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Heart rot of spruce and alder in forests of Latvia
Get PDFHeart rot causes great decrease in timber quality throughout the world. In the conifer forests of Northern Hemisphere the most significant losses are caused by fungi from the Heterobasidion annosum species complex. The spread of the disease is favored by forest management, as the fungus can use freshly cut stumps as an infection court, and so extend through root contacts to infect neighboring trees.
The country-scale inventory revealed that about 22% of Latvian spruce trees contained heart rot, which extended on average 6.6 m within the tree stem; the most commonly associated fungus being H. parviporum. These facts highlight the need to take actions to reduce the level of inoculum in already infested stands. Stump removal and the planting of resistant tree species are two options for that.
Long-term trials carried out in Scandinavia showed that stump removal could significantly decrease the proportion of infected trees in regenerated stands, although the effectiveness of this procedure may eventually decrease with time. In addition, this method is quite drastic and the adverse influence of continuous stump removal on stand biodiversity and productivity should be taken into consideration. The trail conducted in Finland showed that stump removal had a positive impact on seedlings growth, but influenced negatively mycorrhization and species richness.
The other management method which could be employed is the planting of resistant tree species, especially broadleaved trees. In the work undertaken for this thesis heart rot incidence, associated fungi and decay caused yield losses were studied in Latvian grey (Alnus incana) and black alder (A. glutinosa) stands. Despite the high decay incidence and the number of associated fungal species, no single H. annosum s.l. was found. Also, our data showed that the proportion and size of the heart rot column increased with tree age. These data suggest that a short rotation of fast growing broadleaved trees (not only Alnus, but also species of Populus, Betula, and Salix) could be used for clearing up the Heterobasidion inoculum
Xanthomonas campestris pv. campestris race 1 is the main causal agent of black rot of Brassicas in Southern Mozambique
Get PDFSevere outbreaks of bacterial black rot caused by Xanthomonas campestris pv. campestris (Xcc) were observed in Brassica production fields of Southern Mozambique. The causal agent of the disease in the Mahotas and Chòkwé districts was identified and characterised. In total, 83 Xanthomonas-like strains were isolated from seed samples and leaves of cabbage and tronchuda cole with typical symptoms of the disease. Forty-six out of the 83 strains were found to be putative Xcc in at least one of the tests used: Classical biochemical assays, enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies, Biolog identification system, polymerase chain reaction (PCR) with specific primers and pathogenicity tests. The ELISA tests were positive for 43 strains. Biolog identified 43 strains as Xanthomonas, but only 32 as Xcc. PCR tests with primers targeting a fragment of the hrpF gene were positive for all 46 strains tested. Three strains were not pathogenic or weakly pathogenic and all other strains caused typical black rot symptoms in brassicas. Race type differentiation tests revealed the Xcc strains from Mozambique as members of race 1. The prevalence of this pathogenic race of the Xcc pathogen in Mozambique should be considered when black rot resistant cultivars are evaluated or introduced into the production regions of this country
Calonectria species associated with cutting rot of Eucalyptus
Get PDFDecline in the productivity of Eucalyptus hybrid cutting production in the Guangdong Province of China is linked to cutting rot associated with several Calonectria spp. The aim of this study was to identify these fungi using morphological and DNA sequence comparisons. Two previously undescribed Calonectria spp., Ca. pseudoreteaudii sp. nov. and Ca. cerciana sp. nov. were identified together with Ca. pauciramosa. Calonectria pseudoreteaudii resides in the Ca. reteaudii complex and Ca. cerciana is closely related to Ca. morganii. Connected to the discovery of Ca. pseudoreteaudii, species in the Ca. reteaudii complex were re-considered and the group is shown to accommodate two cryptic species. These originate from Australia and are described as Ca. queenslandica sp. nov. and Ca. terrae-reginae sp. nov
Vloga poveljniško štabne šole v rzvoju kadrov Slovenske vojske : diplomsko delo magistrskega študija
Get PDFCharacterization of isolates that cause black rot of crucifers in East Africa
Get PDFA study was conducted in the East African countries of Kenya, Tanzania and Uganda in the months of July and August 2009 with the objectives of assessing the status of black rot and race structure of Xanthomonas campestris pv. campestris in the three countries. Samples infected with black rot were collected from farmers’ fields mainly from Brassica oleracea crops (broccoli, cabbage, cauliflower and kales). A total of 399 farms were surveyed of which 260 were from Kenya, 91 from Tanzania and 48 from Uganda. Following successful isolations, a total of 249 isolates of the causal agent, Xanthomonas campestris pv. campestris were recovered. Pathogenicity of all isolates was confirmed on B. oleracea susceptible cultivars Copenhagen Market F1 and Wirosa F1. Sixty of the 250 isolates were race-typed using a differential set Brassica spp. Only two races, 1 (Kenya and Tanzania) and 4 (Kenya, Tanzania and Uganda) were observed however, another race (5) was observed from one isolate recovered from a B. rapa sample obtained from Tanzania in 2003. Genomic fingerprinting with repetitive-PCR revealed clusters that did not depict significant correlations between isolates and geographical location, isolates and host adaptation or isolates and race. However, it did demonstrate existence of genetic differences within the East African X. campestris pv. campestris population indicating that it is not a similar clonal population of the same genetic background
