III.2 Screening for primary trisomics in the progenies of telotrisomics.
T. Tsuchiya, Agronomy Department, Colorado State University, Fort Collins, Colorado 80521, U.S.A.
It has been difficult to maintain the primary trisomic for chromosome 1 (Bush) in cultivated varieties of barley. In the study of telotrisomics, it was found that primary trisomics could be obtained at a low frequency in the progeny of telotrisomics. In the progeny of 14 + 1 telo 1S, it is easy to detect the primary trisomic Bush because telotrisomics for Telo 1S does not show any diagnostic morphological characteristics while the primary trisomic for chromosome 1 has extremely conspicuous features even at very early seedling stages. The procedure is as follows:
1. Grow many 14 + 1 telo 1S plants.
2. Germinate many seeds from 14 + 1 telo 1S.
3. Isolate seedlings with narrow leaves and collect root tips.
4. Count the chromosome number to make sure that 2n = 15.
Primary trisomics are also obtained in the telotrisomic for 1L and 2L. However, it is almost impossible to distinguish morphologically the primary trisomic for complete chromosome l (Bush) and 2 (Slender) from the telotrisomics for 1L and 2L, respectively. Therefore, the chromosome numbers of all plants showing typical diagnostic characteristics for each trisomic type should be counted.