Abstract
For the pentaploid hybridization, Avena barbata, A. abyssinica and Tt-1 (a barbata like derivative from triploid hybrids, A. barbata×A. strigosa) were used as tetraploid parents and certain varieties of A. sativa and A. nuda as hexaploid ones. Young seedlings of the pentaploid hybrids were treated with 0.05% colchicine solution and their chromosome number was successfully doubled in some of them, producing decaploid amphiploids or chimera plants consisting of pentaploids and decaploids.
Decaploid plants or panicles (C1) showed high seed fertility although the pentaploid ones set usually no seeds. Decaploids amphiploids, however, failed to maintain their high seed fertility. In C8-C12 generations, however, some amphiploid lines recovered fertility equal to the original parents but other lines still showed low or wide variation in fertility.
Cytological investigations were attempted with certain lines in C9-C13. It is especially noted that certain lines have 2n=42, 54, 56, or 58, instead of the expected chromosome number, 70(2n) and those lines show regular meiotic behavior of chromosomes. In the other lines the chromosome number varied over a limited range (2-4) and still others over a wide range (4-8).
Some characters such as plant height, tillering, and date of maturity were studied and compared with one of the parents, A. sativa var. Banner. Most of these synthetic oats are new forms possessing some characters from both tetraploid and hexaploid parents, and are much improved in certain agronomic characters.
