Pedigreed Mutant Library—A Unique Resource for Sorghum Improvement and Genomics

Sorghum is a versatile crop used for food, feed, fodder, and biofuel. Because of its resilience to environmental stresses and low soil fertility, sorghum is becoming increasingly important in meeting the growing need for food and energy in the face of declining arable land and fresh water resources. Low grain yield and poor nutritional quality are two major limiting factors for sorghum production. New resources are needed to overcome these limits. We have developed a pedigreed mutant library in BTx623, the inbred line for generating the reference genome sequence. The library consists of 6400 M4 seed pools, each of which was derived from an independent M1 seed through singleseed descent. The mutant library displays a wide range of visible phenotypes, and many are beneficial traits that have potential to be used as breeding materials to improve grain yield and quality. A selection of 256 lines was sequenced to 16x coverage of the whole genome. More than 1.8 million canonical ethyl methanesulfonate (EMS)-induced guanine/cytosine to adenosine/thymine single nucleotide polymorphisms (SNPs) were discovered, covering 94% of the genes in the sorghum genome. Over 57% of the genes carry large effect mutations that may alter the function of the gene product. In comparison with natural variations, 97.5% of the EMS-induced mutations are novel. Thus, the pedigreed mutant library can serve as a unique resource for selection of novel agronomic traits and identifying their causal mutations for sorghum improvement and for elucidating gene function through isolation of mutant series for the traits of interest.