Study On The Breeding System And Hybrid Breeding Of Manglietia Chingii And Manglietia Maguanica

Manglietia chingii and Manglietia maguanica,evergreen arbor in Magnoliaceae,are materials and ornamental plant with graceful tree shape and aroma.In this study,we systematically studied the characteristics of flower parts?OCI?P/O?and artificial pollination to understand the characteristics of these two plant breeding systems and to reveal the reasons for the low seed setting rate in natural conditions.In addition,this study explored the reproductive adaptability of the two plants in two-times opening-closure flowering by observing flowering phenology,flowering dynamics,species and activities of pollinating insects and determining pollen and stigma activity.Finally,reciprocal cross experiments were carried out with the two plants as parents in order to enrich new varieties of Magnoliaceae plants and reciprocal hybrid were identified by morphological identification and ISSR molecular markers.The main results are as follows:1?Characteristics of Breeding System(1)M.chingii:The OCI and the P/O were respectively 4 and 12430±510.Artificial pollination test showed that the percentage of fruit set without bagging and bagging was 0.00%,which indicated that there was no apomixis.The percentage of fruit set with cross-pollination was 65.00%,which was higher than 25.00%in natural pollination.Therefore,the breeding system of M.chingiiis is heterosexual and needs pollination media.(2)M.maguanica:The OCI and the P/O were respectively 4 and 7269±332.The rate of fruit setting was 0.00%in male-free and non-male-free bagging treatments,which indicated that there was no apomixis.The fruit setting rate of cross-pollination was 55.00%higher than that of natural pollination(15.00%),but the fruit setting rate of M.maguanica was only 5.00%lower than that of cross-pollination.Therefore,the breeding system of M.maguanica is partial self-compatibility and outcrossing,and pollinators are needed.The inappropriate pollination climate and lack of pollinating insects under natural conditions could lead to low seed setting rate.2?Reproductive adaptability of two-times opening-closure flowering(1)M.chingi:The first open pistil group has strong receptivity to provide polluted stigma for outcrossing,the second open pistil group carries out pollination to provide more vigorous pollen for outcrossing,and the evening beetle is its effective pollinating insect.Therefore,the second opening and closing is an adaptation to its outcrossing reproductive mechanism.(2)M.maguanica:The first opening is the time when the female characteristics begin to express,and the second opening is close to the time when the male characteristics begin to express.The expression period of the male and female characteristics overlaps for 1 to 4 hours,which enables more pollen resources to mate with one plant and another.Therefore,secondary opening is an adaptation to the mechanism of partial self-compatibility and cross-pollination.3?Cross-breeding(1)M.chingii xM.maguanica:Fruit setting rate(65.00%)was basically the same as that of parents(55.00%,65.00%).The seed setting rate(10.56±1.56%)was slightly lower than that of the female parent(11.32 ±1.06%)and the male parent(12.23±2.50%).Seed weight(392.31 + 25.40g)was higher than that of female parent(318.23+ 29.91g).Hybrid seedlings died in the course of growth due to abiotic factors and non-adversity physiology.(2)M.maguanica xM.chingii:Fruit setting rate(50.00%)was basically the same as that of parents.The seed setting rate(11.46 ±2.26%)was between that of parents.Thousand-grain weight(596.35 ± 64.15g)was higher than that of the female parent(575.62± 61.51g)and there were significant differences.Hybrid seedlings died in the course of growth due to abiotic factors and non-adversity physiology.In conclusion,the cross'compatibility between Manglietia chingii and Manglietia maguanica is high,and there are some reproductive barriers.4?Identification of hybrids(1)M.chingii × M.maguanica:In morphological aspect,the leaf morphological indexes of hybrid progenies were between parents or consistent with those of parents.Morphological indexes showed that the progenies were true hybrids.For ISSR molecular markers,4 primers were screened from 14 primers for hybrid identification.A total of 46 loci were detected by four primers,with an average of 11.5 bands per primer.Among them,39 were polymorphic DNA bands,and the proportion of polymorphic bancds was 84.78%.The amplified bands were not only common to both parents,but also single-parent and specific bands.The clustering results classified the tested materials into three types:partial parent type,intermediate parent type and paternal parent type.Morphological markers were consistent with ISSR markers,and hybrids generation were true hybrids.(2)M.maguanica × M.chingii:In morphological aspect,the leaf morphological indexes of hybrid progenies were between parents or consistent with those of parents.Morphological indexes showed that the progenies were true hybrids.In ISSR molecular markers,44 loci were detected by four primers,with an average of 11 bands per primer.Among them,39 were polymorphic DNA bands,and the proportion of polymorphic bands was 88.78%.The amplified bands were not only shared by parents,but also single-parent and specific bands.The clustering results classified the tested materials into two types:parent-biased and paternal-biased.Morphological markers were consistent with ISSR markers,and hybrids generation were true hybrids.