Prospects for Durable Resistance Against an Old Soybean Enemy: A Four-Decade Journey from Rpp1 (Resistance to Phakopsora pachyrhizi) to Rpp7

Abstract

Soybean rust (SBR), caused by Phakopsora spp., is a major global concern for soybean producers. SBR causing fungi are polycyclic and obligate biotrophs, rendering the study of their biology particularly tedious. Over the past four decades, substantial progress has been made towards understanding the epidemiology of the disease, the identification of sources of resistance, and the mapping of soybean loci conferring resistance to P. pachyrhizi (Rpp genes), since this species is particularly well established and widespread in many soybean growing areas. Although host-plant resistance is generally considered as the most desirable solution from an environmental, economic, and social perspective, other disease control approaches such as agronomic practices and chemical application are also important, and influence rust epidemiology as well as the durability of host plant resistance. This review focusses primarily on genetic aspects of SBR management and summarizes the research in the following areas: SBR symptoms, aetiology, pathogenic variation and population structure of Phakopsora populations, expression of soybean resistance to Phakopsora infection, genetics and molecular diagnostics of host resistance to pathogen, and resistance gene deployment approaches. Finally, the role of multidisciplinary strategies is discussed for achieving higher durability of SBR resistance in soybean.

Genetic Diversity and Population Structure of Soybean Lines Adapted to Sub-Saharan Africa Using Single Nucleotide Polymorphism (SNP) Markers

“…is the fourth most widely grown crop worldwide, and often termed as "miracle crop" because it is a main source of both protein and oil [1]. Despite the relatively low oil content in the seeds of soybean (about 20%) vis-à-vis other oilseed crops, the better adaptability to different latitudes, and climatic and soil conditions have enabled this crop to become the most important leguminous oilseed crop worldwide, accounting for about half of the global production of major oilseeds [2,3]. Over the decade, soybean production is projected to grow at a higher rate (1.6% per annum) than that of other major oilseeds such as rapeseed, sunflower, and groundnut (1.4% per annum) [4].…”

Molecular Breeding to Overcome Biotic Stresses in Soybean: Update

“…According to a recent review published by Chander et al [ 1 ], seven loci ( Rpp 1 to Rpp 6) have been identified to date with varying degrees of resistance. A virus-induced gene silencing method is being applied in the molecular detection of resistance in plants.…”

“…In a similar way, the gene pyramiding approach was also used to combine Rpp 2, Rpp 3 and Rpp 4 with cumulative resistance [ 53 ]. These reports are clear reflections of the gene pyramiding approach to increase disease resistance in soybean crop [ 1 ]. Recent research on applications of marker-assisted selection in combination with line breeding was found to be useful in developing soybean cultivars containing ASRresistance genes.…”

“…Soybean is a well-known leguminous crop with a high percentage of protein and oil in seed [ 1 ]. Despite having its origin in China [ 2 ], it is extensively cultivated in most parts of the world [ 3 ].…”

Rpp-Gene pyramiding confers higher resistance level to Asian soybean rust

“…ASR is caused by the fungus Phakopsora pachyrhizi (Sydow and Sydow), an obligatory biotrophic basidiomycete, which has multiple infection cycles in the same crop, with a high capacity to produce uredospores and to easily disseminate (Chander et al 2019). In addition, it has a high intraspeci c variability of isolates and wide geographic distribution and is extremely severe and di cult to control (Darben et al 2020).…”