DETERMINATION OF RECOMBINATION FREQUENCIES IN Hordeum vulgare - H. Bulbosum HYBRIDS AND CHARACTERISATION OF THEIR PROGENY USING IN SITU HYBRIDIZATION

¹ School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand

² New Zealand Institute for Crop & Food Research Limited, Private Bag 4704, Christchurch, New Zealand

Hordeum bulbosum is an important donor of resistance genes against pathogens of cultivated barley (H. vulgare). However, low crossing-over in hybrids hinders the transfer of H. bulbosum DNA into barley, and selecting hybrids with high crossing-over is desirable. The objectives of this study were first, to use genomic in situ hybridization (GISH) to investigate meiotic crossing- over in hybrids and second, to use fluorescence in situ hybridization (FISH) with an oligonucleotide sequence (CCT)10 followed by GISH, to map introgressions in selfed progeny from hybrids. Meiotic recombination frequencies in two genotypes of diploid hybrids differing in their meiotic pairing behaviour, were determined by GISH. Hybrids 102C2 and 103K5 showed high and low frequencies of bivalents, respectively, at metaphase I. GISH established that pairing was intergenomic and pairing frequency exceeded recombination. 102C2 had higher crossing-over frequencies than 103K5, and in both hybrids chromosomal recombination was distal. Selfed progeny from chromosome-doubled 102C2 were screened agronomically in the field and putative recombinants were subjected to FISH and GISH to localize introgressed H. bulbosum DNA on particular barley chromosomes. Leaf rust resistance was associated with distal regions of chromosomes 2HL and 2HS, and mildew resistance with the distal region of 2HS.