Abstract
Onions and potatoes are economically important crops throughout the world, within the United States, and specifically within Idaho. They account for around one and a half billion dollars of annual revenue for the state which can be significantly impacted by disease outbreaks due to various pathogens throughout Idaho’s agricultural growing regions. Bacterial pathogens are the causal agents of many important diseases of onion and potatoes and are responsible for millions of dollars in revenue loss every year. They play significant roles in yield reduction, plant health/quality reduction, and in a loss of product marketability. One important component of bacterial diseases on onions and potatoes is the occurrence of disease symptoms and progression in storage. Many infections may not present in-field and result in high levels of bulb/tuber degradation, and further disease spread, once in storage under optimal conditions after significant monetary input into the harvesting and storing of the product by the grower. This is further complicated by occurrence of various non-pathogenic bacterial species, opportunistic pathogens, and secondary pathogens that are involved in the bacterial complex of both non-infected and infected bulbs/tubers. Developing and utilizing methods for understanding these microbiome populations, and their dynamic interactions with one another, is integral to developing optimal disease management strategies.Preventative actions against important bacterial diseases of onion and potato include the utilization of good growing practices to ensure quality plants that have a better chance to resist initial infection, the utilization of cultural practices to limit bacterial inoculum and optimal conditions to minimize disease, and in the application of various chemical and biological agents to protect against, or actively combat, infections. These methods, while vital, are limited by a lack of knowledge regarding the specific bacterial populations found within the region. Information about what is present, what disease outbreaks could potentially arise and have arisen, how population dynamics play into the progression of outbreak, and how these populations relate to those found in other growing regions helps inform the use of preventive measures, specific in-season management strategies, better in-storage control measures, and the generation of trend-based disease forecasting models to identify the potential of future outbreaks. The lack of this type of information available, in terms of novel target pathogen presence detection and a general understanding of bacterial populations in Idaho, can limit the ability of growers to predict outbreaks or effectively utilize disease control measures. To facilitate the confirmation of these identifications, improved diagnostic capabilities are needed and this is dependent on knowledge on the bacterial populations occurring in the region.
This study aims to identify and characterize the bacteria species present in potato and onion crops in Idaho and develop real-time PCR tools to diagnose and study them. This study reports for the first time P. parmentieri and D. dianthicola on potatoes in Idaho and describes the development and validation of a new real-time PCR assay for P. parmentieri. The study also conducted a study investigating the diversity of bacterial species in onions in Idaho and determined their pathogenicity with a ‘red scale assay’ and with whole bulbs. Finally real-time PCR assays were designed and validated for key pathogens and used to determine the relative incidence of the individual pathogens in onion seed lots.