Abstract
Genetic resistance against biotic stress is a major goal in many wheat breeding programs. However, modern wheat cultivars have a limited genetic variation for disease and pest resistance and there is always a possibility of the evolution of new diseases and pests to overcome previously identified resistance genes. A total of 125 synthetic hexaploid wheats (SHWs; 2n = 6x = 42, AABBDD, Triticum aestivum L.) were characterized for resistance to fungal pathogens that cause wheat rusts (leaf; Puccinia triticina, stem; P. graminis f.sp. tritici, and stripe; P. striiformis f.sp. tritici) and crown rot (Fusarium spp.); cereal cyst nematode (Heterodera spp.); and Hessian fly (Mayetiola destructor). A wide range of genetic variation was observed among SHWs for multiple (two to five) biotic stresses and 17 SHWs that were resistant to more than two stresses. The genomic regions and potential candidate genes conferring resistance to these biotic stresses were identified from a genome-wide association study (GWAS). This GWAS study identified 124 significant marker-trait associations (MTAs) for multiple biotic stresses and 33 of these were found within genes. Furthermore, 16 of the 33 MTAs present within genes had annotations suggesting their potential role in disease resistance. These results will be valuable for pyramiding novel genes/genomic regions conferring resistance to multiple biotic stresses from SHWs into elite bread wheat cultivars and providing further insights on a wide range of stress resistance in wheat.
Highlights
Wheat (Triticum aestivum L.) is one of the most widely grown cereal crops with a production of more than 756 million tonnes in 2017–2018 [1] and it feeds more than one-third of the world’s population [2]
A wide range of genetic variation for multiple biotic stresses was observed in 125 synthetic hexaploid wheats (SHWs) (Figure 1 and S2u.1p.pPlheemnoetynptiac rDyistTriabubtlieonSo1f D).isAeasse aenxdpPeecstted, seedling and adult plant resistance screening for susceptible cAhewcikdsesrhaonwgeeodf agmenoetdicervaatreialytiosnusfocrepmtiubltlieplteo bvieortiyc ssutrsecsesepstiwbales roebssperovnesdeiann1d25reSsHisWtasnt checks showed(Faigruerseis1taanndt StuopvpelermyernetasriystTaanbtlerSe1s)p
The present study identified SHWs resistant to diseases and pests that can be used for breeding for resistance to multiple biotic stresses
Summary
Wheat (Triticum aestivum L.) is one of the most widely grown cereal crops with a production of more than 756 million tonnes in 2017–2018 [1] and it feeds more than one-third of the world’s population [2]. Global wheat yield losses due to these rusts range from 20% to 100% [5,8,9,10] and were estimated at $5 billion per year since the 1990s [11]. Soilborne pathogens such as the cereal cyst nematode (CCNs; Heterodera spp.) cause significant cereal crop losses [12,13,14]. Hessian fly (HF; Mayetiola destructor), is one of the major destructive pests of wheat that causes grain yield loss of up to 80% [21] and may cause an average annual loss of 5% in the United States wheat production [22]. Breeding for resistance to multiple diseases and pests requires identification of genetic sources of resistance and novel genes [7]
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