Screening techniques and sources of resistance to foliar diseases caused by major necrotrophic fungi in grain legumes

Summary Necrotrophic pathogens of the cool season food legumes (pea, lentil, chickpea, faba bean and lupin) cause wide spread disease and severe crop losses throughout the world. Environmental conditions play an important role in the development and spread of these diseases. Form of inoculum, inoculum concentration and physiological plant growth stage all affect the degree of infection and the amount of crop loss. Measures to control these diseases have relied on identification of resistant germplasm and development of resistant varieties through screening in the field and in controlled environments. Procedures for screening and scoring germplasm and breeding lines for resistance have lacked uniformity among the various programs worldwide. However, this review highlights the most consistent screening and scoring procedures that are simple to use and provide reliable results. Sources of resistance to the major necrotrophic fungi are summarized for each of the cool season food legumes. Marker-assisted selection is underway for Ascochyta blight of pea, lentil and chickpea, and Phomopsis blight of lupin. Other measures such as fungicidal control and cultural control are also reviewed. The emerging genomic information on the model legume, Medicago truncatula, which has various degrees of genetic synteny with the cool season food legumes, has promise for identification of closely linked markers for resistance genes and possibly for eventual map-based cloning of resistance genes. Durable resistance to the necrotrophic pathogens is a common goal of cool season food legume breeders.     

DNA sequence polymorphisms and their application to bread wheat quality

Single-nucleotide polymorphisms (SNPs) constitute an abundant source of DNA polymorphisms, which have been successfully used to identify loci that are associated with a particular phenotype. Additionally, such markers could be efficiently used in combination with doubled haploid technology to improve the efficiency of breeding programmes. Information on such markers in plants is still scarce. For bread wheat, SNP data are restricted to a few genes. This can be explained by the hexaploidy of Triticum aestivum which makes SNP discovery difficult. We developed a novel method for SNP discovery in bread wheat. The strategy is based on the development of highly specific PCR-primers, which were used to sequence 27 lines. SNPs were discovered from sequence alignment data. Some SNPs were identified by mass spectrometry in a collection of 113 lines, which were both evaluated for agronomic traits and genotyped at 42 neutral microsatellite loci. Traits investigated include: protein content, the quantity of high-molecular-weight glutenins and that of the GluBx subunit. The 42 markers were used to infer population structure, which was included in linear models for association studies. The results of this preliminary study showed 89 SNPs in approximately 20 kbp, i.e., one SNP every 223 bp on average. Six SNPs were genotyped: three were located along the sequence of Glu-B1-1, while three non-synonymous SNPs were located along the sequence of the B homoeologous gene coding for SPA (Storage Protein Activator). The SNPs from Glu-B1-1 had a significant effect on the studied variables, whereas those of SPA had no effect. Such results might indicate that some haplotypes for Glu-B1-1 are linked to higher protein content, through an increased amount of high-molecular-weight glutenins, especially the GluBx subunit.     

反刍动物肝片吸虫病--免疫与疫苗策略

反刍动物肝片吸虫病在世界范围内对畜牧业造成严重的经济损失，需要研制疫苗进行防制。本文介绍动物肝片吸虫病的保护性免疫应答的表现形式，对保护性免疫应答效应机制和寄生虫免疫逃避机制展开讨论，阐述选择疫苗候选抗原的不同策略，最后探讨研制抗肝片吸虫疫苗所受到的限制因素。     

Natural cyclopeptides as leads for novel pesticides: tentoxin and destruxin

Difficulties in synthesis make natural cyclopeptides challenging targets for chemists. Our interest focused on two natural toxic cyclopeptide series produced by pathogenic fungi: tentoxin, [cyclo-(N-MeAla¹-Leu²-N-Meδ^zPhe³-Gly⁴)] and the destruxins [cyclo-(Pro¹-Ile²-N-MeVal³-N-MeAla⁴-β-Ala⁵-HA⁶)]. The total syntheses of these two bioactive series were optimised, and several analogues were designed and synthesised to establish structure–activity relationships. The importance of synthetic analogues in the identification of molecular targets and the explanation of mechanisms of action was demonstrated. Such systematic investigations can determine the crucial features responsible for the activity of the natural compound and help the design of more powerful or more selective products. © 1998 SCI.     

