Bioscience Evidence 2025, Vol.15, No.6, 303-312 http://bioscipublisher.com/index.php/be 308 5.2 Correspondence between molecular markers and field resistance In Rpi gene breeding, one thing that researchers are very concerned about is whether the genes detected by molecular markers can really show disease resistance in the field. Although molecular markers can rapidly screen resistant materials, whether genes play a role in the field is also influenced by factors such as the genetic background of the material itself, gene expression levels, and differences in pathogen populations. Often, materials marked with R8, RB or Rpi-blb2 do exhibit strong resistance in the field, especially when these genes are present alone or multiple genes are superimposed. Some materials, although Rpi gene markers have been detected, show unstable or only partial resistance in the field. This may be due to incomplete function of the genes, silencing, or attack by pathogenic bacteria with breakthrough capabilities. On the contrary, there are also some materials that have not been found to have these genes in molecular testing, but still show strong resistance in the field. This may be due to the presence of resistance genes that have not yet been discovered, or they belong to quantitative resistance. 6 Case Comparisons and Comprehensive Analyses 6.1 Differences between single-gene resistance and multi-gene superimposed resistance Single-gene resistance is usually achieved by transferring an R gene from a wild species into cultivated varieties. This approach generally provides relatively strong but narrow-range resistance. Pathogenic bacteria Phytophthora infestans (late blight pathogen) evolve rapidly and often break through this resistance by generating new pathogenic subspecies, rendering the previously effective single R gene ineffective (Rakosy-Tican et al., 2020). gene pyramiding is the process of introducing two or more R genes that recognize different pathogenic effectors together. Potatoes carrying the three superimposed R genes of RB, Rpi-blb2, and Rpi-vnt1.1 all showed complete resistance under different regions and different pathogen pressures, and showed no disease symptoms in multi-season trials (Bubolz et al., 2022). The superposition of multiple genes not only expands the resistance range but also activates more defensive-related genes (Zhao et al., 2025). 6.2 Comparison of the stability of transgenic resistance and traditional breeding resistance Traditional disease-resistant breedingrelies on hybridization to introduce the R gene into varieties, but is limited by the low genetic diversity of cultivated potatoes and the rapid evolution of pathogens (Duan et al., 2021; Rogozina et al., 2023). Many disease-resistant varieties obtained through traditional breeding lose their resistance very quickly as stronger pathogenic bacteria subspecies emerge, and the breeding process needs to be repeated repeatedly. Transgenic technology can precisely superimpose multiple R genes from different sources together, without being limited by hybridization incompatibility, etc., and can rapidly breed varieties with broad-spectrum and persistent resistance. Transgenic potatoes with multiple gene superpositions maintained stable complete resistance under multi-year and multi-site conditions regardless of how high the disease stress was (Bubolz et al., 2022). 6.3 Key factors affecting field resistance performance In areas with high disease stress, transgenic potatoes carrying the superimposed R gene can still maintain complete disease resistance, while susceptible control varieties are quickly infected (Byarugaba et al., 2021). The genetic diversity of the local P. infestans population can affect the effectiveness of resistance. If a region is dominated by a single clonal pathogen and carries a specific effector, the corresponding R gene resistance can be maintained for a relatively long time. However, in regions where there are many types of pathogens and multiple highly virulent subspecies, single-gene resistance is more likely to fail (Rogozina et al., 2023). Environmental factors such as temperature, humidity and rainfall can affect the occurrence of diseases and their resistance performance. Multi-site trials have shown that different environments can lead to fluctuations in disease pressure and yield performance. However, the resistance superimposed with the R gene was stable in different ecological regions such as the African Highlands and Northern Europe.
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