Identification of New Sources of Resistance to Wheat Stem Rust in Aegilops spp. in the Tertiary Genepool of Wheat.

Pablo D Olivera,Yue Jin,Matthew N Rouse

doi:10.3389/fpls.2018.01719

Abstract

Recent stem rust epidemics in eastern Africa and elsewhere demonstrated that wheat stem rust is a re-emerging disease posing a threat to wheat production worldwide. The cultivated wheat gene pool has a narrow genetic base for resistance to virulent races, such as races in the Ug99 race group. Wild relatives of wheat are a tractable source of stem rust resistance genes. Aegilops species in the tertiary genepool have not been exploited to any great extent as a source of stem rust resistance. We evaluated 1,422 accessions of Aegilops spp. for resistance to three highly virulent races (TTKSK, TRTTF, and TTTTF) of Puccinia graminis f. sp. tritici. Species studied include Ae. biuncialis, Ae. caudata, Ae. comosa, Ae. cylindrica, Ae. geniculata, Ae. neglecta, Ae. peregrina, Ae. triuncialis, and Ae. umbellulata that do not share common genomes with cultivated wheat. High frequencies of resistance were observed as 977 (68.8%), 927 (65.2%), and 850 (59.8%) accessions exhibited low infection types to races TTKSK, TTTTF, and TRTTF, respectively. Contingency table analyses showed strong association for resistance to different races in several Aegilops spp., indicating that for a given species, the resistance genes effective against multiple races. Inheritance studies in selected accessions showed that resistance to race TTKSK is simply inherited.

Highlights

Wheat stem rust, caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E
We observed a high percentage of resistance in this Aegilops collection as 977 (68.8%), 927 (65.2%), and 850 (59.8%) accessions produced low infection types to races TTKSK, TTTTF, and TRTTF, respectively (Table 3)
The frequencies of accessions resistant to race TTKSK varied among the species: over 80% in six Aegilops species

Summary

Introduction

Wheat stem rust, caused by Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Wheat stem rust, caused by Puccinia graminis Pers.:Pers. (Pgt), is a devastating disease of durum wheat Durum) and common or bread wheat (T. aestivum L.). Stem rust has been under effective control through the use of genetic resistance. The occurrence and spread of Sr31-virulence races in the. Ug99 race group in East Africa and other virulent races causing epidemics and localized outbreaks in Ethiopia (Olivera et al, 2015), Europe (Bhattacharya, 2017; Olivera Firpo et al, 2017; Lewis et al., 2018) and Central Asia (Shamanin et al, 2018), indicates that the disease is re-emerging as a threat to wheat production. Races in the Ug99 group have been detected across South, East and northern

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