Screening Of Molecular Markers Linked To Gynoecious Locus And Transcriptome Analysis In Bitter Gourd

Bitter gourd?Momordica charantia L.?belongs to the annual creeping herb of the cucurbitaceous.It contains mogroside and momordicin,so it is bitter.It is an important horticultural crop used both for food and medicine,and it has potential economic value.Bitter gourd has the characteristics of continuous flowering.Increasing the percentage of pistillate flowers is beneficial to achieve high yield.The gynoecious line of bitter gourd only bear female flowers during the whole growth process.By using it as a hybrid maternal parent,the seed production process can be simplified and the cost of the hybrid seed can be reduced.The gynoecious line also can increase the pistillate flower ratio of hybrid progeny plant,and it is an ideal material for achieving high-yielding breeding goal.The aim of this study is to screen markers that are likely linked to the gynoecious locus of bitter gourd using the single-gene segregation population of gynoecious and the second-generation high-throughput sequencing technology,further to map the gynoecious locus in bitter gourd.The study can provide fast and accurate methods for screening gynoecious plants in bitter gourd breeding.In addition,differential expression analysis between gynoecious and monoecious plants will be carried out to obtain transcripts that may be related to gynoecy in bitter gourd,which will lay a foundation for cloning the key gene and explaining the mechanism of the gynoecy.The main results were as follows:1.A F₂ segregating population was deprived from a gynoecious plant and its sibling which is a monoecious plant.And F_2:3:3 lines were further obtained by self-bred of the monoecious plants in the F₂ population.The number of monoecious and gynecious plants in the F₂ population and two F_2:3:3 lines were investigated.Statistical analysis shows that the ratio of the number of monoecious plants to gynoecious plants conformed to the ratio of 3:1 segregation(?²<?²_0.05=3.841).The gynoecy is controlled by a single recessive gene.2.Using plants of the F₂ population,two DNA libraries were constructed for gynoecious and monoecious plants,respectively,and Genome re-sequencing and SNP analysis were conducted.After detecting 87 canditate SNP loci which were selected based on the difference of allele frequencies.We successfully obtained 11 markers linked to gynoecious locus.These 11 SNPs are located on two scaffolds.4 of them were located on BDCS01000042.1,7 were located on BDCS01000329.1.The SNP at the position 155827on BDCS01000329.1 is about 4.35 cM from the target gene.The remaining 10 markers show co-segregation and is about 3.11 cM from the target gene.3.Two RNA libraries were constructed for gynoecious and monoecious plants,respectively,using the same F₂ population metioned above.Transcriptome sequencing was performed and differential expression analysis was carried out.88 differentially expressed transcripts were identified.Expression of 8 transcripts selected from the 88differentially expressed transcripts were verified by qRT-PCR analysis.The results of qRT-PCR analysis are consistent with the sequencing analysis.The functional annotation of 88 differential transcripts showed that 36 of them may be transcription factors,44 may be related to flower development,and the remaining 8 genes have unknown functions.These transcripts may be related to sexual differentiation of bitter gourd,and its function needs further study.