A Comparison of Methods of Evaluating Resistance to Cylindrocladium crotalariae in Peanut Field Tests¹

Three methods presently used to evaluate disease resistance in peanut (Arachis hypogaea L.) to Cylindrocladium black rot (CBR) were compared to identify the most efficient method to screen peanut lines in field tests. Forty randomly selected F₂ families in the F₅ generation from a cross of the CBR-resistant source NC 3033 with NC 6 and the two parents were evaluated for percent dead and diseased plants, root rot index and microsclerotia/g of root. Significant differences were detected between the parents (p = 0.05) and among segregates (familes) (p = 0.01) for percent dead and diseased plants only. Error components exceeded the mean square values for differences among segregates for the root rot index and microsclerotia/g of root resulting in no significant differences among entries for these traits and low to no correlations among traits. Percent dead and diseased plants was concluded to be the best of the three methods for screening peanut lines in the field for CBR resistance.