Four parental lines with resistance to early leafspot caused by Cercospora arachidicola Hori and four parental lines with resistance to late leafspot caused by Cercosporidium personatum (Berk. & Curt.) Deighton and the F 1 hybrid progeny from crosses between the two groups of parents were evaluated for resistance to both leafspot diseases in the greenhouse using a detached leaf technique. The subsequent F 2 plants of all crosses were evaluated in the field for resistance to early leafspot in order to estimate combining ability effects for components of partial resistance and to identify parents useful in developing lines resistant to both diseases. General combining ability, attributed largely to additive genetic variance, accounted for the largest portion of the variability among the F 1 and F 2 generations for most parameters of resistance to both early and late leafspots. Reciprocal effects and heterosis toward the susceptible parents were also significant for parameters of resistance to the two pathogens. GP-NC 343 and FESR 5-P2-B1 were the best parents for incorporating genes for resistance to both early and late leafspots. Progenies of NC 17090 had a high level of resistance to late leafspot in detached leaf tests and progeny of PI 350680 had reduced defoliation from early leafspot in the field. Broad-sense heritabilities ranged from 0.2 to 0.4 for parameters of resistance to early leafspot estimated from the pooled variances of F 2 plants of all crosses planted in the field. Parameters of resistance evaluated in the greenhouse for F 1 hybrids were compared to parameters evaluated in the field for the F 2 population by rank correlation of entry means. Latent period and sporulation of the fungus on detached leaves of F 1 generation plants correlated (r = −0.46 and 0.54, respectively) with defoliation of F 2 plants in the field.

The potential for the development of large-seeded, highyielding virginia-type peanuts ( Arachis hypogaea L.) with resistance to Cylindrocladium black rot (CBR) and three insects was examined. Forty randomly selected F 2 families in F 5 generation from a cross of the CBR-resistant germplasm NC 3033 and the cultivar NC 6 were evaluated for yield, fruit traits, and resistance to CBR, thrips ( Frankliniella fusca Hinds), corn earworm ( Heliothis zea Bodie) and potato leafhopper ( Empoasca fabae Harris). Significant differences were found among families for all traits measured except corn earworm damage and number of seed. Transgressive segregation was observed for six of the nine traits measured. Heritabilities were high for pod length, pod weight, and seed weight; moderate for pod yield, CBR resistance, thrips and potato leafhopper damage and low for corn earworm damage. Large negative genotypic correlations were found between CBR resistance (percent dead and diseased plants) and traits indicative of insect resistance. Genotypic correlations between percent dead and diseased plants and yield and fruit traits were large and positive. Based on the predicted response in the other unselected traits when selection is for one trait, selection for increased CBR resistance should result in lines with decreased insect resistance, pod size and weight, seed weight, and yield. These data suggest that unfavorable linkages or pleiotropy among these traits may exist that would prevent selection of desirable genotypes from this cross.

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 F 2 families in the F 5 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.

Selection of large-fruited, high-yielding Cylindrocladium black rot — (CBR) resistant lines from two sets of crosses, each set consisting of crosses in F 2 generation between a virginia and two CBR-resistant lines, was evaluated to determine the potential for selecting cultivars with these traits. Heritabilities, phenotypic and genotypic correlations and estimates of additive and nonadditive genetic effects were determined for yield and fruit traits at two locations and CBR resistance at one location. Crosses with NC 2 as a parent had higher levels of CBR resistance than those with Florigiant as the common virginia-type parent. Heritability estimates for the necrosis index (CBR resistance) were high while estimates for yield and fruit traits were variable over crosses and locations. The necrosis index was significantly and negatively correlated with all fruit and yield traits for three of the four crosses indicating it should be possible to select high-yielding, largefruited lines with low levels of disease from three crosses. Only significant additive genetic effects were found for CBR resistance. Significant additive and nonadditive genetic effects were found for the yield and fruit traits. Estimates of additive and non-additive genetic effects indicate that early generation selection for CBR resistance should be effective, whereas selection for yield and fruit traits would be more effective in later generations.