Hayes and Garber - Cucurbit Breeding

230 BREEDING CROP PLANTS
For the 16-year period from 1890 to 1905, inclusive, the
varieties were kept in a high state of productivity "due, no
doubt, to careful selection and good cultivation each year." In
1906, however, there was a marked falling off in yield due to the
unfavorable season. In the early part of the season there was
sufficient rain but at about the time of the last cultivation, hot
dry weather set in and continued throughout the season. During
July there was also a severe attack by aphis. The vines, therefore,
presented a stunted appearance and dried up early in the fall,
the yield of tubers being very low. In 1907 and 1908 the seasons
were also very unfavorable. The best tubers were again planted
in 1909 and although the tubers used for planting presented a
very favorable appearance, the yields were very low. A comparison
was made in 1909 of tubers grown continuously at the
Central Experiment Farm and newly imported tubers grown under
more favorable conditions. The yielding ability of the imported
tubers exceeded that of the Central Farm tubers by as high as
500 per cent, in some cases.
The plant breeder is naturally interested in the subject of
whether these are instances of bud variations due to unfavorable
environment. If so, they should be permanent changes. If,
on the other hand, they are non-heritable variations, this does
not affect the practical importance of tuber selection as a means
of obtaining high yields. Macoun (1918) has furnished evidence
which helps to clarify our ideas on this question. From time to
time tubers were sent from Ottawa to the branch stations, on the
prairies, where potatoes usually grow very vigorously. In 1916
the following question was asked:
"You will, no doubt, remember that potatoes sent you from Ottawa
are usually weak growers when you receive them. I would be glad if
you would inform me for how many seasons that weak growth continues,
or do they make a strong growth the next year, the same as
the ones you have been growing for several years?"
Answers made by the superintendents of these prairie farms
showed that the first year's crop from tubers sent from the Central
Farm was very small. From one to three years elapsed
before varieties introduced from the Central Experimental
Farm yielded as well on the prairies as those varieties which had
been continually grown on the prairies.
Much of the so-called "running out" or degeneracy in pota-