Abstract Microbe associated molecular pattern (MAMPs) triggered immunity (MTI) is a key component of the plant innate immunity response to microbial recognition. However, most of our current knowledge of MTI comes from model plants (i.e., Arabidopsis thaliana) with comparatively less work done using crop plants. In this work, we studied the MAMP triggered oxidative burst (ROS) and the transcriptional response in two Sorghum bicolor genotypes, BTx623 and SC155-14E. SC155-14E is a line that shows high anthracnose resistance and the line BTx623 is susceptible to anthracnose. Our results revealed a clear variation in gene expression and ROS in response to either flagellin (flg22) or chitin elicitation between the two lines. While the transcriptional response to each MAMP and in each line was unique there was a considerable degree of overlap, and we were able to define a core set of genes associated with the sorghum MAMP transcriptional response. The GO term and KEGG pathway enrichment analysis discovered more immunity and pathogen resistance related DEGs in MAMP treated SC155-14E samples than in BTx623 with the same treatment. The results provide a baseline for future studies to investigate innate immunity pathways in sorghum, including efforts to enhance disease resistance. Keywords: Sorghum bicolor, ROS, innate immunity, MAMPs, RNA-seq, gene expression 1. Introduction Plants are naturally exposed to a variety of stresses, including numerous bacterial, fungal, and viral pathogens [[34]1]. Plants protect themselves from pathogens using pre-formed structures and chemicals, and infection-induced responses of the immune system. The plant immune system employs a two-tiered perception system with two interconnected layers of receptors. The first tier is activated by surface-localized pattern recognition receptors (PRRs), which sense molecules outside the cell by recognizing the invading pathogen through detection of conserved structural motifs, termed Microbe-Associated Molecular Patterns (MAMPs), which trigger a moderate, but broad, defense response [[35]2]. Flagellin, chitin, lipopolysaccharides, peptidoglycans (PGNs), and elongation factor Tu are examples of the well-studied MAMPs [[36]3,[37]4,[38]5]. This defense response is termed MAMP-trigged immunity (MTI) [[39]6]. The second tier of defense known as the Effector-Triggered Immunity (ETI) occurs in response to specific pathogen-derived effector proteins that are recognized by the plant through the action of resistance proteins, resulting in a strong, but highly specific immune response. ETI can often be recognized by the induction of localized cell death termed a hypersensitive response (HR) [[40]7]. Both MTI and ETI systems sense the pathogens and respond by activating antimicrobial defenses in the infected cell and neighboring cells [[41]3,[42]8]. Plants also carry immune receptors that recognize highly variable pathogen effectors, these include the NBS-LRR class of proteins [[43]9]. In addition, systemic acquired resistance (SAR) is a “whole-plant” resistance response that occurs following an earlier localized exposure to a pathogen. SAR is associated with the induction of a wide range of genes (pathogenesis-related genes), and the activation of SAR requires the accumulation of endogenous salicylic acid (SA) [[44]10]. Studies primarily done using Arabidopsis have shown that MTI can cause a variety of responses including changes in reactive oxygen species production (ROS), reactive nitrogen species production such as nitric oxide (NO), callose deposition, intracellular calcium levels, ion flux across the plasma membrane, induction or repression of the expression of several plant defense related genes, alterations in the plant cell wall, induction of antimicrobial compounds and the synthesis of pathogenesis-related (PR) proteins [[45]3,[46]11]. Although several of these MTI responses can be considered general plant responses, their magnitude can be plant-species specific and even cultivar specific [[47]12,[48]13,[49]14,[50]15,[51]16,[52]17]. Methods have been developed to quantify the plant MTI response. These methods include measuring ROS or NO production, mitogen-activated protein kinase phosphorylation, specific MAMP-induced gene expression, seedling growth inhibition, lignin and cell wall-bound phenols, and MAMP-induced resistance to bacterial and fungal pathogens [[53]18,[54]19,[55]20]. Sorghum bicolor (L.) Moench is a key, global cereal crop that has been adapted to a range of habitats and bred for diverse purposes [[56]21]. The cultivation of sorghum is expected to increase substantially worldwide as one of the major crops for food and biomass production [[57]22]. As the practices and geographical areas under sorghum cultivation increase, it is inevitable that the disease pressure will increase. Sorghum is distinguished among other cereals by its unusually broad range of diseases, which is one of the most important constraints to its production. Globally, widespread fungal diseases are the most destructive sorghum diseases that result in huge losses in yield, both in terms of the quantity and quality of the grains [[58]23]. Anthracnose is one of the most severe fungal diseases affecting sorghum grain yield and biomass production. Yield losses due to this pathogen can be 50 to 70% in susceptible cultivars [[59]24,[60]25]. Plants have developed various defense strategies to fight against pathogen invasion. In sorghum, these strategies include activation of PR proteins [[61]26], accumulation of hydrogen peroxide [[62]27], and biosynthesis of flavonoid phytoalexins [[63]28]. Different approaches have been used to study sorghum’s resistance responses, identify defense compounds, and identify physical barriers against anthracnose (see reference [[64]29,[65]30] for review). Gene expression studies were widely used to identify candidate resistance genes in plants based on the differential expression between resistant and susceptible cultivars or non-inoculated and pathogen inoculated plants (e.g., references [[66]31,[67]32,[68]33,[69]34,[70]35,[71]36,[72]37]). Wang et