Epidemiology and enhanced control of Potato virus Y in high grade seed potato production

Show full item record



Permalink

http://urn.fi/URN:ISBN:978-952-10-8892-6
Title: Epidemiology and enhanced control of Potato virus Y in high grade seed potato production
Author: Kirchner, Sascha
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences
Publisher: Helsingin yliopisto
Date: 2014-02-14
URI: http://urn.fi/URN:ISBN:978-952-10-8892-6
http://hdl.handle.net/10138/42693
Thesis level: Doctoral dissertation (article-based)
Abstract: Background: The control of Potato virus Y (PVY, genus Potyvirus, family Potyviridae) is one of the greatest challenges in seed potato production worldwide. PVY can cause substantial economic losses. It reduces the growth of potato plants and the quality and quantity of yield. Therefore, when virus incidence exceeds set thresholds, the potatoes cannot be sold as seed but have to be sold at a lower price for consumption. PVY is transmitted in a non-persistent manner by winged forms of many aphid species. This mode of transmission is characterised by short probing activity, which is sufficient for acquisition and transmission of the virus. Because of these underlying epidemiological factors, PVY is difficult to control. Around 2005, the High grade (HG) seed potato production area in Finland, which is one of the northernmost intensive crop production areas of the world, saw a marked increase in the incidence of PVY in potato seed lots. Therefore, it became necessary to investigate the epidemiology of PVY and establish measures of PVY control in this region. ----- Aims: 1) To characterise the species composition and phenology of the aphid fauna. 2) To determine the incidence of aphid species with documented ability to transmit PVY and to use a modelling approach to determine their relative importance as vectors including timing of virus transmission. 3) To compare the application of straw mulch, mineral oil and birch extract with chemical practices for control of PVY vectors. Methods: The area under study was Tyrnävä-Liminka (latitude 64°) in Finland. Studies were carried out in the potato growing seasons from 2007 to 2012. Aphid flight activity was monitored by yellow pan traps (YPT) placed in 4 8 seed potato fields per year and by one suction trap. Aphid identification was done by morphological characteristics and by DNA barcoding based on a 658-bp long region of the mitochondrial gene for cytochrome c oxidase I (COI). A cluster analysis was used to categorise phenology of species. Incidence of PVY was measured by testing leaves collected two weeks after plant emergence and in the progeny tubers after harvest by enzyme-linked immunosorbent assay (ELISA). To determine the most important time of transmission of PVY, and the main vectors, the seasonal increase in PVY incidence was modelled using aphid counts in traps, the relative vector efficiencies of the aphids, virus resistance of cultivars, and the initial infection rate of the seed tubers as explanatory variables in generalised linear mixed modelling. In addition, small scale experiments (SSE) were conducted in three years and large scale (LSE) field trials in two years. SSE were set up to compare applications of straw mulch, mineral oil and birch extract with chemical control of PVY vectors. LSE were conducted in growers fields to test efficacy of straw mulch to control PVY at farm scale. ---- Results: A total of 58,528 winged aphid individuals were classified into 83 taxa based on morphology: Of these, 34 species were further characterised by DNA barcoding. Four phenology clusters were found. The late-peak cluster was dominated by heteroecious species and the mid-peak cluster was dominated by monoecious species feeding on herbaceous plants. Total abundance showed a recurring triennial cycle according to the catch of aphids using the suction trap in the years 2000-2010. The most abundant species was Rhopalosiphum padi. It occurred mainly at the end of the potato growing season. The highly polyphagous species, Aphis fabae and Aphis gossypii were found to peak at the beginning of the potato growing season. Results of the modelling approach showed that the incidence of seedborne PVY infection and the early-season flight of Aphis fabae are the most important factors contributing to the incidence of PVY in the yield. Other aphid species play a negligible role as vectors of PVY. In the SSEs, only straw mulch reduced of PVY incidence significantly in the progeny tubers, with the reduction ranging from 50% to 70% in all three years. Incidence of PVY was reduced by mineral oil in two years (by 43% to 58%) and by the synthetic pyrethroid insecticide esfenvalerate by 29% in one year. In the LSE, straw mulch significantly reduced PVY in the progeny tubers by 25% to 47%. Average tuber yield following the straw mulch treatment was generally but not significantly higher than that in the untreated control in all experiments. ---- Conclusion: The results demonstrate that early season flight activity of Aphis fabae determines PVY incidence in the HG seed potato production area of Finland with a generally low vector pressure. Furthermore, straw