Research Progress on Mechanisms of Pineapple Blackheart

Pineapple blackheart is one of the major diseases after harvesting. The damaged fruits usually have no obvious external characteristics and are hard to be distinguished from the normal ones. The initial symptoms of pineapple blackheart are translucent spots appearing near the fruit core. With the development of the internal browning, dark-brown pigmentation begins to appear in the pulp and gradually spreads to the whole fruit. In recent years, due to the abuse of gibberellins or other reasons, blackheart has been reported to appear in summer fruits of pineapples, causing huge economic losses to the whole pineapple industry. Scholars at home and abroad have studied the underlying mechanisms of pineapple and proposed various solutions. Therefore, summary of the current research progresses have positive influence on studying the mechanisms of pineapple blackheart, breeding blackheart resistant cultivars and improving the production efficiency of the pineapple industry. This paper summarized the pre-harvest and post-harvest factors affecting the occurrence of pineapple blackheart and the corresponding countermeasures, and proposed a possible model of pineapple blackheart based on the recent progresses of related hormone signaling pathways. The model can be divided into three stages, namely, initial stage, apoptosis execution stage and browning stage. Chilling stress is a major factor of internal browning, which induces ROS and causes membrane damage in the initial stage of pineapple blackheart. Gibberellins act in the downstream of chilling stress, which play an important role in the apoptosis execution stage. The browning reaction catalyzed by PPO in the browning stage might be only a secondary response. There is no direct correlation between the level of PPO and the incidence of pineapple blackheart.