CYTOGENETIC STUDIES IN ETHIOPIAN LANDRACES OF TETRAPLOID WHEAT (TRITICUM-TURGIDUM L) .2. SPONTANEOUS CHROMOSOME TRANSLOCATIONS AND FERTILITY

Meiosis was studied in seven tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace morphotypes of Ethiopian origin and one introdu ced durum variety, 'Boohai'. The objectives were to detect the presenc e of chromosome structural rearrangements by using the variety 'Senato re Cappelli' (SC) as a reference and to investigate if the previously reported low fertility (seed set) of the landraces has a chromosomal b asis. All the parents exhibited a normal bivalent pairing at metaphase I (MI) except one (CD-7) that showed a relatively high proportion of pollen mother cells (PMC) with univalents (0.40/PMC). 'Boohai' and two of the landraces from Ambo district were structurally similar to SC. The remaining five landraces each differed by one translocation from S C. These, in turn, differed from each other by one or two translocatio ns while two of the landraces carried the same translocation. However, in some of the landrace x landrace hybrids there was a tendency of re stricting the formation of more than one quadrivalent per PMC. Four di fferent translocations involving four to six chromosomes are present i n the material studied. Lack of pairing, as measured by univalent freq uency, varied for the different F-1 hybrids. Generally, however, it wa s lower in the F-1 hybrids between the landraces than in hybrids betwe en the landraces and SC. In almost all cases, division stages followin g MI proceeded as normal. Inversions were absent or too small to be de tected. Meiotic irregularities have little to do with the low fertilit y of most of the parental landraces. In the F-1 hybrids, on the other hand, high univalent frequency and multivalent associations impaired s eed set depending upon the cross combination. The results indicate tha t chromosome structural polymorphism for translocations may be common in Ethiopian tetraploid wheat landraces that might have played a role in maintaining their diversity by producing new linkage relationships. From breeding perspective, the bulk selection method and/or backcross ing to high fertility genotypes seem to be appropriate when these land races are employed in hybridisation programmes.