Severe leaf spot disease was observed on Aloe vera plants in the winters of 2011 and 2012 during a survey of various nurseries of Gwalior, India. Irregular, sunken, dark creamish brown spots having reddish brown margin were noticed on both surfaces of the leaves. The causal organism was consistently isolated from symptomatic leaves on potato dextrose agar media (PDA). A total 59 isolates of fungi were recovered from diseased A. vera leaves, and 37 isolates were identified as belonging to the genus Fusarium. On the basis of morphological characteristics and internal transcribed spacer (ITS) region of rDNA amplified using the primers ITS4/ITS5 the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg and pathogenicity of the isolate was confirmed by using Koch’s postulates. To the best of our knowledge, this is the first report of leaf spot disease caused by Fusarium proliferatum on A. vera plants in India.
In order to compare the pathogenicity of different Tembusu virus (TMUV) strains from geese, ducks and chickens, 56 5-day-old Cherry Valley ducklings which were divided into 7 groups and infected intramuscularly with 7´105 PFU/ml per duck of six challenge virus stocks. The clinical signs, weight gain, mortality, macroscopic and microscopic lesions, virus loads in sera of 1, 3, 5, 7, 11 and 14 dpi and serum antibody titers were examined. The results showed that these viruses could make the young ducks sick, but the clinical signs differed with the different species-original strains. All the experimental groups lose markedly in weight gain compared to the control, but there were no obvious distinctions in weight gains, as well as macroscopic and microscopic lesions of dead ducks between the infected groups. However, the groups of waterfowl-derived strains (from geese and ducks) showed more serious clinical signs and higher relative expressions of virus loads in sera than those from chicken-derived. The mortality of waterfowl groups was 37.5%, and the greatest mortality of chicken groups was 12.5%. The serum antibodies of the geese-species group JS804 appeared earlier and were higher in the titers than others. Taken toghter, the pathogenicity of waterfowl-derived TMUV was more serious than chicken-derived TMUV and JS804 could be chosen as one TMUV vaccine strain to protect from the infection.
Ash dieback, caused by Hymenoscyphus fraxineus, is a serious disease of common and narrow-leaved ash in Europe. The resistance of individual trees seems to be important for the maintenance of ash in European forests. In this in situ wound inoculation study, the susceptibility and differences in resistance to H. fraxineus between Fraxinus excelsior and F. angustifolia clones were assessed. Neither of the tested clones revealed total resistance to ash dieback; variety between the tested clones was observed. Differences in necroses lengths were significant between clones and between two ash species. Longer necroses were formed in F. angustifolia than in F. excelsior. Some clones exhibiting some resistance to the pathogen were identified.
Potato leaf blight disease caused by Ulocladium atrum (Syn. Stemphylium atrum) is an important and epidemic disease in potato-growing regions of Iran. In this study, 30 isolates of the disease were collected from the main potato-growing regions of Iran and were analyzed on the basis of morphological characterization and pathogenicity. Based on morphological characteristics, all isolates were identified as U. atrum. Pathogenicity studies indicated that all 30 isolates were pathogenic on potato “Agria” to varying degrees. Five U. atrum isolates causing potato leaf blight disease, obtained from the Plant Pathology Laboratory, Isfahan Research Center for Agriculture and Natural Resources, Isfahan, Iran, were also examined in this study. A total of 35 isolates were genetically analyzed using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers. Cluster analysis using the un-weighted pair group method with the arithmetic average (UPGMA) method for RAPD marker revealed no clear grouping of the isolates obtained from different geographical regions. The groupings, based on morphological characteristics, virulence variability and RAPD analysis, were not correlated. Cluster analysis using Jaccard’s coefficient for ISSR divided the U. atrum isolates into four main groups, in which there was no significant correlation between the isolate groupings regarding their geographic location and pathogenicity. Using molecular techniques genetic variability was detected among the accessions, with cophenetic correlation coefficients (CCC) of 0.80 for RAPDs and 0.89 for ISSRs. The RAPD and ISSR marker results corresponded well, with a correlation of 0.55.
