**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** THE POTATO CYST NEMATODE (PCN) GLOBODERA PALLIDA WAS FIRST DETECTED IN THE UNITED STATES IN 2006 AND HAS BEEN ONE OF THE MAJOR PRODUCTION CONSTRAINTS FOR POTATO AND CAN CAUSE UP TO 100% YIELD LOSS. TO SUCCESSFULLY INFECT AND COLONIZE POTATO ROOTS, PCN PRODUCES PROTEINS, CALLED EFFECTORS, AND USES THE STYLET, A NEEDLE-LIKE APPARATUS, TO DELIVER THEM INTO POTATO ROOT CELLS. ALL THESE EFFECTORS HAVE DIFFERENT BIOCHEMICAL ACTIVITIES IN POTATO CELLS AND FUNCTION TOGETHER TO HELP DEVELOP A FEEDING SITE (CALLED SYNCYTIUM) FOR NEMATODE DEVELOPMENT AND GROWTH. THUS, IN ORDER TO EVENTUALLY GENERATE POTATO VARIETIES RESISTANT TO PCN, IT IS IMPORTANT TO UNDERSTAND HOW EFFECTORS INTERACT WITH EACH OTHER AND MANIPULATE HOST GENES TO OVERCOME PLANT DEFENSE AND ESTABLISH THE FEED SITE. ALTHOUGH SEVERAL PLANT-PARASITIC NEMATODE EFFECTORS HAVE BEEN SHOWN TO SUPPRESS PLANT DEFENSE SIGNALING, THE MOLECULAR BASIS BY WHICH EFFECTORS MANIPULATE HOST PLANTS IS LARGELY UNKNOWN, MAINLY BECAUSE WE DO NOT KNOW WHAT KIND OF BIOCHEMICAL ACTIVITIES EFFECTORS HAVE AND HOW THEY DEAL WITH THE PLANT DEFENSE RESPONSE INSIDE HOST ROOT CELLS.WE HAVE RECENTLY FOUND A PCN EFFECTOR RHA1B, WHICH IS AN ENZYME TERMED UBIQUITIN LIGASE RESPONSIBLE FOR DEGRADATION OF PROTEINS IN ALL EUKARYOTIC CELLS. SIGNIFICANTLY, RHA1B CAN SUPPRESS PLANT DEFENSE SIGNALING, SUGGESTING RHA1B COULD ARM G. PALLIDA WITH A UNIQUE ADVANTAGE IN NEMATODE PARASITISM. PARTICULARLY, RHA1B COULD TARGET PLANT PROTEINS ENCODED BY GENES TERMED SUSCEPTIBILITY GENES WHICH ARE IMPORTANT FOR SUCCESSFUL COLONIZATION OF NEMATODE. IN OTHER WORDS, WE WILL BE ABLE TO MAKE POTATO PLANTS RESISTANT TO NEMATODE IF WE CAN GENETICALLY MAKE THESE GENES NOT FUNCTIONAL OR REMOVE THEM. THUS, TO FURTHER INVESTIGATE THE MOLECULAR BASIS BY WHICH G. PALLIDA MANIPULATES HOST POTATO PLANTS FOR SUCCESSFUL COLONIZATION AND TO IDENTIFY THE HOST SUSCEPTIBILITY GENES THAT ARE ESSENTIAL FOR G. PALLIDA INFECTION, WITH AN ULTIMATE GOAL OF GENERATION OF G. PALLIDA-RESISTANT POTATOES VIA LOSS OF SUSCEPTIBILITY, WE PROPOSE THREE RESEARCH OBJECTIVES:DETERMINE RHA1B CAN FUNCTION AS A MASTER EFFECTOR THAT CAN AFFECT OTHER EFFECTORS' DURING INFECTION OF HOST POTATO ROOTS;DETERMINE WHAT GENES IN HOST POTATO ARE AFFECTED BY RHA1B EFFECTOR AND HOW THESE SUSCEPTIBILITY GENES ARE MANIPULATED TO HELP PRODUCE FEEDING SITE FOR NEMATODE;GENERATE G. PALLIDA-RESISTANT POTATO BY GENETICALLY MANIPULATING THESE SUSCEPTIBILITY GENES, WHICH WILL BE ACHIEVED BY MAKING THESEGENES NOT FUNCTIONAL THROUGH GENE-EDITING TECHNIQUE.IN BRIEF, THE PROPOSED PROJECT WILL HELP US UNDERSTAND THE MOLECULAR BASIS OF HOW THE POTATO CYST NEMATODE (G. PALLIDA) INFECTS THE HOST PLANT (POTATO) AND EVENTUALLY USE THE EVOLVED KNOWLEDGE TO DEVELOP NOVEL, INNOVATIVE AND ENVIRONMENTALLY-SOUND WAYS FOR IMPROVED RESISTANCE TO NEMATODE.