P-069 - RUST NONHOST RESISTANCE RESPONSES IN SORGHUM AND MAIZE

Maize and sorghum are globally important cereals with high synteny, yet both face threats from fungal pathogens. Rust fungi can cause up to 40% yield loss in maize, while reports on sorghum rust disease remain limited. Over the past two decades, Rp1 alleles have been incorporated into maize inbred lines to confer resistance against Puccinia sorghi, but this resistance was compromised by virulent isolates in the 1990s. Interestingly, P. sorghi does not infect sorghum, despite its close genetic relationship to maize, a phenomenon known as nonhost resistance (NHR).  NHR is a durable, broad-spectrum resistance where an entire species remains immune to a pathogen. To elucidate NHR mechanisms, we screened diverse maize and sorghum lines, uncovering distinct defense responses. In a sorghum association panel inoculated with P. sorghi, resistance involved pigment accumulation, with lesion patterns ranging from freckle-like spots to no visible symptoms. In maize nested association mapping parent lines inoculated with the sorghum pathogen P. purpurea, a hypersensitive response at pathogen entry points suggested active recognition and defense. We aim to conduct transcriptomics and genome-wide association analyses to identify genetic components linked to NHR. This research advances understanding of rust resistance in cereals and underscores the potential for integrating NHR mechanisms into breeding strategies for durable disease resistance.