The incidence of Turnip yellows virus in oilseed rape crops (Brassica napus L.) in three different regions of England over three consecutive growing seasons and the relationship with the abundance of flying Myzus persicae

Turnip yellows virus (TuYV) is the most important virus infecting oilseed rape in the UK. The incidence and spatial distribution of TuYV in winter oilseed rape (WOSR) crops in three regions of England was determined over three growing seasons. Leaf samples were collected from three fields in each region, in autumn (November–December) and spring (April) of the three crop seasons and tested for virus presence by enzyme‐linked immunosorbent assay. Infection was detected in all fields except one. Higher TuYV incidences were recorded in the 2007–08 (<89%) and 2009–10 (<100%) crop seasons than in 2008–09 (<24%). Highest incidences were recorded in Lincolnshire (<100%), followed by Warwickshire (<88%), with lowest incidences in Yorkshire (1–74%). There was a significant increase in incidence detected between autumn and spring sampling in eight fields, a significant decrease in one field and no significant change in 18 fields. Rothamsted Insect Survey suction trap data for the aphid Myzus persicae in Lincolnshire, Warwickshire and Yorkshire revealed two peaks of flight activity in most years (2007–2009). The second peak (September–November) coincided with emergence of WOSR. The highest cumulative (August–November) trap catches in the three regions during the three crop seasons occurred in Lincolnshire and the lowest in Yorkshire; catches in autumn 2009 were highest and lowest in autumn 2008. Regression analysis revealed a highly significant association between the cumulative numbers of M. persicae caught in the suction traps closest to the crops between August and November each year and the incidence of TuYV detected in the WOSR crops in the autumn of each year. Results are discussed in the light of factors affecting the spread of TuYV and future possibilities for control

High-resolution temporal profiling of transcripts during Arabidopsis leaf senescence reveals a distinct chronology of processes and regulation

Leaf senescence is an essential developmental process that impacts dramatically on crop yields and involves altered regulation of thousands of genes and many metabolic and signaling pathways, resulting in major changes in the leaf. The regulation of senescence is complex, and although senescence regulatory genes have been characterized, there is little information on how these function in the global control of the process. We used microarray analysis to obtain a highresolution time-course profile of gene expression during development of a single leaf over a 3-week period to senescence. A complex experimental design approach and a combination of methods were used to extract high-quality replicated data and to identify differentially expressed genes. The multiple time points enable the use of highly informative clustering to reveal distinct time points at which signaling and metabolic pathways change. Analysis of motif enrichment, as well as comparison of transcription factor (TF) families showing altered expression over the time course, identify clear groups of TFs active at different stages of leaf development and senescence. These data enable connection of metabolic processes, signaling pathways, and specific TF activity, which will underpin the development of network models to elucidate the process of senescence

Turnip mosaic virus (TuMV) is able to use alleles of both eIF4E and eIF(iso)4E from multiple loci of the diploid Brassica rapa

Three copies of eIF4E and three copies of eIF(iso)4E have been identified and sequenced from a Turnip mosaic virus (TuMV)-susceptible, inbred, diploid Brassica rapa line, R-o-18. One of the copies of eIF4E lacked exons 2 and 3 and appeared to be a pseudogene. The two other copies of eIF4E and two of the three copies of eIF(iso)4E were isolated from a bacterial artificial chromosome library of R-o-18. Using an Arabidopsis line (Col-0::dSpm) with a transposon knock-out of the eIF(iso)4E gene which resulted in a change from complete susceptibility to complete resistance to TuMV, complementation experiments were carried out with the two versions of eIF4E and the two versions of eIF(iso)4E. When transformed into Col-0::dSpm, all four Brassica transgenes complemented the Arabidopsis eIF-(iso)4E knock-out, conferring susceptibility to both mechanical and aphid challenge with TuMV. One of the copies of eIF4E did not appear to support viral replication as successfully as the other copy of eIF4E or the two copies of eIF(iso)4E. The results show that TuMV can use both eIF4E and eIF(iso)4E from B. rapa for replication and, for the first time, that a virus can use eIF4E and eIF(iso)4E from multiple loci of a single host plant

Disturbance of Arabidopsis thaliana development by a potyviral infection maps to the P3/p6k1 viral genomic region

Infections of plants by viruses induce plant disease and associated symptoms result in economic losses in crops. The study of viral infections has led to the discovery of RNA silencing as a plant defence mechanism against plant pathogens and of viral suppressors of gene silencing as the viral mechanism to counter such plant defence. In addition, it has led to the unravelling of the role of small RNAs (sRNAs) in plant development. Developmental symptoms associated with plant disease have been attributed in some systems to the effects of the viral suppressors of gene silencing on the normal performance of the plant sRNA machinery. In the model system Arabidopsis thaliana - Turnip mosaic virus, a potyvirus two different strains of which induce very different disturbances of the plant development, we have identified the viral determinant of developmental symptoms in the P3/p6k1 region, different from the described viral suppressor of gene silencing (HC-Pro). This result emphasises the role of the different viral proteins in disease induction, opens the way to deepen our knowledge of the potyviral proteins in the viral cycle and also to better understand plant growth regulation. Results will be presented and discussed

Exploiting eIF4E-based and associated broad-spectrum recessive resistance to potyviruses in dicots and monocots

The main aim of the proposed project is to exploit sources of recessive eIF4E-based resistance to potyviruses in dicots and monocots including related broad-spectrum resistance. This project is part of the BBSRC 'Innovation in crop science - exploitation of genetics for sustainability' initiative. The following specific objectives will be pursued: Objective 1. Studying the natural allelic variation in eIF4Ee controlling recessive resistance to potyviruses in Brassica rapa and barley and a possible role for eIF(iso)4E in B. rapa . Objective 2. Identifying and characterising novel chemically induced eIF4E and eIF(iso)4E alleles in barley through a TILLING approach. Objective 3. Identifying the gene which in combination with eIF4E provides broad-spectrum resistance to TuMV in the diploid brassica species B. rapa. Objective 4. Producing broadly applicable, transferable molecular markers for superior eIF4E alleles in brassicas and barley and for the additional gene which is involved in broad-spectrum resistance to TuMV in brassicas. Objective 5. Molecular modelling simulation: Homology modelling the 3D protein structure of novel eIF4E variants to predict superior resistance alleles for deployment in breeding and analysis of the interaction between eIF4E and the VPg of bymoviruses and TuMV. The deliverables from the project will be plant lines possessing genes providing new resistances to important viruses, along with allele-specific markers for the genes

Identification of new isolates of Turnip mosaic virus that cluster with less common viral strains

Turnip mosaic virus (TuMV) was found infecting cultivated brassicas and wild and cultivated ornamental Brassicaceae plants in different regions of Spain. Five new TuMV isolates, originating from different host plant species (Brassica cretica, Brassica juncea, Brassica napus, Eruca vesicaria subsp. sativa and Sisymbrium orientale), have been identified. The nucleotide sequences of the coat protein (CP) genes of the five isolates were determined. Phylogenetic analysis of the CP sequences showed that the five isolates grouped into two different clusters. The three isolates from the central region of Spain clustered with a previously reported Pisum sativum isolate from southeastern Spain, whereas the other two isolates from the eastern region clustered with two Italian and two Greek isolates. Both clusters were genetically distinct and belonged to the multi-lineage group OBR. The OBR group contains mainly TuMV isolates from hosts other than Brassica spp. and Raphanus sativus and mostly originating from Mediterranean countries. These new sequences provide further phylogenetic resolution of the OBR group. Although new TuMV isolates have been found in Spain, they were not associated with any serious disease outbreaks