Rice is the second most important grain after wheat in the world and is considered one of the oldest crops. Although its cultivated area in the world is less than wheat, its production amount equals wheat. Rice is the main food of more than half of the world's people and its per capita consumption is 50 kg. In many developing countries, the rice produced does not keep up with consumption due to the growth of the population, and it is expected that this problem will become more acute in the future. Therefore, international organizations have tried to speed up breeding programs, and in this regard, the International Rice Research Institute (IRII) has paid special attention to rice-growing countries. In recent years, the spread of the system of rice cultivation twice a year, along with the risk of water shortage, has seriously limited the area under cultivation of late varieties, which have higher water consumption. Therefore, the development of semi-pure early and dormancy-resistant cultivars with a shorter growth period and less water requirement is one of the most important research priorities. The present research was carried out in the form of two experiments to study the compatibility and stability of pure early and short lines resulting from the cross between local cultivars and improved cultivars.
Materials and methods: To study the adaptability and stability of promising early rice experimental lines in the form of randomized complete block design in 3 replications during two crop years 2022 and 2023 in three regions (Deputy of the Country Rice Research Institute in Amol, Tankabon Rice Research Station and Goldasht Rice Research Station, Babol) were studied. The treatments included five pure early rice lines (70 days from sowing to 50% flowering) and short (85-90 cm) lines, the result of crossing between local cultivars and modified cultivars, along with two cultivars of Kohsar and Tarem Mazand as control cultivars. The studied traits included the number of days to 50% flowering, plant height (cm), number of fertile tillers per plant, cluster length (cm), number of full and empty seeds per cluster, 1000 seed weight (grams), Percentage of full grain and Paddy yield. Statistical analysis of the data, including testing the normality of the data distribution, Bartlett's test to check the homogeneity of the variance of the errors, and the composite variance analysis, assuming the randomness of the year effect, were performed with SAS software version 9.4. AMMI method was used for stability analysis using AMMISOFT version 1.0 software.
Results: The results of two-year compound variance analysis in three places showed that the effect of year on the traits of plant height, spike length, percentage of seed filling, and number of seeds was not significant, but it had a substantial effect on other traits. While the simple effect of location was not significant on any of the traits, the interaction effect of year × location was substantial on all traits except grain yield. Also, the simple effect of genotype was substantial for all studied traits except the number of claws, the percentage of seed filling, and the number of empty seeds. While the interaction effect of year in genotype was significant on most traits, However, the interaction effect of location × genotype was substantial only on thousand seed weight and seed filling percentage traits. The triple interaction effect of year × location × genotype on all traits was statistically significant. Line No. Z3 with 7493 kg/ha had the highest yield in three regions in two years, which was statistically significantly different from other lines.  The highest number of claws with 20 belongs to the Z5 line, followed by the Z1, Z3, and Z4 lines with 18.3, 18.3, and 18.2 cm, respectively, and the Z2 line along with two control characters in the group End was placed The maximum length of the cluster belonged to Tarem Awn variety (26.5 cm), followed by Z5 lines (26.4 cm) and Z4 (25.5 cm), and the cluster length of other lines and Kohsar variety was about 24 cm. Was. The highest number of full seeds in the cluster was assigned to the Z4 line with 144.4 and the lowest amount to the two varieties of Tarem Rishek short and Kohsar respectively with 85.6 and 1.89 seeds in the cluster. The lowest number of seeds Puck in this test was assigned to the Z1 line with 16 numbers and the most to the Z4 line with 27 numbers. The Z4 line had more total number of seeds in the cluster (with an average of 171.4) than the others. The lowest total number of seeds in the cluster was assigned to the two control cultivars Tarem Mazand and Kohsar (103.9 and 112.2 seeds, respectively). The highest weight of 1000 seeds belonged to the Kohsar variety (27.7 grams) and other genotypes did not show any significant difference. The highest percentage of seed filling belonged to Z1 and Z2 lines with 87.5 and 86.0%, respectively. The Kohsar variety had the lowest seed filling rate (79.8%) and the seed filling rate in the Tarem variety was 82.9%. The studied lines were between 79.4 and 83.8 days in terms of the number of days to flowering, similar to the Kohsar variety (79.4 days) and earlier than the short-bearded Tarem variety (88.4). Day) were.
Conclusion: Line Z3 due to its high yield (7493 kg/ha) along with yield stability and short height and short length of growth period almost similar to the early variety of Kohsar, is the first choice, and line Z2 with a yield of 6508 kg/ha and length of growth period identical to the array of Kohsar and short height were chosen as the second option.