Duck viral hepatitis (DVH) is an acute and fatal disease of young ducklings characterized by rapid transmission and damages. The most important agent of DVH is duck hepatitis virus 1 (DHV-1). The effective control of DVH was achieved by active immunization of 1-day-old duck- lings with an attenuated DHV-1 virus vaccine. However, the attenuated virus might reverse to virulence. In this study, a DHV-1 strain, Du/CH/LBJ/090809, was identified and its genomic se- quences were determined. The genome of Du/CH/LBJ/090809 is composed of 7,692 nt excluding poly A and the virus was clustered into genotype A by comparing with other referenced DHV-1 strains. Du/CH/LBJ/090809 could lead to 30% mortality of 10-day-old specific pathogen free (SPF) ducklings. The virus was passaged serially in SPF chicken embryonated eggs and three vi- ruses, passage 16 (P16), P29 and P40, were selected for genomic analysis. P29 and P40 were used to evaluate the attenuation in duckling by inoculating the virus to 10-day-old SPF ducklings. Re- sults of vaccination-challenge assay showed that the inactivated virus P40 could evoke protection against the pathogenic parent virus. Nucleotide and amino acid sequences of the genomes of Du/ CH/LBJ/090809, P16, P29 and P40 were compared. Changes both in nucleotides and amino acids, which might be contributed to the decreasing in virulence by chicken embryo-passaging of DHV- 1, were observed. We speculated that these changes might be important in the adaption and at- tenuation of the virulent virus. Additionally, strains obtained in this study will provide potential candidate in the development of vaccines against DHV-1.
Hass avocado cultivation in Colombia has grown rapidly in area in recent years. It is being planted in marginal areas, which leads to low yields, and in many cases is related to diseases. Ecological niche modeling (ENM) can offer a view of the potential geographic and environmental distribution of diseases, and thus identify areas with suitable or unsuitable conditions for their development. The aim of the study was to assess current and potential distribution of the major diseases on Hass avocado in Colombia. Areas planted with Hass avocado in Antioquia, Colombia were sampled for diseases including the following pathogens: Phytophthora cinnamomi, Verticillium sp., Lasiodiplodia theobromae, Phytophthora palmivora, Colletotrichum gloeosporioides sensu lato, Pestalotia sp., and Capnodium sp., and one disorder hypoxia-anoxia. These pathogens were selected based on their relevance (incidence-severity) and capacity to cause damage in different tissues of avocado plants. Severity and incidence of each disease were related to environmental information from vegetation indices and topographic variables using maximum entropy modeling approaches (MaxEnt). Models were calibrated only across areas sampled, and then transferred more broadly to areas currently planted, and to potential zones for planting. Combinations of best performance and low omission rates were the basis for model selection. Results show that Hass avocado has been planted in areas highly conducive for many pathogens, particularly for Phytophthora cinnamomi and hypoxia-anoxia disorder. Ecological niche modeling approaches offer an alternative toolset for planning and making assessments that can be incorporated into disease management plans.
Although Syrian high-yielding wheat cultivars grown under Mediterranean conditions include acceptable levels of resistance to biotic constraints, little is known about their susceptibility to Fusarium head blight (FHB), a harmful disease of wheat cultivation worldwide. The capacity of 16 fungal isolates of four FHB species to confer the disease on spikes and spikelets of six widely grown old and modern Syrian durum and bread wheat cultivars with known in vitro quantitative resistance to FHB was evaluated. Quantitative traits were visually assessed using spray and point inoculations for determining disease development rates, disease incidence (DI) and disease severity (DS) under controlled conditions. Differences in pathogenicity and susceptibility among wheat cultivars were observed, emphasizing the need for breeders to include aggressive isolates or a mixture of isolates representative of the FHB diversity in their screenings for selection of disease resistant cultivars. Bread wheat cultivars showed lower levels of spike and spikelet damage than durum cultivars regardless of the date of cultivar release. Overall, the six wheat cultivars expressed acceptable resistance levels to initial fungal infection and fungal spread. Quantitative traits showed significant correlation with previous standardized area under disease progress curve (AUDPCstandard) data generated in vitro. Thus, the predictive ability of AUDPCstandard appears to be crucial in assessing pathogenicity and resistance in adult wheat plants under controlled conditions. While in the Mediterranean countries the risk of disease is progressively increasing, the preliminary data in this report adds to our knowledge about four FHB species pathogenicity on a Syrian scale, where the environment is quite similar to some Mediterranean wheat growing areas, and show that Syrian cultivars could be new resistant donors with favorable agronomical characteristics in FHB-wheat breeding programs.
