Abstract
The triploidy has proved to be a powerful approach breeding programs, especially in Citrus since seedlessness is one of the main consumer expectations. Citrus plants face numerous abiotic stresses including water deficit, which negatively impact growth and crop yield. In this study, we evaluated the physiological and biochemical responses to water deficit and recovery capacity of new triploid hybrids, in comparison with diploid hybrids, their parents (“Fortune” mandarin and “Ellendale” tangor) and one clementine tree used as reference. The water deficit significantly decreased the relative water content (RWC) and leaf gas exchange (Pnet and gs) and it increased the levels of oxidative markers (H2O2 and MDA) and antioxidants. Compared to diploid varieties, triploid hybrids limited water loss by osmotic adjustment as reflected by higher RWC, intrinsic water use efficiency (iWUE Pnet/gs) iWUE and leaf proline levels. These had been associated with an effective thermal dissipation of excess energy (NPQ) and lower oxidative damage. Our results showed that triploidy in citrus enhances the recovery capacity after a water deficit in comparison with diploids due to better carboxylation efficiency, restored water-related parameters and efficient antioxidant system.
Highlights
Citrus production is one of the main fruit crops worldwide with more than 133 million tons produced in 2017 (FAOSTAT, 2019) and the Mediterranean basin is considered as a secondary area of citrus diversification
This study was performed triploid (3×) and diploid (2×) hybrids citrus trees obtained by hybridization between the “Fortune” mandarin (Citrus reticulata Blanco) and “Ellendale” tangor (Citrus reticulata Blanco × Citrus sinensis (L) Osb.)
PD decreased significantly in all varieties and there was no significant difference between varieties except for D12× (−1.90 MPa) and T40-3× (−2.38 MPa)
Summary
Citrus production is one of the main fruit crops worldwide with more than 133 million tons produced in 2017 (FAOSTAT, 2019) and the Mediterranean basin is considered as a secondary area of citrus diversification. Most of the citrus breeding program has focused on the production of seedless fruits (Ollitrault et al, 2008; Aleza et al, 2012; Navarro et al, 2015), the main economic trait for fresh fruit and juice market, with special emphasis in mandarins. The effective strategy to develop more drought-tolerant varieties is highly relevant to maintain sustainable crop. The improvement of the citrus fruit market and tolerance to abiotic stresses highlighted the need to develop an efficient strategy to produce seedless citrus varieties withstanding these environmental changes. The modification ploidy level could be an effective way to improve drought stress tolerance in plants and to get seedless fruits
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