Creation Of Tomato Leaf Color Mutant Resources And Gene Mapping

Leaves are the main organ of photosynthesis in higher plants.The formation and variation of leaf color are closely related to factors such as plant growth and development,hormone levels,and environmental response.What’s more,leaves have become a target material with important application potential in horticultural breeding because of their high ornamental and economic value.For Arabidopsis thaliana,based on a large number of resources of leaf color variation mutant,extensive analysis of the molecular mechanism of leaf color variation has been carried out,including exploring plasmids gene functions,analyzing the mechanism of plasmids-nucleus interaction,carrying out study on plant growth and development,physiological metabolism,and disease resistance response,etc.Due to the lack of leaf color mutant resources,in Solanum lycopersicum,an important vegetable crop and plant of developmental model,the research on the mechanism of leaf color mutation formation and the breeding application in quality,yield,resistance,etc.are still underdeveloped.Therefore,the construction of a tomato mutant library to screen quality resources related to leaf color mutations and clone of new tomato leaf color-related genes with functions clarified are of enormous practical significance for the research on the development and resistance mechanism of tomato and the future development of efficiency creative breeding of new tomato varieties and resources.In this study,our research group used the"Micro-Tom"tomato,which has advantages such as pygmyism,short life cycle,and high transgenic efficiency,serving as the genotypic species,has built a high-density tomato mutant library by EMS mutagenesis of 43,000 M₀seeds;furthermore,it has obtained 12 tomato leaf color mutant materials with a stable inheritance of M₃generation via generation screening.The resultant primary findings are as follows:1)Through the identification of physiological phenotypes and disease resistance characteristics of 12 screened leaf color mutant materials at different growth and development stages,it has been found that the tomato leaf color mutant materials obtained by mutations in this study have extensive genetic phenotypic variations in early seed germination,plant morphogenesis,plant height/internode length,flowering and fruit setting,fruit color change process,fruit color,fruit soluble sugar content,and Botrytis cinerea fungal resistance,in addition to a reduction in photosynthetic pigment content and photosynthetic efficiency and variation in chloroplast structure.2)Based on the results of phenotypic identification,this project selected the18M3-327 strain with enhanced resistance to Botrytis cinerea and the 18M3-494strain with early color breakage during fruit development in the leaf color variation mutant population.It has been confirmed that major genes controlling leaf color variation in the 18M3-327 and 18M3-494 strains are of single-gene recessive inheritance through the construction and separation of the high-density hybrid F₂generation of the genetic population.Subsequently,the major single nucleotide polymorphism loci（SNPs）controlling leaf color variation in the two strains are screened and identified by population segregation analysis（BSA）together with high-throughput sequencing and analysis.Finally,in consideration of the results of one-generation sequencing and quantitative expression experiments,5 major candidate genes controlling leaf color variation are screened from the 18M3-327strain and 5 from the 18M3-494 strain.In conclusion,by constructing the"Micro-Tom"tomato EMS mutagenized tomato mutant library,leaf color mutants with extensive genetic variation phenotypes are screened and identified,which greatly enriched the genetic resources of existing tomato leaf color mutants,laying a significant basis for the future research of the mechanism and application of tomato leaf color mutants regarding resources.In addition,the clone of the genes that lead to leaf color variation and relevant functional analysis,on the basis of the phenotypic identification results,are expected to provide a reference for further analysis of the mechanisms of leaf color variation and growth,immune response,and quality improvement in tomato and genetic improvement in the future.