GENERATIVE TRANSMISSION OF THE EXTRA CHROMOSOME IN A RYE TERTIARY TRISOMIC AND ITS RELATION WITH INBREEDING DEPRESSION AND POLLEN QUALITY

Transmission of the extra (translocated) chromosome of tertiary trisomic T282W of rye (Secale cereale L.) upon selfing, through the male and/or the female, ranged from 0% to 36% in different inbred lines. Tetrasomics arising from simultaneous male and female transmission were not recovered and thus apparently not viable. Low seed weight, poor seed germination and a low transmission rate were correlated with low seed weight and reduced plant vigour. Inbreeding depression was concluded to affect transmission rate through its effect on the relative viability of trisomic seeds or seedlings. Male transmission in testcrosses with disomics averaged 7%, but varied between lines. Genetic factors were involved, but their expression remains uncertain. Pollen quality, as determined by a fluorescence reaction, was somewhat lower in trisomics than in disomics of the same genetic background and was not correlated with male transmission rate, which appears to be determined mainly by relative pollen-tube growth of euploid and aneuploid gametophytes. The results are discussed in relation to the use of tertiary trisomics in balanced chromosomal systems for hybrid breeding.