ANEUPLOIDY AND CHROMOSOME MOSAICS IN HEXAPLOID WHEAT (TRITICUM-AESTIVUM (L) THELL) CULTIVARS

Chromosome number instability was studied in eight Brazilian wheat cul tivars. The overall frequency of aneuploid plants was 3.0 percent with no significant variation among cultivars. Seven cultivars presented p lants with chromosome mosaics in pollen mother cells (PMCs). The perce ntage of plants with mosaics differed among cultivars, varying from 1. 8 to 60.0, with an average value of 9.0 percent. Thirty nine different deviating chromosome numbers ranging from 11 to 58 were identified. T he deviating cells presented a high frequency of univalents as well as multivalents. A wide variation in the frequency of PMCs with deviatin g chromosome number was observed among plants of the same cultivar. Al though the plants investigated were grown in different agroecological regions and in a growth chamber, no indication of relationship between mosaicism and place of cultivation was found.