Cylindrocladium black rot (CBR) of peanuts (Arachis hypogaea L.), caused by Calonectria crotalariae (Loos) Bell & Sobers (Cylindrocladium crotalariae (Loos) Bell & Sobers), is potentially one of the most serious peanut diseases in Virginia. Over 60 peanut lines at multiple locations and 140 peanut lines at a single location were screened in the field for resistance to CBR from 1973–1977 in Virginia and North Carolina. Susceptibility to CBR was determined by number of dead plants per plot in 1973 and by percent dead plants per plot in 1974–1977. In addition, in 1974, 1975 and 1977, visual estimates of CBR damage to roots and pods were made. Florigiant, Spancross, VGP 1 and/or NC 3033 were used as checks to determine relative susceptiability.

Results generally indicate that spanish-type peanuts are the most resistant to CBR, valencia-type peanuts the least resistant and Virginia-type peanuts intermediate. Florigiant was consistently one of the most susceptible genotypes, while NC 3033, Spancross and VGP 1 were among the most resistant. Four valencia-type peanuts, 22 virginia-type peanuts, 28 spanish-type peanuts, one segregating line, and one wild species (A. monticola), with resistance equal to or better than Spancross, NC 3033 and/or VGP 1 were identified. Pod and root damage scores generally corresponded with percent diseased plants. However, differences were observed, indicating separate genetic mechanisms may control pod and root resistance to CBR. The significances of variability among sister lines and locations are discussed.