Fusarium crown rot (FCR), caused by Fusarium culmorum (Wm.G.Sm) Sacc., is an important disease of wheat both in Iraq and other regions of wheat production worldwide. Changes in environmental conditions and cultural practices such as crop rotation generate stress on pathogen populations leading to the evolution of new strains that can tolerate more stressful environments. This study aimed to investigate the genetic diversity among isolates of F. culmorum in Iraq. Twenty-nine samples were collected from different regions of wheat cultivation in Iraq to investigate the pathogenicity and genetic diversity of F. culmorum using the repetitive extragenic palindromic (REP-PCR) technique. Among the 29 isolates of F. culmorum examined for pathogenicity, 96% were pathogenic to wheat at the seedling stage. The most aggressive isolate, from Baghdad, was IF 0021 at 0.890 on the FCR severity index. Three primer sets were used to assess the genotypic diversity via REP, ERIC and BOX elements. The amplicon sizes ranged from 200–800 bp for BOX-ERIC2, 110–1100 bp for ERIC-ERIC2 and 200–1300 bp for REP. A total of 410 markers were polymorphic, including 106 for BOX, 175 for ERIC and 129 for the REP. Genetic similarity was calculated by comparing markers according to minimum variance (Squared Euclidean). Clustering analysis generated two major groups, group 1 with two subgroups 1a and 1b with 5 and 12 isolates, respectively, and group 2 with two subgroups 2a and 2b with 3 and 9 isolates, respectively. This is the first study in this field that has been reported in Iraq.
Genetically modified Bt cotton (Gossypium hirsutum) leaves with typical symptoms of Alternaria early blight disease resembling that of tomato and potato were observed in the main cotton growing schemes in Sudan. Symptoms on leaves appeared as either brown 2leaf spot with gray centers or leaf blight with concentric rings. Pathogenicity tests using isolates with both symptoms showed that the isolated fungi were highly pathogenic to both G. hirsutum and G. barbadense cotton varieties. Alternaria alternata isolated from infected tomato and potato leaves with early blight symptoms was included for comparison. Microscopic examination showed that the mean length of conidia from cotton, tomato and potato isolates ranged from 26.25 to 45.45 μm, while the width ranged from 9.56 to 13.64 μm. The mean number of transverse septa among all isolates was 3.4 to 5.7 and the peak length ranged from 3.75 to 7.8 μm. Based on morphological characteristics the two isolates from cotton were identified as A. alternata. Genomic DNA was extracted directly from fungal cultures grown on potato dextrose agar (PDA) plates using a Zymo Research Quick DNA kit. A species-specific primer using the internal transcribed spacer ribosomal DNA (ITS rDNA) PCR scoring indicated the presence of A. alternata using primer pair ITS4/ITS5. Amplifications of the internal transcribed spacer region of 600 bp revealed 100% identity of the isolated fungus from cotton with A. alternata from tomato and potato. These data oblige us to reconsider the presence of A. alternata in the four main cotton growing schemes in Sudan while these symptoms have always been described for tomato and potato early blight disease.
Article published in Science, 2012 by Jennifer A. Doudna, Emmanuelle Charpentier and their team presented a novel tool named as CRISPR/Cas9. The original CRISPR/Cas9 tool and the whole system developed from it since then allow making precise changes in the nucleotide sequence in the defined locus of the genome. The article presents the already known as well the potential future applications of the system for improvement of cultivated plants. The separate section is devoted to present the background of the Court of Justice decision C-528/16. Discussed are the far reaching negative consequences of this, based not on the merit decision, for the future of European green biotechnology.