Gamma irradiation induced powdery mildew disease resistance in fenugreek (Trigonella foenum-graecum L.)

Abstract

Fenugreek variety “Ajmer Fenugreek-3” was irradiated with gamma rays at 250, 300 and 350 Gy for inducting disease resistance in this well adapted high yielding variety. Gamma irradiation caused a reduction in germination of M₁ seed by 8.2, 17.3 and 26.5% and a decrease in  seedling length by 10.3, 23.3 and 42.2% at doses of  250, 300 and 350 Gy respectively as compared to control. From M₁ generation more than eight hundred single plants from each irradiation dose were harvested individually and plant to row progeny were sown to raise M₂ generation. In M₁ and M₂ generation a wide range of variants showed abnormal phenotypes viz.,      stunted growth, absence of branching, narrow and elongated leaves, unusual thick leaves, dwarfness, albinism, and occurrence of terminal or apical flowers instead of the typical axillary flowers. However,  in the M₃ and M₄ generations,      the frequency of abnormal variants was found negligible. Eighty-seven progenies exhibited seed yield more or equal to parental variety and possessing resistance for powdery mildew and downy mildew were selected for further evaluation in M₃ generation.  On the basis of yield performance and disease resistance nineteen progenies were selected from M₃ generation. Thirteen promising M₄ progenies along with three checks varieties were sown in replicated trial for evaluating yield performance, uniformity and stability. Four mutants viz. AFg-3/300/207, AFg-3/300/84, AFg-3/350/48 and AFg-3/350/22 exhibited up to 13.5 % higher seed yield coupled with powdery mildew resistance as comparted to parental variety. The powdery mildew scoring of these mutants ranged from 6.7-14.7% as compared to 42.8-68.7 % in check varieties. All the mutants showed uniformity for most of the targeted traits. The variability generated in the present investigation can either be directly utilized as a new variety after evaluation for uniformity and stability or it may serve as donner germplasm for further varietal improvement programs.