Transfer of GA-sensitive dwarfing gene Rht18 by marker assisted breeding in HD3086 (Triticum aestivum L.) and multi-environment trials under varying seedling emergence regimes

The height reduction caused by the prevalent semi-dwarfing GA-insensitive gene Rht-B1b is associated with numerous negative pleiotropic effects, the major ones being reduced coleoptile lengths and lower early establishment rates, especially in moisture-stressed environments worldwide. Hence, breeding for wheat varieties with alternate GA-responsive (GAR) semi-dwarfing genes, such as Rht18, is an efficient approach for developing varieties for the moisture-stressed regimes globally. In this study, a structured marker-assisted backcross (MABC) breeding program was conducted to transfer the Rht18 gene into the mega wheat variety, HD3086. A total of 46 Rht18 positive BC₂F₅ lines were identified with an average background genome recovery of 88.34% using Wheat Breeder’s 35K Axiom SNP Array. Multi-environment trials were carried out at three locations under two conditions, i.e., stubble retained (SR) and rainfed (RF). ANOVA revealed significant differences for most of the traits in these trials. Plant height (PH) reduction in Rht18 introgressed lines ranged from 8.25-12.97 cm under SR and 5.25-10.15 cm under RF regimes. GGE biplots indicated specifically adapted and stable genotypes for yield in stubble-retained and rainfed regimes. These Rht18 lines hold strong potential for varietal release with further multi-location and multi-season trials. Ultimately, they will contribute to broadening the genetic base of Rht genes, especially for improving wheat adaptation in moisture-stressed environments.