Influence of Rootstock Genotype and Ploidy Level on Common Clementine (Citrus clementina Hort. ex Tan) Tolerance to Nutrient Deficiency

Abstract

Nutrient deficiency, in particular when this involves a major macronutrient (N, P, and K), is a limiting factor on the performance of plants in their natural habitat and agricultural environment. In the citrus industry, one of the eco-friendliest techniques for improving tolerance to biotic and abiotic stress is based on the grafting of a rootstock and a scion of economic interest. Scion tolerance may be improved by a tetraploid rootstock. The purpose of this study was to highlight if tolerance of a common clementine scion (C) (Citrus clementina Hort. ex Tan) to nutrient deficiency could be improved by several diploid (2×) and their tetraploid (4×) counterparts citrus genotypes commonly used as rootstocks: Trifoliate orange × Cleopatra mandarin (C/PMC2x and C/PMC4x), Carrizo citrange (C/CC2x and C/CC4x), Citrumelo 4475 (C/CM2x and C/CM4x). The allotetraploid FlhorAG1 (C/FL4x) was also included in the experimental design. The impact of nutrient deficiency on these seven scion/rootstock combinations was evaluated at root and leaf levels by investigating anatomical parameters, photosynthetic properties and oxidative and antioxidant metabolism. Nutrient deficiency affects foliar tissues, physiological parameters and oxidative metabolism in leaves and roots in different ways depending on the rootstock genotype and ploidy level. The best known nutrient deficiency-tolerant common clementine scions were grafted with the doubled diploid Citrumelo 4475 (C/CM4x) and the allotetraploid FlhorAG1 (C/FL4x). These combinations were found to have less foliar damage, fewer changes of photosynthetic processes [leaf net photosynthetic rate (Pnet), stomatal conductance (gs), transpiration (E), maximum quantum efficiency of PSII (Fv/Fm), electron transport rate (ETR), ETR/Pnet], and effective quantum yield of PSII [Y(II)], less malondialdehyde accumulation in leaves and better functional enzymatic and non-enzymatic antioxidant systems. Common clementine scions grafted on other 4× rootstocks did not show better tolerance than those grafted on their 2× counterparts. Chromosome doubling of rootstocks did not systematically improve the tolerance of the common clementine scion to nutrient deficiency.

Contribution to the optimization of citrus (Citrus clementina Hort. Ex Tanaka) fruit fertilization using mobile lysimetry in orchards of the Souss-Massa region, Morocco

“…6D). These fluctuations were predominantly concentrated in the fruit set and growth stages, signifying the potential impact of nitrogen on the growth and development of clementines (Oustric et al, 2021). The observed variations in nitrogen content suggest that it may be a critical factor in the growth of some clementine varieties (Hammami et al, 2010; Barlas and Kadyampakeni, 2022).…”

Meiotic Behaviors of Allotetraploid Citrus Drive the Interspecific Recombination Landscape, the Genetic Structures, and Traits Inheritance in Tetrazyg Progenies Aiming to Select New Rootstocks

“…Most of the citrus germplasm and worldwide-used citrus rootstocks are diploid. However, during the last decade, several studies have shown that tetraploid citrus rootstock, compared to their diploid counterpart, showed increased tolerance to different pedoclimatic constraints such as salt stress [20][21][22][23], low temperature [24], nutrient deficiency [25,26], and water deficit [27][28][29]. Sivager et al (2022) showed that tetraploid Swingle citrumelo rootstocks improve HLB tolerance in diploid and triploid grafted scions.…”