Comprehensive transcriptome analysis of different potato cultivars provides insight into early blight disease caused by Alternaria solani

Abstract Background Early blight disease in potatoes is one of the economically important diseases affecting the tuber yield and quality worldwide. It is caused by the necrotrophic fungal pathogen Alternaria solani. The disease is mainly controlled by chemical plant protection agents. However, the over-usage of these chemicals leads to the evolution of resistant A. solani strains and is environmentally hazardous. Therefore, identifying resistant potato cultivars or genetic disease resistance factors is the best strategy for the sustainable management of early blight. Results In this study, we have captured transcriptomes from three different potato cultivars with varying susceptibility to A. solani, Magnum Bonum, Désirée, and Kuras, at 18 and 36 hours post-infection. We identified many differentially expressed genes (DEGs) between these cultivars, and the number of DEGs increased with susceptibility and infection time. There were 649 transcripts commonly expressed between the potato cultivars and time points, of which 627 and 22 were up- and down-regulated, respectively. Interestingly, overall the up-regulated DEGs were twice in number as compared to down-regulated ones in all the potato cultivars and time points, except Kuras at 36 hours post-inoculation. In general, transcription factor families WRKY, ERF, bHLH, MYB, and C2H2 were highly enriched DEGs, of which a significant number were up-regulated. The majority of the key transcripts involved in the jasmonic acid and ethylene biosynthesis pathways were highly up-regulated. Many transcripts involved in the mevalonate (MVA) pathway, isoprenyl-PP, and terpene biosynthesis were also up-regulated across the potato cultivars and time points. Compared to Magnum Bonum and Désirée, multiple components of the photosynthesis machinery, starch biosynthesis and degradation pathway were down-regulated in the most susceptible potato cultivar, Kuras. Conclusions This study provides important insights into the molecular events occurring in early disease development and helps to shorten the knowledge gap and supports potato breeding programs for improved early blight disease resistance.