Résumé
Citrus in Morocco is mainly grafted on sour orange (Citrus aurantium L.) rootstock which should be abandoned due to its susceptibility to citrus tristeza virus (CTV). Salinity also becomes a serious problem in citrus growing areas of Morocco. The choice of the right rootstock is the most practical means to overcome the problem. Poncirus trifoliata (L.) Raf. and several of its hybrids (citrange, citrumello, citrandarin) are known to be tolerant to CTV. The purpose of the present work was to evaluate nine trifoliate citrus rootstocks, introduced in 1996 from San Giuliano Inra-Cirad Agronomic Research Station, Corsica France, for their behavior against salt stress. Seedlings of nine citrus rootstocks were evaluated for their leaf chloride accumulation under salt conditions. This study was carried out in greenhouse conditions at Inra Experimental station El Menzeh, Morecco. Three-month-old plants were grown. in 0.5 liter containers of sand and peat moss in proportion of 2/3 or 1/3 (v/v), and irrigated four times per week and fertilized with complete nutritional solution. NaCI at 0 (control), 2 and 5 g/l was added to the watering solution for 2 additional months. Ali rootstocks showed specific symptoms of toxicity when irrigated with NaCI solution. The severity of symptoms increased with time and salt concentration and varied between rootstocks. Diverse effects of salt stress on stem. leaves and roots fresh and dry weights were also observed according to the rootstock genotype. Rootstock leaf analysis revealed that accumulation of chloride, varied in relation with the rootstocks genotype and salt concentration. The relations between the different parameters analyzed are discussed and a standardized method for hybrids population screening proposed. Among the nine trifoliate hybrids tested Citrauge C35 (ICVN 0110177), Citnunelo Sacaton (ICVN 0110144) and Troyer citrange (ICVN 0110197) have been identified, in our experimental conditions as the less sensitive to salt stress. (Texte intégral)