| Pepper(Capsicum annuum L,2n=24),belongs to Solanaceae,is native to a tropical region of Latin America.Pepper is one of the economically important vegetable crops,which is also the most common and extensively cultivated across the world.A wild relative of(C.frutescens L,2n=24)is the wild pepper germplasm resource in China.In addition,some desirable traits for pepper variety improvement in C.frutescens also were reported,including biotic and abiotic resistance.For example,it is tolerant to TMV and CMV,high temperature and humidity,and low-light and poor conditions,especially tolerance to drought.Moreover,it has high fruit rate every plant,and the fruit is so tasty and fragrant.In this paper,two accessions,the wild C.frutescens(xiaomila-P1512)and cultivated pepper(C.annuum-007EA),were used in this experiment.We have some interspecific hybrids were obtained by hand pollination.Then,F2 generation separation groups were obtained from F1 self-fertilization.Subsequently,a high-density genetic map was constructed using GBS(Genotyping-By-Sequencing)technology In the present study,some important agronomic traits in pepper have been studied on quantitative trait loci(QTL)mapping.The main results of present study are as follows:1.Production and identification of interspecific hybrids F1.We obtained 8 viable interspecific hybris F1 between pepper(Capsium annuum)and the wild relative(C.frutescens).Morphology method was usually used to observe characteristic between interspecific hybrids and its parents.There are obvious differences among interspecific hybrids F1 and parents in phenotypic traits,and the morphological traits of interspecific hybrids F1 were in the middle of parents.Furthermore,we also found that interspecific hybrids Fi were extremely similar to the wild species(C.frutescens-007EA).SSR also used for identification of interspecific hybrids F1.Analysis of SSR markers clearly showed that the band was polymorphism.Interspecific hybrid F1 has two bands from the parents:one comes from female parent,and the other comes from male parent.In a word,the F1 hybrids was heterozygous basing on morphological characters and molecular.2.The construction of the high density genetic map in pepper.120 F2 generation separation groups were obtained by self-fertilization of hybrids F1 generation.The high density genetic bin map was constructed by GBS with 120 F2 generation and parents.The total length of the genetic bin map is 5601.79cM,which has 3882 bin markers.The genetic bin map contains 12 linkage groups,which correspond to the 12 chromosomes.These linkage group length:444.62cM,206.22 cM,453.87 cM,597.88 cM,474.45 cM,580.46 cM,535.37 cM,464.16 cM,599.26 cM,407.35 cM,351.25 cM,486.91 cM,.The longest is linkage group 9,and the shortest is linkage group 2.An average bin marker interval is 1.44 cM.Compared with old genetic linkage map,there is a smaller distance between bin mareke in the bin map,which further improves the accuracy of the bin.3.QTL mapping of main agronomic traits.A total of 8 main agronomic traits were used for QTL mapping.These agronomic traits contain initial blooming time,leaf width,leaf length,main stem length,number of main stem,internode length,offshoot number,fruit weight et al.There is abundant phenotypic variation in F2 generation,especially fruit weight and flowering time.A total of 47 QTL sites were detected by QTL scanning for 8 main agronomic traits.These QTL sites are distributed on linkage group 1,4,6,7,8,9,10,11,and 12,Individual QTL explained phenotypic variation is 10.71%-68.55%.Most QTL located on linkage group 4,10 and 11.In the present research,we found some variations about agronomic traits related QTL.Seven QTL sites(qmsl4.1,qmsl4.2,qms19.1 qms19.2,qms19.3,qmsl10.1,qmsl10.2)were detected for the main stem;Ten QTL sites(qlw4.1,qlw4.2,qlw9.1,qlw9.2,qlw10.1,qlw10.2,qlwl0.3,qlw10.4,qlw10.5,qlw12.1)were detected for leaf width.Only 1 QTL site about flowering time,named qibt7.1 was identified.In addition,we also found that multiple traits were controlled by the same QTL,such as:main stem site(qmsl 9.1),leaf width site(qlw 9.2);offshoot site(qon 9.1)located at 424.4 cM on chromosome 9;main stem site(qmsl 9.3)and offshoot site(qon 9.2)located at 450.1 cM on linkage group 9.leaf width site(qlw4.1)and offshoot site(qon4.1)located at 337.5 cM on chromosome 4;main stem site(qms14.2)and leaf width site(qlw4.2)located at 341.4 cM on linkage group 4.These results indicated that these genes may have strong correlation,and are likely to present clusters and are closely linked.It is also possible that the phenomenon is caused by "pleiotropism"The wild C.frutescens(xiaomila-P1512)and cultivated pepper(C.annuum-007EA)were used as parents in this research.We have obtained interspecific hybrids by interspecific hybridization.We also have constructed a high-density genetic bin map using GBS genome technology Meanwhile,the 8 agronomic traits in pepper have been be used for quantitative trait loci(QTL)mapping.These results provide the basis for excavation excellent genes and genetic improvement. |
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