Chromosomal loci associated with endosperm hardness in a malting barley cross.

A breeding objective for the malting barley industry is to produce lines with softer, plumper grain containing moderate protein content (9-12%) as they are more likely to imbibe water readily and contain more starch per grain, which in turn produces higher levels of malt extract. In a malting barley mapping population, 'Arapiles' × 'Franklin', the most significant and robust quantitative trait locus (QTL) for endosperm hardness was observed on the short arm of chromosome 1H, across three environments over two growing seasons. This accounted for 22.6% (Horsham 2000), 26.8% (Esperance 2001), and 12.0% (Tarranyurk 2001) of the genetic variance and significantly increased endosperm hardness by 2.06-3.03 SKCS hardness units. Interestingly, Arapiles and Franklin do not vary in Ha locus alleles. Therefore, this region, near the centromere on chromosome 1H, may be of great importance when aiming to manipulate endosperm hardness and malting quality. Interestingly, this region, close to the centromere on chromosome 1H, in our study, aligns with the region of the genome that includes the HvCslF9 and the HvGlb1 genes. Potentially, one or both of these genes could be considered to be candidate genes that influence endosperm hardness in the barley grain. Additional QTLs for endosperm hardness were detected on chromosomes 2H, 3H, 6H and 7H, confirming that the hardness trait in barley is complex and multigenic, similar to many malting quality traits of interest.

Resistance gene analogues of wheat: molecular genetic analysis of ESTs.

Using two divergent nucleotide binding site (NBS) regions from wheat sequences of the NBS-LRR (leucine rich repeat) class, we retrieved 211 wheat and barley NBS-containing resistance gene analogue (RGA) expressed sequence tags (ESTs). These ESTs were grouped into 129 gene sequence groups that contained ESTs that were at least 70% identical at the DNA level over at least 200 bp. Probes were obtained for 89 of these RGA families and chromosome locations were determined for 72 of these probes using nullitetrasomic Chinese Spring wheat lines. RFLP analysis of 49 of these RGA probes revealed 65 mappable polymorphic bands in the doubled haploid Cranbrook x Halberd wheat population (C x H). These bands mapped to 49 loci in C x H. RGA loci were detected on all 21 chromosomes using the nullitetrasomic lines and on 18 chromosomes (linkage groups) in the C x H map. This identified a set of potential markers that could be developed further for use in mapping and ultimately cloning NBS-LRR-type disease resistance genes in wheat.