Marker Development and Saturation Mapping of the Tan Spot Ptr ToxB Sensitivity LocusTsc2in Hexaploid Wheat

Abstract

Ptr ToxB is a host-selective toxin produced by the tan spot fungus, Pyrenophora tritici-repentis, that induces chlorosis in wheat lines harboring the Tsc2 gene, which was previously mapped to chromosome arm 2BS in tetraploid wheat (Triticum turgidum L.). In this study, molecular mapping in a recombinant inbred line (RIL) population derived from the Ptr ToxB-sensitive 'Katepwa' and the Ptr ToxB-insensitive landrace Salamouni (Salamouni × Katepwa [SK] population) confi rmed the location of Tsc2 on 2BS in hexaploid wheat (Triticum aestivum L.). Analysis of an F 2 population derived from the same parents indicated that a single dominant gene governed Ptr ToxB sensitivity. Thirteen microsatellite markers were used to construct a basic linkage map of the Tsc2 region in the SK population, and 14 additional markers developed from bin-mapped expressed sequence tags (ESTs) and from ESTs identifi ed based on colinearity with rice (Oryza sativa L.) and Brachypodium distachyon (L.) P. Beauv. were mapped to the Tsc2 region. Tsc2 was delineated to a 3.3 cM interval and cosegregated with marker XBE444541. Spore inoculations and composite interval-regression mapping demonstrated that a compatible Tsc2-Ptr ToxB interaction accounted for 54% of the variation in disease expression. Analysis of Ptr ToxB-sensitive and-insensitive genotypes suggested that XBE444541 is diagnostic for Tsc2 and should be useful for marker-assisted selection.

New Insights into the Roles of Host Gene-Necrotrophic Effector Interactions in Governing Susceptibility of Durum Wheat to Tan Spot and Septoria nodorum Blotch

“…QTL analysis revealed a major QTL on 2BS explaining 69% of the variation and corresponding to the Tsc2 locus, thus indicating that the Tsc2 -ToxB interaction was significantly associated with development of the disease in the ITMI population. Other studies have also demonstrated that the Tsc2 gene is a major susceptibility factor in hexaploid wheat (Abeysekara et al 2010; Singh et al 2010). …”

“…For example, early work with Ptr ToxA showed strong correlations between sensitivity to culture filtrates containing Ptr ToxA and susceptibility to Ptr ToxA-producing isolates (Tomas and Bockus 1987; Lamari and Bernier 1989). Similarly, studies using Ptr ToxB and Ptr ToxC showed that these NEs were also strongly associated with tan spot caused by isolates that produced them (Effertz et al 2002; Friesen and Faris 2004; Abeysekara et al 2010). Therefore, the NEs were considered virulence factors, and it was assumed that sensitivity to an NE would lead to disease susceptibility (Anderson et al 1999).…”

Analysis of agronomic and domestication traits in a durum × cultivated emmer wheat population using a high-density single nucleotide polymorphism-based linkage map

“…Four sequence-tagged site (STS) markers previously developed by Abeysekara et al (2010) for mapping the Tsc2 gene on chromosome 2B were also mapped in the BP025 population. One of the four markers was derived from the expressed sequence-tag (EST) BF484320, and the other three were developed from the tentative consensus (TC) sequences TC454839, TC432379, and TC422669.…”

Evaluation and Association Mapping of Resistance to Tan Spot and Stagonospora Nodorum Blotch in Adapted Winter Wheat Germplasm

“…The four NE genes ToxA, ToxB, SnTox1, and SnTox3 have been cloned from the two fungal pathogens and heterologously expressed in the Pichia pastoris yeast strain x33 (Abeysekara et al 2010;Liu et al 2009Liu et al , 2012. The yeast strains expressing individual NE genes were grown in yeast potato dextrose broth (Liu et al 2012) for 24 to 48 h at 30°C with agitated shaking.…”