The Role of the Plant Hormones IAA and Ethylene on Split-Pit Formation of Peach Fruit

Few studies were mentioned to illustrate the role of plant hormones-IAA and ethylene in split-pit formation. Here, a random sample of 100 developing fruits from 7-year-old early maturing nectarines (Prunus persica L. Batsch cv. Ruiguang 5) was used as test material. The shape index and growth index of the sampled nectarines was comparatively analyzed to show the relation between fruit un-uniform growth and their split-pit formation. The split-pit fruits were found to have a higher degree of un-uniform growth than that of the normal fruits, which were demonstrated by higher ratio of transverse diameter/lateral diameter and bigger difference between the flesh thickness of the two sides in the middle part of the fruits (along the line of the transverse diameter) about twelve weeks after full anthesis (p < 0.05). Subsequently, a higher degree of unbalanced distribution of IAA and especially ethylene was observed in the split-pit fruits compared to the normal fruits, which may correlate with un-balanced expansion of the nectarines flesh. Higher concentration of IAA and especially ethylene was found in the middle part of the split-pit fruits than those in the sutures, while those in the normal fruits were not significant. Furthermore, the caliosity was specifically observed in the internal surface of the split-pit nectarines endo carp as early as four weeks after full anthesis, but not in the normal nectarines. The occurrence of caliosit in the endo carp may be an early signal of spilt-pit.