Irrigation's effect and applied selection on the fiber quality of Ethyl MethaneSulfonate(EMS)treated upland cotton(Gossypium hirsutum L.)

Background: Producing rainfed cotton(Gossypium hirsutum L.) with high fiber quality has been challenging in the Texas High Plains because of extended periods of insufficient rainfall during sensitive boll developmental stages.Genetic variation created by Ethyl MethaneSulfonate(EMS) mutagen has successfully improved fiber quality of cotton. However, little is known about the effect of water deficit environments on fiber quality. Three EMS treated populations were advanced from the first to the fourth generation(M1 to M4) as bulk harvested populations. In2014, single-plant divergent selection was applied based on perceived morphological and agronomic differences seen during and at the end of the season.Results: Analyses from these selections in 2014-2016 showed significant(P< 0.05) improvement between and within populations for fiber traits(micronaire, length, strength, uniformity, and elongation) when compared with the original non-treated EMS source; some selections were found to have excellent fiber quality under diverse irrigationregimes.Conclusions: Some of these selections are being considered for germplasm release and could be useful for improving the fiber quality of cotton under water limited conditions, thereby helping to ensure the long-term survival of the cotton industry on the Texas High Plains.

Gene-lndexed Mutations in Maize

The availability of the B73 inbred reference genome sets the stage for high-throughput functional charac- terization of maize genes on a whole-genome scale. Among the 39 324 protein-coding genes predicted, the vast majority are untapped due to the lack of suitable high-throughput reverse genetic resources. We have generated a gene-indexed maize mutant collection through ethyl methanesulfonate mutagenesis and de- tected the mutations by combining exome capture and next-generation sequencing. A total of 1086 mutated MI plants were sequenced, and 195 268 CG〉TA-type point mutations, including stop gain/loss, missplice, start gain/loss, and various non-synonymous protein mutations as well as 4610 InDel mutations, were identified. These mutations were distributed on 32 069 genes, representing 82% of the predicted protein-coding genes in the maize genome. We detected an average of 180 mutations per mutant line and 6.1 mutations per gene. As many as 27 214 mutations of start codons, stop codons, or missplice sites were identified in 14 101 genes, among which 6232 individual genes harbored more than two such muta- tions. Application of this mutant collection is exemplified by the identification of the ent-kaurene synthase gene, which encodes a key enzyme in the gibberellin biosynthesis pathway. This gene-indexed genome- wide mutation collection provides an important resource for functional analysis of maize genes and may bring desirable allelic variants for genetic breeding in maize.