Productivity of rice is adversely affected by salinity and water logging stresses in coastal zones, and affected areas are progressively expanding as consequences of climate change and overexploitation of natural resources to meet the needs of increasing populations. Several varieties were developed and commercialized in this region in recent years, including some salt and stagnant flood (SF, medium deep, 25-50 cm water depth) tolerant varieties. However, suitability of these varieties based on adaptation to local conditions across the region and farmers" preferences have not been sufficiently evaluated. Genotype by environment analysis leads to identification of varieties with stable performance, or suitability to specific regions. Two

46Variations in concentration and distribution of health-related elements affected by environmental and genotypic differences in rice grains Ren Xue-liang, Liu Qing-long, Wu Dian-xing, and Shu Qing-yao 45 QTL mapping of low temperature on germination rate of rice

Agricultural land and resources reduced annually because of climate change thus it is necessary to further increase the productivity of the major staple food rice to sustain food security worldwide. However, rice productivity enhancement is one of the key challenges in abiotic stress-prone environments. The integration of cutting-edge breeding approaches and research management methods in the current varietal improvement pipelines can make a step-change towards varietal improvement for the abiotic stress-prone environments. Proper implementation of breeder’s equations in the crop improvement pipeline can deliver a higher rate of genetic gain. Single Seed Descent based Rapid Generation Advance (RGA) technique in field and greenhouse is the most promising innovations and low-cost, high-throughput marker-assisted selection approaches are applied for rapid and efficient selection for abiotic stress-tolerances. Also improving efficiency, intensity, and accuracy of selection and reducing breeding cycle time through holistic rice breeding that can play an important role in developing climate-smart abiotic stress-tolerant rice for target environments. This information can use as the future direction for rice breeders and other researchers.

Rice is relatively sensitive to salinity at reproductive stage. Screening of rice cultivars for salt tolerance at the reproductive stage is difficult at field conditions because of the heterogeneity of soil salinity. The present investigation aimed to characterize reproductive growth and yield potential of elite breeding lines in controlled saline environment at net house conditions. The experiment involved three advanced breeding lines, BR7100-R-6-6, IR78794-B-Sal29-1 and IR59418-7B-21-3 and a salt-tolerant check (BRRI dhan47) and susceptible check (BRRI dhan28) under four salinity levels (0, 4, 8, and 12 dS/m) at reproductive stage. The factorial experiment was conducted in randomized complete block design with three replications. Salinity × genotypes demonstrated significant interactions on some yield contributing characters and grain yield. Salinity stresses, at 8 and 12 dS/m, decreased plant height, tiller and panicle numbers, panicle length, filled grain number and grain yields of all the tested genotypes in different magnitude. The breeding line IR59418-7B-21-3 performed greater tolerance to salinity than other tested lines and check varieties. At 8 dS/m IR59418-7B-21-3 produced 72% relative grain yield compared to that of 31% in BRRI dhan47. The breeding lines, BR7100-R-6-6 and IR78794-B-Sal29-1 produced 40 and 59% relative grain yield respectively, at 8 dS/m. At 12 dS/m, all the tested genotypes produced less than 20% relative grain yield. Based on the salinity pressure (8 dS/m) at the reproductive stage, IR59418-7B-21-3 produced 68% higher yield than that of BRRI dhan47. BR7100-R-6-6 and IR78794-B-Sal29-1 out yielded BRRI dhan47 by 45 and 49% respectively. All the three breeding lines performed better than that of BRRI dhan47 in terms of salinity tolerance at the reproductive stage.

The major purpose of this research was to introgress Saltol QTL into the genetic background of BRRI dhan49 through marker-assisted backcrossing. FL478 was used as a donor parent of Saltol QTL. Marker assisted backcrossing strategies were applied to develop BRRI dhan49-Saltol lines. A primer polymorphism survey was carried out between the two parental genotypes viz. BRRI dhan49 and FL478. A total of 363 SSR and InDel primers were surveyed and a total of 96 markers (27%) were found polymorphic. A cross was made between BRRI dhan49 and FL478 to produce F1 seeds and F1 was confirmed by RM493. Foreground selection was carried out using RM493 in all generations. Fifty six SSR markers were used for background selection. The Graphical Genotype (GGT) software was used to estimate the percentage recovery rate of the recurrent parent genome and to find out the genome ratio of the parents in the selected progenies of the backcross populations. From BC1F1 generation five best plants were selected based on background recovery of recurrent parent and backcrossed with recurrent parent. From BC2F1 generation, six plants were selected based on the highest background recovery of 80.7% to 89.5%. BC2F2 seeds were produced by selfing of selected BC2F1 individuals. The Saltol introgressed lines performed better in salt stress condition in hydroponic screening. The developed BRRI dhan49-Saltol lines would be useful for developing salt tolerant rice varieties or for using in other breeding programs.