10 Donald Reddtck 



total amount of radiant energy was greater for the period or even if it 

 were distributed differently ; and there are places in the State where the 

 growing season for beans is one hundred and twenty days or more. Like- 

 wise those sorts that mature at Ithaca in eighty-five to ninety days might 

 mature differently elsewhere. Furthermore, varieties that do not yield 

 well on the heavy clay soil at Ithaca might produce very well on a dif- 

 ferent type of soil. Burkholder found this to be true in the case of 

 Perry Marrow (oral communication). 



Biological problems 



Several of the problems just referred to as practical are essentially 

 biological in nature but have to do with the inherent qualities of the 

 plants themselves. There are in addition some external biological con- 

 ditions that may bear on the problem. 



Bacterial blight. If the hybrids should prove particularly susceptible 

 to bacterial blight, their usefulness in New York culture would be de- 

 cidedly limited. It is to be noted that Wells' Red Kidney is especially 

 susceptible to this disease (or group of diseases) and that the advantage 

 of anthracnose resistance is practically offset by the disadvantages of 

 blight susceptibility. 



Bacterial blight has been found in certain of the hybrids and a record 

 made of its occurrence and severity. Xo systematic inoculation of the 

 plots Avas undertaken, but the use of Wells' Red Kidney in alternate 

 rows has given abundant opportunity for natural spread of the disease 

 and it is likely that the absence or the infrequent occurrence of the dis- 

 ease in some of the hybrids suggests that they possess a considerable re- 

 sistance to the disease — certainly as much resistance as Robust, which 

 has been classed by Burkholder (1924) as among the more resistant of a 

 Large number of varieties which he has tested. 



Root-rot. The root-rot disease, caused by Fusarium martii f. sp. pha- 

 seoli, is a factor to be considered in producing field beans in practically 

 all parts of New York. Burkholder (1919) has shown that, in infested 

 soil, annual losses from this disease range from 5 to 50 per cent of the 

 crop. He has recorded also (1919 : 10.'50) the existence of a resistant 

 variety of very undesirable type. Although second-generation hybrids 

 with this type were in existence as early as 1919, it is significant that no 

 root-rot-resistant plant has yet been offered to New York farmers. Burk- 

 holder remarks that a very complex segregation has been found to exist 

 in the hybrids made, and this doubtless has complicated the problem 

 especially as the resistant parent is undesirable in a number of charac- 

 ters. McRostie (1921) suggests tentatively a two-factor hypothesis to 

 account for the inheritance of susceptibility to root-rot. Thus far noth- 

 ing further on this question seems to have been offered. 



