γ-Aminobutyric acid delays fruit softening in postharvest kiwifruit by inhibiting starch and cell wall degradation

The effects of 10 mM γ-aminobutyric acid (GABA) treatment on fruit softening, starch degradation, cell wall disassembly in cold-stored ‘Hongyang’ kiwifruit after harvest were investigated. The results depicted that GABA treatment maintained firmness and delayed fruit softening during storage by retaining high starch content due to the inhibition of the transcription levels of related starch-degrading genes, such as AcGWD, AcPWD, and AcBAMs. In addition, compared with the control, higher level of chelated-soluble pectin, Na2CO3-soluble pectin, hemicellulose and cellulose content but lower water-soluble pectin content were observed in the treated kiwifruit as GABA suppressed cell wall breakdown by down-regulating the expression of AcPE, AcPG, AcBGALs, and AcXTHs. In summary, our results indicated that exogenous GABA contributes to maintaining fruit firmness, delaying softening in postharvest kiwifruit by inhibiting starch degradation and preserving cell wall metabolism.