112 PROTECTION OF PLANTS — 1922-23 



Greenhouse inoculations. 



Van Hall (10) states that artificial infection can be easily produced by ino- 

 culating the pathogen into the base of the stem by means of needle pricks through 

 the epidermis. He does not state on what medium the cultures were grown or 

 how old they were when used for inoculation. He states, however, that after 

 cultures have been carried on artificial media for a few months they lose their 

 virulence and are unable to cause infection of the Iris tissues. 



On December 5th., after the plants in the greenhouse had become well 

 established, they were inoculated with two-day old cultures grown on Iris leaf 

 infusion agar. The plants were inoculated by needle pricks at the base of the 

 shoots and the placed under glass bell jars to keep them moist and at a fairly 

 even temperature. After four days plants 15 and 19b showed slight traces 

 of rotting around the points of inoculation. Two weeks after inoculation 2, 3a, 

 4CI, 4, 15, 15C, 151, and 26bC showed nothing but a very slight rotting at the 

 inoculated points. The infection from 19b had increased till one leaf had entire- 

 ly rotted and the rhizome at the leaf base had just commenced to decay. Once 

 the disease had reached this stage nothing further developed. An isolation 

 was taken from the diseased leaf, labelled 19bG and used later for inoculation 

 purposes. 



Since practically no results had been obtained from the first series of inocu- 

 lations, the writer decided to work only with the organisms that had caused the 

 rotting of the sliced Iris rhizomes in the petri plates, as these would be the most 

 likely disease producers. 



On January 13th., seven plants were inoculated with one-day old been 

 broth cultures of organisms laC, 4, 7a, 10, 15, 19bG, and 26b, and placed in the 

 greenhouse under bell jars.. After two weeks no visible sign of infection had 

 appeared, so the series was discarded and negative results recorded. 



As no definite posite results had been obtained with either beef broth or 

 agar cultures, it was thought advisable to use some other medium to see if be - 

 ter results could be obtained. 



On February 8th., plants were inoculated with cultures la, laC, IbC, Ca3, 

 4, 4C, 4C1, 7al, 15, 5C, 19b, 26b, and 26bC, which had been prepared in the 

 following way;^Original agar slope cultures were taken and transfers made 

 from them to beef broth tubes. These tubes were incubated at 27°C for twenty 

 four hours and then 1 c.c. of this bacterial suspension in the beef broth was trans- 

 ferred to 10 c.c. of a sterile 2% dextrose solution. The final culture was incu- 

 bated for twenty -four hours and then used for the inoculation. The plants 

 were inoculated by pouring the cultures at the base of the shoots and at the 

 same time pricking the tissues with a sharp sterile needle. The plants thus ino. 



