The development of PCR-based markers for the selection of eyespot resistance genes Pch1 and Pch2

Abstract

Two eyespot resistance genes (Pch1 and Pch2) have been characterised in wheat. The potent resistance gene Pch1, transferred from Aegilops ventricosa, is located on the distal end of the long arm of chromosome 7D (7DL). Pch2 derives from the variety Cappelle Desprez and is located at the distal end of chromosome 7AL. The RFLP marker Xpsr121 and the endopeptidase isozyme allele Ep-D1b, are very closely linked to Pch1, probably due to reduced recombination in the region of the introgressed A. ventricosa segment. Pch2 is less closely linked to these markers but is thought to be closer to Xpsr121 than to Ep-A1b. In the present study simple sequence repeat (SSR) markers were integrated into the genetic map of a single chromosome (7D) recombinant (RVPM) population segregating for Pch1. Sequence-tagged-site (STS)-based assays were developed for Xpsp121 and a 7DL wheat EST containing a SSR. SSR markers Xwmc14 and Xbarc97 and the Xpsr121-derived marker co-segregated with Pch1 in the RVPM population. A single chromosome (7A) recombinant population segregating for Pch2 was screened for eyespot resistance and mapped using SSRs. QTL interval mapping closely associated Pch2 with the SSR marker Xwmc525.

How do eyespot resistance genes transferred into winter wheat breeding lines affect their yield?

“…ventricosa chromosome 7DL. This loci is linked to simple sequence repeat (SSR) markers XustSSR2001-7DL as well as Xbarc97 Chapman et al 2008). However, Santra et al (2006) showed that EP-D1b is more effective than XustSSR2001-7DL.…”

“…However, Johnson (1992) reported that Pch2 is less effective than Pch1. The Pch2 gene was identified in Cappelle Desprez wheat using three closely linked SSR markers (Table 1) (Chapman et al 2008). Muranty et al (2002) showed that Pch2 caused resistance to eyespot at the seedling stage and an additional gene on chromosome 5A was responsible for eyespot resistance at the adult stage.…”

“…jic-5A loci) and negative (Ozon and Patras, eyespot susceptible) control varieties. Pch1, Pch2 and Q.Pch.jic-5A loci identification was made using eight verified markers (Table 1) according to McMillin et al (1986); Groenewald et al (2003); Chapman et al (2008) and Burt et al (2011). Based on the marker analysis, we selected five groups of breeding lines, carrying: (1) the Pch1 gene alone: one line; (2) the Pch2 gene alone: four lines; (3) the Q.Pch.jic-5A alone: one line; and (4) Pch1 + Q.Pch.jic-5A: three lines.…”

Using markers and field evaluation to identify the source of eyespot resistance genePch1in the collection of wheat breeding lines

“…STS marker predicted disease reaction with approximately 90% accuracy (Santra et al 2006). Further markers to the distal end of long arm of chromosome 7D are required for the fine mapping of Pch1 (Chapman 2008). Wheat SSR markers, such as Xwmc14 (Somers et al 2004) and Xbarc97 (Shi et al 2003), are often dominant, producing a specific product from wheat but failing to amplify one from the Ae.…”

Mapping QTL for resistance to eyespot of wheat in Aegilops longissima

“…Later, Burt et al (2011) mapped a major QTL on chromosome 5AL and associated it with simple sequence repeat (SSR) marker gwm639. Three SSR markers (wmc346, wmc525, and cfa2040) were closely linked to Pch2 on chromosome 7A (Chapman et al 2008). The eyespot resistance in Cappelle Desprez has been durable; however, its effectiveness is not sufficient under severe eyespot conditions and fungicide application is required to prevent yield loss (Macer 1966;Hollins et al 1988).…”