Differences in potato leafhopper (Empoasca fubae Harris) injury symptoms were noted in 22 cultivars or lines of dry beans (Phaseolus vulgaris L.) in a 1991 field trial at North Platte, Neb. Seed yield, biomass, and plant injury symptoms were recorded. The same 22 dry bean cultivars or lines were planted in a split-plot design, with main plots protected (sprayed with insecticide) vs. unprotected (not sprayed) and cultivars or lines as subplots in 1992 and 1993. Significant differences were observed between cultivars/lines for leafhopper injury and yield in all 3 years. `Tacaragua' (black-seeded) and pinto `Sierra' were highly resistant to leafhoppers, with no visual leafhopper injury symptoms in all 3 years. Significant negative correlation coefficients between leafhopper injury symptoms and yield were recorded in the protected (4.50) and unprotected (-0.33) plots in 1993 but only in the unprotected (-0.46) plots in 1992. A cultivar x spray interaction response to leafhoppers occurred in 1992 but not in 1993. The degree of leafhopper injury symptoms varied between years.
Excised roots were used for evaluating methods and in identifying differences in rates of P absorption by 59 lines of Phaseolus vulgaris. Large variations in P absorption rates between lines were noted. Although the P absorption rate was negatively correlated with root dry weight, it was possible to isolate lines with similar excised root dry weights which displayed large differences in P absorption rates. Rates of P absorption by the terminal 3.5 cm root segment satisfactorily expressed P absorption by other portions of the root system. The rate of P absorption by excised roots was influenced by the amount of P in the solution in which plants were cultured prior to root excision. As the pretreatment P level increased from 3 to 31 mg/plant, P absorption by excised roots decreased and as the P level increased from 31 to 62 mg/plant, P absorption by excised roots leveled off. Rates of P absorption by excised roots also varied with the age of the plant. However, relative values between efficient and inefficient lines remained constant at each plant age. Variance for P absorption by excised roots due to environment was high. Narrow sense heritability estimates derived from parent offspring regression in families of efficient × inefficient lines were estimated to be about 40%. Data on P uptake by excised roots did not predict P uptake and translocation in intact plants. A reliable standardized technique for intact plant ion absorption studies is necessary to make accurate comparisons between plants.