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In Central Asia, stem rust (Puccinia graminis f.sp. tritici) causes considerable damage, especially during growing seasons with high rainfall. Ug99 is a race of stem rust that is virulent to the majority of wheat varieties. To develop disease-free germplasm, wheat material was screened using the predominant stem rust races of Kazakhstan and tested in two nurseries, CIMMYT-Turkey and the Plant Breeding Station at Njoro, Kenya. A total of 11 pathotypes of P. graminis f.sp. tritici were identified in Kazakhstan from the stem rust samples collected in 2008-2009. In particular, pathotypes TDT/H, TPS/H, TTH/K, TKH/R, TKT/C and TFK/R were highly virulent. Of the 170 advanced lines of wheat, 21 CIMMYT lines resistant to 5 aggressive Kazakhstani pathotypes of P. graminis were identified. A high level of resistance was observed in 11 wheat cultivars and advanced lines: Taza, E-19, E-99, E-102, E-572, E-796, E-809 (Kazakhstan), Ekinchi (Azerbaijan), Dostlik, Ulugbek 600 (Uzbekistan) and Umanka (Russia). Based on data obtained from Turkey-CIMMYT and the Plant Breeding Station Njoro, out of 13 tested entries, 6 wheat breeding lines which were resistant to both stem and yellow rust and 10 wheat lines which showed high and moderate levels of resistance to Ug99 were selected. Using the sequence tagged site molecular marker Sr24No.12, associated with Sr24/Lr24, seven wheat entries resistant to stem rust were identified.

The aim of this study was to prepare some phenolic acids alkyl esters (methyl, ethyl, propyl, butyl and hexyl) and to determine their antioxidant and antimicrobial activities. The antimicrobial activity against Escherichia coli DMF 7503, Bacillus cereus DMF 2001, Listeria monocytogenes DMF 5776, Fusarium culmorum DMF 0103, and Saccharomyces cerevisiae DMF 1017 was investigated and expressed by minimum inhibitory concentration (MIC) in the range of 1.2-20mM. The inhibitory activity of phenolic acids butyl esters was found to be higher than that of methyl esters (MIC below 1.25mM). The antioxidant activity of the selected phenolic acids alkyl esters was investigated by Rancimat method. The esters of 3,4-dihydroxyphenolic acids (protocatechuic and caffeic acids) exhibited higher antioxidant activities in comparison with the respective phenolic acids. The highest antioxidant activity was found in the case of caffeic alkyl esters.

Endophytic fungi, especially asexual, systemic endophytes in grasses, are generally viewed as plant mutualists, mainly through the action of mycotoxins, such as alkaloids in infected grasses, which protect the host plant from herbivores. Most of the evidence for the defensive mutualism concept is derived from studies of agronomic grass cultivars, which may be atypical of many endophyte-host interactions. I argue that endophytes in native plants, even asexual, seed-borne ones, rarely act as defensive mutualists. In contrast to domesticated grasses where infection frequencies of highly toxic plants often approach 100%, natural grass populations are usually mosaics of uninfected and infected plants. The latter, however, usually vary enormously in alkaloid levels, from none to levels that may affect herbivores. This variation may result from diverse endophyte and host genotypic combinations that are maintained by changing selective pressures, such as competition, herbivory and abiotic factors. Other processes, such as spatial structuring of host populations and endophytes that act as reproductive parasites of their hosts, may maintain infection levels of seed-borne endophytes in natural populations, without the endophyte acting as a mutualist.

The weaning time is a crucial period in the management of piglets. The risk of development of post-weaning diarrhoea (PWD) in piglets is high. PWD is the cause of serious economic losses in pig herds. Since 2006, the use of antibiotic growth promoters for prevention of diarrhoeal diseases in piglets has been banned. This measure also led to the investigation of alternative suitable feed supplements that would be reasonably efficient in protecting and sustaining animal health and performance. Various natural materials such as probiotics, prebiotics, organic acids, zinc and plant extracts have been tested as effective alternatives to antibiotics. Recently, owing to their high adsorption capacity, research efforts have been conducted on the application of natural clays and clay-based feed supplements. The purpose of this review is to summarize the effect of different alternative components as growth promoters on the health and performance of weaned and growing piglets.

In response to infection, insects produce a variety of antimicrobial peptides (AMPs) to kill the invading pathogens. To study their physicochemical properties and bioactivities for clinical and commercial use in the porcine industry, we chemically synthesized the mature peptides Bombyx mori moricin and Hyalophora cecropia cecropin B. In this paper, we described the antimicrobial activity of the two AMPs. Moricin exhibited antimicrobial activity on eight strains tested with minimal inhibitory concentration values (MICs) ranging between 8 and 128 μg/ml, while cecropin B mainly showed antimicrobial activity against the Gramnegative strains with MICs ranging from 0.5 to 16 μg/ml. Compared to the potent antimicrobial activity these two AMPs displayed against most of the bacterial pathogens tested, they exhibited limited hemolytic activity against porcine red blood cells. The activities of moricin and cecropin B against Haemophilus parasuis SH 0165 were studied in further detail. Transmission electron microscopy (TEM) of moricin and cecropin B treated H. parasuis SH 0165 indicated extensive damage to the membranes of the bacteria. Insights into the probable mechanism utilized by moricin and cecropin B to eliminate pathogens are also presented. The observations from this study are important for the future application of AMPs in the porcine industry.

