We have used a reverse transcriptase polymerase chain reaction procedure (differential display) to identify cDNAs corresponding to transcripts affected by water stress in peanuts ( Arachis hypogaea
L.). Using this method, we have identified several mRNA transcripts that are up- or down-regulated following water stress. With 21 primer combinations, a total of 1235 differential display products were observed in irrigated samples, compared to 950 differential display products in stressed samples. These products demonstrated qualitative and quantitative differences in the gene expression. The differentially expressed transcripts were collectively named PTRD (Peanut Transcripts Responsive to Drought). We have identified a total of 43 PTRD, which were significantly altered due to water stress. Slot blot analysis of 16 PTRD indicated that 12 were completely suppressed due to prolonged drought, two were down-regulated, and two were up-regulated under drought stress conditions. The 12 completely suppressed transcripts were studied further by RNA dot-blot analysis to compare their expression in drought tolerant and susceptible lines, which underwent three weeks of water stress. PTRD-1, -10, and -16 expressed for longer period in tolerant line compared to the susceptible line and can be used as molecular markers for screening peanut lines for drought tolerance.