Gene markers generating polygenic resistance in wheat - Bipolaris sorokiniana interaction pathosystem

Abstract

Wheat crops (Triticum aestivum, family Poaceae) are seriously threatened by a fungal-disease known as commonroot-rot-(CRR), which is caused by Bipolaris sorokiniana (Sacc.) Pleosporaceae-family, and significantly lowers yields worldwide. The best and most sustainable way to manage CRR is to incorporate genetic resistance into cultivated wheat varieties. However, it is challenging to identify the underlying mechanisms of CRR-resistance, since it is regulated by several genes (quantitative resistance). There is very little information in this regard, so the findings in this research will yield novel results in this issue. In our study, we investigated the resistance-mechanisms to wheat-Bipolaris sorokiniana interaction pathosystem by analyzing the total phenol content (TPC) and the activities of several defense related enzymes; catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), beta,1,3-glucanase (GLU), and chitinase (CHI), in the three wheat genotypes resistant to B. sorokiniana: "Alvand," "Bam," and "Mehregan" at three time points of first, second and third week following inoculation. Additionally, real time quantitative PCR (RT-qPCR) was conducted on leaf and root samples to assess the expression of ten novel candidate defense genes, including Cre3, EDS1, LTP5, PGIP, PR-1, PIEP1, TLP, UGT, Stb6, verses housekeeping Actin gene. The gene expression analysis revealed an upregulation of the defense related genes, ranging from 1.24 to 3.5-fold in the root and leaf tissues of the related resistant wheat following inoculation with B. sorokiniana. Among the genotypes, 'Bam' exhibited the highest increase in PPO and GLU activities, while 'Alvand' showed the most significant rise in SOD, PAL, and CHI activities. In contrast, 'Mehregan' had the highest CAT, POX, and TPC activities. Interestingly, in this research, resistance to the CRR was also enhanced by the Cre3 gene, which is known to provide resistance against the cereal cyst nematode (Heterodera filipjevi). CRR defense was further enhanced by EDS1, which is often connected to resistance to Blumeria graminis f. sp. Tritici powdery mildew, and Stb6, which is linked to resistance to Septoria tritici blotch. Additionally, the examined wheat genotypes exhibited resistance to B. sorokiniana due to PR-1 and UGT, which were previously recognized for providing resistance against Puccinia triticina (leaf rust). Although this research represents a preliminary investigation into the wheat B. sorokiniana interaction, the insights gained can help enhance our understanding of the role of defense related genes in wheat protection.