The effect of didactic games on the size of the vocabulary of synonyms in 4th and 5th grade
Get PDFV sklopu magistrske naloge smo preučevali napredek v obsegu besedišča sopomenk učencev 4. in 5. razreda na osnovni šoli, in sicer s pomočjo lastnih didaktičnih iger. Naš glavni namen je bil preveriti, ali dva- do trikratna tedenska uporaba didaktičnih iger na začetku ali ob koncu učne ure pozitivno vpliva na obseg njihovega besedišča. Prvo preverjanje poznavanja sopomenk smo izvedli v začetku meseca februarjav njem je sodelovalo 100 učencev iz obeh razredov. Drugo preverjanje smo izvedli ob koncu meseca aprila in v njem je sodelovalo 98 učencev. Med prvim in drugim preverjanjem so učenci 4. A in 5. A razreda pri pouku uporabljali izdelane didaktične igre, medtem ko učenci 4. B in 5. B razreda didaktičnih iger niso bili deležni. Rezultati so glede na skupino med prvim in drugim preverjanjem pokazali velike razlike v prid skupine, ki je izvajala didaktične igre. Pokazale so se tudi razlike v številu doseženih točk glede na zahtevnost naloge po Bloomovi taksonomiji (poznavanje, razumevanje in uporaba).The master\u27s thesis studies the progress in the vocabulary of synonyms of the pupils of the 4th and 5th grade of elementary school through the use of didactic games. The main purpose was to check whether the use of didactic games at the beginning or at the end of the lesson two to three times per week has a positive effect on the size of their vocabulary of synonyms. The first test of the vocabulary of synonyms was done at the beginning of February and the second test at the end of April. 97 pupils participated in the study in total. Between the first and the second test, the pupils of classes 4. A and 5. A played didactic games, while classes 4. B and 5. B pupils did not. The results of the first and second test have shown significant differences in the size of the vocabulary of synonyms in favour of the classes who played didactic games. There were also significant differences in the number of points achieved considering the complexity of the task according to Bloom\u27s taxonomy (knowledge, understanding and use)
Xanthomonas campestris pv. campestris (cause of black rot of crucifers) in the genomic era is still a worldwide threat to brassica crops
Get PDFBackground
Xanthomonas campestris pv. campestris (Xcc) (Pammel) Dowson is a Gram-negative bacterium that causes black rot, the most important disease of vegetable brassica crops worldwide. Intensive molecular investigation of Xcc is gaining momentum and several whole genome sequences are available.
Taxonomy
Bacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Xanthomonadales; Family Xanthomonadacea; Genus Xanthomonas; Species X. campestris.
Host range and symptoms
Xcc can cause disease in a large number of species of Brassicaceae (ex-Cruciferae), including economically important vegetable Brassica crops and a number of other cruciferous crops, ornamentals and weeds, including the model plant Arabidopsis thaliana. Black rot is a systemic vascular disease. Typical disease symptoms include V-shaped yellow lesions starting from the leaf margins and blackening of the veins.
Race structure, pathogenesis and epidemiology
Collections of Xcc isolates have been differentiated into physiological races based on the response of several brassica species lines. Black rot is a seed-borne disease. The disease is favoured by warm, humid conditions and can spread rapidly from rain dispersal and irrigation water.
Disease control
The control of black rot is difficult and relies on the use of pathogen-free planting material and the elimination of other potential inoculum sources (infected crop debris and cruciferous weeds). Major gene resistance is very rare in B. oleracea (brassica C genome). Resistance is more readily available in other species, including potentially useful sources of broad-spectrum resistance in B. rapa and B. carinata (A and BC genomes, respectively) and in the wild relative A. thaliana.
Genome
The reference genomes of three isolates have been released. The genome consists of a single chromosome of approximately 5 100 000 bp, with a GC content of approximately 65% and an average predicted number of coding DNA sequences (CDS) of 4308.
Important genes identified
Three different secretion systems have been identified and studied in Xcc. The gene clusters xps and xcs encode a type II secretion system and xps genes have been linked to pathogenicity. The role of the type IV secretion system in pathogenicity is still uncertain. The hrp gene cluster encodes a type III secretion system that is associated with pathogenicity. An inventory of candidate effector genes has been assembled based on homology with known effectors. A range of other genes have been associated with virulence and pathogenicity, including the rpf, gum and wxc genes involved in the regulation of the synthesis of extracellular degrading enzymes, xanthan gum and lipopolysaccharides
Response of arum lily calli to culture filtrate of Pectobacterium carotovorum subsp. carotovorum
No full textThis report demonstrated that culture filtrate of Pectobacterium carotovorum ssp. carotovorum isolate ZT0505, the pathogen of bacterial soft rot disease of arum lily (Zantedeschia sp.), contained extracellular enzymes and caused arum lily leaf tissue and callus maceration. Arum lily leaf tissue and callus sensitivity to culture filtrate coincided with the host susceptibility to the pathogen. The rates of survival of callus pieces were determined after exposure for various times to culture filtrate. Survival of callus pieces (%) increased with reduction of exposure time from 20 to 14 h and from 14 to 8 h. One out of 30 callus pieces was still viable after 3 cycles of 8 h exposure. Subsequently, the surviving cells in this callus pieces proliferated and differentiated into shoots. Based on this initial work, the callus screening using culture filtrate as selection agent may be useful for in vitro selection of soft rot resistant germplasm in arum lily
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