Exploring effector-host interactions in Pyricularia oryzae infections: A molecular and structural approach to rice blast resistance

Rice blast, caused by Pyricularia oryzae , is one of the most destructive diseases affecting global rice production, often leading to severe yield losses and threatening food security. Understanding the virulence diversity and race dynamics of this pathogen is crucial for developing effective and sustainable disease management strategies. Despite the global importance of rice blast, there is a lack of comprehensive data on the race dynamics of Pyricularia oryzae in temperate ecosystems such as Kashmir, particularly using the newly designated U-i-k-z-ta system, which employs an expanded set of 25 resistance genes and a susceptible check for precise race characterization. Therefore, in this study, twenty P. oryzae isolates were collected from eight districts in the temperate regions of Kashmir, India, and characterized using 26 monogenic differential rice varieties (MDs) harboring diverse blast resistance genes. Virulence frequencies among the isolates ranged from 30.76 % to 92.30 %, with the highly virulent isolate Po-kp-meel overcoming resistance in all MDs except for Pikh and Pi12(t) . Race profiling based on the U-i-k-z-ta system identified 20 distinct races, including the highly aggressive U73-i7-k137-z17-ta333 race. Comparative analysis suggests that these races exhibit unique profiles compared to those reported in other regions of India and globally, highlighting the distinct evolutionary pressures in the temperate Kashmir ecosystem. To elucidate resistance mechanisms, we employed molecular docking and protein-protein interaction (PPI) network analyses. These analyses revealed moderate but essential interactions between rice resistance proteins (Pita, Pi9-like protein, and NBS-LRR) and the fungal effector Avr-PITA. The Pita protein exhibited critical electrostatic interactions while avoiding stable effector binding, suggesting a transient resistance mechanism. Protein-protein interaction networks further highlighted the complex nature of rice defense responses. This study underscores the genetic diversity of P. oryzae in Kashmir and identifies key resistance genes ( Pita2-Re , Pi7(t) , Pita-CP1 , Pish , Pik , and Pita2-Pi ) as promising targets for breeding durable and broad-spectrum blast-resistant rice varieties. These findings provide a valuable framework for enhancing sustainable rice blast management in temperate ecosystems. • Characterized 20 P. oryzae isolates from Kashmir using 26 rice differential varieties. • Virulence frequencies ranged from 30.76 % to 92.30 %, highlighting pathogen diversity. • Identified 20 distinct P. oryzae races, including the aggressive U73-i7-k137-z17-ta333. • Conducted molecular docking to explore interactions between rice proteins and effectors. • Pita protein showed critical interactions while avoiding stable binding with Avr-PITA.