A DISSERTATION SUBMITTED IN PARTIAL FULFILLMENT FOR THE REQUIREMENT OF THE DEGREE OF MASTER OF SCIENCE IN MOLECULAR BIOLOGY AND BIOTECHNOLOGY OF SOKOINE UNIVERSITY OF AGRICULTURE. MOROGORO, TANZANIAThis was an experiment to determine the presence and level of expression of OsCIPK15 salt responsive gene in Tanzanian rice breeders’ lines. Abiotic stress is one of the factors affecting rice cultivation in Tanzania. The calcineurin B- like protein interacting protein kinases (OsCIPKs) responsive genes have been observed to express in abiotic stress. The calcineurin B- like protein interacting protein kinases-15 (OsCIPK15) salt responsive gene, which is usually a silent gene expresses in saline soils which is abiotic factor affecting yield. In this experiment eighty-four breeders’ lines were used for the study. The lines were grown in sterilized sandy soil and grown for two weeks in the greenhouse. After this period the two week old seedlings were uprooted and the roots submerged in saline solution of 200mM concentration for forty-eight hours. Leaf samples were collected exactly twenty-four hours, twenty-nine and forty hours and stored at -80˚C The samples were thereafter analysed using quantitative real-time polymerase chain reaction (QRT-PCR). Of the eighty-four breeders’ lines twenty-two gave a quantifiable analysis using the Livak delta analysis. Of the lines CSR 27, TXMS 1-2, TXM 18-1 and TXM 27 were the most tolerant and expressed the gene highly and TXM 13-2-3, GIZA 179, TXMS 14 and TXM 13-2-1 were the least. This experiment proves that Tanzanian breeders’ rice have inherent ability to tolerate abiotic stress, such as salinity and the lines studied can be used in breeding programs to develop rice salt tolerant varieties to be cultivated in susceptible areas in order to provide profitable yield for paddy growing rice farmers.