Re3.(Dityl. j:3 



at tills low dos£ge rate we produce a very good percentaf^n of Infected 

 plantjj, whether resistant or not. In the work with rj-e, however, such 

 a yirple method of inoculating does not work at all. It is neoesr.ary 

 to get the nematodes botvjeen the unfolding leaves. 



To inoculate the rye seedlings we use a hypodermic svringe. It is not 

 possible to use a plain water suspension of the neniatodes for .IdocuIuiti, 

 as the nematodes soon clump together and will not come through t)ie needle. 

 To avoid difficulties like that, we prepare the nematode suspension vrith 

 methylcellulose which keeps the nematodes fi-om settling out. Precautions 

 must be taken to eliminate air from the syringe. For routine vrork vxe use 

 a large syringe with an accurate metering device which permits giving any 

 uniform doses of the nematode suspension. The suspension can be prepared 

 to contain any desired number of nematodes per fraction of a milliliter 

 of the suspension used for each inoculation. 



The rye seedlings are inoculated by putting the needle into the plant 

 just about at the point where the roots come out of the seedling. About 

 500 nematodes are applied per plant. This is a very high number as com- 

 pared with the low numbers of stem nematodes which can cause damage in 

 the field, ,/e do not know what is t'le reason for it, but to be sure of 

 getting attack and sumptoms on about 98 percent of the plants, we have 

 to use that high number of nematodes. In the case of red clover, about 

 ]0 nematodes per plant is sufficient to produce sjmiptoms. 



■n the testing of rye seedlings the use of a low temperature is necessary 

 50 obtain recognizable symptoms, as well as for retarding growth of the 

 molds and bacteria. If rye seedlings are kept at higher temperatures, 

 they grow so fast no symptoms develope. Vfe, therefore, use a 5° C night 

 temperature and 18° C during the day, or a mean temperature below 10° C, 

 in order to get recognizable symptoms. 



The two methods described can be used for various monocotyledonous and 

 many dicotyledonous plants, too. We have used the methods for oats. In 

 this case, it is necessary to take the hulls off the seed to get easier 

 access to the coleoptile. Stem eelvrorm of oats is a problem in England 

 and Scotland. 



We rate the plants from these tests as follows: no symptoms, doubtful 

 (question of whether it is nematode attack or damage by inoculation), 

 light attack, and heavy attack. 



The next par't of the work is the evaluation of the resistance. In previous 

 talks we have already indicated what types of resistance there are in 

 plants against attack by stem nematodes. In the case of red clover, we 

 mostly use necrosis as an indication of resistance, although necrosis is 

 not the only symptom. In rye, however, we must use another method, as the 

 resistant rye plants do not show necrosis. 



In the resistant red clover, it is possible to see the necrosis which is 

 indication that the plants have been attacked and that nematodes are in 

 the tissues. However, no normal disease symptoms develope, and there is 



