Preharvest spray application of methyl jasmonate promotes fruit colour and regulates quality in M7 Navel orange grown in a Mediterranean climate

Muneer Rehman,Zora Singh,Tahir Khurshid,Vijay Yadav Tokala,Rahil Malekipoor

doi:10.21475/ajcs.21.15.03.p2812

Abstract

Poor rind colour in cv. M7 Navel (Citrus sinensis L. Osbeck) at harvest time severely affects the profits of the growers in Western Australia. The effects of the preharvest spray application of different concentrations (0, 1.25, 2.5, 5.0 and 7.5 mM) of methyl jasmonate (MJ) on the rind colour development and fruit quality of M7 Navel were investigated at 6 or 3 weeks before anticipated harvest (WBAH) during 2015 and 2016. The preharvest spray application of MJ (5.0 or 7.5 mM) resulted in enhanced rind colour, reduced hue angle (ho) angle (55.7, 54.3) as well as increased citrus colour index (CCI) (11.0, 12.0) and total carotenoid levels (35.3, 58.3 mg kg-1) of flavedo, respectively in M7 Navel, during 2015 and 2016. During 2015, comparatively higher levels of total carotenoid (40.4 mg kg-1) were recorded when MJ was applied at 3 WBAH as a single spray. However, the time of MJ application did not influence hue angle (h°) and CCI. In 2015, all the preharvest MJ treatments except (1.25 mM) exhibited reduced fruit firmness. Furthermore, soluble solids concentration (SSC) in the fruit juice was reduced after MJ treatment. All the MJ treatments showed reduced levels of total sugars and organic acids in the juice, during 2015. In conclusion, MJ (5.0 or 7.5 mM) reduced h° but increased the total carotenoids levels and CCI in the flavedo of M7 Navel orange, when applied as a preharvest spray at 3 WBAH

Highlights

The fruit colour is one of the major factors which influence the consumers’ preference to purchase the citrus fruit
Jasmonates (JAS) are cyclopentanone forms, which are naturally present in plants as jasmonic acid (JA) and methyl jasmonate (MJ)
No other research has been reported on the effects of MJ application on the colour development and levels of carotenoids in the flavedo as well as fruit quality of M7 sweet orange

Summary

Introduction

The fruit colour is one of the major factors which influence the consumers’ preference to purchase the citrus fruit. The orange colour development in the citrus flavedo is due to the degradation of chlorophyll and accumulation of carotenoid pigments (Gross, 2012). Rehman et al (2018 a and b) have reported that application of paclobutrazol (PBZ), abscisic acid (S-ABA) or prohexadione-calcium (Pro-Ca) as preharvest spray 3 to 6 weeks before harvest has enhanced fruit rind colour in M7 sweet orange. No other research has been reported on the effects of MJ application on the colour development and levels of carotenoids in the flavedo as well as fruit quality of M7 sweet orange. The objective of the present study was to explicate the effects of preharvest application of MJ in enhancing deep orange colour development and total carotenoids accumulation in the flavedo while maintaining the fruit quality of M7 Navel orange, grown in the Mediterranean climate of Western Australia

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