Enhancing rice crop resistance against brown plant hopper infestation through the foliar application of sodium nitroprusside

Brown planthoppers (Nilaparvata lugens) are major herbivores pests that severely impact rice (Oryza sativa) productivity worldwide. This study aimed to investigate the role of nitric oxide (NO) in rice defense against brown planthopper (BPH) stress using two chemical modulators sodium nitroprusside (SNP), a nitric oxide donor, and carboxy-PTIO potassium salt (cPTIO), a nitric oxide scavenger. Two resistant rice lines (Cheongcheong and Nagdong Double Haploid CNDH-78 and CNDH-87) and two susceptible rice lines (CNDH 14-2 and CNDH 48-3) were evaluated for agronomic traits, relative water content, electrolytic leakage, gene expression, and nitric oxide (NO) production. Interestingly, the water control (Distilled water spray) and 100 µM cPTIO-treated seedlings showed decreased root and shoot growth, reduced relative water content, and induced electrolytic leakage under BPH stress. Similarly, the water control and 100 µM cPTIO-treated seedlings exhibited decreased survival percentage and increased death rate under BPH stress. Gene expression analysis revealed that after 6, 12, and 24 h of BPH stress, the levels of Oryza sativa Nitric oxide associated 1 (OsNOA1) were significantly higher in the resistant rice lines Cheongcheong and Nagdong Double haploid CNDH-78 and CNDH-87, while OsNOA1 and Oryza sativa Nitrate Reductase (OsNR) were upregulated in the susceptible rice lines CNDH 14-2 and CNDH 48-3. Moreover, the resistant lines exhibited increased NO content after 6, 12, and 24 h, and susceptible rice lines showed high NO content after 24 h of BPH stress. These findings suggest that the application of 100 µM SNP enhanced internal NO production and content, improved the overall agronomic traits, increased the relative water content, decreased electrolytic leakage, and protected rice from the harmful effects of BPH.