Date: July 2, 2026 | Thursday | 1:30 PM, Manila Time

Abstract

Narrow Brown Leaf Spot (NBLS), caused by the hemibiotrophic fungus Cercospora janseana, is an endemic disease that inflicts severe yield and quality losses of up to 40% in global rice production. With the rapid emergence of pathogen resistance to primary QoI-class fungicides, the introgression of host-plant genetic resistance represents the most economically and environmentally sustainable management strategy. This study elucidates the genetic architecture of CRSP2.1, a major dominant resistance locus previously identified in the resistant rice cultivar ‘LaGrue’. Utilizing a combined fine-mapping and comparative genomics approach, the CRSP2.1 locus was delimited from an initial 532 kb region to a high-resolution 240 kb interval on chromosome 2. Large-scale genotyping of 6,780 F₂:₃ Heterozygous Inbred Families (HIFs) derived from a ‘LaGrue’ × ‘Cypress’ cross identified 26 critical recombinants. Phenotypic evaluation of fixed recombinant haplotypes confirmed a 3:1 segregation ratio, characteristic of single-gene dominant resistance. Concurrently, a de novo assembly of the ‘LaGrue’ reference genome using Nanopore sequencing enabled comparative microsynteny analysis with the ‘Nipponbare’ reference genome. The refined 240 kb target interval in ‘LaGrue’ contains 24 putative genes, including four highly diverse Nucleotide-binding leucine-rich repeat (NLR) candidate genes. Ongoing work involves validating these top candidate genes through CRISPR/Cas9 genome editing and overexpression in susceptible cultivars, alongside characterizing fast-neutron-induced resistance-compromised ‘LaGrue’ mutants. Ultimately, the positional cloning of CRSP2.1 will expedite the development of disease-resistant elite rice varieties and advance fundamental understanding of host-pathogen interactions.

About the Speaker:

Jeshurun Asher Tarun, PhD

Balik Scientist, Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development, Department of Science and Technology (DOST-PCAARRD)