Functional analysis and RFLP-mediated mapping of the Mlg resistance locus in barley

Abstract

SummaryThe semi-dominantly acting allele of the Mlg locus in barley confers a race-specific resistance to the causal agent of powdery mildew, Erysiphe graminis f.sp. hordei. High resolution genetic mapping via RFLP analysis enabled us to identify a set of markers on chromosome 4 which are either tightly linked or cosegregate with the resistance function. Comparison of marker distances in segregating F2 populations originating from different genotypes revealed an unexpected variation of recombination frequencies in the vicinity of the locus. Based on near-isogenic lines carrying either resistance gene Mlg or Mia12 and a cell-type specific analysis it was demonstrated that Mlgacts at an earlier stage of fungal development than MIa12. A time-course analysis of the early infection process combined with gene dosage experiments provided strong evidence that attacked cells retain viability after the defence response and that hypersensitive cell death (HR) is a secondary consequence, but not causally required for Mlg-mediated arrest of fungal growth. It is speculated that gene dosage experiments may provide a means to separate primary from secondary defence reactions.

Barley MLA Immune Receptors Directly Interfere with Antagonistically Acting Transcription Factors to Initiate Disease Resistance Signaling

“…Significantly, silencing of MYB6 in MLA1-, MLA6-, or MLA10-containing backgrounds compromised MLA-triggered resistance to Bgh, resulting in increased HI% of ;20 to 25% compared with ;6 to 9% for EV controls ( Figure 6C, bars 1 to 6). Notably, the MLG-triggered race-specific and the mlo-mediated broad spectrum resistance to Bgh were not affected by MYB6 silencing ( Figure 6C, bars 7 to 10) (Büschges et al, 1997;Görg et al, 2005). Second, we performed virus-induced gene silencing using a barley stripe mosaic virus (BSMV) vector (Yuan et al, 2011) to silence MYB6 or MLA12 in a MLA12-containing barley line.…”

Newly discovered genes for resistance to powdery mildew in the subtelomeric region of the short arm of barley chromosome 7H

“…In the late 1980s and early 1990s, restriction fragment length polymorphism (RFLP) markers were developed for mapping. Many of them were linked and co-segregating with the known powdery mildew resistance genes (Görg et al 1993;Kürth et al 2001). Simple sequence repeat (SSR) markers randomly distributed in the genome have proved to be very useful for rough mapping.…”

Mapping of genomic regions associated with net form of netblotch resistance in barley

“…In this region, several genes such as Ml-g and ml-o for resistance to Blumeria graminis f. sp. hordei (Görg et al 1993), QTLs for quantitative resistance to Puccinia striiformis f. sp. hordei and net blotch in both seedling and adult plant stages, were identified (Hinze et al 1991;Chen et al 1994;Steffenson et al 1996;Manninen et al 2000).…”