Alternaria leaf spot disease of chilli is an emerging problem in different chilli growing regions of the world including India. To understand the biochemical and molecular backbone of defense response against Alternaria alternata (A. alternata), two chilli cultivars (one tolerant and one susceptible) were selected. Different biochemical and histochemical methods were employed to understand the differential defense responses of two chilli cultivars in response to Alternaria invasion. Semiquantitative RT-PCR analysis showed higher transcript accumulation of different defense related genes in tolerant cultivar. The nitric oxide (NO) status was also monitored during activation of defense responses. In response to this fungus, reactive oxygen species (ROS) generation, callose deposition, cell death was also checked in both the cultivars. The tolerant cultivar showed enhanced defense responses (including NO) in response to the fungus, than that of susceptible cultivar. However, the tolerant cultivar showed reduced disease symptoms, lower amount of lipid peroxidation, lower amount of hydrogen peroxide (H₂O₂) generation and lower amount of cell death. In NO depleted condition pathogen induced defense responses were significantly compromised in both the cultivars. Overall, our present study provides a glimpse of NO participation in activation of defense responses in chilli against Alternaria invasion.

在包括印度在内的世界不同的辣椒生长地区，辣椒的交链孢菌叶斑病是一个新出现的问题。为了了解对链格孢菌（A. alternata）的防御反应的生化和分子骨架，选择了两个辣椒品种（一种耐性和一种易感性）。使用不同的生化和组织化学方法来了解两个辣椒品种对链格孢菌的不同防御反应入侵。半定量RT-PCR分析显示，在耐性品种中，不同防御相关基因的转录本积累较高。在防御反应激活过程中还监测了一氧化氮（NO）的状态。针对这种真菌，还检查了两个品种中的活性氧（ROS）生成，call质沉积，细胞死亡。与易感品种相比，耐性品种对真菌的防御反应增强（包括NO）。但是，耐性品种显示出减轻的疾病症状，较低的脂质过氧化量，较低的过氧化氢（H ₂ O _2）量。）的产生和较低的细胞死亡量。在NO耗尽的条件下，两个品种的病原体诱导的防御反应均明显受损。总的来说，我们目前的研究提供了NO参与辣椒对抗链霉菌入侵的防御反应激活的一瞥。