1a.Objectives (from AD-416)
The overall objective of this proposal is to refine the current management strategies based on industry needs to reduce overall levels of PVY and prevent the continued spread of necrotic and recombinant strains.
1b.Approach (from AD-416)
Our overall objective in this proposal is to refine the current management strategies used by the certification agencies to reduce the initial virus inoculum planted in the field and those used by growers to reduce the spread of virus within the crop. Specifically, we will
1. Work with seed certification agencies to monitor PVY strains and develop new diagnostic and training tools to better identify and eliminate PVY from seed stocks.
"Specialty Crops Research Initiative"
2. Work with breeding programs to better recognize and screen for virus resistance and symptom expression.
3. Work with growers to develop cost effective virus control strategies for both minituber and conventional seed production that can be implemented on the farm.
A majority of the effort in the second year of this project was the continued monitoring of PVY strain distribution and relative incidence in the US seed potato crop, the development and implementation of a national PVY resistance evaluation network for the U.S. potato breeding programs, the establishment of a web based training module on PVY symptom expression for major U.S. potato cultivars, and the analysis of first year field experiments. The ordinary strain of PVY still predominates in the US seed potato crop, but the relative incidence of PVYO is decreasing, while the recombinant strains PVYN-Wi and PVYNTN are increasing. We are also documenting an increase in the distribution of the tuber necrotic strain, PVYNTN. This strain is being identified in more Midwest and Eastern seed potato production areas. There is also an increase in the number of reports by growers of identifying tuber necrosis disease in commercial fields. Many of the most widely planted potato cultivars are being screened in both greenhouse and field studies to determine their susceptibility to tuber necrosis disease caused by PVY. A majority of the yellow flesh, white cultivars are especially susceptible, whereas red skin and russet cultivars tend not to display tuber necrotic symptoms. However, we have identified some red skin and russet cultivars that are susceptible to tuber necrosis. Working with several US breeding programs we have generated clean seed for over 30 promising potato clones suspected of have some degree of resistance to PVY. Clean seed was distributed to three trial sites (NY, WI, ID) and is currently being tested for foliar and tuber reactions to several PVY strains. 2010 field studies evaluated the effect of initial PVY inoculum in the planted seed on the levels of disease developing in the crop during the growing season. Current certification rules allow replanting of seed that has up to 5% virus for recertification. Levels of 10% or higher are allowed for potatoes planted for commercial production. Preliminary findings indicate virus incidence can be expected to increase 5-10 fold and yield can be decreased by up to 1000 pounds per acre for every 1% of virus. Field trails also evaluated a number of insecticides and feeding inhibitors for their ability to decrease virus incidence by decreasing the aphid populations or their ability to transmit virus. Preliminary data indicate that a few compounds may be effective when applied at appropriate intervals.