Small Molecule Compounds for Management of Bacterial Spot Disease in Tomatoes

Reduces Disease Severity and Progress by Targeting Copper-Resistant Bacterial Species for Spot Management

These small molecule organic compounds serve as bactericides for treating and preventing bacterial spot disease in tomatoes. Tomato is among the most widely consumed vegetable crops with significant economic importance in the USA and worldwide. The total crop value is over $1.8 billion in the USA and $336.5 million in Florida, which ranks first in fresh market tomato production and second in total tomato production. Bacterial spot disease, caused by four species of the genus Xanthomonas, is an economically important tomato disease, causing destructive infection and resulting in significant crop loss. In Florida, X. perforans is the primary pathogen causing bacterial spot on tomatoes. The warm and wet conditions of the state favor disease development, particularly during the growing season. X. perforans spreads by contaminated seed and transplants, wind-driven rain, irrigation waters through overhead sprinklers, and the clipping of tomato transplants. The management of bacterial spot of tomato is a major challenge for tomato growers.

Currently, bacterial spot management largely relies on applying fixed copper-based bactericides. However, control by copper-based compounds is often marginal or ineffective in Florida, with a widespread presence of copper-resistant strains of the pathogen. The accumulation of copper in the environment is also a concern regarding the excessive use of copper-based products in agriculture. To date, breeding programs have been largely unsuccessful in developing acceptable tomato varieties with durable resistance to bacterial spot. It is imperative to address these deficiencies and inadequacies in tomato bacterial spot control.

Researchers at the University of Florida discovered that the small molecules: hexanoic acid, piperidine, and pyrrolidine, have antibacterial properties against X. perforans. The three compounds perform better than the industry standard against the copper-resistant pathogen, reducing yield loss in tomatoes and better controlling the bacterial infection.

Application

Small molecule compounds treat, control, and reduce bacterial spot disease in tomatoes, advancing the disease management

Advantages

• Treatment targets copper-resistant X. perforans, effectively suppressing and reducing the pathogen infection and disease development
• Application by spraying the plant or soil drenching reduces disease severity in the field, making it more effective and scalable than seed treatment targeting seed-borne pathogens
• Eliminates and/or decreases the need for copper-based treatments of bacterial spot, reducing copper accumulation in the environment
• Treatment targets bacterial spot disease, decreasing marketable fruit yield loss
• The small molecules could target other copper-resistant strains responsible for bacterial spot in tomatoes and peppers, increasing the potential number of applications

Technology

These small molecule compounds, with a molecular weight lower than 900 Daltons, demonstrate bactericide properties against the copper-resistant X. perforans, one of the main species responsible for bacterial spot of tomato (BST). The lower molecular weight enables the compounds to permeate intercellular components interacting and interfering with biological processes. Results from in vitro assays and in planta experiments demonstrate hexanoic acid, piperidine, and pyrrolidine are effective in suppressing X. perforans growth and reducing BST. Field experiments reveal a greater effect on disease reduction and an increase in marketable fruit yield when applying the compounds as root drenches (hexanoic acid) or foliar sprays (piperidine and pyrrolidine) in comparison to the application of standard copper-based bactericides.