Using a Hybrid Mapping Population to Identify Genomic Regions of Pyrenophora teres Associated With Virulence

Abstract

Net blotches caused by Pyrenophora teres are important foliar fungal diseases of barley and result in significant yield losses of up to 40%. The two types of net blotch, net-form net blotch and spot-form net blotch, are caused by P. teres f. teres (Ptt) and P. teres f. maculata (Ptm), respectively. This study is the first to use a cross between Ptt and Ptm to identify quantitative trait loci (QTL) associated with virulence and leaf symptoms. A genetic map consisting of 1,965 Diversity Arrays Technology (DArT) markers was constructed using 351 progenies of the Ptt/Ptm cross. Eight barley cultivars showing differential reactions to the parental isolates were used to phenotype the hybrid progeny isolates. Five QTL associated with virulence and four QTL associated with leaf symptoms were identified across five linkage groups. Phenotypic variation explained by these QTL ranged from 6 to 16%. Further phenotyping of selected progeny isolates on 12 more barley cultivars revealed that three progeny isolates are moderately to highly virulent across these cultivars. The results of this study suggest that accumulation of QTL in hybrid isolates can result in enhanced virulence.

Multi-parental fungal mapping population study to detect genomic regions associated with Pyrenophora teres f. teres virulence

“…QTLs identified in our study were also co-localised with QTLs reported in previous bi-parental and GWAS studies. The location of the QTL identified on chromosome 5 for Prior virulence was similar to the QTLs AvrHar 24 , PttBee2 (Koladia et al 28 ) , PttBee_5, PttSki_5, QTL11 , QTL12 (Martin et al 4 ) and USQV5 (Dahanayaka et al 31 ) identified previously through bi-parental and GWAS studies. The QTL, PttBee2 28 and PttBee_5 4 , 29 associated with Beecher virulence were co-localised with our QTL on chromosome 5 associated with Prior virulence.…”

“…Phenotyping of the progeny isolates was performed following a completely randomised design in a controlled environment room at the University of Southern Queensland, Australia, with three replicates, as described in Dahanayaka et al 31 . The four barley cultivars (Beecher, Commander, Prior, and Skiff) were grown in pots with 5 cm diameter and 14 cm height with each pot containing four plants each of the four barley cultivars.…”

“…The conidial suspensions for inoculations were prepared as described in Dahanayaka et al 31 . Three millilitres of the suspension diluted to 10,000 conidia/mL were used per pot for inoculations 14 days after sowing.…”

“…To date, six bi-parental mapping studies have been conducted to discover genomic regions accounting for avirulence/virulence of Ptt/Ptt populations 24 – 29 while other studies have detected QTLs responsible for the virulence in Ptm/Ptm 30 and Ptt/Ptm hybrid mapping populations 31 . Two GWAS have also been conducted to identify genomic regions responsible for the virulence of P. teres in Ptt 29 and Ptm 32 populations.…”