CHARACTERIZATION OF SUN-II OAT MONOSOMICS THROUGH C-BANDING AND IDENTIFICATION OF 8 NEW SUN-II MONOSOMICS

Monosomics are a powerful tool for genetic mapping in allopolyploid pl ant species such as oat (Avena sativa L., 2n = 6x = 42). A C-banded ka ryotype of the oat cultivar Sun II was compared with previously descri bed oat karyotypes and was used to identify the missing chromosome in each line of Sun II aneuploids. These included new aneuploids, isolate d among derivatives of oat haploids obtained from Sun II oat x maize c rosses, along with the original Sun II aneuploid set which had been ob tained by cytological screening of a Sun II population for spontaneous aneuploids. Eight new Sun II monosomics were identified among the der ivatives of haploids from the oat x maize crosses, to give a total of 18 unique Sun II monosomic/nullisomic lines. All seven C-genome chromo somes are represented by Sun II monosomics. Chromosomes 13, 14 and 17 are not represented by Sun II aneuploids but are found in the Kanota m onosomic series. Therefore, monosomics of some form are now available for all 21 oat chromosomes, A reciprocal translocation involving chrom osomes 3C and 14, found in a portion of the original set of Sun II mon osomic lines, was also described. No new translocations were detected in the Sun II x maize crosses.