Development of wheat lines resistant to blast disease using gamma-ray-induced mutagenesis

Wheat blast, caused by the fungus Magnaporthe oryzae Triticum (MoT), is an escalating threat to global food security due to its devastating impact on yield. Classical breeding for durable resistance is limited by scarce genetic resources. This study aimed to address this critical need by utilizing mutation breeding with gamma-ray irradiation to develop blast-resistant wheat lines.

Seeds from five popular high-yielding Bangladeshi wheat varieties viz. BARI Gom 27, BARI Gom 28, BARI Gom 29, BARI Gom 30, and BARI Gom 33, were treated with doses of gamma rays (200 Gy, 250 Gy, and 300 Gy). The mutant population was screened in subsequent generations for disease resistance and agronomic performances. Detached leaf assay (DLA) was used as a preliminary screening method on M2 progenies. The resistance of selected lines was then validated through artificial inoculation of MoT under field conditions in the M3 generation.

Out of 1710 total M1 plants that survived gamma-ray treatment, preliminary bioassay results (DLA) revealed that nine gamma-irradiated M2 progenies demonstrated strong resistance against MoT. After field screening with artificial inoculation in the M3 generation, we identified five mutants out of 225 plants. These artificially inoculated M3 plants showed differential reactions to MoT infection. Specifically, two entries were observed to be completely free from blast infection (0% disease incidence and severity), while another three entries had low disease severity (0.17-1.0%) and disease incidence (3-4%) with high grain yield.

The two promising M3 mutant lines developed through gamma irradiation of seeds represent strong candidates for the development of a blast-resistant wheat variety. Their high level of resistance and improved grain yield under field conditions make them invaluable genetic resources. Further field screening and bioassays are warranted to ensure stable varietal development.