The Bacterial Diseases of the Bean 



77 



HOST RANGE 



In the past many bacterial plant pathogenes have been described as 

 occurring on certain hosts, as if this character definitely placed them. If 

 sufficient cultural characteristics accompany such a report, no misunder- 

 standings are likely to arise. If an insufficient description of the organism 

 is given, however, synonyms will undoubtedly occur. Not only may 

 a number of bacteria cause similar diseases in one species of plant, but 

 the pathogenes themselves may have the ability to infect other species 

 and genera of plants. This should be recognized, but just how far one 

 should go in determining a host range for an organism it is difficult to 

 state. The field is extremely large. When there is any doubt, however, 

 concerning two or more species on different hosts, a certain amount of 

 cross inoculation is necessary. With the bacterial pathogenes attacking 

 beans, this is especially true. Here we have several green-fluorescent 

 forms occurring on the common bean (Phaseolus vulgaris), and it is known 

 that a number of green-fluorescent bacteria are pathogenic to other legu- 

 minous species. It is very desirable to know the host range of each 

 organism. With the yellow species the confusion is not so great, but 

 among these Phyt. phaseoli var. sojense is separated from Phyt. phaseoli 

 mainly on its pathogenicity for a certain host. 



A host range for a pathogene is important also for other than taxonomic 

 reasons. For control measures it is very desirable to know what other 

 plants may harbor the organism. Susceptible plants may then be eradi- 

 cated, or their planting avoided. 



Present knowledge concerning the susceptibility or the immunity of 

 fourteen legumes to the six bean pathogenes under discussion here, is 

 summarized in table 3. The results from many hundreds of inoculations 



TABLE 3. Host Range (Legume) of Six Bacterial Pathogenes of the Bean 



(Phaseolus vulgaris)* 



Phytomonas 



medicaginis 



var. phaseo- 



licola 



Phyto- 

 monas 

 vignae 

 var. 

 legu- 

 minophila 



Phyto- 

 monas 

 viridi- 

 flava 



Phaseolus vulgaris 



P. lunatus 



P. coccineus 



P. angularis 



Vigna sinensis 



V. sesquipedalis 



Glycine max 



Lupinus polyvhyllus 



Dolichos lablab 



Pueraria hirsuta 



Vicia faba 



Pisum sativum var. arvense . 



Melilotus alba 



Medicano saliva 



+ 



+ 



+ (pod) 



+ (pod) 



+ 

 + 



(pod) 



+ 

 + 



* A plus sign denotes that infection has been obtained; a minus sign, that there is no infection; and a 

 zero sign, that no inoculation experiments have been conducted. A plus sign followed by the word " pod " 

 means that infection has been obtained on the pod only. 



