A Tomato EMS-Mutagenized Population Provides New Valuable Resources for Gene Discovery and Breeding of Developmental Traits

Abstract

Tomato (Solanum lycopersicum L.) is a major horticultural crop and a model species among eudicots, especially for traits related to reproductive development. Although considerable progress has been made since the tomato genome sequence project was completed, most of the genes identified remain predictions with an unknown or hypothetical function. This lack of functional characterization hampers the use of the huge amount of genomic information available to improve the quality and productivity of this crop. Reverse genetics strategies such as artificial mutagenesis and next-generation sequencing approaches build the perfect tandem for increasing knowledge on functional annotation of tomato genes. This work reports the phenotypic characterization of a tomato mutant collection generated from an EMS chemical mutagenesis program aimed to identify interesting agronomic mutants and novel gene functions. Tomato mutants were grouped into fourteen phenotypic classes, including vegetative and reproductive development traits, and the inheritance pattern of the identified mutations was studied. In addition, causal mutation of a selected mutant line was isolated through a mapping-by-sequencing approach as a proof of concept of this strategy’s successful implementation. Results support tomato mutagenesis as an essential tool for functional genomics in this fleshy-fruited model species and a highly valuable resource for future breeding programs of this crop species aimed at the development of more productive and resilient new varieties under challenging climatic and production scenarios.

Insights into the functional role of tomato TM6 as a transcriptional regulator of flower development

“…The sus2 mutant was identified as part of the screening of a chemically mutagenized population obtained in the tomato cultivar Moneymaker (MM) using EMS, as previously described [ 15 ]. The sus2 mutant was selected based on the conspicuous homeotic changes observed in the flowers of an M 2 segregating family.…”

“…The wild relative S. pimpinellifolium accession LA1589, retrieved from the Tomato Genetics Resource Center ( http://tgrc.ucdavis.edu/ ), was employed to generate the F 2 mapping population. All experiments were conducted under greenhouse conditions, as previously described by Fonseca et al [ 15 ].…”

“…In this work, we have characterized a tomato male sterile mutant identified as part of an ethyl methanesulfonate (EMS) mutant collection [ 15 ], which shows clear alterations in flower morphogenesis. We have named this mutant su cculent s tamens 2 ( sus2 ) since most stamens in sus2 mutant plants show a carpel-like identity and remain in mature fruits as succulent structures.…”

Resilient Response to Combined Heat and Drought Stress Conditions of a Tomato Germplasm Collection, Including Natural and Ethyl Methanesulfonate-Induced Variants

“…EMS mutant population has been developed by a chemical mutagenesis program carried out in the cv. Moneymaker background of S. lycopersicum [14]. As a result, 7769 M2 families were phenotyped.…”

“…With the aim of identifying new sources of resilience to climate change impact, we evaluated germplasm collection under combined heat and drought stress conditions. This collection includes an ethyl methanesulfonate (EMS) mutagenized population [14] and natural germplasm accessions represented by wild and cultivated tomato species. The tolerant variants identified provide valuable insights into understanding the genetic basis of tomato thermotolerance and, simultaneously, serve as suitable materials for breeding programs aimed at increasing tomato resilience to adverse climate conditions.…”