ESTIMATION OF GENE EXPRESSION FOR THE OSMYB48 GENE AND PROLINE CONCENTRATION IN SEVERAL RICE GENOTYPES IN TERMS OF WATER STRESS
Keywords:OsMYB48 gene, proline concentration, rice genotypes, water stress.
A field experiment was carried out at the rice research station in Al-Mishkhab- Al-Najaf Governorate during the summer agricultural season 2022. The aim of this study is to estimate the gene expression of the OsMYB48 gene and to measure the concentration of proline in the leaves of several rice genotypes in terms of water stress. The first factor were genotypes (Anber-33, jasmine, Al-Baraka, Al-Furat, K1, K35, and K45), and the second factor was water stress. The treatment began with drought stress after two weeks (from the date of transferring the seedlings to the land of the permanent field), and continued until the physiological maturity using three levels are: daily continuous flood irrigation (control), flood irrigation every five days, and flood irrigation every 10 days. The results of gene expression showed a clear variation in the seven studied genotypes at the level of the barrier cycle Ct, intensity and cycles, as the average values for expression start from the threshold of 15 upwards in all studied genotypes, there is a varying relationship between mostly inverse and positive sometimes between the values of the barrier cycle (Ct ) and gene expression values (fold change), and the results indicated that the highest decrease in CT values occurred at the genotypes (Anber-33, K1, K35), which amounted to (27.97, 28.83, 29.27) sequentially, which also showed a very high level of The gene expression of the target gene OsMYB48 at the treatment (irrigation period every 10 days), which was (831.74645, 40.78594, 7.41270) for Anber-33, K35 and K1, respectively. The results also showed that there are clear differences in the degree of gene expression between the other genotypes for water stress tolerance and the studied gene, as the target gene OsMYB48 gave the highest value of gene expression in the second treatment (every five days) in the genotype K45, which amounted to 2.44528 compared to the cultivar Jasmine, who recorded a relatively low expression in the three irrigation periods, on the other hand, the level of gene expression did not differ for the two cultivars (Al-Furat and Al-Baraka) and they were given (1.75321 and 1.72864) sequentially when third treatment (irrigated every 10 days) with high Ct values of (35.35 and 32.53). Sequentially, while the genotype K45 recorded the lowest value of gene expression when third treatment (every 10 days), amounting to 0.00128. With regard to the results of estimating the proline content in the leaves, the genotype K35 recorded the lowest average for this trait, amounting to 21.06 mg 100g-1, while the genotype K1 gave the highest mean of 31.85 mg 100g-1, which was not significantly different from the genotype K45, which recorded an average of 30.33 mg 100g. -1. Based on the aforementioned, it is possible to adopt the gene expression technique as an indicator to distinguish between genotypes and select them under conditions of exposure to water stress, in addition to adopting the ability of genotypes to accumulate proline as a good indicator of the possibility of drought tolerance in rice crop breeding and selection of the best varieties in water-limited environments.