Abstract
Blackberry fruits are appreciated as a source of nutrients and compounds related to benefit human health. However, they are highly perishable and very susceptible to decay factors. Current methods to improve and maintain blackberry quality are limited in use because of the fruit's fragile physical properties. Regarding these properties, it has been reported that the activities of certain enzymes are linked to senescence and fruit softening processes. This study was aimed to assess the effect of salicylic acid (SA) and chitosan (COS) as preharvest treatments on the physiology related to improving fruit conservation and preserving the marketability index of blackberry fruit. The preharvest treatments were foliar sprayed on blackberry plants at different concentrations. The activities of enzymes superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), and polygalacturonase (PG) were measured. Total soluble solids (TSS), titratable acidity (TA), TSS/TA ratio, and marketability index (MI) were analyzed after 144 h of storage. The application of 3 mM of SA and 0.25% of COS treatments preserved the MI of blackberries by reducing leakage, red drupelet reversion (RDR), and mycelium presence in the fruit. SA application increased SOD, CAT, and PAL activities. Our results also showed that SA and COS preharvest treatments modified the activity of the cell wall degrading enzyme PG, which might play a role in improving the shelf life and resistance to decay factors of blackberry fruit without any significant effects on physicochemical properties like TSS, TA, and the TSS/TA ratio.
Highlights
Blackberries (Rubus sp.) are aggregate fruits formed by multiple arranged drupelets (Hummer, 2017)
salicylic acid (SA) of 3 mM and COS of 0.25% treatments were selected for further discussion since 0.25% of COS presented no statistical difference with the higher COS concentration treatments and SA of 3 mM maintained the marketability index (MI) above the minimum 85% required for the study
The MI of the control group dropped to 68.63% after 144 h, SA of 3 mM and COS of 0.25% significantly preserved the MI showing 92.67 and 93.15%, respectively
Summary
Blackberries (Rubus sp.) are aggregate fruits formed by multiple arranged drupelets (Hummer, 2017). Blackberries have become highly popular worldwide, mainly due to their distinctive taste, nutritional properties, and high content of compounds that provide beneficial effects to human health (Złotek et al, 2014) Their thin skin cause leakage and accelerated decay and make them susceptible to mechanical damage, which can reduce their shelf life (Junqueira-Gonçalves et al, 2016). SA and COS have exhibited the potential to prevent fruit decay by activating plant defensive responses (Lucini et al, 2018; Shi et al, 2018; El-Mogy et al, 2019; He et al, 2019; Hidangmayum et al, 2019) These responses can include the phenylpropanoid metabolism activation, which is related to defense activities such as cell wall reinforcement and antimicrobial effects (Taiz and Zeiger, 2006; Li et al, 2012). There are no previous reports regarding the effect of preharvest treatments of blackberry plants and fruits with SA and COS, to evaluate the effects on its shelf life, enzymatic activity, and physiochemical properties, which was the purpose of the present study
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