Inducing mutations with EMS are useful in breaking the established correlations among economically important traits in cotton

Abstract

Expanding the extent of genetic diversity, eroded during the process of domestication and breeding efforts, is essentially required for developing climate resilient cultivars as well as for pinning down the genetic pathways of complex traits. A total of 224 mutants were developed by exposing seed of a candidate cotton variety ‘PGMB-2467ʼ with an optimized concentration of ethyl methanesulfonate (EMS). These mutant lines along with the wild type were phenotypically characterized by sowing trials at two sites using alpha lattice design for three successive generations, M₄, M₅ and M₆. The variations observed in the studied traits at both extremes as compared to the wild type were largely due to genetics as was confirmed by their stable expression as well as their heritability (H²) estimates. Correlations between the traits as reported in early studies remained intact which was possibly due to the mutations induced in genes with pleiotropic effect. However, positive correlation between fiber strength (FS) and micronaire (MIC) value, contradictory to several studies, was possibly due to mutations induced in gene(s) conferring either of the traits of mutant population or genetic background of the wildtype. Principal component analysis (PCA) elucidated that first five components explained 61.2 % and 59 % of total variations at Nuclear Institute for Agriculture and Biology (NIAB) and National Institute for Biotechnology and Genetic Engineering (NIBGE) location, respectively. The genotype by trait (GT) bi-plot revealed significant associations between plant height (PH), ginning out turn percentage (GOT%) and fiber quality traits. Mutant lines PGMB-139 and PGMB-140 exhibited maximum GOT% and MIC value. Also, PGMB-143 and PGMB-48 were found to be the best mutant lines for fiber strength (FS), PGMB-463 for upper half mean length (UHML) and PGMB-62-1 for PH. It was concluded that EMS can be used as an alternative to physical mutagens and recombinational breeding for inducing mutations in the genome. These newly developed mutants can be used by the international cotton community for exploring their potential in improving cotton cultivars, hybrid vigor and also for unravelling the genetic mechanisms of the studied traits which would lead to initiate breeding by design.