Development and Characterization of an Efficient Mutant Resource of the Mega Variety, Samba Mahsuri for Rice Improvement

Abstract Background:Novel variants of rice (Oryza sativa L.) can be obtained from induced mutations. The objective of the present study is to induce mutations in the background of Samba Mahsuri (BPT-5204), a popular and mega rice variety of India for creating novel variants for morphological, physiological and biotic stresses through using Ethyl Methane Sulphonate (EMS).Results: A population derived from 10, 500 M1 plants and their descendants was phenotyped for a wide range of traits leading to the identification of 124 mutants having variations in key agro-morphological traits, and 106 mutants exhibited variation for physiological traits. Higher yield is the ultimate goal of crop improvement and we identified 574 mutants having higher yield compared to wild type by having better yield attributing traits. Further, a total of fifty mutants showed better panicle exsertion phenotypes as compared to Samba Mahsuri leading to enhancement of yield. Upon rigorous screening for three major biotic stresses, nine mutants showed enhanced tolerance for yellow stem borer, and thirteen different mutants each showed enhanced tolerance for sheath blight and bacterial leaf blight, respectively. On the whole, 1406 desired mutant lines identified at M2 were forwarded to an advanced generation (M5). Whole genome re-sequencing and analyses of 15 stable mutants revealed high level of similarities (99.91 to 99.99%) with the Samba Mahsuri. Conclusions:The lines showing enhanced tolerance to important biotic stresses (YSB, ShB and BLB) as well as several economically important traits are unique genetic resources which can be utilized for the identification of novel genes/alleles for different traits. The lines which have better agronomic features can be used as pre-breeding lines. The entire mutagenic population is maintained as a national resource for genetic improvement of the rice crop.