Recent advances in the molecular biology of Leifsonia xyli subsp. xyli, causal organism of ratoon stunting disease

Twelve years ago our understanding of ratoon stunting disease (RSD) was confined almost exclusively to diagnosis of the disease and control via farm hygiene, with little understanding of the biology of the interaction between the causal agent (Leifsonia xyli subsp. xyli) and the host plant sugarcane (Saccharum spp. hybrids). Since then, research has focused on developing the molecular tools to dissect L. xyli subsp. xyli, so that better control strategies can be developed to prevent losses from RSD. Within this review, we give a brief overview of the progression in research on L. xyli subsp. xyli and highlight future challenges. After a brief historical background on RSD, we discuss the development of molecular tools such as transformation and transposon mutagenesis and discuss the apparent lack of genetic diversity within the L. xyli subsp. xyli world population. We go on to discuss the sequencing of the genome of L. xyli subsp. xyli, describe the key findings and suggest some future research based on known deficiencies that will capitalise on this tremendous knowledge base to which we now have access.

Antifungal activity of Bacillus subtilis filtrate to control Fusarium oxysporum f.sp. lentis, the causal organism of lentil vascular wilt

In dual cultures, the supernatant filtrate of the biological control agent Bacillus subtilis was evaluated against (Fusarium oxysporum f.sp. lentis) the causal organism of lentil vascular wilt. The antagonistic activity was evaluated as percent reduction of fungal growth (certainly due, in part, to the antifungal metabolites produced by the antagonistic bacterium). The in-vitro experiments showed that B. subtilis filtrate, whether solid or liquid media, had a strong inhibiting activity on the spore germination and mycelial growth of F. oxysporum f. sp. lentis. In a glasshouse experiment, soil was drenched with B. subtilis filtrate at 30 ml/kg (vol/wt) around seedlings of a susceptible lentil line (ILL 4605). In this treatment there was only 31% mortality compared with 100% kill of plants in the control treatment (P≤0.05).

Recent advances in the molecular biology of Leifsonia xyli subsp xyli, causal organism of ratoon stunting disease

Twelve years ago our understanding of ratoon stunting disease (RSD) was confined almost exclusively to diagnosis of the disease and control via farm hygiene, with little understanding of the biology of the interaction between the causal agent (Leifsonia xyli subsp. xyli) and the host plant sugarcane (Saccharum spp. hybrids). Since then, research has focused on developing the molecular tools to dissect L. xyli subsp. xyli, so that better control strategies can be developed to prevent losses from RSD. Within this review, we give a brief overview of the progression in research on L. xyli subsp. xyli and highlight future challenges. After a brief historical background on RSD, we discuss the development of molecular tools such as transformation and transposon mutagenesis and discuss the apparent lack of genetic diversity within the L. xyli subsp. xyli world population. We go on to discuss the sequencing of the genome of L. xyli subsp. xyli, describe the key findings and suggest some future research based on known deficiencies that will capitalise on this tremendous knowledge base to which we now have access.

Estrutura genética de populações de Amphobotrys ricini, agente causal do mofo cinzento da mamoneira

