Identification and mapping of PmG16, a powdery mildew resistance gene derived from wild emmer wheat

Abstract

The gene-pool of wild emmer wheat, Triticum turgidum ssp. dicoccoides, harbors a rich allelic repertoire for disease resistance. In the current study, we made use of tetraploid wheat mapping populations derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16) to identify and map a new powdery mildew resistance gene derived from wild emmer wheat. Initially, the two parental lines were screened with a collection of 42 isolates of Blumeria graminis f. sp. tritici (Bgt) from Israel and 5 isolates from Switzerland. While G18-16 was resistant to 34 isolates, Langdon was resistant only to 5 isolates and susceptible to 42 isolates. Isolate Bgt#15 was selected to differentiate between the disease reactions of the two genotypes. Segregation ratio of F(2-3) and recombinant inbreed line (F(7)) populations to inoculation with isolate Bgt#15 indicated the role of a single dominant gene in conferring resistance to Bgt#15. This gene, temporarily designated PmG16, was located on the distal region of chromosome arm 7AL. Genetic map of PmG16 region was assembled with 32 simple sequence repeat (SSR), sequence tag site (STS), Diversity array technology (DArT) and cleaved amplified polymorphic sequence (CAPS) markers and assigned to the 7AL physical bin map (7AL-16). Using four DNA markers we established colinearity between the genomic region spanning the PmG16 locus within the distal region of chromosome arm 7AL and the genomic regions on rice chromosome 6 and Brachypodium Bd1. A comparative analysis was carried out between PmG16 and other known Pm genes located on chromosome arm 7AL. The identified PmG16 may facilitate the use of wild alleles for improvement of powdery mildew resistance in elite wheat cultivars via marker-assisted selection.

Evolution and Adaptation of Wild Emmer Wheat Populations to Biotic and Abiotic Stresses

“…The DIC donor line of PmG3M conferred resistance to all 55 tested Bgt isolates from Israel, Switzerland, the United States, Chile, Paraguay, the Netherlands, and China (141). However, the PmG16 donor line was susceptible to 13 isolates and resistant to 34 isolates, suggesting a gene-for-gene type of interaction in the Bgt-DIC pathosystem, which evolved during host-parasite coevolution (5). The Triticum durum cultivar Langdon was susceptible to 42 isolates and resistant to only five, demonstrating the vulnerability of wheat crops to destructive pathogens.…”

“…However, due to rapid change in the virulence of the pathogen, most Bgt R-genes tend to become ineffective within a short period. DIC populations contain a considerable allelic reservoir for resistance to Bgt (5,8,42,91,141). The Bgt resistance in DIC populations displays ecogeographic variation and appears to have coevolved with the pathogen.…”

“…Several DIC R-genes conferring broad-spectrum Bgt resistance were recently identified (5,55,141,151). For example, the new recessive R-gene pm42 was highly effective against 18 of 21 differential Chinese isolates (55).…”

Molecular detection of disease resistance genes to powdery mildew (Blumeria graminis f. sp. tritici) in wheat (Triticum aestivum) cultivars

“…In an attempt to control the diseases, use of resistant or tolerant cultivars has been one of the effective methods widely used by scientists as it is economical as well as environmentally friendly (Song et al, 2009;Ben-David et al, 2010). Several wheat cultivars are being developed and tested for resistance to wheat powdery mildew but their resistance is easily broken down due to continuous development of new and more virulent strains through genetic recombination (Piarulli et al, 2012;Hurni et al, 2014).…”

Fine Physical and Genetic Mapping of Powdery Mildew Resistance Gene MlIW172 Originating from Wild Emmer (Triticum dicoccoides)

“…dicoccoides [ T. dicoccoides , (AABB; 2n = 4x = 28)], as the progenitor of the cultivated tetraploid and hexaploid wheat, is crossable with both durum and common wheat and has great potential for wheat improvement [5]. Wild emmer is a valuable source of powdery mildew resistance [6]–[9] and has been extensively studied for identification of new alleles and genes useful for wheat improvement. Among the characterized wheat powdery mildew genes, Pm16 , Pm26 , Pm30, Pm36 , Pm41, Pm42, MlIW72 , MlZec1, PmG3M, MlIW170, PmG16, PmAS846 and HSM1 have been identified in wild emmer and introduced into cultivated wheat [3], [10].…”