The effects of water stress were studied on proline, soluble sugar and Chlorophyll a and b in nine Asian and a European pear Genotypes. Asian pear genotypes introduced to Iran by Dept. of Horticulture, Tarbiat Modarres University from Belgium in 1998. Asian pear genotypes named KS6, KS7, KS8, KS9 , KS10, KS11, KS12, KS13 and KS14 . Also a native European pear cv. Shah Miveh was used. All genotypes planted in 20L pots in which three irrigation treatments were applied: Control, -0.5 MPa and -1 MPa, which irrigated when soil water potential reach -0.03, -0.5 and -1 MPa, respectively. A factorial experiment based on randomized complete block design was used. Proline accumulation increased in water stress treatments and was highest in KS14 in compare with other genotypes. RWC decreased in drought stress treatments and was lower in ‘Shah Miveh’ cultivar. Under drought stress conditions (-0.5 and - MPa) Total Soluble Sugar (TSS) was accumulated in leaves. TSS accumulated at the beginning of stress period was more than at the end of stress period. In general, TSS was highest in KS14 and lowest in KS9. In addition, chlorophyll a, b and total chlorophyll was reduced under drought stress. Chlorophyll content under drought conditions in KS9 and KS6 genotypes were lowest among genotypes.
