained at 18 to 25°C. At about six days post inoculation lesions developed only on inoculated leaves and Alternaria sp. was consistently reisolated. This is the first report of Alternaria sp. on S. leucantha in Italy as well as in the world.
01 Feb 2015
TL;DR: The systemic dispersal of the bacteria in strawberry plants was investigated and X. fragariae could be found in all tissues tested including the inoculated leaf, its petiole, the rhizome, the heart bud up to the youngest fully expanded leaf and itspetiole and the systemic spread was also detectable in partially resistant genotypes.
Abstract: The angular leaf spot disease caused by Xanthomonas fragariae is an important plant disease with major impact for the strawberry nursery industry. Currently there is no plant protection product available for controlling the disease effectively. Planting of resistant cultivars seems to be promising, but all commercially used cultivars are susceptible and no donor with a high level of resistance has yet been found. Therefore, a total of 145 genotypes from the Fruit Genebank Dresden (Germany) were evaluated for resistance to X. fragariae by artificial inoculation. Six genotypes were classified as partly resistant, out of which only two (US4808 and US4809) are octoploid. Fragaria vesca f. alba, Fragaria nilgerrensis ‘Yunnan’, F. vesca ‘Illa Martin’ and F. moschata ‘Bauwens’ were also classified as partially resistant, but they are only of limited use for breeding because of their variable ploidy level. Fully resistant genotypes could not be detected. The systemic dispersal of the bacteria in strawberry plants was investigated after inoculation of leaves with X. fragariae strain XF3.9.C and the GFP-tagged strain XF3.9.C(pKAN). The systemic spread was evaluated after 3, 7, 14 and 28 days post-inoculation (dpi) by nested PCR and fluorescence microscopy. After 3 dpi, X. fragariae could be found in all tissues tested including the inoculated leaf, its petiole, the rhizome, the heart bud up to the youngest fully expanded leaf and its petiole. The systemic spread was also detectable in partially resistant genotypes.
TL;DR: The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae, and Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees with maximum and minimum temperatures of 33 and 26°C.
Abstract: In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming gray...
TL;DR: During 2010–2011, a severe leaf spot disease of sweet potato was found in Haikou City, Hainan province of China and the fungal species was identified as Stemphylium solani Weber, and its pathogenicity was confirmed by Koch's postulates.
Abstract: During 2010–2011, a severe leaf spot disease of sweet potato (Ipomoea batatas) was found in Haikou City, Hainan province of China. The disease is characterized with large, irregular, brown, necrotic lesions on the margin or in the centre of leaves. A species of Stemphylium was consistently recovered from pieces of symptomatic tissues on PDA. Based on morphological characteristics and molecular identification by rDNA-ITS gene analysis, the fungal species was identified as Stemphylium solani Weber, and its pathogenicity was confirmed by Koch's postulates. This is the first report of leaf spot on sweet potato caused by S. solani in China.
TL;DR: Soil infestation with sclerotia resulted in wilting and crown rot symptoms with 90% disease and 100% leaf spot incidence and no such symptoms were observed on control plants and the identity was confirmed through morphological and cultural characteristics.
Abstract: Common bean (Phaseolus vulgaris L.) is an economically important crop grown worldwide. In India, it is grown for both green bean and dry pods (seeds). During 2012-2014, sudden wilt and leaf spots were observed during early growth to preflowering stage in the Mysore and Mandya districts of Karnataka State. The disease incidence was 30 to 35% in nearly 45 to 48 ha. Symptoms include wilting of foliage, tan lesions on stems at ground level, and gradually drying of the whole plant. Leaf spot symptoms on 30- to 45-day-old plants were water-soaked lesions with concentric necrotic spots (5 to 12 mm). White mycelial strands with spherical dark brown sclerotial bodies at the stem-soil interface were observed. Infected tissues were disinfected with 2% sodium hypochlorite solution for 3 min, and plated on potato dextrose agar and incubated at 28 ± 2°C. A single associated fungal pathogen was consistently isolated. It was characterized by dense, aerial, whitish cottony mycelium. Uniformly globoid sclerotia were observed after 10 to 12 days of incubation. Whitish sclerotia (1 to 3 mm) turned to dark brown at maturation. Based on etiology, and morphological and cultural characteristics, the pathogen was identified as Sclerotium rolfsii Sacc. (syn. Athelia rolfsii (Curzi) Tu & Kimbrough) (Mordue, 1974). Identity was further confirmed through PCR amplification of internally transcribed spacer (ITS) region using ITS1/ITS4 universal primer. Amplified PCR product (550 to 570 bp) was sequenced and BLASTn search comparison revealed 99% homology to Sclerotium rolfsii (GenBank Accession Nos. DQ093668 and JX914480). Representative sequence of S. rolfsii was deposited in GenBank as KP412468.1 and KP412469.1. Pathogenicity tests were conducted on 15-day-old common bean plants (cv. S-9) by soil infestation and foliar inoculation of sclerotial bodies obtained from a 12-day-old culture of S. rolfsii. The experiment was conducted on 30 plants along with control plants. Soil infestation with sclerotia resulted in wilting and crown rot symptoms with 90% disease and 100% leaf spot incidence and no such symptoms were observed on control plants. The fungal pathogen was reisolated from inoculated plants and the identity was confirmed through morphological and cultural characteristics. Southern blight and leaf spot diseases of common bean are a major constraint for its production in India. To our knowledge, this is the first report on the occurrence of S. rolfsii causing southern blight and leaf spot of common bean in India.
