Studies of the life cycle of <i>Diplocarpon rosae</i> Wolf on roses and the effectiveness of fungicides on pathogenesis

The blackspot disease of roses caused by Diplocarpon rosae Wolf teleomorph (anamorph Marssonina rosae) is a widespread and important disease on outdoor grown roses. The development of D. rosae in rose leaves is not clearly understood and no detailed well-documented photographs of the fungus development in the host are available. The control of this pathogen heavily relies on fungicides. The objective of this study was to provide a detailed growth pattern the D. rosae inside the rose leaves and to test the effectiveness of fungicides, the strobilurins and azoles, on the various fungal structures formed by this fungus. The aggressiveness of various Kenyan and Germany isolates was investigated. A German isolate was used to study the life cycle of D. rosae. The life cycle of the fungus was studied using different staining techniques for the light microscopy and the conventional preparation for electron microscopy: A conidium germinated to form a germ tube, from which an appressorium was sometimes formed. A brown ring that was presumably melanized was formed at the point of penetration of the host cuticle. Upon penetration an infection vesicle was formed in the subcuticular region. Primary hyphae spread from the infection vesicle into the subcuticular and intercellular regions in the host. The subcuticular, intercellular and intramural hyphae formed haustoria of varying shapes in the epidermal cells. The intercellular hyphae also formed haustoria in palisade mesophyll cells. Intracellular hyphae were formed just before the formation of the reproduction structures. Brown heavily ornamented structures formed in the overwintering leaves, opened in spring of the following year to release small thin-walled structures. No ascospores were formed in the subepidermal apothecia-like structures. The strobilurins completely inhibited germination of the conidia of D. rosae but the azoles did not. The azoles were able to destroy the fungal structures in the host even when they were applied after the fungus was fully established in the host but the effectiveness of the strobilurins was limited. Protective and curative tests of the effectiveness of the fungicides were carried out with 100 ppm of the active ingredients. The study showed that D. rosae is a hemibiotroph: The biotrophic phase is marked by the formation haustoria and the necrotrophic phase by the formation of the intracellular hyphae. The weather conditions in Germany may not be suitable for the development of the ascospores in the subepidermal apothecia. The strobilurins were only effective when applied protectively. The azoles were effective when applied pre and post inoculation.Untersuchungen zum Lebenszyklus von Diplocarpon rosae Wolf an Rosen und zum Einfluss von Fungiziden auf die Pathogenese Der Sternrußtau (Schwarzfleckigkeit), Hauptfruchtform Diplocarpon rosae Wolf, (Neben-fruchtform Marssonina rosae), ist eine häufige und weit verbreitete Krankheit an Freilandrosen. Bisher war weder die Entwicklung des Pilzes im Blattgewebe geklärt, noch waren in der Literatur fotografische Aufnahmen zur endophytischen Pilzentwicklung zu finden. Die Bekämpfung des Pilzes wird überwiegend mit Fungiziden durchgeführt. Die Untersuchungen vorliegender Arbeit umfassen sowohl mikroskopische Studien zur exakten Ausbreitung des Erregers im Rosenblatt als auch die Wirkung unterschiedlicher Fungizide, insbesondere Strobilurine und Azole, auf pilzliche Strukturen. Zunächst wurde die Aggressivität verschiedener Isolate aus Kenia und Deutschland getestet. An einem deutschen Isolat konnte der Entwicklungszyklus von D. rosae mit verschiedenen Färbetechniken lichtmikroskopisch sowie nach konventioneller Präparation elektronenmikro-skopisch studiert werden: Nach der Konidienkeimung entsteht eine Keimhyphe, von der aus meist ein Appressorium gebildet wird. Auf der Wirtskutikula zeigt sich dann an der Stelle der späteren Penetration ein brauner Ring, der vermutlich melanisiert ist. Nach der Penetration bildet sich in der subkutikulären Region ein Infektionsvesikel. Primäre Hyphen durchdringen von diesem Infektionsvesikel ausgehend subkutikuläre und interzelluläre Wirtsgewebezonen. Subkutikuläre, interzelluläre und intramurale Hyphen bilden in den epidermalen Zellen Haustorien unterschiedlicher Formen. Interzelluläre Hyphen produzieren ebenfalls Haustorien im Palisadenparenchym. Intrazelluläre Hyphen entstehen erst kurz vor der Bildung der Reproduktionsorgane. Braune, stark ornamentierte Strukturen werden vom Pilz auf den überwinternden Blättern gebildet. Diese öffnen sich im Frühjahr des Folgejahres und entlassen dünnwandige Organe. In diesen subepidermalen Apothezien-ähnlichen Strukturen entstehen aber keine Ascosporen. Strobilurine hemmten die Konidienkeimung vollständig, während Azole einen weniger starken Einfluss auf die Keimung hatten. Dagegen zerstörten die Azole alle Pilzstrukturen im Inneren des Gewebes, auch wenn sie sich bereits gut etabliert hatten. Diese Reaktion konnte bei Einsatz der Strobilurine nicht so deutlich beobachtet werden. Alle Fungizidtests zur protektiven und kurativen Wirkung wurden mit jeweils 100 ppm reinem Wirkstoff durchgeführt. Die Untersuchungen zeigten, dass D. rosae eine hemibiotrophe Lebensweise besitzt: die biotrophe Phase besteht aus der Haustorienbildung und die nekrotrophe Phase aus der Bildung interzellulärer Hyphen. Die deutschen Witterungsbedingungen eignen sich offenbar nicht für eine subepidermale Apothezienbildung. Strobilurine zeigten nur nach protektiver Applikation eine Wirkung. Azole wirkten sowohl bei prä- als auch bei post-inokulativer Behandlung

