Resistance to Asian soybean rust in soybean lines with the pyramided three Rpp genes

Naoki Yamanaka,Ricardo V Abdelnoor,Yuichi Yamaoka,Alessandro L Braccini,Noelle G Lemos,Kazuhiro Suenaga,Hajime Akamatsu,Miori Uno

doi:10.1590/s1984-70332013000100009

Abstract

In this study, the influence of genetic background on the resistance level of a soybean line carrying Rpp2, Rpp4, and Rpp5 was evaluated by backcrossing it with a susceptible variety. It was also evaluated eight lines which carry these Rpp genes against five Asian soybean rust (ASR) isolates, in order to determine the likely range of resistance against ASR isolates differing in pathogenicity. The results indicated that a high level of resistance against various ASR isolates could be retained in lines carrying the three Rpp genes in susceptible genetic backgrounds, although minor influences of plant genetic background and ASR pathogenicity to the ASR resistance could occur. Thus, lines with the pyramided three Rpp genes should be effective against a complex pathogen population consisting of diverse Phakopsora pachyrhizi isolates.

Highlights

The fungus Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), is an airborne foliar disease considered to be one of the most serious economic threats for soybean producers (Goellner et al 2010)
It was evaluated eight lines which carry these Rpp genes against five Asian soybean rust (ASR) isolates, in order to determine the likely range of resistance against ASR isolates differing in pathogenicity
The results indicated that a high level of resistance against various ASR isolates could be retained in lines carrying the three Rpp genes in susceptible genetic backgrounds, minor influences of plant genetic background and ASR pathogenicity to the ASR resistance could occur

Summary

Introduction

The fungus Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), is an airborne foliar disease considered to be one of the most serious economic threats for soybean producers (Goellner et al 2010). ASR was first detected in the American Continent, in Paraguay, in May 2001 (Yorinori et al 2005), and has caused severe losses of soybean production in South America (Yorinori 2008). Management strategies such as the use of fungicides, the adoption of a free host period, and the use of genetic resistance are important for controlling ASR (Yorinori 2008). The pyramiding of available ASR resistance genes in a single soybean cultivar may provide more durable resistance against P. pachyrhizi populations expressing a wide range of pathogenicity in the field (Arias et al 2008). Six resistance loci (Rpp: resistance to P. pachyrhizi, Rpp1–6) have been mapped with molecular markers for ASR (Hyten et al 2007, Silva et al 2008, Garcia et al 2008, Chakraborty et al 2009, Ray et al 2009, Monteros et al 2010, Li et al 2012); it can be tagged and pyramided using molecular markers (Yamanaka et al 2008, Lemos et al 2011)

Objectives

Methods

Results