POTATO BREEDING AND SELECHOIfr. 

 RECIPROCAL CROSSES. 



15 



In the reciprocal crosses presented in Table II, some additional 

 light is shed upon the prolificacy of certain seed parents. 



Table II. — Comparative behavior of reciprocal crosses of 1909 grown in 1910. 



Average 



Parentage Of cross. ^^-^ ^«-- -ageof --9^ "o'-ed- 



Imgs per 

 seed ball. 



Keeper X Norcross 



Norcross X Keeper 



Keeper X Round Pinkeye. 

 Round Pinkeye X Keeper 



Keeper X Venezuela 



Venezuela X Keeper 



Keeper X Keeper 



Number 



Number 



Percent- 

 age of 



Number 



of 



of seed 



of tuber- 



flowers 



balls de- 



bearing 



crossed. 



veloped. 





seedlings. 



5 



2 



40.0 



13 



51 



12 



23.5 



480 



14 



9 



64.3 



227 



37 



22 



59.5 



553 



9 



1 



11.1 



10 



12 



8 



66.7 



457 



7 



2 



28.6 



30 



6.5 

 40 

 25.2 

 25.1 

 10 

 57.1 

 15 



The reciprocal cross between Norcross and Keeper shows that when 

 Keeper was fertilized with pollen from Norcross, 2 seed balls were 

 secured from 5 flowers fertilized, and from these 2 seed balls 13 tuber- 

 bearing plants were produced. When Norcross was crossed with 

 Keeper, 12 seed balls were secured from 51 flowers crossed, and from 

 these 12 seed balls 480 tuber-bearing plants were obtained, or an 

 average of 40 plants per seed ball, as against 6.5 from the reciprocal 

 cross. From these data we may either assume that Keeper is not as 

 prolific a seed parent as Norcross or else that Norcross does not pro- 

 duce sufficient viable pollen. On the basis of the first assumption, 

 we may compare the behavior of both seed parents to other pollen. 

 Keeper when polHnated with Irish Seedling gave an average of 17.3 

 plants per seed ball (Table I), and when crossed with Round Pinkeye 

 it produced 25.2 plants per berry. Norcross when crossed with 

 Round Pinkeye gave an average of 30 plants per berry (Table I). 

 This evidence would seem to indicate that the Norcross was a more 

 prolific seed parent than Keeper; but it also points to the conclusion 

 that Keeper is the best pollen parent, at least in so far as pertains to 

 the production of viable pollen. 



The reciprocal crosses between Round Pinkeye and Keeper are of 

 considerable interest, owing to their apparent similarity. Keeper X 

 Round Pinkeye gave 9 seed balls out of 14 blossoms fertilized and 

 these averaged 25.2 plants per berry. Round Pinkeye when crossed 

 with Keeper produced 22 seed balls from 37 flowers pollinated, and 

 from these an average of 25.1 plants were produced. The rather low 

 number of ])Iant.s forming tubers from these reciprocal cross(;s would 

 indicate that n<ither parent seemed to possess potency. Apparently, 

 the mating of these two varieties was not a congenial one in either case. 



In the reciprocal cross between Venezuela and Keeper, wiUi 

 Venezuela as the seed parent, 12 pollinated flowers developed 8 seed 

 balls, from which an average of 57.1 plants was secured. Nino 

 floweiB of Keeper crossed with Venezuela resulted in but 1 seed ball, 



