Better tolerance to water deficit in doubled diploid ‘Carrizo citrange’ compared to diploid seedlings is associated with more limited water consumption

Tolerance to water deficit in diploid (2 x ) and doubled diploid (4 x ) ‘Carrizo citrange’ ( Citrus sinensis [L.] Osbeck × Poncirus trifoliata [L.] Raf) was investigated. Water deficit was applied for 4 weeks. Physiological parameters, including stomatal conductance ( g s ), photosynthesis ( A ), transpiration ( E ), leaf and soil water potentials ( Ψ leaf ; Ψ soil ), and pot water loss, were monitored throughout the stress. Moreover, ABA, H 2 O 2 contents, and the expression of genes involved in ABA biosynthesis ( NCED3 ), regulation of abscisic acid signaling ( ABI1 ), and coding for a catalase enzyme ( CAT2 ) known to favor H 2 O 2 scavenging were monitored. During the experiment g s , A , and E values were most of the time higher in 2 x compared to 4 x . During the water deficit period, pot water loss decreased faster in 2 x compared to 4 x , leading to a faster decrease in all physiological parameters in 2 x . The higher sensitivity of 2 x compared to 4 x was correlated with more numerous thinner roots, higher leaf ABA and H 2 O 2 contents, and with the lower leaf water potential. ABI1 and NCED3 expression was not strictly correlated with the ABA content. However, the higher CAT2 expression in 4 x was correlated with the lower leaf H 2 O 2 contents. Therefore, the better tolerance observed in 4 x ‘Carrizo citrange’ compared to 2 x was associated with more limited water consumption and better and H 2 O 2 scavenging.