AN INTRASEASONAL BIOECONOMIC MODEL OF PLRV NET NECROSIS

A bioeconomic model is developed as an IPM planning tool to combat PLRV net necrosis in the PNW potato industry. Environmental/biological and production processes are linked to marketing activities using discrete time control. We find that pesticides can be optimally timed to reduce applications and still protect against net necrosis.Crop Production/Industries, Environmental Economics and Policy,

Distribution and incidence of viruses in Irish seed potato crops

peer-reviewedVirus diseases are of key importance in potato production and in particular for the production of disease-free potato seed. However, there is little known about the frequency and distribution of potato virus diseases in Ireland. Despite a large number of samples being tested each year, the data has never been collated either within or across years. Information from all known potato virus testing carried out in the years 2006–2012 by the Department of Agriculture Food and Marine was collated to give an indication of the distribution and incidence of potato virus in Ireland. It was found that there was significant variation between regions, varieties, years and seed classes. A definition of daily weather data suitable for aphid flight was developed, which accounted for a significant proportion of the variation in virus incidence between years. This use of weather data to predict virus risk could be developed to form the basis of an integrated pest management approach for aphid control in Irish potato crops

Molecular characterization, cloning and sequencing of coat protein gene of a Pakistani potato leaf roll virus isolate and its phylogenetic analysis

Total RNA was extracted from potato leaf roll virus (PLRV) positive potato plants and complementary DNA were synthesized. Reverse transcriptase polymerase chain reaction (RT-PCR) based detection conditions were optimized by using coat protein (CP) gene specific primers. A 346 bp amplicon of PLRV- coat protein (CP) gene was amplified. Amplified CP-gene of PLRV was cloned in TA cloning vector, PCR ® 2.1. The clone was confirmed subsequently through restriction digestion analysis. PCR amplification used cDNA clone as a template and nucleotide sequencing. Expected nucleotide sequence of amplified PLRV-CP gene show homology of 94 to 97% when compared to the sequences already reported in GenBank database. This explored novel PLRV-CP gene was submitted at NCBI GenBank for characterization of PLRV Pakistani isolate (Accession No. JN039286). Phylogenetic analysis was also carried out and tree was made by using MEGA 4.0.Key words: Potato, potato leaf roll virus (PLRV), coat protein (CP) gene, reverse transcriptase polymerase chain reaction (RT-PCR), PLRV-CP Pakistani isolate

Molecular studies on the sweet potato virus disease and its two causal agents

The studies presented in this thesis contribute to an increased understanding of the molecular aspects, variability and interaction of the two most important viral pathogens of sweet potato (Ipomoea batatas L): Sweet potato feathery mottle virus (SPFMV) and Sweet potato chlorotic stunt virus (SPCSV), which cause the severe sweet potato virus disease (SPVD) when co-infecting sweet potato plants. SPVD is the most important disease affecting sweet potato in Africa, and may be the most important virus disease of sweet potato globally. The coat protein gene sequences of several African SPFMV isolates were determined and compared by phylogenetic analyses. Results showed that East African SPFMV isolates were genetically distinct. They could furthermore be divided into two serotypes which differed in their ability to systemically infect the sweet potato cultivar Tanzania. The aetiology of SPVD was studied in sweet potato plants co-infected with SPFMV and SPCSV using nucleic acid hybridisation, bioassays, tissue printing and thin section immunohistochemistry. Resistance to SPFMV in East African sweet potato cultivars was found to be due to inhibition of virus replication rather than movement and resistance was suppressed by infection with SPCSV, resulting in a ca. 600-fold increase in titres of SPFMV. Furthermore, in SPVD affected plants SPFMV is detected outside of the phloem, whereas SPCSV is detected only inside the phloem, which suggests novel as yet unknown mechanisms how SPCSV synergises SPFMV. The genomic sequence of SPCSV was determined. It was composed of two RNA molecules (9407 and 8223 nucleotides), representing the second largest (+)ssRNA genome of plant viruses. The genomic organization of SPCSV revealed novel features for the genus Crinivirus, such as i) the presence of a gene putatively encoding an ribonuclease III-like protein, ii) near-identical, 208 nucleotides long 3’-sequences on both viral RNAs, and iii) the placement of the SHP gene at a new position on the genome of SPCSV relative to other closteroviridae. Northern analyses showed the presence of several sub-genomic RNAs, of which the accumulation was temporally regulated in infected tissues. The 5’-ends of seven sub-genomic RNAs were determined using a PCR based method, which indicated that the sgRNAs were capped

Detection of potato leafroll virus isolated from potato fields in Tehran province in aphids by immunocapture reverse transcription polymerase chain reaction

The surveys conducted during 2006 and 2007 revealed the infection of the virus in potato fields in Tehran province. Due to the important roll of aphids in transmission of the virus, immunocapture reverse transcription polymerase chain reaction (IC-RT-PCR) and reverse transcription polymerase chain reaction (RT-PCR) was developed using potato leafroll virus (PLRV) specific antibodies and specific primer pair (20 mer) located in the virus capsid gene to detect the virus in aphids. A 336-bp PCR product was detected from aphids (Myzus persicae) which had been fed on PLRV-infected plants. The PCR band was specific to PLRV as determined in PLRV-infected plants. This inquiry shows that this method is applicable to assess viroliferous nature of aphids in yellow -pan traps during season

Pyramiding of Ryd2 and Ryd3 conferring tolerance to a German isolate of Barley yellow dwarf virus-PAV (BYDV-PAV-ASL-1) leads to quantitative resistance against this isolate

Barley yellow dwarf virus (BYDV) is an economically important pathogen of barley, which may become even more important due to global warming. In barley, several loci conferring tolerance to BYDV-PAV-ASL-1 are known, e.g. Ryd2, Ryd3 and a quantitative trait locus (QTL) on chromosome 2H. The aim of the present study was to get information whether the level of tolerance against this isolate of BYDV in barley can be improved by combining these loci. Therefore, a winter and a spring barley population of doubled haploid (DH) lines were genotyped by molecular markers for the presence of the susceptibility or the resistance encoding allele at respective loci (Ryd2, Ryd3, QTL on chromosome 2H) and were tested for their level of BYDV-tolerance after inoculation with viruliferous (BYDV-PAV-ASL-1) aphids in field trials. In DH-lines carrying the combination Ryd2 and Ryd3, a significant reduction of the virus titre was detected as compared to lines carrying only one of these genes. Furthermore, spring barley DH-lines with this allele combination also showed a significantly higher relative grain yield as compared to lines carrying only Ryd2 or Ryd3. The QTL on chromosome 2H had only a small effect on the level of tolerance in those lines carrying only Ryd2, or Ryd3 or a combination of both, but the effect in comparison to lines carrying no tolerance allele was significant. Overall, these results show that the combination of Ryd2 and Ryd3 leads to quantitative resistance against BYDV-PAV instead of tolerance