Location: Emerging Pests and Pathogens Research
Project Number: 8062-22410-007-053-I
Project Type: Interagency Reimbursable Agreement
Start Date: Mar 1, 2024
End Date: Feb 28, 2027
Objective:
In 2022, cotton, Gossypium spp. (Family: Malvaceae), was one of the top 10 plant commodities in the United States (US) corresponding to 13.7 million acres of production and valued at approximately $6.45 billion. Cotton leafroll dwarf virus (CLRDV) is a phloem-limited polerovirus that represents a persistent threat to cotton production in the US. Since its discovery in Alabama in 2017, CLRDV subsequently spread to almost all cotton-producing states in the US [2,5]. CLRDV is transmitted by the cotton aphid, Aphis gossypii, and is the causative agent of cotton blue disease (CBD) in South America, Africa and Asia, and cotton leafroll dwarf disease (CLRDD) in the US.
In this project, ARS will pursue the following three objectives:
Objective 1. Identify and characterize the aphid proteins involved in CLRDV transmission.
Objective 2. Determine biological factors regulating transmission of CotV-A.
Objective 3. Characterize population dynamics of CLRDV, CotV-A and potential new viruses in upland cotton and weed reservoirs.
These research objectives will provide a holistic understanding of CRLDV, its cotton aphid vector, interactions with CotV-A and possible interactions with other viruses found in upland cotton production fields in the US cotton belt. The objectives will be pursued in parallel and while synergistic, the success of one does not rely on the other.
Approach:
Cotton leafroll dwarf virus (CLRDV), a polerovirus, is a persistent threat to cotton production in the United States. ARS developed a CLRDV infectious clone and nanobodies that bind to the CLRDV structural proteins. These tools, together with aphid colonies that vary in CLRDV transmission efficiency, will be used to identify aphid proteins that regulate CLRDV transmission. Recently, ARS characterized a new DNA virus from CLRDV-infected plants, cotton virus A (CotV-A, genus Caulimovirus), with endogenous virus elements in the cotton genome. We have the expertise to develop a reverse-genetics system and nanobodies for CotV-A to develop a deeper understanding of multi-trophic interactions that regulate CotV-A spread in upland cotton. Lastly, we will leverage our expertise in high throughput sequencing (HTS) to characterize CLRDV and CotV-A population dynamics in upland cotton and weed reservoirs. The impact of CotV-A on cotton production is unknown, and management strategies are nonexistent. This research is vital for the cotton industry, as we do not yet have the tools to evaluate the impacts of CotV-A on yield potential or on plants that are carrying a high viral load. Our research is critical for the industry because a new and serious pathology has increased its incidence in numerous upland cotton-producing states and the cause is unknown. Our HTS survey will inform the industry about this emerging issue and determine whether it involves CLRDV, CotV-A or additional viral agents. We recognize that our proposal is ambitious. Our team is highly productive, collaborative and up to the task.