Size and dispersion of urticating setae in three species of processionary moths

Larvae of the processionary moths of the Palaearctic region bear urticating setae that are released against vertebrate predators, especially insectivorous birds. A few species are pests of forest and urban trees and, consequently, may threaten human and animal health during outbreaks, causing dermatitis, conjunctivitis and respiratory distress. Although some studies provide detailed information about the setae, particularly those of the pine processionary moth Thaumetopoea pityocampa, there is little knowledge on the morphological traits of the setae and their release by the larvae. In the present study we identify major traits of the setae of 3 species of processionary moth, T. pityocampa, T. pinivora and T. processionea, which are potentially helpful in the understanding of setae dynamics in the environment: (i) diameter and length of setae and (ii) analysis of dynamical properties of the setae in the airborne state. Setae are highly variable in size, with bimodal distribution in T. pityocampa and T. pinivora; in these 2 species, short and long setae are interspersed within the integument fields where they occur. The difference in the seta size has important consequences in dispersion, as smaller setae can spread 5 times further than their bigger counterparts. This information is relevant for a full understanding of the defensive importance of larval setae against natural enemies of the processionary moths, as well for elucidating the importance of the processionary setae as air pollutants, both close to the infested trees and at longer distances.     

The invasion process of bovine erythrocyte by Babesia divergens: knowledge from an in vitro assay

ABSTRACT: Babesia divergens is a tick-transmitted apicomplexan parasite for which asexual multiplication in its vertebrate hosts is restricted to erythrocytes. Current knowledge of invasion of these target cells is limited. An efficient in vitro invasion assay was set up to gain access to this information. Parasites prepared from infected RBC, lysed by electroporation, and mixed with bovine RBC in a selected synthetic medium (RPMI 1640 supplemented with calcium) were able to establish subsequent cultures with parasitemia ranging from 6 to 14%. Free parasites remaining in the invasion medium could be eliminated by Percoll gradient and culture could be pursued with the freshly invaded erythrocytes. In this way, the invasion time window could be shortened to obtain a synchronised start of the culture or to study the kinetics of invasion. With this assay we demonstrate that 1) erythrocyte invasion by B. divergens is a rapid process since 70% of the invasion-competent parasites invaded the RBC in less than 45 s; 2) all invasion-competent parasites achieved invasion within 10 min of contact; 3) one erythrocyte could be invaded concomitantly by two merozoites; 4) despite a synchronous start, the parasite population evolved heterogeneously resulting in a progressive loss of synchronisation. Western blot analysis of proteins collected from invasion medium were performed with sera from animals experimentally infected with B. divergens and highlighted several proteins. The dose-dependent, inhibitory effects of these sera on B. divergens invasion suggest that these proteins might be involved in the invasion process. Further investigations are required for their characterisation.     

A side effect of decreased fertility associated with vaccination against bluetongue virus serotype 8 in Holstein dairy cows

Inactivated virus vaccines have been widely used to control bluetongue after introduction of serotype 8 of the bluetongue virus (BTV) in northern Europe in 2006. To evaluate vaccination, quantitative knowledge of its possible side effects is needed. One current adverse reaction with inactivated vaccines is a rise in body temperature, which could reduce cow reproductive performance. The objective of this study was to quantify a possible side effect of vaccination on fertility before the implantation of the embryo of dairy cows under field conditions. The study was performed on herds that were not exposed to BTV. Fertility was assessed by return-to-service following artificial insemination (AI). Biological assumptions for a possible side effect of vaccination were conception failure and embryonic death. Associations between return-to-service rates and vaccine injections were assessed using mixed-logistic regression models and survival analysis. Two models were considered: a 3-week-return-to-service model comparing cows vaccinated between 3 days before and 16 days after AI and unvaccinated cows (assuming an effect on conception failure or early embryonic death), and a 90-day-return-to-service model comparing cows vaccinated between 3 days before and 42 days after AI and unvaccinated cows (assuming an effect on conception failure, early or late embryonic death). Only cows receiving a second vaccine injection between 2 and 7 days after AI had a significantly higher risk of 3-week-return-to-service (RR=1.19 [1.07-1.33]). This corresponds to an increase of return-to-service by 4 percentage points. A side effect of vaccination could be due to early embryonic death. The slight side effect on fertility associated with vaccination was low compared to effects of BTV-8 exposure on fertility.