Blueberry cultivars with large fruit are particularly advantageous to the majority of New Zealand growers who
hand-harvest their crop. Fruit weight (FW) varied significantly with cultivar which accounted for the majority of the
total variation (87%). The individual FW of cultivars within the species varied greatly (Table 5). Within V. corymbosum
we found the cultivar with the highest and lowest individual FW. ‘Nui’ had the highest mean FW and no significant
variation was found between years (Table 5). The cultivar with the lowest average FW was ‘Blue Bayou’, and its
fruit size was consistently small across the years.
The anthocyanins are found only in the skin of blueberries, so it would be expected that small fruit, with relatively
more skin area, would tend towards high total ACY. This relationship holds for ‘Dolce Blue’ and ‘Centurion’, but
not for small ‘Blue Bayou’ fruit or large ‘Blue Moon’, ‘Nui’ or ‘Cosmopolitan’. This suggests that small fruit size
is one of a number of influences on total ACY and has been reported previously [4, 29].
Fruit diameter (FD) reflected greatly the FW for species and cultivar effects in our study (Tables 2B and 5). The
difference in FD among cultivars can be of practical importance to New Zealand growers because the fruit can be
packed and sold by diameter with a premium price for those fruit with diameter over 18 mm.
Blueberry ripening is accompanied by changes of the fruit firmness, decreases in acidity and increases in sugars
[34]; the fruit firmness varies with the stage of maturity [35]. Once initial ripeness has been achieved a further process
of overripe softening occurs which is accompanied by further decrease of acidity and increase in sugars. Consequently
we felt the need to develop a standard sampling procedure which allowed us to identify when 50% of the fruit on
the bush was ripe and before any sign of softening occurred. The regular fruit harvest at 50% of maturity has proven
to be a reliable method and of critical importance when comparing results of a number of different cultivars over a
number of different seasons.
Fruit of V. virgatum has been reported to be firmer than that of V. corymbosum [36–39]. According to our results the
difference between species was minor and the majority of the variation was found between cultivars (67% of the total
variation – Table 2B). Firmness varied greatly among cultivars (Table 5), the firmest fruit was harvested from ‘Centra
Blue’ (235 g/mm) and the softest were from ‘Reka’ (159 g/mm) and ‘Dolce Blue’ (160 g/mm) (Table 5). Previously
authors reported a similar average firmness for ‘Reka’ (154 g/mm) and defined a firmness of 150–160 g/mm as above
the average across their germplasm collection [37]. ‘Reka’ was released by PFR in 1989 and since then a lot of effort
was put into repeating cycles of selection for firmer fruit, resulting in cultivars such as ‘Centra Blue’, ‘Blue Bayou’
and ‘Velluto Blue’ that have improved firmness. There was no significant seasonal variation in firmness (Table 5).
V. corymbosum fruit had generally lower soluble solids content (SSC) and higher total acidity (TA) than V. virgatum
(Table 6). The differences in SSC and TA between cultivars were significant. SSC ranged between 9.1 to 14.9%