The gray mold, causal organism Amphobotrys ricini, is one of the major diseases of castor bean. Difficulties in managing plant disease arises form the limited understanding of the genetic structure of A. ricini, their complexity and variability make it difficult to control. Genetic structure can be used to infer the relative impact of different forces that influence the evolution of pathogen populations, that allow to predict the potencial for pathogen populations to envolve in agricultural ecosystems. Growers protect their crop by applying fungicides, but there aren t fungicides to provide significant control of gray mold of castor bean. The objectives of this work were use RAPD to determine the genetic structure of A. ricini subpopulations in Paraíba and assay the sensitivity of A. ricini isolates to azoxystrobin and carbendazim. To determine the genetic structure of A. ricini subpopulations in Paraíba, 23 isolates were colleted from two different geographic location (subpopulation). These isolates were analysed by RAPD using 22 random decamer primers, purchased from OPERON, produced a total of 80 markers polimorphics. The resulting matrixes were analysed using PopGene version 1.32. Sensitivity to azoxystrobin and carbendazim of 30 isolates, colleted form Paraíba and Alagoas, was estimated based on spore germination and colony growth inhibition. The stock solutions were added toV8 medium after sterilization to produce final concentrations of 0, 0.01, 0.1, 1, 10, and 100 µg/ml of carbendazim and 0, 0.001, 0.01, 0.1, 1, and 10 µg/ml of azoxystrobin. All statistical analyses were performed using SAS to estimate the dose that inhibited fungal growth by 50% (ED50 values). The genetic diversity within subpopulations (Hs=0,271) accounted for 92% of the total genetic diversity (Ht=0,293), while genetic diversity between subpopulations (Gst = 0,075) represented only 7,5%. The estimated number of migrants per generation (NM ) was 6,15. Nei s average gene identity across 80 RAPD loci was 0,9468. Individual ED50 values, for the 30 isolates screened for their sensitivity to azoxystrobin, ranged From a maximum of 0,168 µg/ml to a minimum of 0,0036 µg/ml. The ED50 values for carbendazim varied within the range of 0,026 to 0,316 µg/ml

Identification and characterization of non-pathogenic Fusarium oxysporum capable of increasing and decreasing Fusarium wilt severity

Fusarium wilt of banana is a potentially devastating disease throughout the world. Options for control of the causal organism, Fusarium oxysporum f.sp. cubense (Foc) are limited. Suppressive soil sites have previously been identified where, despite the presence of Foc, Fusarium wilt does not develop. In order to understand some aspects of this disease suppression, endophytic Fusarium oxysporum isolates were obtained from banana roots. These isolates were genetically characterized and compared with an isolate of Fusarium oxysporum previously identified as being capable of suppressing Fusarium wilt of banana in glasshouse trials. Three additional isolates were selected for glasshouse trials to assess suppression of Fusarium wilt in two different cultivars of banana, Cavendish and Lady Finger. One isolate (BRIP 29089) was identified as a potential biocontrol organism, reducing the disease severity of Fusarium wilt in Lady Finger and Cavendish cultivars. Interestingly, one isolate (BRIP 45952) increased Fusarium wilt disease severity on Cavendish. The implications of an isolate of Fusarium oxysporum, non-pathogenic on banana, increasing disease severity and the potential role of non-pathogenic isolates of Fusarium oxysporum in disease complexes are discussed.

Teratosphaeria pseudoeucalypti, new cryptic species responsible for leaf blight of Eucalyptus in subtropical and tropical Australia

Sub-tropical and tropical plantations of Eucalyptus grandis hybrids in eastern Australia have been severely affected by anamorphs of Teratosphaeria (formerly Kirramyces) causing a serious leaf blight disease. Initially the causal organism in Queensland, Australia, was identified as Teratosphaeria eucalypti, a known leaf parasite of endemic Eucalyptus spp. However, some inconsistencies in symptoms, damage and host range suggested that the pathogen in Queensland may be a new species. Isolates of T. eucalypti from throughout its known endemic range, including Queensland and New Zealand, where it is an exotic pathogen, were compared using multiple gene phylogenies. Phylogenetic studies revealed that the species responsible for leaf blight in Queensland represents a new taxon, described here as Teratosphaeria pseudoeucalypti. While the DNA sequence of T. pseudoeucalypti was more similar to T. eucalypti, the symptoms and cultural characteristics resembled that of T. destructans. The impact of this disease in central Queensland has increased annually and is the major threat to the eucalypt plantation industry in the region.

