Scientists with Tunisian and Swedish universities recently wrote “Salinity–Chloride Interaction Effects on Novel Citrus Combinations Under Various Field Conditions,” which was published in Horticulturae. The authors are Hend Askri, Sywar Haffani, Hager Snoussi, Rim Zitouna-Chebbi, Tarek Fezzani and Asma Najar — all with Université de Carthage in Tunisia — and Ronny Berndtsson with Lund University in Sweden. A brief summary of the article follows.
Citrus production is increasingly constrained worldwide by rising soil salinity, particularly in arid and semi-arid regions. In Tunisia, the expansion of saline soils represents a major abiotic stress limiting orchard productivity.
The identification of salt-tolerant rootstocks has become a priority, especially as alternatives to sour orange, which is highly susceptible to citrus tristeza virus. In recent years, several outbreaks of the disease have been reported in the Cap Bon citrus-growing region, posing a threat to citrus production in Tunisia.
WHAT WAS EVALUATED
This study evaluated the salt tolerance of the following commercial cultivars:
- New Hall (NH) orange
- Washington Navel (WN) orange (mid-season maturity)
- Marisol (MAR) clementine (early maturity)
- Hernandina (HER) clementine (late maturity)
The cultivars were grafted onto Citrus volkameriana (CV, Citrus aurantium × Citrus limon) and three Poncirus trifoliata hybrids (CC, C35 and CTR) under irrigation water of varying salinity. Data were collected between 2020 and 2021 in five young citrus orchards located in the main citrus-producing region of Tunisia. Key physiological measurements were conducted during the high-evaporation period.
RESULTS AND CONCLUSIONS
Salt stress affected multiple physiological processes, notably ion homeostasis, sodium ion/potassium ion selectivity, stomatal traits, photosynthesis and growth.
Based on growth parameters, leaf chlorosis symptoms and plant mortality, citrus combinations grafted onto sour orange and CV rootstocks exhibited higher salt tolerance compared to those grafted onto C35, CC and CTR. Within this latter group, C35 showed the highest tolerance, while CTR was the most sensitive rootstock.
The highest leaf chloride ion concentration was recorded in the sensitive HER/CC combination. Increased salinity was associated with a 0.86% reduction in canopy growth.
Plant tolerance to salinity depends on soil salinization levels and the ability of both rootstocks and scions to regulate the uptake and accumulation of sodium and chloride in leaves. Irrigation with moderate saline water inevitably increases soil salinity. However, rainfall events, coupled with adequate water supply and the implementation of agricultural practices that enhance salt leaching, can mitigate salinity effects and restore soil solution salinity to levels compatible with plant growth.
Rootstock tolerance was strongly linked to the ability to restrict chloride ion accumulation in leaf tissues.
Under higher salinity conditions, CV showed superior performance and represents a suitable alternative to sour orange.
At moderate salinity levels, CV emerged as a promising candidate to replace sour orange. Orange cultivars were more adapted than clementine cultivars.
Under slight salinity conditions, C35 also represents a suitable alternative to sour orange.
Read the full article here.
Source: MDPI
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