SOMATIC CHROMOSOME-NUMBERS OF COLCHICINE- TREATED SHINANO WALNUT (JUGLANS-REGIA L) AND ITS F1 SEEDLINGS

Shoots of Shinano walnut cv. 'Mituru' (main cultivar in Nagano prefect ure) which is said to be a hybrid between Teuchi walnut (Juglans regia var. orientis Kitamura) and the Persian walnut (J. regia L.), was tre ated in 1970 with 0.4% colchicine solution containing 1 ppm NAA. Scion s from the colchicine-treated 'Mituru' trees, known as 'Col-Mituru', w ere grafted on several rootstocks and grown to maturity. 'Col-Mituru' trees were then self- and open-pollinated. Shoot tips from 'Mituru', ' Col-Mituru', and F-1 seedlings were reacted with Feulgen's reagent and silver iodide (Ag-I) to stain the chromosomes; their chromosome were then counted. 1. In 'Mituru' with 32 chromosomes, 62 nuclear plates we re observed in the shoot tips, an amount which is twice the normal dip loid number in J. regia and 'Mituru'. 2. Chromosome number of 'Col-Mit uru', and its grafted propagagules, 84-1, 84-2, and 84-3, is 64 in 90 out of 95 nuclear plates counted. This is four times the basic haploid number; thus, the trees are tetraploids. 3. The chromosome numbers in 7 F-1 seedlings obtained from open pollinated 'Mituru' is 32 in 192 o ut of 193 cells counted; hence, they are diploids. 4. Twenty seedlings obtained from 'Col-Mituru' (4x) x 'Mituru' (2x) and 'Housho' (2x) hav e 48 chromosomes. Likewise, the 14 open-pollinated seedlings of 'Col-M ituru' had 48 chromosomes in 408 out of 410 nuclear plates. They are t riploids. 5. In two seedlings obtained in 1983 from self-pollination o f 'Col-Mituru', one had 64 and the other 48 chromosomes; they are tetr aploid and triploid, respectively. The pollen for the triploid probabl y came from a diploid source. Of 10 self-pollinated seedlings derived in 1984. all had 64 chromosomes; they are, therefore, believed to be t etraploids.