Forage production of four alfalfa (Medicago sativa) cultivars under salinity

Growth response of four alfalfa (Medicago sativa L.) cultivars to salinity was studied under N2‐dependent growth conditions in a nethouse. The cultivars tested were Hairy Peruvian (HP), Moapa 69 (M69), and Alic (TUR). They were compared to a local cultivar, Ghilboa, in two consecutive years (1988 and 1989). Under nonsa‐line conditions, the forage production of cv. Ghilboa was significantly higher than that of all other cultivars. Application of 170 mM NaCl to the root zone caused a remarkable decrease in forage production of HP, M69, and Ghilboa, but only a minimal and insignificant reduction in TUR. Nevertheless, the amount of biomass obtained after exposure of Ghilboa to salinity was still higher than that of TUR, the salt‐resistant cultivar. Thus, if forage is considered, Ghilboa seems to be the best cultivar to be grown under these environmental conditions. Reduction of salt level by extensive washing of the root zone resulted in a recovery of the forage production of all cultivars tested. Photosynthesis and transpiration were drastically reduced in all cultivars by salinity. A slight accumulation of sugars, as well as proline followed salt application. Proline content was significantly increased only in TUR. The possible causes for the different behavior of the cultivars are discussed as well as the implication of high forage yield of Ghilboa at any growth conditions, in spite of the significant inhibitory response to salinity.