Study On Inbreeding Depression Of Liriodendron Based On SSR Markers

Inbreeding depression is common in the world, but its mechanism is not clear. Liriodendronchinense is an endangered species and the existing population size is small, so inbreedingdepression may occur in this species.Studies on inbreeding depression of Liriodendron based onDNA molecular makers may help to explore mechanism of inbreeding depression. In this paper,we analyzed inbreeding depression of Liriodendron by taking5selfing progenies as experimentalpopulations,4intra-species progenies and8inter-species progenies as reference populations. Thegenetic diversity, percentage of homozygous, the growth and survival rate were compared indifferent mating types. Moreover, the possible SSR loci that may relate to recessive lethal gene inLiriodendron were also screened. The main results were as follows:The inbreeding depression (ID) level in Liriodendron: In traits as height,GLD andsurvival rate, significant variations among different mating types were foun. For GLD, the IDextent (δ value) of selfing progeny are0.46,0.45respectively compared to intra-species crossand inter-species cross progenies; for height, the δ value are0.32,0.35respectively; as tosurvival rate, the δ value are0.25,0.30respectively. For GLD, the order of different matingtypes is: self-cross progenies<inter-species progenies<intra-species progenies; while for heightand survival rate, they have similar trend, that is: self-cross progenies<intra-species progenies<inter-species progenies. In a word, it is certain that the selfing depression in Liriodendron issignificant.Offspring genetic diversity comparision among various mating types: The progenies of17mating combinations of3mating types in Liriodendron were analyzed by using20polymorphic SSR primers. the shannon diversity index of selfing progeny is0.3354, while forintra-species and inter-species, the shannon diversity index are as196%,224%respectively asselfing progeny; the observed heterozygosity of selfing progeny is0.23, while for intra-speciesand inter-species, the value are as278%,328%respectively as selfing progeny. So inbreedingcould lead to a siginificant drop in genetic diversity and hererozygosity. The order of geneticdiversity from low to high is: self-cross progenies,intra-species progenies, inter-speciesprogenies.The percentage of SSR homozygote of the different mating combinations: Thehomozygote percentage of the selfing progeny is the highest (77.26%), while the inter-speciescross progeny is the lowest (24.89%). The order of homozygote percentage from high to low is:self-cross progenies,intra-species progenies, inter-species progenies. Screening of candidate recessive lethal genes: The progenies of17mating combinationsin Liriodendron were analyzed by using576polymorphic SSR primers, and2candidate SSR locithat might relate to recessive lethal gene were screened.