Haplo-pheno association forOsNRT1.1paralog in rice reveals superior haplogroup with high nitrate uptake efficiency

Abstract

Haplotype-based breeding approaches hold promise for enhancing crop improvement strategies, allowing for targeted selection of superior genetic combinations to develop high-yielding and resilient varieties. The current study aimed at identification ofNRT1.1nitrate transporter haplotype that could serve as “donors” in haplotype-based breeding. We phenotyped 272 rice accessions in hydroponics with sufficient and low nitrogen (N) for nitrate uptake efficiency. By employing principal component and hierarchical cluster analysis, the accessions were grouped into N efficient, intermediate, and inefficient clusters. Haplotype analysis unveiled the presence of two haplogroups forOsNRT1.1A, three forOsNRT1.1B, and five forOsNRT1.1C. Through haplo-pheno association, the comparison of mean trait values revealed H2 and H3 as the superior haplotypes (SH) for OsNRT1.1A and OsNRT1.1B, respectively. In the case of OsNRT1.1C, H3 and H1 emerged as SH within the N-efficient cluster. Conversely, the inferior haplotypes (IH) consisted of H1 in OsNRT1.1A, H3 in OsNRT1.1B, and H3 and H2 in OsNRT1.1C within the N-inefficient cluster. However, relative expression ofOsNRT1.1(with specific paralogs) in contrasting rice accessions revealed that a few of the inferior accession exhibited higher expression levels in the root but lower in the shoot, which might have contributed to their N-inefficiency. Furthermore, amino acid change at position 403 (Isoleucine to Valine) in inferior accessions influences the active site OsNRT1.1C protein causing N-inefficiency. Ours is the first report on haplotype analysis ofNRT1.1gene demonstrating its genetic diversity, as well as its association with phenotype will have potential implications for improving nitrate uptake efficiency.