Characterizing Nematode Resistance 



Background 



Summary of Resistance Information by Nematode Species 



Not much is known about the damage caused by many 

 nematodes associated with alfalfa according to Graham 

 and others (29). This lack of information is due in part to the 

 lack of research on alfalfa nematodes and the lack of dis- 

 tinctive aboveground symptoms caused by nematode injury. 

 Presently, the stem nematode and two species of root-knot 

 nematode are the primary parasitic nematode species 

 known on alfalfa. Resistant cultivars or germplasm have 

 been developed to all three species. 



Distribution and severity maps for the three primary para- 

 sitic nematode species on alfalfa in the United States ap- 

 pear on page 19. Scientists who can serve as resource peo- 

 ple for problems concerned with developing nematode- 

 resistant cultivars are identified. Check cultivars and 

 standardized-screening procedures have been established 

 for the three types of nematode resistance. 2 Availability and 

 type of screening and evaluation procedures (L = 

 laboratory, F = field tests) are indicated also. 



Tabulation summarizing available resistance information by nematode species 



Stem Nematode 



Ditylenchus dipsaci 

 (Kuhn) Filipjev 



Northern Root-Knot 

 Nematode 



Meloidogyne hapla 

 Chitwood 



Southern Root-Knot 

 Nematode 



Meloidogyne incognita 

 Chitwood and 

 Meloidogyne javanica 

 (Treub) Chitwood 



Distribution and severity map: Figure 27 



Scientists and locations with expertise: 3 6, 11, 12, 25, 28, and 35 



Check cultivars: 



Dormant and semidormant types: 

 Nondormant types: 



Resistant 



Lahontan 

 Caliverde 65 



Screening procedures: L 

 Evaluation procedures: L (p. 30) 



Distribution and severity map: Figure 28 



Scientists and locations with expertise: 6, 11, 12, 25, and 34 



Check cultivars: 



Dormant and semidormant types: 

 Nondormant types: 



Resistant 



Nev. Syn. XX 

 Nev. Syn. YY 



Screening procedures: L 

 Evaluation procedures: L (p. 30) 



Distribution and severity map: Figure 28 



Scientists and locations with expertise: 6, 11, 12, 25, and 34 



Check cultivars: 



Dormant and semidormant types: 

 Nondormant types: 



Resistant 



Moapa 69 



Screening procedures: L 

 Evaluation procedures: L (p. 30) 



Susceptible 



Ranger 

 Moapa 69 



Susceptible 



Lahontan 

 Mesa-Sirsa 



Susceptible 



Lahontan 

 Caliverde 65 



2 See appendix, p. 37, for approximate levels of pest resistance 

 expected for the check cultivars. 

 3 See listing of resource scientists on p. 12. 



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