Mapping of Rym14 Hb , a gene introgressed from Hordeum bulbosum and conferring resistance to BaMMV and BaYMV in barley

Abstract

Hordeum bulbosum represents the secondary gene pool of barley and constitutes a potential source of various disease resistances in barley breeding. Interspecific crosses of H. vulgare x H. bulbosum resulted in recombinant diploid-barley progeny with immunity to BaMMV after mechanical inoculation. Tests on fields contaminated with different viruses demonstrated that resistance was effective against all European viruses of the soil-borne virus complex (BaMMV, BaYMV-1, -2). Genetic analysis revealed that resistance was dominantly inherited. Marker analysis in a F5 mapping family was performed to map the introgression in the barley genome and to estimate its size after several rounds of recombination. RFLP anchor-marker alleles indicative of an H. bulbosum introgression were found to cover an interval 2.9 cM in length on chromosome 6HS. The soil-borne virus resistance locus harboured by this introgressed segment was designated Rym14(Hb). For marker-assisted selection of Rym14(Hb) carriers, a diagnostic codominant STS marker was derived from an AFLP fragment amplified from leaf cDNA of homozygous-resistant genotypes inoculated with BaMMV.

Recent progress in barley improvement using wild species of <i>Hordeum</i>

“…In one unpublished study, we screened a segregating population of 225 plants derived from a heterozygous introgression on chromosome 2HL and detected only three offspring that had undergone further recombination within the introgressed chromatin segment. Recombination was also reduced by a factor of 7 in a recombinant line (RL) involving chromosome 6HS (Ruge et al, 2003).…”

“…Several selfed progeny from the hybrids exhibited traits, such as prostrate growth habit and leaf sheath pubescence, which probably originated from the wild parent. Progeny from these hybrids were also sometimes disease resistant and have been used as a source of leaf rust and mosaic virus resistance to improve cultivated barley (Walther et al, 2000;Ruge et al, 2003). In the late 1980s Pickering et al (1987) described a plant derived from a tetraploid "VVBB" hybrid that was resistant to powdery mildew.…”

“…Amplified fragment length polymorphisms (AFLPs) have also been used to generate markers directly from RLs with known introgression locations, but when converted to single locus PCR markers these AFLP sequences often result in amplification from only a subset of parental H. bulbosum genotypes. cDNA-AFLP has been used effectively in the mapping of a soil-borne virus (BaMMV/ BaYMV) resistance locus in an RL (Ruge et al, 2003) and is now being investigated as a more efficient means to develop markers for H. bulbosum genes that are expressed in characterised RLs. To extend this method we are using distally mapped cDNA sequences in conjunction with the EST database Harv-EST (Wanamaker and Close -http://harvest.ucr.edu) as templates for generating a collection of PCR-based markers.…”

“…These RLs were derived from backcrosses of triploid "VBBs" to barley or from selfed progenies of tetraploid "VVBB" hybrids (Zhang et al, 2001). Loci transferred from H. bulbosum by ourselves and other research groups (Walther et al, 2000;Ruge et al, 2003) confer disease resistance and other traits, and have been located on particular chromosomes (Table 3). Thirteen of the well-characterised lines have been grown in trials to assess their yield potential in New Zealand, eight of which equalled or exceeded the yield of the backcross parent when fungicide was not applied.…”

Recent advances in breeding of cereals for resistance to barley yellow dwarf virus

“…Until now, rym genes named rym1 to rym13 and rym15 have been described in the genome of resistant cultivars of hordeum vulgare (le gouis et al 2004; ordon et al 2004). apart from these recessive resistance genes, two dominant resistance genes, Rym14 hb and Rym16 hb , have been introgressed into cultivated barley from hordeum bulbosum (Ruge et al 2003;Ruge-wehling et al 2006). a comprehensive survey of progress in breeding of barley resistant to BaYMv was given by ordon et al (2004).…”