36 Genetic Studies in Potatoes; Steri/iti/ 



From the cross Edgecote Purple x Edzell Blue 41 plants flowered. 

 Both quantity and quality of pollen were repeatedly tested; all were 

 fully fertile. The constant production of "abundant" pollen of high 

 quaUty was a characteristic of every plant. The results from separate 

 berries were consistent and the observations of 1920 were therefore fully 

 confirmed (see Table I). 



An F2 family from a fully fertile F^ plant from this cross was raised 

 in 1921 and 15 plants flowered. All had "abundant" pollen of high 

 (jiiality (sec Table I). Thus there is no evidence here of sterility arising 

 either in ^1 or -Fj- 



In Edzell Blue < Edgecote Purple grown on 19 plants flowered; both 

 quantity and quahty were again repeatedly observed with the following 

 results : 



Abundant ... 13 Small 8 



Medium ... 10 Very few grains 1 8 



In the qualitative test (Table 1) only four of the plants showed any con- 

 siderable proportion of good grains; the majority of jilants tested had 

 no good grains. Again the results from separate berries were consistent. 

 The difference in berry production which first attracted our attention 

 was as remarkable in 1921 as in the previous year. In Edgecote Purple 

 X Edzell Blue over 50 per cent, of the individuals bore self-set berries, 

 often in the greatest profusion ; of those grown under more favourable con- 

 ditions at Oruiskirk, actually 20 out of 28 (over 90 per cent.) bore berries. 

 In the family Edzell Blue x Edgecote Purple only si.x plants bore self- 

 set berries and here it is interesting to note the correlation between good 

 quality pollen and the setting of natural berries. All of the four plants 

 having good pollen had self-set berries, but only one of the sixteen plants 

 having no good pollen had self-set berries and even these were probably 

 due to insect-borne pollen. These figures give no idea of the contrast in 

 quantity of berries per plant which was even more remarkable (see 

 Plate). That there is no evidence of female sterility here is indicated by 

 the presence of natural berries on the six plants and on two others which 

 set seed when artificially crossed with fertile plants. 



It has therefore been shown that whilst Edgecote Purple x Edzell 

 Blue gives a wholly fertile Fj^ the reciprocal cross gives some sterile and 

 some fertile plants. 



