Setayesh, a new rice cultivar suitable for cultivation in cold and cold temperate regions

Local rice cultivars have decreased their purity, and yield due to continuous cultivation. Recognition and production of high and stable yield cultivars are one of the goals of achieving new cultivars (Gravois, et al., 1991). The reaction of the different genotypes in different environments, and thus evaluation of genotype interaction in the environment helps plant breeders to evaluate genotypes more accurately and select the best one (Finlay & Wilkinson, 1963). Due to severe drought, late ripening, disease susceptibility, and very low yield of local rice cultivars, achieving new high-yielding cultivars that are cold tolerant and adaptable, and stable in cold regions has been one of the important goals of this activity. The introduction of new 53 line can be suitable for cold and temperate cold regions of the country.

The 97 rice lines were planted in 2008 with local control cultivars in Yasuj Agricultural Research Station in a preliminary experiment. 15 lines were selected based on important agronomic characteristics. Then they were compared in a randomized complete block design, and were selected 4 lines 53, 71, 32, and 39. The lines were evaluated in two regions for two years for compatibility and performance stability. A combined analysis of variance was performed to determine the genotype interaction. Before combined analysis, the Bartlett test was used to correct the homogeneity of variance of years and places. From the method proposed by Eberhart & Russell (1966) and environmental variance stability criteria, Wricke (1962), Shukla stability variance (1972), and Francis & Kannenberg (1987) environmental change coefficient, stability analysis was performed to determine compatible cultivars.

A simple analysis of variance showed genetic differences among the genotypes. The combined analysis of variance was performed after the Bartlett test, the combined analysis of variance indicated the significant effects of genotype, location and interactions of genotype × location, and genotype × year × location. The mean grain yield of genotypes showed that out of 97 studied genotypes, 4 genotypes produced higher yields than the average yield of genotypes in all environments. So that the highest grain yield was seen in genotypes 53 and 71, followed by genotypes 32 and 39. According to the calculation of the mean of genotypes, the highest grain yield was related to genotypes 53 and 71. The lowest environmental variance had the control cultivar and genotype 53. Control cultivar and genotype 53 had the lowest coefficient of environmental change, so these genotypes had the maximum stability of grain yield. The lowest stability variance and as a result the highest compatibility and yield stability were related to control cultivar and genotypes 53. The results showed that genotype 53 had the lowest mean squared deviation from the regression line, the lowest stability variance, and the lowest environmental variance among the promising lines and this genotype had the highest stability in different environments compared to other genotypes. In general, based on all methods of genotype 53 stability parameters, due to high average yield in different regions, yield stability and suitable environmental adaptation are identified as superior genotypes. The results of recording blast disease showed that 53 line was resistant and local cultivars were sensitive. In the research-extension design, the average yield of line 53 in all regions was higher than other lines and control cultivars. Line 53 for one week to ten days earlier than the control cultivar. The results show that line 53 is among the very good quality lines in terms of grain cooking quality. And having 72.4% of total conversion and 52.2% of healthy rice has good conversion quality.

The new genotype (line 53), gave a high average grain yield and was also stable. This line has always been selected as one of the top lines under all experimental designs and conditions such as preliminary, advanced, compatibility, and stability. In general, line 53 with high yield, early ripening, blast disease resistance, stability in the study areas, and very suitable quantitative and qualitative characteristics of grain, was introduced to the agricultural community as a variety of Setayesh rice in 2021.