To detect at least one desirable mutant with a minimum total number of X
2-plants or of combined X
1- and X
2-plants, two methods were established as suitable in relation to tillers of X
1-plants.
They are: a type of the “one-plant-two-grain method” (method D
2) and of the “one-plant-three-grain method” (method E
3) in which one grain is taken from each of two or three heads of an X
1-plant respectively.
These methods have been evaluated by considering the probability that one or more plants with the mutant allele in homozygous recessive form will appear in the total X
2-plants in relation to the number of heads per X
1-plant and to the independent degrees of mutation among the heads of the X
1-plant.
The “one-plant-one-grain method” (method C) proposed by Yoshida (1962) is the best when the number of heads per X
1-plant (t) is equal to or smaller than three and method C or D
2 is the best when t_??_4.
No single method is known to cover all of the advantages. However, methods D
2 and E
3 will be better than the “one-plant-two-grain method” and the “one-plant-three-grain method” proposed in the first report of this series when t_??_2 and t_??_3 respectively. Generally speaking, it does not seem advantageous to use the “one-ear-one-grain method”. especially the “one-ear-two-grain method” and the “one-ear-three-grain method”.
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