Near-isogenic soybean lines carrying Asian soybean rust resistance genes for practical pathogenicity validation

Takeshi Kashiwa,Naoki Yamanaka,Yukie Muraki

doi:10.1038/s41598-020-70188-7

Takeshi Kashiwa, Naoki Yamanaka + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-70188-7

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Abstract

Asian soybean rust caused by the fungal pathogen Phakopsora pachyrhizi is the most devastating disease of soybean. The host cultivar specificity of the pathogen shows considerable differentiation depending on the area and season of its emergence. Although resistance genes for P. pachyrhizi (Rpp) have been reported in several soybean varieties, the genetic background of these varieties is highly differentiated. Furthermore, some of the varieties harbor unknown genetic factors in addition to Rpp that could influence resistance reactions against the pathogen. In order to gain a comprehensive understanding of Rpp–P. pachyrhizi interactions, homogenous plant material harboring Rpp genes is necessary. In this study, we bred Rpp-near isogenic lines (Rpp-NILs), which retained identical plant characters originating from a single genetic background, and accordingly showed low-variant compatible/incompatible reactions against the pathogen. These Rpp-NILs can be used as genetic resources for studying P. pachyrhizi epidemiology and elucidating resistance mechanisms. Compatible/incompatible relationships between the soybean rust resistance gene Rpp and isolates of the pathogen P. pachyrhizi are clearly distinguishable using the Rpp-NILs bred in this study.

Highlights

Asian soybean rust caused by the fungal pathogen Phakopsora pachyrhizi is the most devastating disease of soybean
The results obtained for Rpp1-near-isogenic lines (NILs) indicate that this NIL shows a weaker resistance reaction against the pathogens than the donor variety, which can be attributed to the fact that the genetic background of this NIL was P. pachyrhizi susceptible, and that the NIL lacks the benefits conferred by other genes contributed to resistance against Asian soybean rust (ASR)
Apart from the target resistance genes for P. pachyrhizi (Rpp), Rpp-NILs theoretically share more than 95% similarity with respect to genetic background, these homogenous genetic resources are applicable for studies on gene-for-gene relationships between soybean Rpp genes and the avirulence genes of P. pachyrhizi

Summary

Introduction

Asian soybean rust caused by the fungal pathogen Phakopsora pachyrhizi is the most devastating disease of soybean. We bred NILs for Rpp[1], Rpp[2], Rpp[3], Rpp[4], Rpp[6], and Rpp1-b from the ASR-susceptible soybean variety BRS 184, which shows low valiant inoculation results compared with those from other Rpp donor varieties. Nine Rpp-NILs (BC5F2 lines) carrying single Rpp genes of donor ASR-resistant varieties were successfully developed by backcrossing and SSR marker screening.

Results

Conclusion