Location: Vegetable Crops Research2013 Annual Report
1a. Objectives (from AD-416):
Build on previous work and study new opportunities to advance our abilities to manage late blight in commercial settings as well as breed resistant varieties. Characterize late blight resistance of the best RB/conventionally bred progeny from previous work and continue to breed new late blight resistant combinations in elite breeding material Determine the survival potential and epidemic initiation risk of P. infestans genotypes in tubers
1b. Approach (from AD-416):
A multi-disciplinary approach will be undertaken to study P. infestans, apply emerging genetic approaches, breed resistant germplasm, conduct field studies, and provide recommendations to the growers. An understanding of molecular interactions between host R gene products and pathogen effectors has provided valuable data that will allow us to identify or engineer novel R-genes that can be used in breeding programs. Characterization of the overwintering ability of novel P. infestans genotypes as mycelia on currently grown potato varieties and as oospores in field soil will provide needed biological information to production scientists for estimating epidemic risk for improved control recommendations. Cooperator will be responsible for studies on the overwintering capabilities of various P. infestans strains on potato tubers as well as assisting in field screening of germplasm.
3. Progress Report:
This project was renumbered from 3655-21000-049-19S to 3655-21220-002-06S. Weather based integrated pest management (IPM) tools have been shown to be very cost effective for the management of late blight, by allowing growers to reduce the amount of fungicide needed to achieve optimal disease control. Since this disease has caused significant economic damage and requires a considerable amount of management (particularly chemical), it is ideally suited for incorporation into an IPM program, which uses weather based IPM tools. Current IPM strategies to control potato late blight have consisted of using cultural management components and making foliar fungicide timing and application more efficient. These strategies have been aided by the development of the late blight risk model available on the Late Blight Risk Management website. However, if the major goals of a late blight IPM program are product quality, environmental stewardship, and producer profitability, then measures that prevent or reduce the risk of disease initiation and development, such as destruction of sources of initial inoculum (cull piles and volunteer potatoes), planting of certified seed, and the timely application of efficacious and cost effective fungicides will prove most beneficial. For the past three years, potato late blight has not been reported in Michigan and to a large extent has resulted from the implementation of IPM models. The potato industry is a $150 million farm gate value and provides direct and indirect work opportunities and indirect through the processing industries. The industry continues to expand in Michigan due in part to effective disease management programs. For the past few years’ crop protection for disease management has been about $100/A whereas in states with late blight epidemics the cost is closer to $200-300/A. The tuber inoculation studies were conducted at Clarksville Horticultural Experimental Station, Clarksville, Michigan from November 2011 to May 2013. Tubers of the commonly grown varieties “Snowden,” “Pike,” “Russet Norkotah,” and “Superior” were inoculated with isolates of two genotypes of P. infestans (2 x US-22 isolates; 2 x US-8 isolates; 1 x non-inoculated) and buried at 4 depths (0, 15, 30, and 45 cm). The trial design was a split block with depth as the main effect, and cultivar and genotype as interacting variables. The tubers were left to overwinter. The number of emerged plants was recorded over a 60-day period after soil temperature at 15 cm reached 10°C and final plant stand (%) was measured. Signs and symptoms of potato late blight were recorded. In both years of the study 3 and 5 plants emerged as volunteers in 2012 and 2013, respectively, both from non-inoculated treatments. All inoculated tubers rotted prior to emergence in both years. Soil temperatures recorded at the site over both seasons indicated a moderate risk of volunteer survival. In addition, sample tubers were recovered from a separate site in 2012 and survival of P. infestans determined at each depth x cultivar x genotype interaction. The pathogen did not survive well in tubers buried at 45 cm but could be recovered to varying degrees at 15 and 30 cm depths. This research relates to objective 3 of the project through the evaluation of late blight resistant potato advanced breeding lines and further relates to objective 4 in the updated project through the determination of the overwintering potential of P. infestans genotypes on potato tubers.