Abstract
In the F3 generation of triploid hybrids from Avena barbata (n, 14) × strigosa (n=7), the author has found a diploid strain which always segregates green and albino seedlings in a 1 : 1 ratio and gives no homozygous greens. This strain is called “green-inconstant”. This green-inconstant is especially characterized by very early maturity as compared with normal diploids or A. strigosa. The genetic analysis has shown that the green-inconstant may have a genic formula al++/+Reλ.where al is a gene for albino, Re for early ripening and λ for zygotic mortality.
In the cross, green-inconstant × normal (A. strigosa) two types of F1 hybrids have been obtained, one being green heterozygotes (al++/+++) and the other early heterozygotes (+++/+Reλ) In the following generations, green heterozygotes give green and albino seedlings in either a 6 : 1 or 5 : 1 ratio. By selfing, on the other hand, early heterozygotes always segregate early and normal plants in a 1 : 1 ratio. Owing to the coupling of Re and λ, all of these early segregates are heterozygous, but there is rarely found homozygous earliness which is probably free from the lethal factor. In F2., generation of early heterozygotes (1 : 1 type) a new strain has been found, in which the earliness is obviously controlled by the normal monogenic inheritance (3 : 1). And it is further confirmed that about one third of early segregates bred true for earliness. From these results, it can be seen that all cases, except the last one, exhibit remarkable deviation from expectation on the Mendelian basis.
By crossing experiments, a new fact has been discovered that pollens with different genic formula accomplish fertilization in different frequencies as given in Table 11. Assuming such certations of pollens the genetic data mentioned above are clearly understood.
The origin of green-inconstants and the different frequency of the occurrence of homozygous earliness in different genotypes are discussed on the hypothesis of the structural change of chromosomes.
In conclusion the writer wishes to express his hearty thanks to Prof. H. Kihara, by whose direction this work was made.
