TRANSFER AND MAPPING OF THE SHOOT-DIFFERENTIATION LOCUS SHD1 IN BARLEY CHROMOSOME-2

The locus Shd1, which we previously mapped to the long arm of chromoso me 2 of Hordeum vulgare L., controls the differentiation of shoots fro m immature barley embryo callus. The locus has major effects and its a ction explains more than 65% of the total genetic variance in the shoo t-differentiation rate. The allele of cultivar Kanto Nakate Gold desig nated Shd1(K) has a significant positive effect on the shoot-different iation rate, whereas Shd1(A) of cultivar Azumamugi does not promote sh oot differentiation. To identify gene products and characterize the fu nction of Shd1, a set of near-isogenic lines is essential. In this stu dy we produced BC5F1 plants by repeated backcrossing of 'Azumamugi' to F-1 plants ('Azumamugi' X 'Kanto Nakate Gold'). The BC5F1 plants were examined for their RFLP genotype and for the shoot-differentiation ab ility of immature embryo-derived callus. The results indicated that th e Shd1 locus was located in a chromosomal region between MWG2081 and M WG503 that flanks the MWG801, cMWG699, nu (ear type), and MWG865 loci. Shd1(K) from 'Kanto Nakate Gold' functions effectively in the genetic background of 'Azumamugi', an indication that backcross breeding is p ossible for production of near-isogenic lines that would be very suita ble for tissue culture.