Cytogenetic Studies in Ethiopian Landraces of Tetraploid Wheat (Tviticum Turgidum L.). II. Spontaneous Chromosome Translocations and Fertility

Abstract

Belay, G. and Merker, A. 1997. Cytogenetic studies in Ethiopian landraces of tetraploid wheat (Triticum turgidurn L.). 11. Spontaneous chromosome translocations and fertility. -Hereditas 126: 35-43. Lund, Sweden.Meiosis was studied in seven tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace morphotypes of Ethiopian origin and one introduced durum variety, 'Boohai'. The objectives were to detect the presence of chromosome structural rearrangements by using the variety 'Senatore Cappelli' (SC) as a reference and to investigate if the previously reported low fertility (seed set) of the landraces has a chromosomal basis. 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 SC. These, in turn, differed from each other by one or two translocations while two of the landraces carried the same translocation. However, in some of the landrace x landrace hybrids there was a tendency of restricting the formation of more than one quadrivalent per PMC. Four different translocations involving four to six chromosomes are present in the material studied. Lack of pairing, as measured by univalent frequency, vaned for the different F, hybrids. Generally, however, it was lower in the F, hybrids between the landraces than in hybrids between the landraces and SC. In almost all cases, division stages following MI proceeded as normal. Inversions were absent or too small to be detected. Meiotic irregularities have little to do with the low fertility of most of the parental landraces. In the F, hybrids, on the other hand, high univalent frequency and multivalent associations impaired seed set depending upon the cross combination. The results indicate that 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 backcrossing to high fertility genotypes seem to be appropriate when these landraces are employed in hybridisation programmes.

Cytogenetics, Geographical Distribution, Pollen Stainability and Fecundity of Santolina impressa (Asteraceae: Anthemideae)

“…The presence of univalents presumably indicates the failure of pairing at pachytene (Sisodia 1971;Jackson 1991;Spies et al 1992;Belay and Merker 1997), or may result from the precocious separation of chromosomes at an early or late stage of meiotic division (Jos et al 1968b), or from competitive chromosome pairing (supporting the presence of trivalents in diakinesis), or be a consequence of inadequate homology for chromosome pairing. If these univalents do not attach to the spindle, they may persist as laggards or become excluded from the nucleus.…”

Genetic Behaviour of Induced Translocation Heterozygote in Poppy

“…Translocation has been reported in a number of plants like Oenothera (Cleland 1936), Tradescantia (Giles 1940), Melandrium (Chaudhari 1968), Lens (Sinha and Acharia 1974), Capsicum (Meshram et al 1981), wheat (Belay and Merker 1997), Nigella (Saha and Dutta 2000) etc. Translocations or segmental interchanges are chromosomal aberrations involving the exchange of parts between heterologous or non-homologous pairs of chromosomes.…”