¹New Zealand Institute for Crop & Food Research Limited, Private Bag 4704, Christchurch, New Zealand;

²Mühlbergstr. 6, D-18276 Gülzow, Germany;

³Wheat Genetics Resource Center, Department of Plant Pathology, Kansas State University, Manhattan, KS 66506-5502, USA

Hordeum bulbosum is probably the most closely related species to cultivated barley (H. vulgare) and has been widely used in plant breeding programmes for production of doubled haploids. The wild species also possesses resistance genes to many fungal and viral pathogens that are worth transferring to barley. The methods for gene introgression involve backcrossing fertile triploid and tetraploid H. vulgare x H. bulbosum hybrids to barley (Xu and Kasha, 1992; Pickering et al., 1995). Recombinants and chromosome substitutions have been identified and characterized cytologically (Pickering, 1992) and with RFLP analyses and genomic in situ hybridization (GISH) (Timmerman et al. 1993; Pickering et al., 1997). We describe here the partial characterization of a recombinant (K301) with H. bulbosum introgressions on two H. vulgare homologues.

K301 was selected from a cross of the winter barley 'Valja' x F₃ BBVV tetraploid hybrid derived from 'Stamm 5' H. vulgare (2n = 28) x unknown H. bulbosum (2n = 28) (Pohler and Szigat, 1982). K301 is more profusely pubescent on its leaf sheaths, including the upper leaf sheaths, than its H. vulgare parents. This trait is connected with delayed development of the plants (see also Pickering et al., 1997) and was probably transferred from H. bulbosum. Seed sets on K301 were slightly lower than normal (80%) and all selfed progeny were strongly pubescent. F₁ progeny from K301 x 'Emir' (glabrous) were all strongly pubescent whereas F₂ progeny segregated 61 pubescent : 14 glabrous, a ratio that did not differ from 3 pubescent:1 glabrous. Thus, pubescent leaf sheaths appear to be governed by a single dominant gene. Three of the pubescent plants were, however, only moderately pubescent, a feature of the barley parents 'Valja' and 'Stamm 5'. All 242 F₂ plants from a cross between 53A7 (a pubescent H. vulgare - H. bulbosum recombinant, (Pickering et al 1997)) and K301 were strongly pubescent and the two genes in 53A7 and K301 must either be allelic or closely linked. Since the gene for pubescent leaf sheath in 53A7 is located on 4HL, a similar location for the gene for pubescence in K301 is likely.

K301 had 14 chromosomes in somatic root tip cells and C-banding patterns were similar to those of H. vulgare. At meiotic Metaphase I (MI), 50 pollen mother cells (PMCs) of K301 that were examined contained seven bivalents, 88% of which were closed rings but the bivalents were scattered irregularly on the metaphase plate. One hundred PMCs were examined at Anaphase I and in 93 of them multi-polar migration of half-bivalents was observed and interkinetic polyads were formed at Telophase I. Some of the polyads were very small and resembled micronuclei, although no univalents or bridges and fragments were recorded during meiosis. These meiotic disturbances probably had an effect on the fertility causing the reduced seed sets. No meiotic abnormalities were observed in PMCs of the F₁ K301 x 53A7.

K301 gave a positive result with the repetitive sequence probe pSc119.2, which hybridizes to H. bulbosum DNA but only weakly with H. vulgare. Using two single-copy probes that hybridize to sequences located on chromosome 4HL, an H. bulbosum-specific signal was obtained in K301 using probe MWG616 but not with ABG366. The locus labelled by the latter is located more proximally than Xmwg616 (Graner pers. comm.). With three single-copy chromosome 1HL probes, H. bulbosum-specific bands were obtained with the two more distal probes (MWG912 and ABC261) whereas no such bands were observed for ABC160, which is the most proximal of the probes according to the consensus map of Langridge et al. (1995). No H. bulbosum bands were obtained after using distal probes specific to chromosomes 2HL, 2HS, 3HL, 4HS, 5HS, 5HL, 6HL and 7HL.

After performing GISH on mitotic and meiotic preparations of K301, distal introgressions of H. bulbosum DNA were observed on four chromosomes at mitosis and two bivalents at meiotic MI. Presumably, two of the signals were located on chromosome 4H homologues and two on homologues of 1H that were identified as possessing H. bulbosum DNA in the RFLP analyses. The presence of one or both the introgressions in homozygous form may have caused the disturbances at MI and later stages of meiosis as described above.

Although K301 does not show any resistance to several fungal and viral pathogens, other unknown desirable attributes of H. bulbosum may have been transferred such as improved feed value and tolerance to abiotic stress. A seed sample will be lodged in the gene bank at the Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstr. 3, D-06466 Gatersleben, Germany.

We thank Dr A Graner (IPK, Gatersleben, Germany) and Dr A Kleinhofs (Washington State University, Pullman, USA) for supplying the probes used in this investigation and Dr Matthew Cromey (Crop & Food Research, Lincoln, New Zealand) for pathological analyses.

References :

Langridge, P., A. Karakousis, N. Collins, J. Kretschmer, and S. Manning 1995. A consensus map of barley. Mol. Breed. 1: 389-395.

Pickering, R.A. 1992. Monosomic and double monosomic substitutions of Hordeum bulbosum L. chromosomes into H. vulgare L. Theor. Appl. Genet. 84: 466-472.

Pickering, R.A., A.M. Hill, M. Michel, and G.M. Timmerman-Vaughan 1995. The transfer of a powdery mildew resistance gene from Hordeum bulbosum L. to barley (H. vulgare L.) chromosome 2 (2I). Theor. Appl. Genet. 91: 1288-1292.

Pickering, R.A., A.M. Hill, and R.G. Kynast 1997. Characterization by RFLP analysis and genomic in situ hybridization of a recombinant and a monosomic substitution plant derived from Hordeum vulgare L. x H. bulbosum L. crosses. Genome 40: 195-200.

Pohler, W. and G. Szigat 1982. Versuche zur rekombinantiven Genübertragung von der Wildgerste Hordeum bulbosum auf die Kulturgerste H. vulgare. 1. Mitt. Die Rückkreuzung VV x BBVV. Arch. Züchtungsforsch., Berlin 12: 87-100.

Timmerman, G.M., R.A. Pickering, and G. Melz 1993. Characterization of Hordeum vulgare - Hordeum bulbosum chromosome substitution lines by restriction fragment length polymorphism analysis. Genome 36: 507-511.

Xu, J. and K.J. Kasha 1992. Transfer of a dominant gene for powdery mildew resistance and DNA from Hordeum bulbosum into cultivated barley (H. vulgare). Theor. Appl. Genet. 84: 771-777.