Identification And Evaluation On The Tolerance Of An Extensive-source Garlic(Allium Sativum L.) Collection To Abiotic Stresses And Association Study Of Tolerance-allelic Variation

Allium sativum L.is an economically important diploid species of the genus Allium belonging to the Alliaceae family.This crop is considered to be one of the oldest horticultural crops.China is main producer of the garlic in the world.Like other crops,garlic is also affected by various biotic and abiotic stresses.The dramatically changing climate and soil salinization may affect garlic production.Yield components of garlic is susceptible to environmental conditions.Thus,it needs the attention of breeders to develop climatic-smart garlic cultivars for better adaption to environmental changes by utilizing available genetic resources and modern biotechnological tools to ensure production sustainability.For these reasons,three experiments were conducted:Firstly,identification and evaluation of salt tolerance of garlic germplasm.Secondly,identification and evaluation of tolerance of garlic germplasm to low temperature.Thirdly,the association study of phenotypic traits under salt stress and low temperature stress with single-nucleotide polymorphisms(SNPs)markers through GBS sequencing.The main results are summarized as follows.Soil salinization is a serious problem that limits growth and yield of many agricultural crops worldwide.There is a need for a sustainable long-term solution to this problem.In this study,354diverse germplasms were evaluated for their salt-tolerance at the seedling stage by being exposed to Na Cl(0.25mol)stress for four weeks.The salt injury index(SII)along with several plant growth parameters were investigated.The results showed a wide variation of SII from 16.51 to 98.15 among these accessions.All accessions were classified into five groups according to their SIIs,corresponding to different grades of the tolerance to salinity.Among then,two highly tolerant and twenty-four salt-tolerant accessions were screened out.The response of distinct germplasms to salt stress was somewhat different in various traits.Moreover,an extremely significantly negative correlation was observed between SII and agronomics traits(PH,LL,LW,RHL)and physiological traits(gs,A,E,Ch)under salt stress.This study provides sustainable solution,original salt-tolerance evaluation technology and valuable materials for the garlic salt-tolerant genetic improvement.Low temperature is a major environmental constraint that limits crop productivity.There is a need for a long-term,viable approach to this issue.In this study,312 diverse garlic germplasm were evaluated for their cold tolerance at the seedling stage by being exposed to the lowest natural low-temperature stress of-10～-15~oC at night for about eight days.The cold injury index(CII)along with several plant growth parameters were investigated.The results showed a wide variation of CII from19.91 to 70.38 among these accessions.All germplasms were classified into five groups according to their Clls,corresponding to different grades of tolerance to low-temperature stress.Among them,four highly tolerant and six low temperature-tolerant germplasm were screened out.The response of distinct germplasm to low-temperature stress was somewhat different in various trait.Moreover,an extremely significantly negative correlation was observed between CII and agronomic traits(PH,LL,LW,RHL)and bulb traits(LD,TD,BW)at initiation.This study provides a sustainable solution,original salt-tolerance evaluation technology,and valuable materials for the garlic low temperature-tolerant genetic improvement.Salinity and low temperature stress are not only the major environmental factors that limit plant growth and productivity,but they have also become global problems.However,little is known about the genetic basis underlying salt and the low temperature tolerance in garlic.To address this issue,an association study of salt tolerance and SNP markers was performed on a collection of a genetically diverse population of upland garlic(Allium sativum L.)comprising 226 accessions various geographic origins of 15 provinces of China and 30 other countries.Phenotypic data of 9 traits were collected from these germplasms under 1.5%concentration of Na Cl(0.25 mol/L)treatment.SNPs among these accessions were collected from GBS.A number of 105(SNPs)significantly associated with salinity stress tolerance-related traits were found.Among them,21,12,8,8,9,10,12,16 and 9 SNPs were associated with SII,PH,LL,LW,RPH,RLL,RLW,RHL and RRHL traits,respectively.A fifteen different number of SNPs sites were associated with more than one trait of the growth attributes under salt stress.In addition,we did an association study of SNPs and low-temperature stress tolerance in 196accessions with nine traits of seedlings exposed to the lowest temperature of-10~oC～-15~oC at night for eight days.A number of 123 SNPs significantly associated with the tolerance to low temperature were discovered.Among them,14,18,10,15,14,21,8,9 and 14 of SNPs were associated with CII,PH,LL,LW,RHL,RPH,RLL,RLW and RRHL traits,respectively.Thirty-two of SNPs sites were associated with more than one trait of the growth attributes under cold stress.GBS offers a greater degree of complexity reduction followed by concurrent SNP discovery and genotyping for species with complex genomes.Our association study results provide helpful knowledge about the genetic control of salt tolerance and low temperature at the seedling stage,which could help elucidate the genetic and molecular mechanisms of tolerance to salinity and low temperature stress in garlic.