Volume VIII APRIL, VJVJ No. 2 



ON FORMS OF THE HOP (IIUMULUS LUPULUS L.) 

 RKSISTANT TO MU.DKW {SPIIAEROTIIECA 

 HUMUrj (DC.) BURR.); H'. 



By E. S. salmon, 

 Mycologist, S.E. Agricultural College, Wye, Kent, EngUiud. 



In a previous article* attention wjus called to the fact that certain 

 forms of the Hop (Huutulus Lupulus L.) are resist<ant t-o the attjicks <>{' 

 the }\oi^-i\\\V\q\s {Spluierotheca Huinuli (DC.) Burr.). These '* innnune " 

 plants fall into two groups, ((/) certjiin individual seedlings of the wild 

 hop raised from .seed obUiined from Vittorio, Italy ; (6) the female 

 variety with yellow leaves known as the "golden hop." The present 

 article describes further exj)eriments carried out during 1917 with these 

 and other plants. 



Group (a). Of this gi*oup 2 seedlings were discovered in 1914, and 

 7 seedlings in 1916. As already mentioned, the two 1914 seedlings were 

 planted out during the winter 1914 — 15 in the Experimental Hop- 

 garden at Wye College; the next season one plant (Ref. No. OR^H) 

 proved to be female, the other (Ref. No. 0RS9) male. These two 

 plants were sufficiently established by the winter of 1916 to enable 

 "cuts" to be taken from them; 5 were potted up from OR^H and 2 

 from Oi^ 39. These potted plants were the ones used in the following 

 experiments (Expers. 1 to 5) : 



Exper. 1. A ix)tted "cut" of 0RS9 and a similar potted "cut" of 

 another seedling (Ref. No. Z 54) of the wild hop from Italy were treated 

 as follows: a fully-expanded leaf at the 3ixl node from the base of the shoot 

 (which had 7pjiirsof leaves) was sprayed with water,using an "atomiser," 

 until numerous small drops had collected on the leafs upper surface ; 

 conidia were then placed on these drops at three similar places on each leaf 

 The conidia were taken from various " powdery " patches of the mildew 

 occurring on different susceptible hop-plants stiinding in the greenhouse 



^ See Journ. Agric. Sci. Vol. viii. p. 455 (1917). 

 Joum. of Gen. viii 6 



