Gf. Mclaren et al., SOME FACTORS INFLUENCING FRUIT-SET IN SUNDROP APRICOT, New Zealand journal of crop and horticultural science, 24(1), 1996, pp. 55-63
Two apricot (Prunus armeniaca L.) cultivars, 'Sundrop' and 'Moorpark'
were found to be cross-compatible with pollen of 32 genetically divers
e cultivars. The flowers of 'Valleygold', 'CluthaGold', and 'Moorpark'
remained receptive to pollination for up to 8 days after emasculation
at the balloon stage. Floral receptivity declined in 'Moorpark', 'Sun
drop', and 'CluthaGold' (but not 'Valleygold') over the 8 days. 'Sundr
op' had the lowest receptivity and 'Moorpark' the highest. Percentage
set of 'Sundrop' flowers varied between properties and years in Centra
l Otago, New Zealand, with significantly lower sets being recorded in
1992 and 1993 than in 1991. In these three seasons, a 2 ha block of 'S
undrop', with no pollenisers within it, showed a decrease in fruit set
as the distance from the nearest polleniser on the edge of the block
increased; fruit set was unacceptably low beyond the first four or fiv
e rows. Bee density did not decline across the block in the same manne
r. The fruit were smaller on trees adjacent to the polleniser but were
generally of similar storage quality to those from 10 rows away. The
addition of extra beehives in 1992 and 1993 increased the bee numbers
per tree throughout the block, but not fruit set. In comparison, anoth
er 1.7 ha block of 'Sundrop' on the same property with just 3% of the
trees planted at random in the cultivar 'Trevatt', produced a better s
et ii each of the 3 years. Over 8 years, correlations were found betwe
en percentage fruit set and the meal temperature between 5 and 90% blo
om; the number of days when the maximum temperature exceeded 18 degree
s C between 5 and 90% bloom; and the meal temperature over the 3 weeks
from 90% bloom. The roles of in-hive pollen exchange and self-pollina
tion in 'Sundrop' are discussed. Planting of pollenisers within the bl
ock remains the most reliable method of increasing fruit set in large
blocks of 'Sundrop'.