232 MUTATION AND PLANT BREEDING 



these last-mentioned 28 may be considered as small mutations, and 

 generally they are not earlier than 2 days (on the average of several 

 observations). The resnlts reported in Table 7 are not representative 

 with regard to the relative frequencies of small and large earliness 

 mutations because they are derived from various experiments and the 

 selection methods have been inconsistent. There is no doubt that 

 the frequency of small earliness mutants is considerably higher than 

 indicated. These mutants have not been considered enough in the 

 earlier experiments and perhaps not in some later ones too. 



The distribution of these earliness mutants on yield classes is 

 indicated in Table 8. The various yield data are derived from differ- 

 ent experimental arrangements. Most results are based on drilled 



Table 8. — Distribution of the Earliness Mutants of Barley on Yield Classes.* 



•Mutants from Table 7. Kernel yield of Haisa II is taken as 100. Tentative results. 



trials, some on plots sown by hand, and some on hills. The lack of 

 yield data in Table 7 indicates poor-looking mutants which have not 

 been tested for yield. These mutants yield definitely less than 80 per 

 cent of the control. Particularly, the results of those mutants having 

 more than 95 per cent yield of Haisa II were based mainly on drilled 

 trials, which had often a plot size of about 10 m 2 and three replica- 

 tions. The yield of two of the three mutants recorded in the class 

 > 1 10 per cent of Table 8 is based on one year only (1960), and the 

 plot size was smaller. 



The results shown in Table 8 seem to indicate that 12 out of the 

 56 earliness mutants possess a greater yielding potential than the 

 mother line. These tentative investigations will be continued to 

 obtain more reliable results. However, even if the proportion of 

 high-yielding earliness mutants goes down to 1 / w , earliness seems to 

 be an indicator character of practical interest. Yet it has to be con- 

 sidered that these results are valid only for one variety (Haisa II) 

 and for one location (Koln-Vogelsang). It may be expected that with 

 other varieties and growing conditions, the proportion of high- 

 yielding earliness mutants will be lower or higher. 



