Course of fruit cracking in ‘Whansan’ pears

Abstract

This study was evaluated on time of occurrence and tissue characteristics in fruit cracking of mid-season cultivar Whansan Asian pears (Pyrus pyrifolia Nakai) with high amount of precipitation from 60 to 120 days after full bloom (DAFB). Fruit cracking was observed at different topographic ‘Whansan’ pear orchards as a pre-experiment. Pear trees at mountainous orchards received low amount of precipitation in June, between 50 and 80 DAFB, and had a high defoliation and low average of fruit weight and fruit cracking (2.5%) compared to those of pears grown at plain and middle-mountainous orchards. In a main experiment, cracked fruit contained lower concentrations of Ca and higher water soluble pectin in flesh or peel than those of values observed on the intact fruit. Fruit diameter rapidly increased at 40 DAFB and mostly 70–80 DAFB under repeated fluctuation of soil water potential between − 28 and − 67 kPa. Fruit were early completed their cell division and converted into cell enlargement phase between 30 and 50 DAFB, advancing formation of cork cells, while the number of large stone clusters significantly increased at 50 DAFB. Besides of less Ca uptake, both formation of cork and stone cells reduced cell flexibility in the flesh, causing initiation of internal micro-cracking under repetition of rapid change of soil water potential. Fruit cracking was visually progressed at 75 DAFB when fruit were mostly enlarged.