P-501 - GENOME SEQUENCING SHOWS LOW DIFFERENTIATION AMONG DOWNY MILDEW (Peronosclerospora philippinensis [W. Weston] CG. Shaw) ISOLATES FROM PHILIPPINES

Monday, August 4, 2025

4:30 PM - 5:15 PM HST

Location: Exhibit Hall 3

Presenting Author(s)

FD

Fe Mangaban Dela Cueva (she/her/hers)

Scientist
Institute of Plant Breeding, University of the Philippines Los Banos
Los Baños, Laguna, Philippines

Author(s)

BC

Benjamine William P. Cordez

MS Graduate fellow
Institute of Plant Breeding, University of the Philippines Los Banos
Los Banos, Laguna, Philippines
CC

Cris Q. Cortaga

University Researcher II
Institute of Plant Breeding
Los Banos, Laguna, Philippines
CA

Charlotte B. Acharya

Staff Research Associate 4
University of California - Davis
Davis, California, United States
KD

Kuntal Kumar Dey

Postdoctoral scholar
University of California - Davis
Davis, California, United States
RT

Rizalina M. Tiongco

Laboratory Technician
Institute of Plant Breeding, University of the Philippines Los Banos
Los Banos, Laguna, Philippines
RM

Richard W. Michelmore

Distinguished Professor
University of California, Davis
Davis, California, United States
FM

Frank M. Martin, Research Plant Pathologist

Research Plant Pathologist
U.S. Department of Agriculture, Agricultural Research Services
Salinas, California, United States

Abstract Text: Significant losses in global corn and sugarcane production are attributed to downy mildew, a disease characterized by extensive leaf chlorosis that leads to stunting and reduced yield in affected crops. Downy mildew is caused by several Peronosclerospora spp., with P. philippinensis being one of the most virulent and widespread species in the Philippines. Despite its long-standing presence, the genetic diversity of P. philippinensis remains relatively unknown. This study employed a next-generation sequencing (NGS) approach to elucidate the genetic diversity of P. philippinensis in the Philippines. Spores from downy mildew-infected corn and sugarcane were collected across different regions of the country (Luzon, Visayas, and Mindanao). A total of 50 samples were collected from different regions of the Philippines. DNA was extracted, and short-read sequences were obtained using the Illumina/Aviti platform. The filtered reads ranged from 3 to 54 million, with genome coverage ranging from ~3x to 40x. The reads were aligned to the genome assembly of P. philippinensis, and variant calling was performed, with subsequent filtration retaining only biallelic SNPs with quality ≥50, missing genotypes < 70%, minor allele frequency >5%, and depth ≥40. Population genetic metrics suggest that P. philippinensis populations may exhibit low differentiation in Luzon, Visayas, and Mindanao, which may be due to conidial dispersal and the year-round availability of susceptible hosts.