Molecular Plant Breeding 2025, Vol.16, No.2, 146-155 http://genbreedpublisher.com/index.php/mpb 150 closely linked to the known resistance genes RPPC and RPPK. Resistance evaluation revealed diversity in disease resistance across different DH and hybrid populations (Figure 2) (Li et al., 2023).. Another research identified seven SNPs associated with partial resistance to SCR, highlighting the importance of resistant germplasms such as 'DH02' and 'Zheng39' (Zhou et al., 2018). Additionally, the discovery of the major QTL qSCR6.01 on chromosome 6, which accounted for up to 24.15% of phenotypic variation, further underscores the potential of DH breeding in SCR resistance (Lu et al., 2020). The identification and cloning of the RppM gene, encoding a CC-NBS-LRR protein, also demonstrate the effectiveness of integrating molecular markers in breeding programs (Wang et al., 2022). Figure 2 Southern Corn Rust Resistance Score (SCRRS) and its distribution (Adopted from Li et al., 2023) Image caption: (A): The manifestation of susceptible leaves, the SCRRS of leaves were 9, 7, 5, 3, 1 from left to right; (B): the SCRRSs in DH founders and testers; (C): The distribution of SCRRS in DH (top) and hybrid (bottom) populations (Adopted from Li et al., 2023) 5.2 Case study on resistance breeding for northern leaf blight Northern leaf blight (NLB), caused by Exserohilum turcicum, is another major disease affecting maize. The use of integrated technologies, including DH breeding and genomic tools, has facilitated the identification and promotion of resistant genotypes. For example, a study on multiple DH populations identified several SNPs associated with resistance to NLB, providing valuable markers for breeding programs (Sadessa et al., 2022). The use of genome-wide association studies (GWAS) and linkage mapping has also been instrumental in dissecting the genetic architecture of resistance to common rust, a related foliar disease, revealing significant SNPs and QTLs that can be targeted for NLB resistance breeding (Ren et al., 2020). These integrated approaches enable the accumulation of resistance alleles and the development of robust, resistant maize varieties. 5.3 Case study on breeding for multi-disease resistance Breeding for multi-disease resistance in maize involves the accumulation of multiple resistance genes to provide broad-spectrum protection. The use of DH breeding has been particularly effective in this regard. For instance, the introgression of resistance loci from European flint landraces into elite maize lines has significantly improved resistance to Gibberella ear rot (GER) while maintaining desirable agronomic traits (Akohoue et al., 2023). Similarly, the evaluation of DH lines under various conditions, including artificial inoculation of maize lethal necrosis (MLN), has identified SNPs associated with resistance to multiple diseases, such as gray leaf spot and turcicum leaf blight (Sadessa et al., 2022). These findings highlight the potential of DH breeding to combine multiple resistance genes, thereby enhancing the overall disease resistance of maize cultivars. The integration of genomic prediction models further aids in the selection of superior lines with enhanced resistance profiles (Ren et al., 2020; Sadessa et al., 2022; Li et al., 2023). 6 Advantages and Limitations of the Integrated Strategy 6.1 Advantages of the integrated breeding strategy The integration of haploid breeding and germplasm innovation in maize disease resistance breeding offers several significant advantages. Firstly, it improves the efficiency and precision of breeding programs. Doubled haploid (DH) technology accelerates the development of pure lines, which is crucial for heterosis utilization in maize
RkJQdWJsaXNoZXIy MjQ4ODYzNA==