Screening for resistance to Pyrenophora graminea in hulless barley germplasm and subsequent morphological and transcriptomic analyses.

backgroundBarley leaf stripe, caused by Pyrenophora graminea, is a seed-borne fungal disease that significantly impacts the production of hulless barley (Hordeum vulgare var. nudum) on the Qinghai‒Tibet Plateau. In this study, we conducted an indoor disease resistance screen of 28 hulless barley germplasm resources using the highly pathogenic P. graminea strains L-7 and FS-18 and identified resistant (ZYM2179) and susceptible (Chaiqing No. 1) materials. We then inoculated these two resources with the highly pathogenic P. graminea strain L-7 and performed morphological observation of sections stained with WGA-AF488 and RNA-seq at different time points.

resultsAs the duration of infection increased, the degree of P. graminea invasion and the number of hyphae significantly increased. In addition, the incidence rate of P. graminea infection in the susceptible resource was greater than that in the resistant resource. A total of 18,523 differentially expressed genes were identified in the transcriptome analysis, functional annotation revealed significant enrichment of transcription factor families such as B3 (539), ERF (294), and NAC (150). Trend analysis identified 20 distinct expression profiles, with differences in gene expression patterns between the two resources. The differentially expressed genes were dynamically regulated over time, with the susceptible resource showing an increasing trend in gene expression, while the resistant resource exhibited an initial increase followed by a decrease. With significant differences in the number of differentially expressed genes enriched in different GO and KEGG pathways between the resistant and susceptible resources. One hundred and four differentially expressed genes were identified in the resistant resource, and these genes were enriched mainly in pathways such as metabolism and plant–pathogen interactions. It is noteworthy that the Rboh and RbohD genes, which are involved in reactive oxygen species production and plant-pathogen interactions, were upregulated in the resistant variety.

conclusionsThe relative expression levels of the 10 candidate genes validated by RT-qPCR, such as HSP70-4 and PER1, were Significantly different between resistant and susceptible resources at 12 h post-inoculation. This is consistent with the results of morphological and transcriptome analysis, indicating that these genes are likely related to barley leaf stripe resistance. This study provides a theoretical basis for the discovery of barley leaf stripe resistance genes and the study of resistance mechanisms in hulless barley and is important for the breeding of new disease-resistant varieties and the development of the hulless barley industry.