mulch emerges as a reliabe and effective measure in diminishing the spread of PVY in areas with early vector flight activity.Background: The control of Potato virus Y (PVY, genus Potyvirus, family Potyviridae) is one of the greatest challenges in seed potato production worldwide. PVY can cause substantial economic losses. It reduces the growth of potato plants and the quality and quantity of yield. Therefore, when virus incidence exceeds set thresholds, the potatoes cannot be sold as seed but have to be sold at a lower price for consumption. PVY is transmitted in a non-persistent manner by winged forms of many aphid species. This mode of transmission is characterised by short probing activity, which is sufficient for acquisition and transmission of the virus. Because of these underlying epidemiological factors, PVY is difficult to control. Around 2005, the High grade (HG) seed potato production area in Finland, which is one of the northernmost intensive crop production areas of the world, saw a marked increase in the incidence of PVY in potato seed lots. Therefore, it became necessary to investigate the epidemiology of PVY and establish measures of PVY control in this region. ---- Aims: 1) To characterise the species composition and phenology of the aphid fauna. 2) To determine the incidence of aphid species with documented ability to transmit PVY and to use a modelling approach to determine their relative importance as vectors including timing of virus transmission. 3) To compare the application of straw mulch, mineral oil and birch extract with chemical practices for control of PVY vectors. --- Methods: The area under study was Tyrnävä-Liminka (latitude 64°) in Finland. Studies were carried out in the potato growing seasons from 2007 to 2012. Aphid flight activity was monitored by yellow pan traps (YPT) placed in 4 8 seed potato fields per year and by one suction trap. Aphid identification was done by morphological characteristics and by DNA barcoding based on a 658-bp long region of the mitochondrial gene for cytochrome c oxidase I (COI). A cluster analysis was used to categorise phenology of species. Incidence of PVY was measured by testing leaves collected two weeks after plant emergence and in the progeny tubers after harvest by enzyme-linked immunosorbent assay (ELISA). To determine the most important time of transmission of PVY, and the main vectors, the seasonal increase in PVY incidence was modelled using aphid counts in traps, the relative vector efficiencies of the aphids, virus resistance of cultivars, and the initial infection rate of the seed tubers as explanatory variables in generalised linear mixed modelling. In addition, small scale experiments (SSE) were conducted in three years and large scale (LSE) field trials in two years. SSE were set up to compare applications of straw mulch, mineral oil and birch extract with chemical control of PVY vectors. LSE were conducted in growers fields to test efficacy of straw mulch to control PVY at farm scale. ---- Results: A total of 58,528 winged aphid individuals were classified into 83 taxa based on morphology: Of these, 34 species were further characterised by DNA barcoding. Four phenology clusters were found. The late-peak cluster was dominated by heteroecious species and the mid-peak cluster was dominated by monoecious species feeding on herbaceous plants. Total abundance showed a recurring triennial cycle according to the catch of aphids using the suction trap in the years 2000-2010. The most abundant species was Rhopalosiphum padi. It occurred mainly at the end of the potato growing season. The highly polyphagous species, Aphis fabae and Aphis gossypii were found to peak at the beginning of the potato growing season. Results of the modelling approach showed that the incidence of seedborne PVY infection and the early-season flight of Aphis fabae are the most important factors contributing to the incidence of PVY in the yield. Other aphid species play a negligible role as vectors of PVY. In the SSEs, only straw mulch reduced of PVY incidence significantly in the progeny tubers, with the reduction ranging from 50% to 70% in all three years. Incidence of PVY was reduced by mineral oil in two years (by 43% to 58%) and by the synthetic pyrethroid insecticide esfenvalerate by 29% in one year. In the LSE, straw mulch significantly reduced PVY in the progeny tubers by 25% to 47%. Average tuber yield following the straw mulch treatment was generally but not significantly higher than that in the untreated control in all experiments. --- Conclusion: The results demonstrate that early season flight activity of Aphis fabae determines PVY incidence in the HG seed potato production area of Finland with a generally low vector pressure. Furthermore, straw mulch emerges as a reliabe and effective measure in diminishing the spread of PVY in areas with early vector flight activity.
Subject: plant Pathology
Rights: This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.


Files in this item

Total number of downloads: Loading...

Files Size Format View
Kirchner_Thesis.pdf 616.8Kb PDF View/Open

This item appears in the following Collection(s)

Show full item record