6 Donald Reddick 



Segregation 



In the case of anthracnose a fairly sharp segregation was soon evident. 

 All affected plants were discarded without record. Unfortunately, cer- 

 tain plants which did not show more infection than was produced on 

 White Imperial by race alpha were saved for further test. Eventually 

 all such progenies were discarded. 



The segregation for mosaic was not so easily effected. The principal 

 difficulty in this connection lies in the fact that there is no positive 

 method of securing 100 per cent infection even on a susceptible variety 

 such as Navy Pea. Furthermore, the symptoms of mosaic do not come 

 out sharply in the greenhouse during the short cloudy days of winter, 

 such as usually prevail at Ithaca, or in the field in summer if the 

 weather is very warm and dry. On this account one lot of plants readied 

 the sixth generation before it was finally discarded as susceptible to 

 mosaic. Then, too, some of the plants, following White Imperial, did not 

 show clear-cut cases of mosaic, and it became necessary to make inocula- 

 tions from such plants on a susceptible variety. 



Field tests 

 As soon as the quantity of seed warranted it — and usually this was in 

 the fifth generation — the plants were grown in the field where they were 

 subjected to the usual vicissitudes. When the lots were small, suscepti- 

 ble varieties (Navy Pea and White Marrow) were grown in the same 

 row and inoculated; but later the susceptible varieties were mixed and 

 grown in alternate rows. The anthracnoses were introduced as soon as 

 the plants were well out of the ground, and in this way a very severe 

 field test was secured in practically every year. In the early stages it 

 was possible to inoculate every plant for mosaic, but later only a rela- 

 tively small number of plants could be inoculated. Unfortunately, mo- 

 saic has never been observed to spread naturally in the test plots. Many 

 susceptible varieties have been grown in adjacent rows every year, and 

 Navy Pea. which is extremely susceptible to mosaic, has been used each 

 year for a check and inoculated both for mosaic and for anthracnose. 

 Small lots of plants were grown in the greenhouse from winter to winter 

 and tested for mosaic. The progeny of such plants was marked for spe- 

 cial observation the following summer in order to locate any that did 

 not show clear cases of mosaic in the greenhouse. This is a very de- 

 sirable precaution to take, as it is an excellent check on winter tests, due 

 to seed transmission of the disease. 



Isolation of types 



Sorting for growth types, seed types, earliness and lateness, and so 

 forth, began in the third generation. The sorting was not done too vig- 



