Behavior of Diploid and Tetraploid Genotypes of 'Carrizo' Citrange under Abiotic Stress

Tetraploidy is a spontaneous phenomenon in citrus that leads to some anatomical differences between tetraploid (4x) and the corresponding diploid (2x) citrus seedlings, and interesting phenotypes like dwarfism and tolerance to abiotic constraints. The choice of a suitable rootstock is often very restricted by a combination of biotic and abiotic stresses. In this work we investigated the behavior of 4x and 2x 'Carrizo' citrange (Citrus sinensis x Poncirus trifoliata) subjected to the main abiotic stresses that threat the Spanish citrus industry. Seedlings were exposed to salinity, drought and iron deficiency, and physiological parameters were measured. Results suggest that 4x plants stressed by drought were less affected than 2x. Under salt stress no difference was found in leaf ion content, neither in gas exchange parameters, but leaf burn was less severe in 4x than in 2x. Concerning iron deficiency, a better tolerance of 4x compared to 2x was supported by higher Ferricchelate reductase activity, SPAD index and chlorophyll fluorescence. These preliminary results suggest that 4x 'Carrizo' citrange could be a promising rootstock, having nearly the same performance than the original 2x, but producing smaller trees more tolerant to abiotic stresses.