Self incompatibility and temperature affect pollen tube growth in 'Sundrop' apricot (Prunus armeniaca L.)

Comparison of fruit set after controlled self and cross pollination in two New Zealand regions confirmed that 'Sundrop' apricot was effectively self sterile (fruit set <2%). Fluorescence microscopy showed that tubes from 'Sundrop' pollen were self-incompatible and generally aborted in the upper part of the style. The strength of the inhibition reaction varied so that the tubes occasionally reached the ovary but none penetrated ovules. Measurement of tube growth in 'Sundrop' styles at 5 degrees, 10 degrees, 15 degrees, 20 degrees and 25 degrees C showed that temperature affected the rate with which self incompatible pollen tubes were inhibited. Self tube penetration was strongest at 10 degrees and 15 degrees C and weaker at higher temperatures. However, fertilization by 'Sundrop' pollen did not occur at any temperature and so the need to cross pollinate this cultivar is not an interaction with low temperatures during bloom.