Studies On The Genetic Diversity Of Trifoliate Orange(Poncirus Trifoliata[L.] Raf) And Genetics Of Its Hybrids With Red Tangerine(Citrus Reticulata Blanco)

During the past years, the pest and disease, and increasing labor cost have become the major obatacles for restricting citrus development. Exploring pests and diseases resistant types and dwarf rootstocks is a feasible way and very important. However, the loss of resistant germplasm and the decreasing of genetic diversity have been serious problems now. This study aimed at collecting, preserving and evaluating trifoliate orange germplasm. Research included the genetic diversity of the collected accessions; the characteristics of the phenological traits of the progenies of red tangerine(C.reticulata Blanco) ×trifoliate orange(Poncirus trifoliata(L.) Raf); the pigment analysis of the peels of the hybrid parents and offsprings by HPLC. The main results were as follows:1.One hundred and sixty-nine trifoliate orange accessions were collected from Shanxi, Henan and Hubei province in 2012. Then, they were preserved in two experiment stations, located in Hanzhong, Shanxi and Danjiangkou Hubei. Sixteen pairs special genomic SSR primers were selected for the analysis. From these primers, a total of 73 alleles were amplified and the average locus was 4.6, the mean PIC is 0.42. AMOVA analysis revealed that the majority of the gentic diversity occurred within population, representing 92.00% of the total variation on the nuclear DNA level. Besides, 171 accessions including 169 trifoliate orange accessions and 2 accessions(red tangerine and trifoliate orange) which growed in HZAU were divided into four groups through UPGMA method. The results of structural analysis and principal coordinates analysis were similar to UPGMA.The gentic diversity of DJK(Danjiangkou group) accessions was the highest, and it might be appropriate to expand the scope of collection, at the same time, this kind of group should also be given priority protection.2. Through two successive years? observation on the agronomic traits of the hybrid progenies of red tangerine with trifoliate orange, the leaf began to defoliate in October, and last for 67 days. The sprout of the progenies began from early March, and continued to the end of April. The flower buds were light yellow or pink. The flower opened at the end of April. A few purple flowers on some trees were observed. The coloring of the fruit for this cross progenies began in the early of November, and gradually full colored in the middle of December.3. There were three main fruit colors in the progenies, eg. red, yellow and between them. The main fruit-shaped was oval, and with pear-sheped sometimes. The characteristics of the fruit shape were inherited from Red tangerine.The titratable acid content of fruits was high, ranging from 2.00 to 5.56%. The TSS content ranged from 10.7 to 16.5%, which was close to the 13.4% of Red tangerine. The proportion of monoembryonic and polyembryonic plants was about 3:1(χ2=0.39,χ20.05=3.84),and it was in accord with one gene controlling trait model.4. According to the cartenoids types and contents in the peel of hybrid parents and offspring by HPLC. There was no β-crytoxanthin both in the peel of red tangerine and trifoliate orange, the violaxthin was high in the peel of red tangerine, low in the trifoliate orange peel and the progenies were between the parents. The lutein content had the similar trend. The content of Zeaxanthin in the peel was higher in the progenies than in their parents. And the levels of β-carotene in both the parents and hybrid populations were low. However, β-crytoxanthin and Zeaxanthin in the progenies were higher than their parents. Also, the violaxthin, Zeaxanthin and β-crytoxanthin varied continuously among the progeny plants.