Studies on seed pathology and seedling diseases of some important indigenous tree species of kerala

In forestry, availability of healthy seeds is an important factor in raising planting stock. Initial seed health and storage conditions are the major factors governing the germinability of seeds. Like seeds of agricultural and horticultural crops, forest tree seeds are also liable to be affected by micro-organisms during storage, which affects the germination, and reduces the viability. Further introduction of seed-borne diseases into newly sown crops/areas on account of using unhealthy seeds is also not ruled out. Availability of healthy stock of seedlings is intrinsic for raising plantations and to meet this requirement elimination of nursery diseases by appropriate chemicals is of prime imortance. As exotic tree species may become susceptible to various native pathogens, it is generally considered better to select indigenous tree species for large scale plantations as they are well adapted to local environment. However, before taking up large scale afforestation progranme involving any indigenous tree species, it is essential to have knowledge about seed disorders and seedling diseases and their management. with a View to select appropriate tree species with fewer seed disorders and seedling disease problems for use in further plantation programme, four indigenous tree species such as Albizia odoratissima (L.f) Benth., Lagerstroemia microcazpa Wt., Pterocazpus marsupiwn Roxb. and Xylia xylocarpa (Roxb.) Taub. were evaluated to meet the above parameters

Sarna del manzano : detección de la forma sexual (Venturia inaequalis ) en Mendoza (Argentina)

El aumento de los daños provocados por la sarna del manzano [Fusicladium dendritichum (Wallr.) Fuckl.] en montes frutales de Mendoza (Argentina), motivó estudios para aclarar la biología del hongo y buscar la presencia de la forma sexual, no detectada aún en la provincia. Al momento de la brotación se muestrearon hojas del año anterior que se encontraban en el suelo de dichos montes. En el laboratorio fueron observadas bajo estereomicroscopio. Los cuerpos negros inmersos en el tejido de la hoja fueron montados en preparados microscópicos y observados para establecer su identidad. Se confirmó la presencia en la zona de la forma teleomórfica del agente causal de la sarna del manzano. Este hecho tiene importancia en la epidemiología de la enfermedad y en las estrategias de control.

Highly plastic chromosomal organization in Salmonella typhi.

Gene order in the chromosomes of Escherichia coli K-12 and Salmonella typhimurium LT2, and in many other species of Salmonella, is strongly conserved, even though the genera diverged about 160 million years ago. However, partial digestion of chromosomal DNA of Salmonella typhi, the causal organism of typhoid fever, with the endonuclease I-CeuI followed by separation of the DNA fragments by pulsed-field gel electrophoresis showed that the chromosomes of independent wild-type isolates of S. typhi are rearranged due to homologous recombination between the seven rrn genes that code for ribosomal RNA. The order of genes within the I-CeuI fragments is largely conserved, but the order of the fragments on the chromosome is rearranged. Twenty-one different orders of the I-CeuI fragments were detected among the 127 wild-type strains we examined. Duplications and deletions were not found, but transpositions and inversions were common. Transpositions of I-CeuI fragments into sites that do not change their distance from the origin of replication (oriC) are frequently detected among the wild-type strains, but transpositions that move the fragments much further from oriC were rare. This supports the gene dosage hypothesis that genes at different distances from oriC have different gene dosages and, hence, different gene expression, and that during evolution genes become adapted to their specific location; thus, cells with changes in gene location due to transpositions may be less fit. Therefore, gene dosage may be one of the forces that conserves gene order, although its effects seem less strong in S. typhi than in other enteric bacteria. However, both the gene dosage and the genomic balance hypotheses, the latter of which states that the origin (oriC) and terminus (TER) of replication must be separated by 180 degrees C, need further investigation.

