BEHAVIOR OF DIPLOID AND TETRAPLOID GENOTYPES OF 'CARRIZO' CITRANGE UNDER ABIOTIC STRESS

Abstract

Tetraploidy is a spontaneous phenomenon in citrus and some anatomical differences have been described between tetraploid (4x) citrus plants and their corresponding diploids (2x). The choice of a suitable rootstock is often very restricted by a combination of biotic and abiotic stresses. Recent data points out that tetraploidy in citrus induces interesting phenotypes like dwarfing and tolerance to abiotic constraints. 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 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 able to maintain high leaf water potential more efficiently than 2x, thus gas exchange parameters (transpiration, stomatal conductance, and photosynthesis) were less affected. Under salt stress no difference was found in leaf chloride 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 the same general performance than the original 2x, but producing smaller trees more tolerant to abiotic stresses. (Resume d'auteur)