**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** FOOD CROPS ARE CONSTANTLY THREATENED BY NEW VARIANTS OF ESTABLISHED PATHOGENS AND BY NEWLY-EMERGED PATHOGENS. THE RICE BLAST FUNGUS MAGNAPORTHE ORYZAE HAS A LONG HISTORY OF VARIATION TO OVERCOME RESISTANCE DEPLOYED IN RICE CROPS, AND A NEW M. ORYZAE VARIANT EMERGED IN 1985 TO CAUSE DEVASTATING DISEASE ON WHEAT IN BRAZIL. WHEAT BLAST SPREAD WITHIN SOUTH AMERICA FOR DECADES, AND THEN JUMPED CONTINENTS TO SOUTH ASIA IN 2016 AND AFRICA IN 2018. WHEAT BLAST DISEASE IS PROVING EVEN HARDER TO CONTROL THAN RICE BLAST, BECAUSE POTENTIAL RESISTANCE GENES IDENTIFIED USING STRAINS FROM THE 1980'S ARE NO LONGER EFFECTIVE IN CONTROLLING RECENT AGGRESSIVE ISOLATES FROM WHEAT FIELDS. GLOBAL SPREAD OF THE DISEASE AND LACK OF EFFECTIVE CONTROL MEASURES ENHANCE FEARS ABOUT GLOBAL FOOD SECURITY. RECENT STUDIES INDICATED THAT DISPENSABLE SUPERNUMERARY CHROMOSOMES FROM BLAST FIELD ISOLATES MIGHT ACCELERATE ADAPTIVE EVOLUTION AND CONTRIBUTE TO PATHOGENICITY AND VIRULENCE OF THE FUNGUS. PARTICULARLY, SUPERNUMERARY CHROMOSOMES ARE HYPOTHESIZED TO PLAY ROLES IN THE EVOLUTION OF A PARTICULAR PATHOGEN GENES THAT ARE CRITICAL FOR RESISTANCE IN HOST PLANTS, INCLUDING HOST SPECIFICITY AT THE PLANT SPECIES/GENUS LEVEL AND AT THE CROP CULTIVAR LEVEL. THE PROJECT WILL COMBINE METHODOLOGIES IN BLAST DISEASE BIOLOGY, MOLECULAR BIOLOGY, GENOMICS, AND CYTOLOGY TO STUDY SUPERNUMERARY CHROMOSOMES TO UNDERSTAND THEIR PREVALENCE, MOVEMENT BETWEEN STRAINS, DNA EXCHANGE WITH CORE-CHROMOSOMES, STABILITY, AND CONTRIBUTIONS TO PATHOGENICITY AND VIRULENCE. PROJECT OUTCOMES WILL BE VALUABLE FOR UNDERSTANDING GENOMIC DYNAMICS OF THE BLAST PATHOGEN, AND, IN GENERAL, HELP REVEAL ROLES OF SUPERNUMERARY CHROMOSOMES IN MANY PLANTS, ANIMALS AND OTHER FUNGI.