Preliminary Study On Interspecific Hybridization Of Prunus Conradinae

Prunus conradinae is a deciduous tree of Prunus subg.Cerasus in Rosaceae.It has a large number of flowers,beautiful colors,flowers before leaves.It is widely distributed in China.It has the advantages of good adaptability and good resistance,and has great prospects for garden applications.In order to develop local cherry resources and cultivate new varieties of cherry blossom with good ornamental effect and strong adaptability,this study was conducted to determine the breeding system of P.conradinae and determine its best hybridisation period.In order to explore the effects of pollen moisture content and storage temperature on the pollen viability of P.conradinae,experiments were designed according to the preservation conditions of P.conradinae pollen.In order to compare the cross compatibility of P.conradinae and the other four species(P.campanulata,P.discoidea,P.dielsiana,P.× subhirtella var.pendula),P.conradinae was uesd as female and P.campanulata,P.discoidea,P.dielsiana,P.× subhirtella var.pendula were used as male parent respectively for artificial hybridization,the intraspecific hybridization of P.conradinae was used as the control.Morphological and cytological identification methods were used to identify the 41 offspring obtained from distant hybridization in order to judge the authenticity of the hybrids.The main results are as follows:(1)P.conradinae breeding system:The group-florescence of P.conradinae is about 14 days,and the flowering period of single flower is 4-5 days.According to the opening state of the single flower,it can be divided into six periods:Bud period;Bell flowering period;Initial flowering;Early flowering;Full flowering;Flower withering period.Among them,the pollen activity was the highest in the early flowering stage,the stigma receptivity was the strongest in the initial flowering stage,and the pollination effect was the best after 2 h in the bell flowering period.Pollen preservation of P.conradinae:The lower the temperature,the better the preservation effect.The preservation effect of pollen after silica gel drying at 25℃ for 8 h was better than that of drying for 2,4,24 h.In addition,the Out-crossing index(OCI)of P.conradinae was 3,and the pollen-ovule ratio(P/O)was 20424±1156.The controlled pollination test showed that there was no apomixis,and a small amount of automatic self-pollination could be performed.The seed setting rate of artificial cross-pollination was higher than that of same plant same flower pollination and homogamy.The breeding system of P.conradinae is dominated by outcrossing and partial self-compatibility.(2)Hybrid affinity of P.conradinae:In the detection of male pollen viability,the pollen viability of P.conradinae,P.campanulata,P.discoidea,P.dielsiana and P.x subhirtella var.pendula were 87.81%,95.18%,62.96%,91.35%and 47.26%,respectively.When P.conradinae were hybridized with P.campanulata and P.dielsiana,the pollen germinated in 2 h,while the pollen of P.discoidea and P.x subhirtella var.pendula germinated in 4 h on the stigma of P.conradinae.Although the growth rate of each pollen tube in the stigma was different,all of them could enter the ovule within 48 h and complete double fertilization without pre-fertilization obstacles.The seed setting rate and seed germination rate of intraspecific hybridization were higher than those of interspecific hybridization,which were 68.00%and 71.43%,respectively.The seed setting rate and germination rate were 20.33%and 63.93%,6.00%and 22.22%,14.33%and 18.60%,2.00%and 0,respectively,when P.campanulata,P.discoidea,P.dielsiana and P.× subhirtella var.pendula were used as male parents.Among these distant hybridization combinations,the P.conradinae is the most affectionate to the P.campanulata,followed by the P.dielsiana and then the P.discoidea,and the least affectionate to the P.× subhirtella var.pendula.(3)The results of morphological and cytological identification:The results of morphological identification of hybrid offspring showed that the leaf margin serration traits of P.conradinae × P.campanulata hybrid offspring were biased towards the male parent,the leaf tip of P.conradinae × P.discoidea hybrid offspring was biased towards the male parent,and the leaf shape and leaf margin serration of P.conradinae × P.dielsiana hybrid offspring were biased towards the male parent,all hybrids were true hybrids.Cytological identification of the hybrid offspring was carried out,the statistical results of chromosome number of parents and offspring showed that the P.conradinae was tetraploid,the P.campanulata and the P.discoidea were diploid,and the P.dielsiana was triploid.The hybrid offspring of P.conradinae with P.campanulata and P.discoidea were triploid,and the hybrid offspring of P.conradinae with P.dielsiana were triploid and tetraploid.Cytological identification showed that 41 hybrids were true hybrids,which was consistent with the results of morphological identification.