Tyagi, WrichaDas, Sudip2023-01-252023-01-252016-09https://krishikosh.egranth.ac.in/handle/1/5810192760P is one of the macronutrients required for plant growth and development, whereas Fe is a micronutrient required for various metabolic functions of plant. However, under acidic soil condition, due to low pH Fe2+ toxicity and P deficiency occurs leading to decrease in crop productivity. The molecular mechanism underlying the Fe toxicity and P deficiency tolerance in rice is not well understood. Therefore, current study was undertaken to identify the novel loci for Fe2+ toxicity and P deficiency tolerance using bi-parental population derived from the cross between a tolerant donor Shasharang (LR 11) and a susceptible recipient (KMR 3) genotype. The phenotypic data in terms of tolerance basis under lowland acidic soil condition and hydroponics, suggests that LR 11 was the most tolerant genotype out of four genotypes (KMR 3, LR 15 nd LR 60) used in our study in support. Positive and negative correlation was obtained for various traits upon evaluation of 225 F2 progeny derived from cross between KMR 3 and LR 11, at 1 and 5% level of significance. Positive correlation was found between tiller numbers at 60 days with plant dry weight (PDW) (0.642) and panicle number (PN) (0.984). PDW was positively correlated with PN (0.667) and filled grains per panicle (FGPP) (0.295). Bronzing score at 60 DAT (BS 60) was positively correlated with bronzing score at 110 DAT (BS110) (0.454). Interestingly, BS60 was negatively correlated with Fe content (0.21) at 5% level of significance. P content was positively correlated with P uptake (0.572) and negatively correlated with P use efficiency (PUE) and Fe content at both the levels of significance, respectively. P uptake was positively correlated with PUE (0.398) and Fe uptake (0.557) but negatively correlated with Fe content (-0.41). PUE was positively correlated with Fe uptake (0.623), Fe content with Fe uptake (0.619) at both 5% and 1% level of significance. Number of tillers at 60 days, plant dry weight, and number of panicles per plant showed significant positive correlation with grain yield per plant. Out of total of 377 SSR markers and 60 candidate gene based primers run on the parents, LR11 and KMR 3, eight and 60 candidate gene based and HvSSR markers, respectively were found to be polymorphic. Marker trait association study revealed significant association of five markers i.e. HvSSR06-46, HvSSR08-17, and HvSSR11-25, HvSSR05-12, HvSSR08-35 with PUE uptake at P value between 0.9-0.95. HvSSR03-26, HvSSR06-46, HvSSR06-54, HvSSR08-14, HvSSR08-35 and HvSSR12-08, were found to be correlated with PUE with r values ≥ 0.3. However, three markers, namely HvSSR01-47, HvSSR07-09 and HvSSR11-23 with P value between 0.9-0.95 were associated for PUP. HvSSR07-09, HvSSR11-12, and PR062-3 contributing for LR 11 and HvSSR08-17 and HvSSR10-21 for KMR 3 for the trait PUP. HvSSR06-09 with Fe content was found to be highly significant, whereas, HvSSR03-26, HvSSR09-30 and FR032-3 were less significantly associated with probability value between 0.9-0.95 for the trait Fe content. LR 11 alleles for three markers namely HvSSR03-26, HvSR11-27 and HvSSR12-08 were found to be associated with high Fe content in flag leaf, whereas, for HvSSR08-14 and HvSSR10-27, KMR 3 alleles showed association with high Fe content. These markers could be used for molecular assisted breeding programme for Fe2+ toxicity tolerance as well as P deficiency tolerance after further validation. Under Fe (II) toxic conditions, OsYSL16 was upregulated in shoots in susceptible genotype (KMR 3) and downregulated in roots of tolerant genotype (LR 11). OsNAS3 was downregulated in shoots in susceptible genotype under Fe(II) toxic conditions.Whereas, transcription factors OsIRO3 and OsIRO2 were downregulated in shoots of susceptible genotype and expressed only in shoots of tolerant genotypes, respectively. This study, therefore, suggests that genes reported for iron deficiency tolerance can be potential targets for enhancing rice production under P deficiency and iron toxicity field conditions. Our data also suggests that maintaining Fe homeostasis under Fe toxicity and P deficiency conditions as shown by the genotype, LR 11, could be vital to better performance under poor soil conditions.EnglishThesis