Tomatoes are a high value crop for growers. High tunnels and greenhouses are used with increasing frequency as a means to extend the growing season and to increase incomes on farms. In New York State, 489 farms grew tomatoes in protected environments such as greenhouses and high tunnels in 2017, which is more than triple the number of farms compared to 10 years ago. Sales from these tomatoes amounted to over $28 million dollars in 2017. Unfortunately, the fungal pathogen Passalora fulva also thrives in these protected environments and causes tomato leaf mold each year. The pathogen causes defoliation of leaves, and over time, this reduces yields. Little is known about the diversity of the pathogen and how aggressive current strains are to popular tomato varieties that are described as resistant. The purpose of my research project is to assist growers in the management of tomato leaf mold through characterization of pathogen isolates collected between 2017-2019 in New York State. The research will allow us to provide better recommendations to growers and extension specialists about the most resistant varieties of tomatoes to grow, and if the pathogen is surviving on-farm over winter. The research will be shared with extension educators and growers at meetings, expositions, and in newsletters. The results will also be presented to scientists at a national scientific conference and in a peer-reviewed journal.
Project objectives from proposal:
The purpose of my research project is to assist growers in the management of tomato leaf mold through characterization of isolates collected between 2017-2019. The research will allow us to provide better recommendations to growers and extension specialists about the most resistant varieties of tomatoes to grow, and if the pathogen is surviving on-farm over winter.
1) Complete a final collection of tomato leaf mold samples from high tunnels throughout New York State in 2019. A final year of sample collection from across NYS State will contribute to an isolate collection that began in 2017. Samples will be received from growers and extension specialists and I will travel to collect samples in August in locations where tomato leaf mold has been a concern. Isolates will be obtained from lesions on foliage and single conidial isolates will be obtained in order to ensure that each isolate is genetically pure. I will have a total sample size of ~50 isolates.
2) Determine the race of Passalora fulva isolates collected between 2017-2019. To determine race, each isolate will be inoculated on a differential set of tomatoes containing a specific resistance gene. There will be three replications of each inoculation and negative water controls. Observations will be recorded based one whether disease symptoms are seen on any of the 11 tomato varieties carrying a different resistance gene after inoculation with each isolate. This protocol has been used to correctly determine the race of P. fulva isolates [7,8].
3)Evaluate the efficacy of currently available resistant tomato varieties. As we are determining the race of each isolate, each isolate will also be used to inoculate commercially available varieties that have been described as resistant and were found to be resistant in our previous trials using only a single isolate. Varieties include: Primo Red, Red Mountain, Red Deuce, BeOrange, Rebelski and Gereonimo. The susceptible grower favorite SunGold will also be included as a control. Because growers have reported some disease on tomato varieties thought to be resistant, testing each isolate against each tomato variety is critical.