Effect of Planting Dates on Stability of New Rice Genotypes Traits Grown in Iraqi Conditions

Selecting the appropriate date for planting rice can be one of the viable solutions for proper growth and development of rice to avoid unsuitable conditions that can lead to lower productivity. Two experiments were conducted in the field of Al-Mishkhab Rice Research Station in Najaf City / Iraq during 2020 and 2021. In each season, eight genotypes used and two germination dates (15 and 30 Jun). After 20 days, seedlings were transferred to the field and planted on 5th and 20th of July respectively. The experiment was based on a three-blocks in RCBD design to study the performance of eight genotypes at two planting dates in two seasons. Results showed significant differences for genotypes and planting dates for all traits, while seasons showed significant differences only for the number of days to 50% flowering and panicle length. The values of heritability in the broad sense (h2BS %) were medium for all studied traits, which in turn led to an increase in the values of expected genetic advance as a percentage of the general mean (GA %), which was slightly high for grain yield (13.66 %). The genotypes showed a significant response to the late sowing date of 20th July compared to the early date of 5th July in the two growing seasons for most of the studied traits, including grain yield. The stability of the genotypes in four environments was highly variable. Genotype T93 had the most stable grain yield and the highest 1000-grain weight, while Forat1 showed a response to late sowing. Furthermore, the Forat1 responded to suitable environmental conditions of the number of days to 50% flowering, 1000-grain weight, and grain yield. Therefore, the genotypes which have superiority and stability over various environments could be successfully used as crucial material in the future breeding programs.