Several comprehensive literature reviews have been published recently, so in this article we review recent findings that relate to specific steps in the SAR signal transduction pathway. In particular, we address progress in the identification of biochemical markers for SAR, the role of salicylic acid in SAR, chemical activators of SAR, and progress in establishing genetic systems to further elucidate steps in the SAR signaling cascade.m

A total of 669 individual cow milk samples originating from asymptomatic cows from 16 dairy farms were examined for the presence of microorganisms with the potential to cause mastitis. Coagulase-negative staphylococci clearly predominated (53.5% positive samples) followed by streptococci and enterococci (both occurring in 16.1% samples). Among streptococci, so-called mastitis streptococci (S. uberis, S. dysgalactiae and S. agalactiae) prevailed (11.7% positive samples). Enterobacteriaceae were found in 10.0% samples, most of which (6.6% samples) were positive for Escherichia coli. Yeasts (mainly Candida spp.) were found in 8.2% samples. One of the major mastitis pathogens, Staphylococcus aureus subsp. aureus, was isolated from 9.0% of samples. S. aureus isolates were further characterised in terms of their capability to form biofilm, antimicrobial susceptibility and clonality (PFGE). All S. aureus isolates were capable of biofilm formation and were generally susceptible to the majority of tested antibiotics. The exception was ampicillin, resistance to which was observed in 27.7% isolates. Therefore, the relatively frequent occurrence of S. aureus could be attributed to persistent intramammary infections due to biofilm formation rather than low efficacy of particular antibiotics. PFGE analysis revealed clonal spread of certain S. aureus isolates within and between farms indicating that certain lineages of S. aureus mastitis strains are particularly successful.

▪ Abstract  Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.

The antimicrobial activity of six plant extracts from Ocimum basilicum, Azadirachta indica, Eucalyptus chamadulonsis, Datura stramonium, Nerium oleander, and Allium sativum was tested for controlling Alternaria solani in vitro and in vivo. In in vitro study the leaf extracts of D. stramonium, A. indica, and A. sativum at 5% concentration caused the highest reduction of mycelial growth of A. solani (44.4, 43.3 and 42.2%, respectively), while O. basilicum at 1% and 5% concentration and N. oleander at 5% concentration caused the lowest inhibition of mycelial growth of the pathogen. In greenhouse experiments the highest reduction of disease severity was achieved by the extracts of A. sativum at 5% concentration and D. stramonium at 1% and 5% concentration. The greatest reduction of disease severity was achieved by A. sativum at 5% concentration and the smallest reduction was obtained when tomato plants were treated with O. basilicum at 1% and 5% concentration (46.1 and 45.2 %, respectively). D. stramonium and A. sativum at 5% concentration increased the fruit yield by 76.2% and 66.7% compared to the infected control. All treatments with plant extracts significantly reduced the early blight disease as well as increased the yield of tomato compared to the infected control under field conditions.

Plants are constantly being challenged by aspiring pathogens, but disease is rare. Why? Broadly, there are three reasons for pathogen failure. Either (1) the plant is unable to support the niche requirements of a potential pathogen and is thus a non-host; or (2) the plant possesses preformed structural barriers or toxic compounds that confine successful infections to specialized pathogen species; or (3) upon recognition of the attacking pathogen, defense mechanisms are elaborated and the invasion remains localized. All three types of interaction are said to be incompatible, but only the latter resistance mechanism depends on induced responses. Successful pathogen invasion and disease (compatibility) ensue if the preformed plant defenses are inappropriate, the plant does not detect the pathogen, or the activated defense responses are ineffective. In this review, we examine the essential prerequisites for pathogen recognition and the induction of localized defense responses. Preformed defenses are considered elsewhere in this issue. Race-specific pathogen recognition is hypothesized to result from the direct or indirect interaction of the product of a dominant or serodominant plant resistance (R) gene with a product derived from the corresponding dominant pathogen avirulence (Avr) gene. Subsequent signal transduction events are assumed to coordinate the activation of an array of defense responses. This \"simple\" model appears to explain much but begs many questions. For example, R gene products are likely to provide key components for recognition, but how do the distinct classes of R proteins characterized to date activate the defense response? Do different R gene classes activate distinct responses? The regulation of some components of defense mechanisms has been studied in plant cell cultures in response to non-race-specific elicitors, but to what extent do such studies provide a model for R gene function? Plant resistance is often correlated with the activation of specific defense responses, but which (if any) are required to abolish or retard pathogen growth, and how? Which are primary responses and which are secondary? Does the first response involve transcriptional regulation, the activation of preformed enzymes, and/or the opening of ion channels, or are these possibilities nonexclusive? Is the response fine-tuned to the specific pathogen that elicits it? Do the defense responses differ between plant organs, or do they vary according to the attack strategy of the pathogen? To address these questions, we first review the responses that have been correlated with the activation of defense mechanisms in R-Avr gene-dependent resistance and in plant species in which the pathogen never causes disease, that is, nonhost resistance. We then assess the significance of these mechanisms in a few selected examples involving R genes. After considering possible signaling mechanisms and the mechanisms that could initially amplify and subsequently attenuate the response, we discuss the difficulties involved in assessing the functional significance of responses that are correlated with resistance. Some interesting related topics, such as the relationship between R gene structure and function, the significance of disease lesion mimics, and the phenomenon of systemic acquired resistance (SAR), receive limited attention here and are covered elsewhere in this issue. In Figure 1, various induced defense responses encountered by invading microbes are depicted.