Potomac (PI 617594).-A fire blight-resistant mid-season pear with good fruit quality. Released in 1993 jointly by R.L. Bell and T. van der Zwet, U.S. Dept. of Agriculture, Appalachian Fruit Research Station, Kearneysville, W.Va., and The Ohio State University Moonglow x Beurre d'Anjou; cross made by H.J. Brooks in Beltsville, Maryland, in 1961; tested as U.S. 62537-048. Not patented. Fruit: medium size, 65 mm in diam.; ovate-pyriform; skin light green, glossy. Flesh moderately fine, buttery with some small grit under skin; flavor subacid and mild, similar to Anjou. Ripens 2 weeks after Bartlett; stores for 8 weeks or less. Tree: medium size; precocity and productivity similar to Anjou; fire blight resistance greater than Seckel. - Brooks and Olmo Register of Fruit and Nut Varieties 'Potomac' originated from a cross of 'Moonglow' x 'Beurre d' Anjou' made in l961 by H.J. Brooks. The seedlings of the progeny were grown at the Beltsville Agricultural Research Center, Beltsville, Md. 'Potomac' was selected in 1968 and was tested under the original seedling number US 62537-048. The original source of resistance to fire blight is the American cultivar Seckel. The parentage is entirely derived from P. communis germplasm. The fruit of' Potomac' is ovate-pyriform or obovate-obtuse pyriform in shape and is assigned an International Board for Plant Genetic Resources (IBPGR) shape rating of 13 (Thibault et al., 1983). Symmetry is regular, with occasional sligh bumpiness. The cavity is obtuse and occasionally lipped. The basin is open, narrow, medium in depth, with a convergent, persistent calyx. Fruit are moderate in size, averaging 68 mm in diameter, with a mean fruit weight of 167 g. The core is small, averaging 21 mm in diameter. The skin color is light green and the finish is glossy with inconspicuous lenticels. In some years, light calyx-end russet can develop. Fruit sometimes have a light red blush on the sun-exposed side. The stem is moderate in length and thickness, flexible, and slightly oblique. Harvest maturity is 14 days after 'Bartlett'. The flesh is creamy white, The flesh texture is moderately fine, buttery, and juicy. Grit cells are small and confined to a thin layer under the skin. The flavor is subacid, with mild aroma, and similar to 'Beurre d'Anjou' in character. The fruit may be ripened after harvest without postharvest chilling, but is as susceptible to storage scald as 'Beurre d'Anjou' if stored for more than 2 months in air at -1 C. It is, therefore, not suitable for long-term commer-cial storage without application of scald control measures. The tree is moderately vigorous and spread-ing. Flowers have white petals, and the anthers are pink to red. Full bloom at Kearneysville occurs with 'Beurre d'Anjou', -2 to 4 days before 'Bartlett'. 'Potomac' is self-incompatible and reciprocally cross-compatible with 'Bartlett' and 'Beurre d'Anjou'. Fruit are home on terminal flower buds of short lateral shoot and spurs in young trees, but production shifts almost exclusively to spurs as trees age. In a preliminary yield trial on 'Bartlett' seedling rootstock, 'Potomac' has been less precocious than 'Bartlett', and with lower yield until 6 years after planting (Table 2). Yield per tree rapidly surpassed 'Bartlett' after year 6, due in part to loss of bearing surface to fire blight in 'Bartlett' trees.