## 4 Discussion  
### Landraces Are Important Germplasm Resources for Maize Improvement  
Landraces are crucial sources for developing inbred lines, with the majority of inbred lines derived from these genetically diverse populations and exhibiting superior agronomic traits. The exploration and utilization of these genetic resources enable breeders to develop novel resistant germplasms and cultivars that possess multiple genes that confer resistance to a range of biotic and abiotic stresses, including drought, salinity, and diseases. This approach significantly addresses agricultural disease challenges. For instance, a new rust resistance allelic gene, _Sr22b_, which exhibits significant resistance to the Ug99 race, was discovered in wheat landraces from Romania [41]. Moreover, _YrBDT_ has been identified in the Chinese wheat landrace 'Baidaton', a new dominant single gene conferring stripe rust resistance [42]. A key strategy for using landrace traits and improving germplasm is to introduce desirable alleles from landraces into breeding materials via backcrossing, creating introgression lines. In our study, we introduced the SCR resistance locus from the landrace SLN into the susceptible inbred line N531, developing the resistant inbred line N531_R. While numerous studies have reported maize inbred lines resistant to SCR, few directly identified resistance genes from landraces for SCR resistance. Our study provided initial evidence demonstrating that the locus conferring resistance to SCR was directly identified from the landrace SLN. However, considering the highly variable physiological races of SCR, this resistance may diminish over time. Thus, identifying additional sources of resistance is essential for maize breeding, which will strengthen disease-resistant breeding efforts and support sustainable agricultural production. Exploring Resistant Loci That Could Achieve Durable Resistance to SCR by Aggregating Multiple Resistance Genes Is Essential  
R-genes enable crops to withstand pathogenic attacks, and they demonstrate considerable variability across different plant species, though they primarily exist in two forms, which are independent loci and clusters [43]. Clustered resistance genes are particularly advantageous for gene sequence exchange, facilitating the emergence of new resistance genes and significantly contributing to expanding resistance gene families [44]. To further verify the existence of a potential synergistic effect between the R genes _Zmays10G000430_ and _Zmays10G000440_, we analyzed the time-series expression in the N531_R line. _Zmays10G000430_ has a high similarity with _R1_ in the _RppK_-resistant locus, which is not the target resistance gene in the K22 inbred line, but along with _Zmays10G000440_, it collectively enhances the resistance expression level in the N531_R line. This finding suggests that multiple resistance genes can synergistically contribute to a more robust defense mechanism against pathogens. Some studies have reported that two NBS-LRR genes mediate rice blast disease in rice. It has also been observed that the deletion or mutation of either of these genes can impact disease resistance. Additionally, _Rpp2A_ and _Rpp2B_ mediate specialized resistance against downy mildew in Arabidopsis [45], and _Pikm1 TS_ and _Pikm2 TS_ collectively mediate resistance against Pikm identified in rice [46], while _RRS1_ and _RRS4_ mediate resistance against multiple bacterial pathogens [47]. In these instances, either two resistance proteins combine to form a resistance protein complex or one resistance protein acts as an inducing protein or downstream resistance protein for the other. These interactions enhance plant resistance to pathogens and protect plants from disease damage [48]. It is noteworthy that we observed a lower expression level of the only R gene, _NR5_, in the resistant parent after reinfection. However, there is a lack of a shared 3'-UTR between _NR5_ and the common amino acids encoded by _Zmays10G000440_ and _R3_.