In the short-season winter environment of India and Bangladesh, lentil growth and seed yield are significantly hindered by foliar blight caused by Stemphylium botryosum. As the international germplasm pool lacks a resistance source, the study aims to develop a mutant population to identify a high-yielding mutant resistance against the pathogen. A gamma-irradiated population was developed based on its GR50 dose of 248.8 Gy. The screening of almost 130,000 M2 plants identified a tolerant lentil mutant, MM216. The multi-location trials revealed that MM216 showed an impressive and robust resistance; the selected mutant line could be recommended as a donor in the lentil breeding program against the pathogen globally. A 100 g seed was exposed to a GR50 dose to develop the M1 population. At maturity, at least 100 M2 seeds of each 1300 M1 plant were harvested individually. So, almost 130,000 M2 plants were screened in the disease hot spot. The selected mutants were advanced to M7 by screening in the field and challenged in controlled conditions with the pure pathogen isolate. A resistance mutant, MM216, with a per cent disease index (PDI) of <10, was identified where the mean of the check varieties, WBL 77, was >55. The resistance ability was confirmed further in controlled conditions. The fungal and plant DNA ratio was almost negligible in the tolerant mutant, whereas it was 0.17 in WBL77 at 196 h post-inoculation. The selected mutant did not display any yield penalty, but there was a delay in flowering by a week compared to WBL77.
Keywords: GR50; Induced mutation; Lentil; Resistant; Stemphylium; γ-irradiation.