| Nucleolus organizing chromosome in Einkorn wheats By K. YAMASHITA and M. KOYAMA Biol. Lab., Kyoto Univ. and Doshisha Univ., Kyoto The senior author has established a series of six types of reciprocal translocation (RT) in Einkorn wheats, Triticum aegilopoides and T. monococcum, involving all the seven chromosomes, namely a-b, b-c, c-d, d-e, e-f and f-g. Subsequently, the authors attempted to identify the nucleolus organizing chromosome by using the RT-heterozygotes. Anthers fixed with FARMER's fluid (absolute alcohol: acetic acid=3:1) were placed in 2% iron-alum solution for the first 24 hours and in 45% aceto-carmine for succeeding 24 hours, before the PMC 's were smeared on a slide-glass for cytological observation. Early diakinesis was found to be the proper stage for the analyses. The results are summarized in Table 1. The ring complex of four chromosomes in the d-e heterozygote is attached to the nucleolus which is free from the remaining five bivalents, while in each of the other types, a-b, b-c, e-f and f-g, the ring complex is free from the nucleolus, which appears attached to one of the remaining bivalents. From these observations, it has been concluded that the d-chromosome on which the genes for the mutant characters, old rose, early and lethal-1 are located is the nucleolus organizer. |