ALLELIC VARIATION IN THE DEHYDRIN GENE FAMILY OF HIMALAYA BARLEY (HORDEUM-VULGARE L.)

Variation in the dehydrin gene family of 'Himalaya' barley (Hordeum vu lgare L.) was studied using 3' fragments of dehydrin cDNA clones (DHN1 -4) as hybridisation probes. Each fragment specifically hybridised to the corresponding cDNA clone, but the 3' fragment of DHN1 also hybridi sed to the very closely related DHN7 genomic clone. The same fragments were hybridised to Southern blots of genomic DNA prepared from a pool of 100 plants and digested with different restriction enzymes. DHN1 a nd DHN2 probes hybridised to one or two fragments, but only single ban ds were seen with DHN3 and DHN4 probes. When DNA was prepared from ind ividual plants, the DHN1 and DHN2 probes each hybridised to single ban ds, representing one or other of the two bands in the pooled DNA sampl e. The 'Himalaya' population is therefore polymorphic, with two types of individual, designated P1 and P2. A cross between P1 and P2 types y ielded an F-1 with the same hybridisation profile as the pooled DNA. S egregation observed in the F-2 generation was consistent with a 1:2:1 ratio. Therefore. P1 and P2 individuals contain RFLP alleles detected by DHN1 and DHN2 probes, with the alleles occurring in specific associ ations consistent with linkage between Dhn1 and Dhn2 loci. Allelic var iation was also detected within the Dhn1 locus. Dehydrin RNA from P1 a nd P2, individuals was analysed by reverse transcription/polymerase ch ain reaction using primers specific for DHN1/DHN7 sequences. Sequencin g of the amplified and cloned products indicated that P1 individuals e xpressed only the DHN1 sequence, and P2 individuals only DHN7. These r esults indicate that the DHN1 ana DHN7 clones represent allelic altern atives at the Dhn1 locus (now designated Dhn1-1 and Dhn1-2, respective ly). A stock that contained only P2 individuals was generated from a s ingle seed, allowing hormonal regulation of Dhn1 gene expression to be studied without complications arising from polymorphism.