Advancing soybean rust resistance: Strategies, mechanisms, and innovations in gene pyramiding

Abstract

Asian soybean rust (ASR), caused by the fungus Phakopsora pachyrhizi, is a devastating threat to global soybean production, with potential yield losses of over 80 %. The pathogen's ability to complete multiple infection cycles and its high genetic variability present significant challenges for management, as reliance on fungicides is both costly and increasingly undermined by the development of resistance issues. Genetic resistance, conferred by major resistance genes (Rpp1–Rpp7), offers a sustainable alternative, but the durability of this single-gene-mediated resistance is often lost by evolving pathogen populations. Gene pyramiding, the strategic stacking of multiple Rpp genes within a single cultivar through crossbreeding or DNA recombinant technology, has emerged as a sustainable solution to achieve enhanced resistance against diverse ASR isolates. Pyramiding or stacking of Rpp genes has been proven to increase the resistance level and enlarge the resistance spectrum against a complex ASR population. These multigene pyramided lines demonstrate greater durability of resistance than single Rpp lines, offering a prospective avenue for developing elite soybean cultivars against ASR. Many of these lines could be deployed to characterize pathotype differentiation of P. pachyrhizi with higher precision than differential varieties. However, several challenges, including incomplete transfer of key genetic elements, dominance effects among resistance genes, genotype × environment interactions, linkage drag, and the extended time required for breeding, complicate the implementation of gene pyramiding. Recent advancements in genomic tools, such as marker-assisted selection (MAS), genomic selection (GS), and next-generation genome editing, such as CRISPR/CAS, show potential to revolutionize the gene pyramiding process, improving precision and efficiency. This review synthesizes current progress in gene pyramiding strategies, highlights innovative tools for overcoming existing challenges, and explores future research directions to mitigate ASR's impact and promote sustainable soybean production worldwide.