Fine mapping and preliminary mechanism analysis of tobacco Fusarium root rot resistance genes

Abstract

Tobacco (Nicotiana tabacum L.) is a significant non-food cash crop. However, due to targeted breeding practices, the incidence and severity of tobacco diseases have been increasing. Fusarium root rot, in particular, has a substantial impact on tobacco quality and yield, thereby posing a considerable challenge to the development of the tobacco industry. Therefore, the identification of resistance germplasm and resistant genes, as well as the research on disease resistance mechanisms are crucial for developing effective strategies to combat tobacco Fusarium root rot. In this study, resistance identification revealed that CX14 exhibited significantly stronger disease resistance compared with By37. The F₁ generation displayed disease resistance more closely resembling that of CX14, whereas the disease resistance in the F₂ population followed a normal distribution. Following the completion of BSA-seq and fine mapping, the QTL was successfully mapped to an 8.62 Mb interval containing 103 genes. The results of PCA and heatmap indicate that the responses of the two varieties to the pathogen are similar, possibly due to changes in gene abundance or a few genes affecting the resistance. The analysis of gene expression patterns revealed that both varieties exhibited similar disease resistance responses, with the peak response occurring on the second day post-inoculation. However, the defense response in By37 was delayed compared with CX14. Through go enrichment analysis and gene set enrichment analysis (GSEA), we identified some possible pathways related to resistance, including “response to salicylic acid” and “response to jasmonic acid”. Through WGCNA analysis, we identified five modules that might be related to resistance. Based on the results of fine mapping and RNA-seq analysis, three candidate genes potentially associated with resistance to Fusarium root rot in tobacco were identified. The homologous genes of Nta03g09310, Nta03g0920, and Nta03g09340 in Arabidopsis thaliana are Patatin-like protein 2 (PLP2), which encodes a lipid acyl hydrolase that plays a critical role in cell death regulation and enhancing resistance to pathogen invasion. This study provides a foundation for elucidating the molecular mechanisms of Fusarium root rot resistance and the development of Fusarium resistant tobacco varieties.