Title: Observational trial of rice breeding pure lines at two normal irrigation and drought stress conditions
Author: Ali Moumeni
Improvement of agronomic characteristics, grain quality, environmental stress tolerance such as drought and blast disease along with suitable grain yield of Iranian popular rice cultivars are the main objectives of the rice research plan in Iran. Hence, according to the previous study, 76 improved pure lines off rice, which originated from several crosses among Tarom-mahalli, and Hashemi with exotic rice genotypes including Vandana and IR78908-193-B-3-B, were tested under two conditions a) continuous irrigated and b) drought stress at the reproductive stage during 2020-21. The rice genotypes were arranged into an augmented experiment in which four rice checks such as Hashemi, Neda, Vandana, and Shirodi were arranged in an RCBD with four blocks in the normal irrigated plot to eight blocks in the drought-stress plot, due to different dimensions of normal and drought-stress plots. The plot size was 2.0 by 2.5 meters and seedlings were transplanted in a space of 20 by 20 cm with one seedling per hill. Drought stress was imposed on the experiments three to four weeks after transplanting. Data were collected on several characteristics such as days to 50% flowering (FLR), plant height (PLH), number of tillers per hill (TKR), panicle length (PL), number of filled grain (FG), unfilled grain (NFG), 1000 grain weight (TGW), Grain length and width (BGL, BGW), panicle sterility (STL), amylose content (AC), gel temperature (GT) and finally grain yield (YLD) according to the descriptor. Water stand and soil moisture at 30 cm depth of the soil were monitored regularly. Analysis of the collected data was performed according to the augmented design for checking cultivars and new genotypes. Results indicated that there were significant differences for all traits except for FG and YLD under normal irrigated conditions and FG together with STL under drought stress conditions among the genotypes. Results indicated that imposing drought stress negatively affects most of the traits such as FLR, PLH, FG, TGW as well as YLD of the rice genotypes. Few susceptible genotypes showed yield loss of around 60 %, while intolerant rice genotypes there was no yield loss as compared with normal conditions. Therefore, 22 superior rice genotypes were selected for advanced trials such as normal irrigated, reproductive stress, and aerobic conditions.
Keywords: Pure line, lodging, drought stress, grain quality, rice