Disease resistance in maize

Plants are in constant contact with microbes that utilize diverse mechanisms of attack. To protect themselves plants have evolved layers of defense that encompass diverse mechanisms of resistance and are shaped by the evolutionary dynamics between the plant and the microbe. The Jamann lab focuses on host-microbe interactions in maize and sorghum. The goals of the program are to mine genetic variation for resistance, determine how those genes are influencing the interaction, and better understand how pathosystems co-evolve. We study a diversity of pathogens and are taking a multi-faceted approach utilizing genetics, genomics, molecular biology, and evolutionary biology to understand the interaction between host and microbe. Students and professionals explore questions related to host-microbe interactions and develop a variety of skills related to these approaches. Ultimately exploiting genetic variation and understanding the governing mechanisms will lead to the development of more resistant varieties.

Specific projects:

Exploring the genetic and mechanistic bases of quantitative disease resistance in maize

Quantitative disease resistance (QDR) is the most important form of resistance for maize and crops more broadly. Prior work has shown that QDR is based on diverse genes and mechanisms, most of which are not yet understood. Several quantitative trait loci and genes associated with resistance to multiple maize diseases have been previously identified and characterized. To further dissect disease resistance, as well as other traits, a large population of near-isogenic lines (NILs) has been developed and evaluated for resistance to several diseases. We are using these lines to study the mechanistic basis of vascular disease resistance in maize using microscopy and to identify QDR causal genes using fine mapping and gene editing. This effort uses an integrative approach incorporating genetics, genomics, transcriptomics, histology, pathology/microbiology, quantitative genetics, field research, and CRISPR- mediated gene-editing. We expect to identify key genes, mechanisms, and tradeoffs that can inform the deployment of quantitative disease resistance in crops.

Funding: National Science Foundation

Dissection of bacterial disease resistance in maize

There are several significant bacterial diseases of maize, including Goss’s bacterial wilt (caused by Clavibacter nebraskensis) and blight and bacterial leaf streak (caused by Xanthomonas vasicola pv. vasculorum). We have mapped resistance for both diseases and identified regions that confer resistance to multiple diseases of maize (Qiu et al. 2020 G3; Qiu et al. 2020 Crop Science; Cooper et al. 2018 Crop Science). While identifying regions conferring resistance is critical to breeding more resistant varieties, understanding the host-pathogen interaction is imperative for deploying resistance in a strategic manner. For Goss’s bacterial wilt and blight we developed a system to visualize infection in planta and examined colonization and movement patterns of Clavibacter nebraskensis during infection using green fluorescent protein (GFP)-labeled bacterial strains (Mullens and Jamann 2021 Plant Disease). Resistant maize lines exhibited decreased bacterial spread in the vasculature and the mesophyll. We continue to examine both the genetic and mechanistic basis of bacterial disease resistance in maize.

Funding: Foundation for Food and Agricultural Research, Rapid Outcomes for Agricultural Research