Investigation of changes in photosynthetic pigments and yield of rice genotypes in different irrigation methods

Due to Iran's location in the arid and semi-arid region of the world, the possibility of drought is high. Therefore, implementing low irrigation technologies to increase the efficiency of limited water resources is a scientific solution to reduce water consumption. On the other hand, rice receives two to three times more water than other crops and drought in rice is the most important factor limiting production worldwide, which indicates the need for optimal use of water resources to determine the real water needs of rice plants. Therefore, development and introduction of drought tolerant genotypes, using new irrigation methods, is a useful method to improve water productivity and efficiency in the face of drought and water scarcity. The aim of this experiment was to evaluate rice genotypes by measuring traits related to photosynthetic pigments and yield in order to select drought tolerant genotypes.

The present study, evaluated physiological and qualitative traits of grain with 10 rice genotypes that were known as tolerant genotypes in seedling stage based on the measurement of traits and mechanisms of drought tolerance split-plot arrangement using randomized complete blocks design with three replications in 2016, in Research Institute Rice (Mazandaran), Iran. Experimental research include three different irrigation regime (submerged surface (A0), alternate wetting and drying method up to 10 (A1) and 20 (A2) cm below the soil surface) and 10 genotypes rice that respectively are located in the main plots and sub-plots. The studied traits include physiological characteristics such as chlorophyll a, b and carotenoids, harvest index, biological yield and grain yield. Photosynthetic pigments were measured by spectrophotometer and its concentration was performed by Welburn and Lichtenthaler (1994) method.

The results showed that the amounts of photosynthetic pigments in low irrigation treatments increased compared to flood irrigation. So that the ratio of chlorophyll a to b and carotenoid content in in AWD20 increased by 5 and 20% compared to flood irrigation treatment, respectively. Genotypes also showed a very significant effect on traits related to photosynthetic pigments and quantitative and qualitative grain yield. The AR8 genotype had the highest chlorophyll a and a / b (average of eight and two µgr.ml, respectively). The highest chlorophyll b and a+b were also observed in Vandana genotype with an average of 5.2 and 13 μg.ml. The highest grain and biological yields were related to Shiroodi and IR74428-153-2-3, respectively. The interaction of the treatments showed that Neda genotype among other genotypes during AWD20 water stress has a greater advantage over the studied traits.

The results of this study indicated the preservation of quantitative and qualitative traits of genotypes under drought stress. Also, genotypes showed different reactions to the studied traits. Neda, Vandana, AR8 and IR74428-153-2-3 genotypes were able to increase photosynthetic capacity and quantitative and qualitative grain yield by applying low irrigation treatments.