The Dietary Decision-Making Process of Women in Nigeria

Nigerians have been opting for a more processed Western diet. These changes in dietary choices have aligned with obesity and undernutrition, attributable to micronutrient deficiencies or malnutrition. Many scholars have presented varying intervention strategies ranging from consumption of a variety of foods containing the necessary micronutrients to food fortification. The purpose of this grounded theory study was to explore the perceptions of women in an urban city in Nigeria on indigenous foods and Western dietary influences to determine social interactions, the consequence of the interactions, and the women’s current perceptions of food choices. The social-ecological model was used to explore the interaction between a woman and her environment. Women between the ages of 20 to 30 from the urban city of Jos, Nigeria, constituted the population of interest, and 12 women were chosen for the sample. From the in-depth interviews, a thematic analysis was employed to provide sociocontextual reasoning for changes in diet that have led to the loss of interest in traditional foods and cultures. This study found that Jos has a variety of foods, yet women choose the same staple foods to feed their families. Additionally, despite a marginal understanding of the health impact of diet, most women choose the convenience and palatability of Western options, citing cost as the rationale for choosing to cook staple Western-inspired meals at home. Understanding media, convenience, and cost can impact social change by enlightening communities on the interconnectedness of human health, cultures, and industrialization. Health care providers can monitor the outcomes of those who consume a variety of indigenous foods to see how such a practice could influence the overall health status of Nigerian families

Bacillus pumilus BpCRI 6, a promising candidate for cellulase production under conditions of catabolite repression

Cellulose degrading organisms have been used for the conversion of cellulolytic materials into soluble sugars or solvents in several biotechnological and industrial applications. In this report, a mutant of Bacillus pumilus was obtained after chemical mutagenesis and screened for cellulase production. This mutant named BpCRI 6 was selected for its ability to produce cellulase under catabolite repression. Cellulase yield by BpCRI 6 was four times higher than that of the wild type under optimum growth conditions (pH 6.5, 25°C and Ca2+ 1mM). In shaking flask cultures, production of cellulase  by the wild type was completely repressed in the presence of 25 mM glucose, while BpCRI 6 strain still exhibited a residual cellulase production of 80 and 40% at 25 mM and 40 mM of glucose concentrations respectively. The mutant strain is stable and grows rapidly in liquid and solid media. Under conditions of catabolite repression (40 mM of glucose), the production of cellulase by this mutant is particularly significant when compared to Trichoderma reesei a well-known cellulase producer, which is under control of end-product inhibition. This is the first report of a successful catabolite repression insensitivity of cellulase production by a mutant of B. pumilus. (African Journal of Biotechnology: 2003 2(6): 140-146

The molecular initiation and subsequent acquisition of disease resistance in plants

Interactions between disease resistance (R) genes in plants and their corresponding pathogen avirulence (Avr) genes are the key determinants of whether a plant is susceptible or resistance to a pathogen attack. Evidence has emerged that these gene-for-gene interactions in the perception of pathogenic invasions and development of acquired resistance in plants involve different molecular and hormonal transduction pathways, which are still poorly understood. It has become apparent that plants actively produce several phytohormones such as ethylene, jasmonate, salicylic acid, and reactive oxygen intermediates prior to upregulation of R genes. The physiological role of these molecules in plant resistance to pathogens is beginning to attract attention. The use of transgenic plants in recent attempts, including development of mutants with altered R genes, has provided new insights into the mechanisms involved in pathogen perception, signal transduction and subsequent resistance to disease in plants. This review tries to summarize current knowledge of pathogen-related genes in plants, and how they can be use to improve disease resistance in agronomically valuable plants. It also describes the molecular basis of defense mechanisms in plants under pathogen attack. (African Journal of Biotechnology: 2003 2(2): 26-32

A home made kit for plasmid DNA mini-preparation

Many methods have been used to isolate plasmid DNA, but some of them are time consuming especially when extracting a large number of samples. Here, we developed a rapid protocol for plasmid DNA extraction based on the alkaline lysis method of plasmid preparation (extraction at pH 8.0). Using this new method, a good plasmid preparation can be made in approximately one hour. The plasmids are suitable for any subsequent molecular applications in the laboratory. By applying the recommendations to avoid contaminations and to maximize the plasmid yield and quality during extraction, this protocol could be a valuable reference especially when analyzing a large number of samples. (African Journal of Biotechnology: 2003 2(4): 87

