PRODUCTION AND IDENTIFICATION OF TRISOMIC TYPES INBETA VULGARIS

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Abstract
Three primary trisomic types were obtained with a frequency of 35.48% in the progeny of a triploid X diploid cross of an inbred line of sugar beets. Trisomic type 1 was cytologically identified as the trisomic for the satellited chromosome. Pollen fertility in the trisomics ranged from 4.81 to 84.49%, with type 1 exhibiting the lowest level. Pollen grain diameter ranged from 17.80 + 0.31 to 23.07 + 0.41 u. The mean transmission frequency of the extra chromosome was 22.07% (17.33 - 30.88%). No transmission of the extra chromosome through the pollen was detected, nor were there any unrelated trisomics detected in the progeny of the trisomics. In the MI of pollen mother cells (PMC) of these trisomics, 2 configurations (8II + 1III and 9II + 1I) occurred in 94.68% of the cases. The most common form of the trivalent was a chain (73.8%). Partial synapsis was observed, there being 0.269, 0.288 and 0.597 univalents and 0.778, 0.795 and 0.724 trivalents per cell for types 1, 2 and 3 respectively, and 6.56 trivalents for the triploid. The high rate (34.0%) of elimination of the extra chromosome in type 3 was attributed to the high frequency of univalents in this type.