Salinity-Induced Physiological Responses of Three Putative Salt Tolerant Citrus Rootstocks

Lamiaa Mahmoud,Manjul Dutt,Jude Grosser,Christopher Vincent

doi:10.3390/horticulturae6040090

Lamiaa Mahmoud, Manjul Dutt + Show 2 more

Open Access

https://doi.org/10.3390/horticulturae6040090

Copy DOI

Abstract

Our study aimed to evaluate the physiological responses following salinity treatment of three putatively salt-tolerant Citrus rootstocks recently developed by the University of Florida’s Citrus breeding program. Four-month-old seedlings from each of the three rootstocks (HS1, HS17, and HC15) were irrigated with 0, 60, 80, and 100 mm NaCl solution. The seedlings were evaluated together with the salt-tolerant Cleopatra mandarin as a positive control, Volkamer lemon as a moderately salt-tolerant rootstock, and the salt-sensitive Carrizo rootstock as a negative control. Our results demonstrated that chlorophyll content, net CO2 assimilation rate (A), transpiration rate (E), and stomatal conductance (gsw) significantly decreased in response to salinity. Na+ and Cl− levels were higher in leaf tissues than in the roots. Relatively little damage to the cellular membrane was recorded in HC15 and Cleopatra rootstocks under the 100 mm NaCl treatment, along with high accumulation of total phenolic content (TPC), while HS17 had the highest proline levels. Our results indicate that HC15 and HS17 rootstocks exhibited salt tolerance capacity via different strategies under salt stress and could be suitable replacements to the commercially available, salt-tolerant Cleopatra rootstock.

Highlights

Citrus is a major horticultural crop worldwide and is severely affected by several biotic and abiotic stressors
The rootstocks HS1 and HS17 were developed from a cross between two promising trees derived from the Hirado Buntan Pink (HBP) pummelo crossed with the Shekwasha mandarin ([HBP × Shek] × [HBP × Shek])
HC15 showed similar foliar salt damage as Cleo, with visual scores of 4.75 with 100 mm (Table 1). This may have been because the Cleopatra mandarin was one of the HC15 parents

Summary

Introduction

Citrus is a major horticultural crop worldwide and is severely affected by several biotic and abiotic stressors. Climate change and rising sea levels threaten the agricultural sustainability of coastal regions. Citrus trees are classified as a salt-sensitive crop, with a critical level of electrical conductivity of 3 dS m−1 [2,3,4,5]. There are many different sources of salts that can affect the different saline soil areas around the world, such as sodium, chlorides, calcium, potassium and carbonates, and sulfates of magnesium [6]. Different agricultural practices and techniques are used to reduce production loss due to salinity stress. These strategies include using optimal irrigation and nutrition systems, using conventional breeding to generate new tolerant genotypes, and conducting genetic transformation to develop new genotypes that possess salt tolerance-specific traits [8,9]. Grafting onto the proper rootstock is an important factor in citrus production systems

Objectives

Methods

Results

Conclusion