Cumulative yield varied greatly among cultivars and advanced selections (Table 2). A number of clones exceeded 30 kg/tree from 2004-2006 (1-23, 9-58, ‘Sunflower’, ‘Wilson’, ‘Shenandoah’, ‘Wabash’, ‘PA-Golden’, 10-35, and 1-68); however, some clones yielded less than 20 kg per tree over the same period (“Middletown’, ‘Wells’, ‘Mitchell’, and 3-21). CYE also varied greatly (0.38 to 0.91 kg/TCA cm²); no clones had a CYE over 1.0 and a number of clones had a CYE between 0.60 and 0.91 (e.g., 10-35, ‘PA-Golden’, ‘Shenandoah’, ‘Sunflower’, and 1-68). Only ‘Mitchell’ averaged fewer than two fruit per cluster, and two clones, 11-13 and ‘Wilson’, averaged more than three fruit per cluster.

‘PA-Golden’ and 2-10 had the earliest peak ripening dates (August 29 and August 30, respectively) and the fewest GDDs required for ripening (2499 and 2512, respectively). There was a trend for ‘Middletown’ (September 13 and 2823 GDD) and 9-47 (September 13 and 2842 GDD) to display the latest peak ripening dates and required the most GDDs to ripen. ‘Wells’ and ‘Rappahannock’ tended to have the most concentrated harvest period at 18 days and ‘PA-Golden’, 10-35, ‘Shenandoah’, and 11-13 the longest (25 and 30 days).

Yields varied year to year with most cultivars and advanced selections, likely as a result of a frost event in 2003 that destroyed the entire pawpaw crop (Table 3). Biennial BBI values over 0.6 indicate that a selection has a strong tendency towards biennial bearing (14). The BBI varied from 0.22 to 0.63 for the clones examined with 11-13, NC-1, and 7-90 having values greater than 0.60.

Correlations between TCA, number of fruit per tree and cumulative yield were examined. There was no relationship between TCA and the number of fruit per tree, but TCA was linearly related to cumulative yield (r = 0.60, P<0.001).

Princeton, KY trial. In the Princeton planting, 59% of trees survived in 2004 (Table 1). Most of the trees that died were lost during the first summer after planting. ‘Susquehanna’ (13%), ‘Taylor’ (38%), 5-5 (38%), and 9-58 (38%) had the lowest survival rates. This was likely due to the lack of irrigation at the Princeton planting. Vigor and yield of the trees at Princeton were evaluated at 7, 8, and 9 years after planting (in 2002, 2003, and 2004). TCA, number of fruit per tree, average fruit weight, cumulative yield, CYE, and number of fruit per cluster all varied significantly (P < 0.001) among cultivars and advanced selections over the three year period (Table 4). Since only one ‘Susquehanna’ tree survived, this selection was excluded from statistical analysis. Based on TCA taken in 2004, most clones displayed excellent vigor, ranging from 24 to 54.6 cm² in 2004, especially ‘PA-Golden’, ‘Wilson’, and 9-58, although some clones lacked vigor (e.g., ‘Overleese’ and 5-5). ‘PA-Golden’ and ‘Wilson’ had more than 80 fruit per tree and ‘Potomac’ and 5-5 had 18 fruit per tree or less (Table 4). Fruit weight also varied greatly, with some clones averaging under 100 g per fruit (‘Middletown’, ‘Wells’, ‘Wilson’, 9-47, and ‘Rappahannock’) and others over 170 g per fruit (1-68, 5-5, ‘Sunflower’, ‘Wabash’, and ‘Potomac’).

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likely due to the lack of irrigation at the Princeton planting. Vigor and yield of the trees at Princeton were evaluated at 7, 8, and 9 years after planting (in 2002, 2003, and 2004). TCA, number of fruit per tree, average fruit weight, cumulative yield, CYE, and number of fruit per cluster all varied significantly (P < 0.001) among cultivars and advanced selections over the three year period (Table 4). Since only one ‘Susquehanna’ tree survived, this selection was excluded from statistical analysis. Based on TCA taken in 2004, most clones displayed excellent vigor, ranging from 24 to 54.6 cm² in 2004, especially ‘PA-Golden’, ‘Wilson’, and 9-58, although some clones lacked vigor (e.g., ‘Overleese’ and 5-5). ‘PA-Golden’ and ‘Wilson’ had more than 80 fruit per tree and ‘Potomac’ and 5-5 had 18 fruit per tree or less (Table 4). Fruit weight also varied greatly, with some clones averaging under 100 g per fruit (‘Middletown’, ‘Wells’, ‘Wilson’, 9-47, and ‘Rappahannock’) and others over 170 g per fruit (1-68, 5-5, ‘Sunflower’, ‘Wabash’, and ‘Potomac’).

Cumulative yield varied greatly among cultivars and advanced selections, with only ‘Sunflower’ exceeding 30 kg/tree from 2002 to 2004 (Table 4). A number of clones yielded less than 20 kg per tree over the same period (5-5, ‘Overleese’, ‘Wells’, ‘Middletown’, 2-54, 9-47, ‘Mitchell’, ‘NC-1’, ‘Potomac’, and 3-21). CYE varied greatly among the cultivars and advanced selections (0.37 to 1.00 kg/TCA cm2) with ‘Sunflower’ having the highest cumulative yield efficiency of 1.0 kg/TCA cm2. Only three clones had fewer than two fruit per cluster, 5-5, ‘Mitchell’, and ‘PA-Golden’, and no clones averaged more than three fruit per cluster. The BBI was not significantly different among clones, and varied between 0.18 and 0.58, suggesting that there was little tendency towards biennial bearing (Table 5).

Correlations between TCA, number of fruit per tree, and cumulative yield were also examined for the Princeton trial. There were significant linear relationships between TCA and the number of fruit per tree (r = 0.55; P<0.001), and between TCA and cumulative yield (r = 0.60; P<0.05).