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The common rust disease of maize is caused by the obligate biotrophic fungusPuccinia sorghi. The maizeRp1-Dallele imparts resistance against theP.sorghiIN2 isolate by initiating a defense response that includes a rapid localized programmed cell death process, the hypersensitive response (HR). In this study, to identify AvrRp1-D fromP.sorghiIN2, we employed the isolation of haustoria, facilitated by a biotin-streptavidin interaction, as a powerful approach. This method proves particularly advantageous in cases where the genome information for the fungal pathogen is unavailable, enhancing our ability to explore and understand the molecular interactions between maize andP.sorghi. The haustorial transcriptome generated through this technique, in combination with bioinformatic analyses such as SignalP and TMHMM, enabled the identification of 251 candidate effectors. We ultimately identified two closely related genes,AvrRp1-D.1andAvrRp1-D.2, which triggered anRp1-D-dependent defense response inNicotiana benthamiana.AvrRp1-D-inducedRp1-D-dependent HR was further confirmed in maize protoplasts. We demonstrated that AvrRp1-D.1 interacts directly and specifically with the leucine-rich repeat (LRR) domain of Rp1-D through yeast two-hybrid assay. We also provide evidence that, in the absence of Rp1-D, AvrRp1-D.1 plays a role in suppressing the plant immune response. Our research provides valuable insights into the molecular interactions driving resistance against common rust in maize. 

SUMMARY Sorghum is an important food and feed crop globally; its production is hampered by anthracnose disease caused by the fungal pathogenColletotrichum sublineola(Cs). Here, we report identification and characterization ofANTHRACNOSE RESISTANCE GENE 2(ARG2) encoding a nucleotide‐binding leucine‐rich repeat (NLR) protein that confers race‐specific resistance toCsstrains.ARG2is one of a cluster of severalNLRgenes initially identified in the sorghum differential line SC328C that is resistant to someCsstrains. This cluster shows structural and copy number variations in different sorghum genotypes. Different sorghum lines carrying independentARG2alleles provided the genetic validation for the identity of theARG2gene.ARG2expression is induced byCs, and chitin inducesARG2expression in resistant but not in susceptible lines. ARG2‐mediated resistance is accompanied by higher expression of defense and secondary metabolite genes at early stages of infection, and anthocyanin and zeatin metabolisms are upregulated in resistant plants. Interestingly, ARG2 localizes to the plasma membrane when transiently expressed inNicotiana benthamiana. Importantly,ARG2plants produced higher shoot dry matter than near‐isogenic lines carrying the susceptible allele suggesting an absence of anARG2associated growth trade‐off. Furthermore, ARG2‐mediated resistance is stable at a wide range of temperatures. Our observations open avenues for resistance breeding and for dissecting mechanisms of resistance.