The present investigation was aimed to understand early infection process and plant pathogen interactions involved in tolerance and susceptibility in groundnut challenged with Sclerotium rolfsii by Scanning Electron Microscopy (SEM). The histo-pathological changes were recorded at different time intervals in two groundnut genotypes with differential reaction to stem rot disease viz., Cv: “ICGV 86590” (resistant) and Cv: “Narayani” (susceptible). These genotypes were grown in glass house and challenged with stem rot pathogen. The infection process and host-pathogen interactions were examined at cellular level in both resistant and susceptible cultivars at 24, 48 and 72 hours after inoculation (HAI). The SEM observation showed the direct penetration of fungal hyphae through the cuticle was observed within 24 HAI of inoculation in Narayani whereas no sign of mycelial growth was found in resistant genotype ICGV 86590. In the S. rolfsii challenged tissues, fungal hyphae were developed in both inter and intra-cellular layers within 48 HAI in Narayani and completely colonization with fungal mycelium was observed within 72 HAI and thereby lead to tissue collapse in susceptible genotype. In contrast, the resistant genotype has no mycelial growth in xylem vessels even at 72 HAI. In Cv. Narayani, after invasion of the fungus, rapid degradation of cell wall occurred in the stem followed by intercellular and intracellular spread of the fungal mycelium was observed. Finally, tissues of the stem lost their integrity and seemed as rotten mass covering with dense mycelium. The SEM study in groundnut clearly demonstrated the difference in histo-pathological responses in resistant and susceptible cultivars while the infection process of S. rolfsii. | Study of plant pathogen interaction in groundnut challenged with Sclerotium Rolfsii by scanning electron microscopy