DOI•
30 Dec 2015TL;DR: The development of gray leaf spot tolerant populations through tolerance breeding principle is an economical and sustainable approach to manage the disease.
Abstract: Biotic and biotic constraints are yield limiting factors in maize producing regions. Among these gray leaf spot is a yield limiting foliar disease of maize in high land regions of Asia. This review is done from related different national and international journals, thesis, books, research papers etc. The objectives of this review are to become familiar with genetics and inheritance, epidemiology, symptoms and disease management strategies etc. High relative humidity, temperature, minimum tillage and maize monoculture are important factors responsible for disease development. The sibling species of Cercospora zeae-maydis (Tehon and Daniels, 1925) Group I and Group II and Cercospora sorghai var. maydis (Chupp, 1954) are associated with this disease. Pathogens colonize in maize debris. Conidia are the source of inoculums for disease spread. Severe blighting of leaves reduces sugars, stalk lodging and causes premature death of plants resulting in yield losses of up to 100%. Disease management through cultural practices is provisional. The use of fungicides for emergencies is effective however; their prohibitive cost and detrimental effects on the environment are negative consequences. The inheritance of tolerance is quantitative with small additive effects. The introgression of resistant genes among the crosses of resistant germplasm enhances the resistance. The crosses of resistant and susceptible germplasm possess greater stability than the crosses of susceptible and resistant germplasm. The development of gray leaf spot tolerant populations through tolerance breeding principle is an economical and sustainable approach to manage the disease. Journal of Maize Research and Development (2015) 1(1):71-85 DOI: http://dx.doi.org/10.5281/zenodo.34286
TL;DR: Several potential biological control agents as well as a commercial biocontrol product were applied to apple plants and compared with mancozeb for control of GLS on leaves and fruit and showed no effect on GLS in leaves and fruits.
TL;DR: A draft genome sequence of C. arachidicola, causal agent of early leaf spot, is reported for the first time, to help understand the role that potentially diverse genotypes may have in peanut breeding programs.
Abstract: Cercospora arachidicola, causal agent of early leaf spot, is an economically important peanut pathogen. Lack of genetic information about this fungus prevents understanding the role that potentially diverse genotypes may have in peanut breeding programs. Here, we report for the first time a draft genome sequence of C. arachidicola.
TL;DR: Considering the difficulty in reaching a complete disease management level against P. cucumerina, an integrated approach should be considered, and the most effective treatment in terms of disease severity reduction did not always provide a better response in plant biomass.
TL;DR: According to the literature, this is the first report of leaf spot disease on A. vera caused by Curvularia lunata from Madhya Pradesh, and the first reported of Curvularityia ovoidea from India.
Abstract: Avasthi S, GautamAK, Bhadauria R. 2015. Occurrence of leaf spot diseases on Aloe vera (L.) Burm.f. caused by Curvulariaspecies from Madhya Pradesh, India. Biodiversitas 16: 79-83. During 2010-2011, occurrence of leaf spot diseases was observed on Aloevera plants grown in various nurseries of Gwalior, Madhya Pradesh, India. The typical disease symptoms were observed on the abaxialsurface, tips and spiny margins of leaves. Disease spots were sunken, dry, necrotic, dark maroon to dark brown in color. On the basis ofmorphological and microscopic characteristics of the fungus, two species of Curvularia i.e. Curvularia lunata and Curvularia ovoidea,were found to be associated with the leaf spot diseases. Koch’s postulate was applied to confirm the causal organisms of the diseases.According to the literature, this is the first report of leaf spot disease on A. vera caused by Curvularia lunata from Madhya Pradesh, andthe first report of Curvularia ovoidea from India.Key words: Aloe vera, Curvularia lunata, Curvularia ovoidea, leaf spot, India