A major dwarfing region for plant height, asd1, was identified employing the next-generation sequencing-based QTL-Seq approach from a dwarf mutant and is demonstrated to be responsible for the dwarf nature with least penalty on yield in rice. The yield plateauing of modern rice is witnessed since many decades due to the narrow genetic base owing to the usage of a single recessive gene, i.e., semi-dwarf-1 (sd-1) for development of short-statured varieties throughout the world. This calls for the searching of alternate sources for short stature in rice. To this end, we made an attempt to uncover yet another, but valuable dwarfing gene employing next-generation sequencing (NGS)-based QTL-Seq approach. Here, we have identified a major QTL governing plant height on chromosome 1, i.e., alternate semi-dwarf 1 (asd1) from an F mapping population derived from a cross between a dwarf mutant, LND384, and a tall landrace, INRC10192. Fine mapping of asd1 region employing sequence-based indel markers delimited the QTL region to 67.51 Kb. The sequencing of the QTL region and gene expression analysis predicted a gene that codes for IWS1 (C-terminus family protein). Furthermore, marker-assisted introgression of the asd1 into tall landrace, INRC10192, reduced its plant height substantially while least affecting the yield and its component traits. Hence, this novel dwarfing gene, asd1, has profound implications in rice breeding.
Blast caused by Magnaporthe oryzae is the most devastating disease causing significant loss in rice production. The destructive nature of the disease is mainly due to the genetic plasticity of M. oryzae which complicates the breeding strategies. Blast can be effectively managed by the deployment of R genes. In this study, broad‐spectrum blast resistance genes Pi2 and Pi5 were introgressed independently into popular but blast susceptible rice variety, Samba Mahsuri (BPT5204) by applying marker‐assisted backcross breeding approach. Tightly linked markers AP5930 for Pi2 and 40N23r for Pi5 gene were used in foreground selection. Background selection helped to identify the lines with maximum recovery of recurrent parent genome (RPG). The RPG recovery in Pi2 introgression lines was up to 90.17 and 91.46% in Pi5 lines. Homozygous introgression lines in BC3F4 generation carrying Pi2 and Pi5 gene were field evaluated for blast resistance, yield per se and yield‐related traits. The lines showed resistance to leaf and neck blast in multilocation field evaluation. Improved BPT5204 lines with improvement for blast resistance were on par with original BPT5204 in terms of grain yield and grain features.
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