## 1 Introduction  
Southern corn rust (SCR) is a highly destructive airborne disease caused by _Puccinia polysora_ (_P. polysora_), leading to significant maize (_Zea mays_ L.) yield losses. SCR has spread to most major corn-producing regions worldwide, including Asia, the Americas, and Africa [1]. The disease has caused significant yield losses during outbreaks, with losses often reaching 50% [2]. In recent years, global climate change has created conditions favorable for disease development, exacerbating SCR and causing its gradual spread to higher-latitude regions [3]. In China, SCR affected 5.289 million hectares, resulting in a loss of 756 million kilograms of corn in 2015 alone [4]. The scarcity of resistance genes and restricted genetic diversity are the main reasons for SCR epidemics [5]. Therefore, identifying diverse-resistant germplasm resources and additional resistance loci is essential for sustainable disease control [6, 7, 8].  
Plants have developed two forms of resistance mechanisms, which are complete resistance, governed by a single gene (qualitative resistance) [9], and incomplete resistance, governed by multiple genes with partial effects (quantitative resistance) [10]. Resistance genes (R-genes) confer race-specific qualitative resistance against biotrophic pathogens, such as _P. polysora_, which can survive within host plant cells for several days [11, 12, 13].  
However, resistance from a single R-gene is often short-lived. Similarly to other plant pathogenic microbes, _P. polysora_ has a rapid mutation rate, allowing it to overcome maize resistance. For example, the _Rpp9_ gene once provided effective resistance to SCR in the southern United States, but it has since been overcome by a new race of _P. polysora_[14]. This situation underscores the urgent need to discover new resistant genes to combat the emergence of new physiological races and their variations.  
Currently, nearly all materials used to identify resistance to SCR for breeding originated from inbred lines, some of which belong to the P group [15], such as K22, Q319, and X178, carrying resistance sources traced to the Pioneer hybrid PH78599 [16; 17]. The _RppC_ resistance gene, originating from the tropical material CML496, is present in 53.3% of the top 30 commercial hybrids in China, encompassing 72.5% of the total planted area [18]. However, to prevent resistance breakdown caused by limited resistance germplasm and protect maize yields, it is essential to investigate new germplasm resources and resistance loci.  
Landraces are the foundation for the development of modern inbred lines, with their rich genetic diversity providing a vast gene pool for crop breeding and improvement. Here, we discovered a unique landrace exhibiting high resistance to SCR, 'Silunuo' (SLN), with many primordial traits having restricted distribution in southwest Yunnan in China. Therefore, we developed a stably resistant SCR introgression line named N531_R by using the resistant landrace SLN as a donor and the susceptible inbred line N531 as a recurrent parent, following multiple generations of backcrossing and selfing. Subsequently, we identified a single QTL associated with SCR, _Rpp5 LN_, narrowing it down to a 38 kb physical interval on chromosome 10, employing an F\({}_{2}\) population by crossing the resistant line N531_R with the susceptible line F35. Within this interval, we identified two candidate genes that exhibited similar expression patterns when subjected to artificial inoculation with SCR. This study directly identified SCR resistance genes from a landrace variety and further investigation into the mechanisms underlying these candidate genes will be conducted in future research. The aim of this study is to identify resistance loci from landraces and, in conjunction with transcriptome analysis, to recognize candidate genes, thereby providing theoretical support for resistance to SCR.