New Germplasm Creation And Optimization Of Efficient Selection System For PCNA Persimmon Breeding

PCNA persimmon is a new type of persimmon with high economic benefits,which can lose astringency naturally on the tree.At present,most of commercial cultivars cultivated in China are Pollination Constant Astringent（PCA）type,and leading PCNA persimmon were introduced from Japan.The breeding of novel PCNA persimmon genotype with self intellectual property is more desirable in Chinese persimmon industry.We attempted to investigate the suitable time for sowing developing persimmon seeds,and compare different approaches to obtaining hybrid seedlings,further to optimize the genetic improvement system for PCNA persimmon breeding program.‘Eshi 1’,‘Taishuu’and‘Gongcehng Shiushi’were used as the breeding parent for artificial cross to create new germplasm.After artificial pollination and young fruit development,the embryos were collected and cultured at 9-10 week and developing seeds were collected at 23 weeks for sowing immediately,mature seeds were collected at 27 weeks for sowing in early spring of next year to obtain hybrid seedlings.Astringency traits and flower gender of hybrid seedlings were characterized by molecular marker.Hybrid seedlings were grafted on tender shoots of adult Diospyros lotus L.trees planting in greenhouse.In addition,based on observation of fruit section and tannin cell size and content,we characterized the astringency genotype of hybrid individuals which just setting fruit.1.The pollen germination rates of‘Eshi 1’and‘Taishuu’were 25.38%and 19.02%,respectively.The fluorescence observations for pollen growth on stigma showed better pollen-stigma compatibility.There were 1.9 seeds for“Taishuu×Eshi 1”,2.2 for“Eshi1×Taishuu”,4.6 for“Gongcheng Shuishi×Eshi 1”on average.2.A total of 536 in vitro culture seedlings of the three cross combinations were obtained after embryo rescuing,and the average seedling survival rate was 86.8%.A total of 94 seedlings were obtained from sowing developing seed,and the average seedling survival rate was 20.4%.315 seedlings were survived after mature seed sowing,and the average seedling survival rate was 51.6%.DlSx-AF4S,OGI and RO2 molecular marker were employed to identify the sex or astringency loss traits for the seedlings derived from‘Taishuu’and‘Eshi 1’reciprocal cross-breeding,a total of 18 individual with RO2 marker and without DlSx-AF4S and OGI markers were determined,which accounting for 9.8% of the F₁ progeny.3.A total of 305 in vitro seedlings were grafted onto the Diospyros lotus L.,130（42.6%） of them survived.Among the 28 hybrid progeny plants of just setting fruits,only H2-5 was identified as PCNA genotype,27 of them belong to non-PCNA.4.The seeds of ’Eshi1’ sowed since 17 to 23 weeks after flowering,could germinate just at the end of November.The highest germination rate was 33.7% for the seeds developed and collected at 23 weeks after flowering.Those results suggested the developing seed culture can replace embryo rescue or developed seed culture.This approach by using developing seed and culture can increase grafting survival rate and shorten breeding period,which will contribute to improve breeding efficiency and benefit the genetic improvement system for PCNA persimmon breeding program.