Phenotypic characters of yeasts isolated from kpete-kpete, a traditional starter of a Benin opaque sorghum beer

Opaque sorghum beers are the most consumed African alcoholic beverages. Tchoukoutou is one of the Benin opaque sorghum beers. Its fermentation process is carried out using a traditional starter called kpete-kpete. The present study characterized and identified the yeasts isolated from kpete-kpete. A total of 24 samples of kpete-kpete were collected from eight different commercial processing sites in Northern Benin. The mean values of the pH, titrable acidity, dry matter content and refractive index for all samples were respectively 3.58; 0.07% as lactic acid; 16.61% and 7.0. The mean counts of yeasts was 9.24 log cfu/ml. Based on their phenotypic characters and their assimilation profiles, 49 yeasts were isolated and found to belong to five genera with seven species. Seventy one percent (71%) of the isolates were identified as Saccharomyces cerevisiae.Key words: Sorghum beer, tchoukoutou, kpete-kpete, yeast, Saccharomyces cerevisiae

The maize ALDH protein superfamily: linking structural features to functional specificities

<p>Abstract</p> <p>Background</p> <p>The completion of maize genome sequencing has resulted in the identification of a large number of uncharacterized genes. Gene annotation and functional characterization of gene products are important to uncover novel protein functionality.</p> <p>Results</p> <p>In this paper, we identify, and annotate members of all the maize aldehyde dehydrogenase (ALDH) gene superfamily according to the revised nomenclature criteria developed by ALDH Gene Nomenclature Committee (AGNC). The maize genome contains 24 unique <it>ALDH </it>sequences encoding members of ten ALDH protein families including the previously identified male fertility restoration <it>RF2A </it>gene, which encodes a member of mitochondrial class 2 ALDHs. Using computational modeling analysis we report here the identification, the physico-chemical properties, and the amino acid residue analysis of a novel tunnel like cavity exclusively found in the maize sterility restorer protein, RF2A/ALDH2B2 by which this protein is suggested to bind variably long chain molecular ligands and/or potentially harmful molecules.</p> <p>Conclusions</p> <p>Our finding indicates that maize ALDH superfamily is the most expanded of plant <it>ALDHs </it>ever characterized, and the mitochondrial maize RF2A/ALDH2B2 is the only plant ALDH that harbors a newly defined pocket/cavity with suggested functional specificity.</p

Evolutionary relationships between Rhynchosporium lolii sp. nov. and other Rhynchosporium species on grass.

Copyright: 2013 King et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedThe fungal genus Rhynchosporium (causative agent of leaf blotch) contains several host-specialised species, including R. commune (colonising barley and brome-grass), R. agropyri (couch-grass), R. secalis (rye and triticale) and the more distantly related R. orthosporum (cocksfoot). This study used molecular fingerprinting, multilocus DNA sequence data, conidial morphology, host range tests and scanning electron microscopy to investigate the relationship between Rhynchosporium species on ryegrasses, both economically important forage grasses and common wild grasses in many cereal growing areas, and other plant species. Two different types of Rhynchosporium were found on ryegrasses in the UK. Firstly, there were isolates of R. commune that were pathogenic to both barley and Italian ryegrass. Secondly, there were isolates of a new species, here named R. lolii, that were pathogenic only to ryegrass species. R. lolii was most closely related to R. orthosporum, but exhibited clear molecular, morphological and host range differences. The species was estimated to have diverged from R. orthosporum ca. 5735 years before the present. The colonisation strategy of all of the different Rhynchosporium species involved extensive hyphal growth in the sub-cuticular regions of the leaves. Finally, new species-specific PCR diagnostic tests were developed that could distinguish between these five closely related Rhynchosporium species.Peer reviewedFinal Published versio

Anti-Phytopathogenic Activities of Macro-Algae Extracts

Aqueous and ethanolic extracts obtained from nine Chilean marine macro-algae collected at different seasons were examined in vitro and in vivo for properties that reduce the growth of plant pathogens or decrease the injury severity of plant foliar tissues following pathogen infection. Particular crude aqueous or organic extracts showed effects on the growth of pathogenic bacteria whereas others displayed important effects against pathogenic fungi or viruses, either by inhibiting fungal mycelia growth or by reducing the disease symptoms in leaves caused by pathogen challenge. Organic extracts obtained from the brown-alga Lessonia trabeculata inhibited bacterial growth and reduced both the number and size of the necrotic lesion in tomato leaves following infection with Botrytis cinerea. Aqueous and ethanolic extracts from the red-alga Gracillaria chilensis prevent the growth of Phytophthora cinnamomi, showing a response which depends on doses and collecting-time. Similarly, aqueous and ethanolic extracts from the brown-alga Durvillaea antarctica were able to diminish the damage caused by tobacco mosaic virus (TMV) in tobacco leaves, and the aqueous procedure is, in addition, more effective and seasonally independent. These results suggest that macro-algae contain compounds with different chemical properties which could be considered for controlling specific plant pathogens