Cultivars occasionally appear more resistant in the field
than indicated by seedling tests, but generally, good
correla tions are observed between greenhouse and field
Race 2 of Colletotrichum trifolii was discovered in a
limited area in 1978 but is not considered serious.
Saranac AR is resistant to both races, Arc is resistant
to race 1 and susceptible to race 2, and Saranac is
susceptible to both. Saranac AR is approximately 45%
resistant to race 2.
CULTURE OPTIONS AND RANGE OF CONDITIONS
Stock cultures should be maintained because cultures can
lose virulence after several transfers.
Using mixtures of isolates will minimize error due to
differences in virulence among isolates.
Succulent stems of mature plants can be tested for
suscepti bility by needle inoculation (5). Individual
seedlings can be evaluated by cotyledon assay (1). A very
young seedling test also gives good results very quickly
if only percent resistance is required (3).
1. Cucuzza, J.D., and J. Kao. 1986. In vitro assay of
excised cotyledons of alfalfa (Medicago sativa) to screen
for resistance to Colletotrichum trifolii. Plant
Disease 70:111- 115.
2. Elgin, J.H., Jr., and S.A. Ostazeski. 1982. Evaluation
of selected alfalfa cultivars and related Medicago
species for resistance to race 1 and race 2 anthracnose.
Crop Sci. 22:39-42.
3. Morrison, R.H. 1977. A seedling test for evaluating
alfalfa for resistance to anthracnose. Pl. Dis. Reporter.
4. O'Neill, N.R., Elgin, J.H., Jr. and C.J. Baker. 1989.
Characterization of induced resistance to anthracnose in
alfalfa by races, isolates, and species of Colletotrichum.
5. Ostazeski, S.A., and Elgin, J.H., Jr. 1982. Use of
hypodermic inoculations of alfalfa for identifying host
reactions and races of Colletotrichum trifolii.
Crop Sci. 22:545-546
6. Ostazeski, S.A., and Elgin, J.H., Jr. 1984. Standard
tests to characterize pest resistance in alfalfa
cultivars. U.S. Agric. Res. Serv. Misc. Publ. 1434. 38
7. Smith, D. 1984. Maintenance of fungi. Pp.87-88. In
Maintenance of microorganisms, a manual of laboratory
methods. Ed. by Kirsop, B.E. and J.J.S. Snell. Academic Press.