Identification of a major locus conferring resistance to powdery mildew (Erysiphe polygoni DC) in mungbean (Vigna radiata L. Wilczek) by QTL analysis

A major locus conferring resistance to the causal organism of powdery mildew, Erysiphe polygoni DC,, in mungbean (Vigna radiata L. Wilczek) was identified using QTL analysis with a population of 147 recombinant inbred individuals. The population was derived from a cross between 'Berken', a highly susceptible variety, and ATF 3640, a highly resistant line. To test for response to powdery mildew, F-7 and F-8 lines were inoculated by dispersing decaying mungbean leaves with residual conidia of E. polygoni amongst the young plants to create an artificial epidemic and assayed in a glasshouse facility. To generate a linkage map, 322 RFLP clones were tested against the two parents and 51 of these were selected to screen the mapping population. The 51 probes generated 52 mapped loci, which were used to construct a linkage map spanning 350 cM of the mungbean genome over 10 linkage groups. Using these markers, a single locus was identified that explained up to a maximum of 86% of the total variation in the resistance response to the pathogen.

Identification and characterization of non-pathogenic Fusarium oxysporum capable of increasing and decreasing Fusarium wilt severity

Fusarium wilt of banana is a potentially devastating disease throughout the world. Options for control of the causal organism, Fusarium oxysporum f.sp. cubense (Foc) are limited. Suppressive soil sites have previously been identified where, despite the presence of Foc, Fusarium wilt does not develop. In order to understand some aspects of this disease suppression, endophytic Fusarium oxysporum isolates were obtained from banana roots. These isolates were genetically characterized and compared with an isolate of Fusarium oxysporum previously identified as being capable of suppressing Fusarium wilt of banana in glasshouse trials. Three additional isolates were selected for glasshouse trials to assess suppression of Fusarium wilt in two different cultivars of banana, Cavendish and Lady Finger. One isolate (BRIP 29089) was identified as a potential biocontrol organism, reducing the disease severity of Fusarium wilt in Lady Finger and Cavendish cultivars. Interestingly, one isolate (BRIP 45952) increased Fusarium wilt disease severity on Cavendish. The implications of an isolate of Fusarium oxysporum, non-pathogenic on banana, increasing disease severity and the potential role of non-pathogenic isolates of Fusarium oxysporum in disease complexes are discussed. (c) 2006 Published by Elsevier Ltd on behalf of The British Mycological Society.

Interrelationship between two variants of the Circulifer tenellus complex and Spiroplasma citri: the causal agent of stubborn disease

Tese de Doutoramento, Ciências Naturais, Unidade de Ciências e Tecnologias Agrárias, Universidade do Algarve, 1992

Contradictions : Genre, causal layered analysis and analysis of institutional change

In what follows, I put forward an argument for an analytical method for social science that operates at the level of genre. I argue that generic convergence, generic hybridity, and generic instability provide us with a powerful perspectives on changes in political, cultural, and economic relationships, most specifically at the level of institutions. Such a perspective can help us identify the transitional elements, relationships, and trajectories that define the place of our current system in history, thereby grounding our understanding of possible futures.1 In historically contextualising our present with this method, my concern is to indicate possibilities for the future. Systemic contradictions indicate possibility spaces within which systemic change must and will emerge. We live in a system currently dominated by many fully-expressed contradictions, and so in the presence of many possible futures. The contradictions of the current age are expressed most overtly in the public genres of power politics. Contemporary public policy—indeed politics in general-is an excellent focus for any investigation of possible futures, precisely because of its future-oriented function. It is overtly hortatory; it is designed ‘to get people to do things’ (Muntigl in press: 147). There is no point in trying to get people to do things in the past. Consequently, policy discourse is inherently oriented towards creating some future state of affairs (Graham in press), along with concomitant ways of being, knowing, representing, and acting (Fairclough 2000).

The causal effect of income on health: Evidence from German reunification

We investigate whether therewas a causal effect of income changes on the health satisfaction of East and West Germans in the years following reunification. Our data source is the German Socio-Economic Panel (GSOEP) between 1984 and 2002, and we fit a recently proposed fixed-effects ordinal estimator to our health measures and use a causal decomposition technique to account for panel attrition.We find evidence of a significant positive effect of income changes on health satisfaction, but the quantitative size of this effect is small. This is the case with respect to current income and a measure of ‘permanent’ income.