Recipient Organization
UNIVERSITY OF CALIFORNIA, DAVIS
410 MRAK HALL
DAVIS,CA 95616-8671
Performing Department
(N/A)
Non Technical Summary
Root-knot nematodes are highly evolved obligate parasites that threaten global food security. These nematodes have a remarkable ability to modify host cells that serve as their only source of nutrients throughout their life cycle. Resistance to root-knot nematodes conferred by the single dominant gene Mi-1 is available in many varieties of fresh and processing tomatoes. However, an increased reliance on Mi-1 due to limited avaialbility of nematicides has led to the emergence of resistance-breaking nematode populations in tomato fields. The specific aim of this proposal is to use comparative genomics to elucidate the genetic mechanisms and identify genetic factors that contribute to root-knot nematodes outbreaks in resistant tomato fields. Our preliminary data show that resistance-breaking nematodes are less fit on susceptible tomato and have reduced host range. We will investigate the genetic factors that contribute to this fitness cost. Lastly, we will develop a rapid reliable method to identify resistance-breaking root-knot nematodes isolates from fields. The availability of diagnostic tools will facilitate the development of alternative management strategies including the identification of appropriate rotation crops. Overall, the project will contribute to the development of much-needed environmentally safe nematode control strategies. The goal of proposed research is directly relevant to the goals and priorities of the Agriculture and Food Initiative (AFRI), which supports research directed at the long-term improvement and sustainability of U.S. agricultural and food systems.
Animal Health Component
30%
Research Effort Categories
Basic
70%
Applied
30%
Developmental
(N/A)
Goals / Objectives
Plant-parasitic nematodes represent a significant threat to global agriculture, with estimated annual losses of $8 billion for U.S. growers and nearly $78 billion globally. The most severe damage is attributed to a small group of root-infecting endoparasitic nematodes, which include root-knot nematodes (RKNs) and cyst nematodes. Cyst nematodes have a limited host range, but the most damaging RKNs, such as the Meloidogyne incognita group (MIG), comprising M. incognita, M. javanica, and M. arenaria, infect thousands of plant species, including annual and perennial crops, as well as dicots and monocots.The introduction of natural resistance through resistance (R) genes into cultivars is widely regarded as the most effective and environmentally sustainable approach to control plant- parasitic nematodes. Many varieties of fresh and processing tomatoes (Solanum lycopersicum) are resistant to RKNs. This resistance is conferred by the single dominant gene Mi-1 (also referred to as Mi), which was originally introduced into cultivated tomatoes from the wild tomato Solanum peruvianum L. in the 1940s. Despite its efficacy, overreliance on Mi-1 has resulted in the emergence of resistance-breaking nematode populations in tomato fields worldwide.For most characterized interactions, resistance-breaking happens when the pathogen loses an effector or avirulence gene (Avr gene), preventing the plant from recognizing its presence. The Avr gene typically contributes to pathogenicity or defense suppression, and its loss can come with a fitness cost. To develop effective strategies to control virulent pathogens, it is critical to understand the consequences of resistance-breaking mutations, including effector loss. This research proposal seeks to clarify the genetic mechanisms that lead to resistance-breaking and identify genetic factors that enable nematodes to overcome Mi-1-mediated resistance. Additionally, we aim to investigate the potential fitness cost associated with breaking this resistance. This work will provide valuable insights into the evolution and adaptation of these damaging plant parasites and will contribute to the development of much-needed environmentally safe nematode control strategies. This proposal is directly relevant to the goals and priorities of the Agriculture and Food Research Initiative (AFRI), which supports research directed at the long-term improvement and sustainability of U.S. agricultural and food systems.
Project Methods
Objective 1: Identify and validate nematode genes associated with Mi-mediated recognition and virulence differences between VW4 and VW5We have compared the genomes of strains VW4 and VW5, identifying MjCB1 and MjCB2 as potential Avr genes. In this objective, we will validate the roles of MjCB1 and MjCB2 as Avr genes in relation to Mi-1 resistance and test their roles in virulence. If necessary, we will also test additional candidate Avr genes including MjXX within the 20-kb deleted region.Objective 2: Identify host targets of Avr genesWe will functionally characterize Avr genes identified in Objective 1 to identify the host proteins that interact with using protein-protein interaction screens and to determine their role in Mi-mediated resistance.Objective 3: Characterize genomes of Mi-virulent field isolates and develop diagnostic tools for resistance-breaking nematodesMi-virulent RKN isolates collected from fields cannot be distinguished from Avr isolates using currently available molecular and morphological tools. The overall goal of thisobjective is to utilize comparative genomics of field isolates to better understand the genetic origins of this phenotype and to develop a reliable detection method for resistance-breaking RKNs from the field.