Evaluation of Three New Citrus Rootstocks under Boron Toxicity Conditions

Áurea Hervalejo,Francisco J Arenas-Arenas,Frederick G Gmitter,Juan M Arjona-López,Jude W Grosser,Rocío Calero-Velázquez,Lidia Aparicio-Durán

doi:10.3390/agronomy11122490

Abstract

Boron (B) toxicity is a common limiting factor both in arid and semiarid regions, such as the Mediterranean Basin. Citrus trees are sensitive to B-toxicity, which generates a negative impact in citrus orchards. In this work, two promising citrus rootstocks (UFR-6 and 2247 x 6070-02-2) have been assessed against B-toxicity and compared with Carrizo citrange, a common commercial citrus rootstock in Mediterranean Basin. Three B concentration treatments (Control, 1 and 2.5 mM H3BO3) were established, irrigating the plants three times per week for 21 days under greenhouse conditions. During the assay, above-ground symptoms, and chlorophyll index (SPAD) were recorded. At the end of the experiment, stomatal conductance, relative water content, and B concentration in leaves and roots were determined. The increasing B concentration in plants generates visual damage in leaves for all citrus rootstocks assayed. Carrizo citrange displayed the greatest visual symptoms, decreased its chlorophyll index (SPAD), and stomatal conductance throughout the B-treatment. However, UFR-6 and 2247 x 6070-02-2 displayed less symptoms than Carrizo citrange and only reduced its parameters under the 2.5 mM H3BO3 treatment. These results can aid citrus grower rootstock planting decisions with under B-toxicity conditions.

Highlights

The Mediterranean Basin is the second largest citrus producing region in the world, with an overall production more than 26 million tons [1]
Chlorosis symptoms were found in all citrus rootstocks under 1 mM H3BO3, but leaves defoliation were not detected in any citrus at this treatment
Several leaves defoliation were found in Carrizo citrange at the highest boron concentration (2.5 mM H3BO3); whereas UFR-6 and 2247 x 6070-02-2 showed chlorosis symptoms at this highest concentration, and very slight defoliation symptoms were found for these both citrus rootstocks (Figure 1)

Summary

Introduction

The Mediterranean Basin is the second largest citrus producing region in the world, with an overall production more than 26 million tons [1]. Boron (B) is an essential element for plants; this micronutrient is necessary for regular growth and development [5,6]. B-toxicity is more frequent in arid and semiarid regions, such as the Mediterranean Basin, in which citrus are a major crop [8,9]. B-toxicity has an effect on plant growth [14], uptake of other micro- and macro- elements [15], photosynthesis [16,17], and chlorophyll and carotenoid levels [16,18]. Dorta-Santos, M.; Tejedor, M.; Jiménez, C.; Hernández-Moreno, J.M.; Díaz, F.J. Using marginal quality water for an energy crop in arid regions: Effect of salinity and boron distribution patterns.

Methods

Results

Discussion

Conclusion