Phomopsis longanae Chi-Induced Disease Development and Pericarp Browning of Harvested Longan Fruit in Association With Energy Metabolism.

Yihui Chen,Yifen Lin,Junzheng Sun,Hetong Lin,Hui Wang,Shen Zhang,Mengshi Lin,John Shi

doi:10.3389/fmicb.2018.01454

Abstract

Longan fruit is a popular subtropical fruit with a relatively short shelf life at room temperature mainly due to pericarp browning and fungal infection. This study aimed to investigate the infection of Phomopsis longanae Chi in longan fruit and its effects on the storability and shelf life of longan fruit. The relationship between the energy metabolism of harvested longan fruit and disease development and pericarp browning was elucidated. Results show that P. longanae-inoculation accelerated the deterioration of longan fruit and caused pericarp browning. It also led to the energy deficit in pericarp of longan fruit, which was reflected as lower contents of ATP and ADP, higher AMP content, and lower energy charge as compared to the control samples. Additionally, P. longanae-infection reduced the activities of H+-ATPase, Ca2+-ATPase, and Mg2+-ATPase in plasma, vacuolar, and mitochondrial membranes during the storage period. The results demonstrate that P. longanae-infection led to disease development and pericarp browning in harvested longan fruit, which were due to the infection-induced energy deficit and low ATPase activity that caused disorders of ion transport and distribution, and damaged the structure and function of vacuole, mitochondria, and eventually the whole cells of fruit tissues.

Highlights

Longan is a popular subtropical fruit with a short shelf life at room temperature mainly due to pericarp browning and fungal infection (Holcroft et al, 2005; Chen et al, 2014; Zhang et al, 2017, 2018)
Previous literature indicated that hydrogen peroxide treatment could promote longan pericarp browning via decreasing the levels of ATP content and energy charge, and reducing activities of H+-adenosine triphosphatase (ATPase), Ca2+-ATPase and Mg2+ATPase in mitochondria, and damaging mitochondrial structure (Lin Y.X. et al, 2016; Lin et al, 2017b)
The pericarp AMP content of inoculated longans was positively correlated with either fruit disease index (r = 0.952, P < 0.01) or pericarp browning index (r = 0.955, P < 0.01). These results provide convincing evidence that accelerated disease development and pericarp browning of inoculated longan fruit is closely associated with the infection-induced energy deficit

Summary

Introduction

Longan is a popular subtropical fruit with a short shelf life at room temperature mainly due to pericarp browning and fungal infection (Holcroft et al, 2005; Chen et al, 2014; Zhang et al, 2017, 2018). The regular function of the cell and these organelles depends on transmembrane transport of ions, in which active transport serves as an essential pathway with proton electrochemical potential gradient as a driving force (Morsomme and Boutry, 2000; Kasamo, 2003) This driving force of transporting certain ions relies on energy from corresponding adenosine triphosphatase (ATPase) catalyzing ATP hydrolysis (Falhof et al, 2016). Previous literature indicated that hydrogen peroxide treatment could promote longan pericarp browning via decreasing the levels of ATP content and energy charge, and reducing activities of H+-ATPase, Ca2+-ATPase and Mg2+ATPase in mitochondria, and damaging mitochondrial structure (Lin Y.X. et al, 2016; Lin et al, 2017b). The pathogenic infectioninduced tissue browning and the reduction of disease resistance on longan fruit might be related to the damage of biomembranes via influencing energy status and ATPase activity

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