ICAR – Indian Institute of Rice Research (IIRR), Hyderabad
PI: Dr C N Neeraja
Co PIs: Drs K Surekha, Kalyani Kulkarni, D Sanjeeva Rao, S K Mangrauthia, L V Subba Rao, Amtul Waris, U Chaitanya
Identification of Donors: Several genotypes have been screened for their zinc and iron content in brown and polished rice at ED XRF of IIRR. Standardization of estimation of iron and zinc content was done based on the study of evaluation zinc and iron content of brown and polished rice grains with two ED-XRF machines from IIRR and M S Swaminathan Research Foundation (MSSRF), one ICP (Punjab Agriculture University, Ludhiana) of grains of forty rice accessions grown in DRR fields. High correlation values were obtained for zinc between DRR XRF and ICP in brown (0.88) and polished rice (0.90), but for iron the correlations are relatively lower (0.10 and 0.16). Two landraces (Chittimutyalu and Kala Jeera Joha) and one popular improved variety (BPT 5204) were grown under zinc sufficient soil and their analyses showed high zinc in straw of improved variety, but high zinc in polished rice in landraces suggesting better translocation ability of zinc into the grain in landraces.
Development of mapping populations and identification of genomic regions associated with high zinc in polished rice: Using three donors viz., Chittimuthyalu, Jalpriya, BR2655, Type 3 and Surkasha, 17 mapping populations were developed with Swarna, IR64, RPBio226, MTU1010 and PR116 and are now in fixed RIL stage. A total of five genomic regions associated with high zinc in polished were identified till now. In addition to the earlier identified genomic regions associated viz., with high zinc in brown rice using 300 RIL population derived from BPT5204/Chittimuthyalu. Under OSYS18 on chromosome 12, OSYSL 8 chromosome 4, OsZIP1 on chromosome 3 and OsZIP8 on chromosome 5, OSYS18 on chromosome 8, genomic region associated with OsYSL 9 gene has shown significant association with zinc content of brown and polished rice grains (0.46, 0.48).
Selection of promising lines with high zinc in polished rice: Targeting high zinc in polished rice and yield, 25 breeding lines were selected from MTU1010/Chittimutyalu, IR 64/Chittimulyalu, Swarna/BR 2655, Swarna X Chittimulyalu and MTU 1010/ Suraksha developed developed during XII plan period of CRP Biofortification. Invitro bioavailability studies demonstrated that the zinc content and bioavailability from DRRDhan 45 was almost twice that of the control IR 64 variety.
Identification of candidate genes associated with high zinc in polished rice: Transcriptome analyses of the panicle tissue showed 41182 novel transcripts across three samples. Out of 1011 differentially expressed transcripts exclusively by two landraces mostly comprising transporters and transcription factors, 311 were up regulated and 534 were down regulated. Out of 24 genes subjected to quantitative real time analyses for confirmation, eight genes showed significant differential expression in landraces. Through mapping, six rice microsatellite markers spanning the genomic regions of six differentially expressed genes were validated for their association with zinc in brown and polished rice using RIL population of BPT 5204/Chittimutyalu.Forty genotypes comprising donor landraces as source of high zinc in polished rice and popular high yielding varieties were subjected to SNP genotyping using Double Digestion Restriction site Associated DNA Sequencing (ddRAD- seq). Analysis of GBS data suing GAPIT with nine phenotype traits viz., zinc in polished and brown rice, iron in polished and brown rice, single plant yield, number of tillers, panicle length, days to flowering and plant height for 2013, 2014 and 2015 showed 73 SNPs common across three years. For polished zinc, four uncharacterized genes found to be consistent and the characterization of these genes is in progress.
Transcriptome analyses of panicle tissue of two landraces and one improved variety
