An Analysis Of Variation In Traits Of Seeds And Seedlings And Genetic Diversity In Castanopsis Tibetana Of Zhejiang And Anhui

Castanopsis tibetana is an evergreen tree species of Castanopsis,which is not only of value asa woody food species with its seeds but also has the potential to be used as an ornamental species.Since research on this species is still in its infancy,there are few reports about it.Based on the investigation and collection of germplasm resources in Anhui and Zhejiang Provinces prescribed by a project,we studied variation in traits of seeds and seedling growth and genetic diversity among geo-provenances by stratifying seeds to promote early germination,arranging field trials and analysis with SSR molecular markers in order to provide a theoretical basis for cultivation-oriented selection and breeding and to guide seed collection in production.The main results are as follows:1.C.tibetana is naturally distributed in the southern part of both Zhejiang and Anhui.The investigation of germplasm resources conducted in Longquan,Taishun,Hangzhou,Songyang,Kaihua,Yunhe,Qingyuan and Jiande of Zhejiang Province and Xiuning of Anhui Province found thatC.tibetanatrees had been destroyed or even died in some places because of developmental construction;mostly C.tibetana trees were sparsely distributed and large populations were seldom observed;some trees were fruitless,some didn't fruit annually,and many was characterized by singlely fruitingbut some had clustered fruit.Besides,the seeds of C.tibetana were preferred as one of top choices for food by rodents.So it was relatively difficult to collect seeds.2.With the seeds from 5 micro-populations and 16 families of Xiuning of Anhui and Longquan of Zhejiang,it was found that the percentage of insect bored seeds was 13.15-21.05%.In terms of geographical provenances and seed-bearing trees,there was significant difference among provenances as well as among seed-bearing trees in seed size,germination rate,seed viability and single seed weight,in which the geographical provenance and seed-bearing trees of Longquan were superior to those of Xiuning and the good trees of Longquan are LQ2,LQ3,LQ4 and LQ6;and the variation coefficient(CV)ofgermination ratewas high(61.31%),followed by single seed weight(49.49%)and seed viability(37.33%),and the heritability of these 3 parameters at the geo-provenance level was relatively high,which was in decreasing order as compared with germination rate,but the heritability of germination rate was high at the level of seed-bearing trees,which reached 0.73.In terms of provenances and populations,there was significant difference among geographical provenances and among seed-bearingtrees in thegermination rate,which had a CV of 51.91%;and it was also the geographical provenance and trees of Longquan were superior to those of Xiuning and the best populations were Heli followed by Xiaowukeng and Zuyuan.3.The seed germinated late in these two provinces and the growing season was short in the first year.Thus the seedlings grew slowly and could be used in afforestation at least when they were 2 years old.In terms of growth,seedlings had a CV of 45.14% in the first year in seedling height and the CV decreased in the following 2 years in seedling height and ground diameter;the difference either among geographical provenancesor among families was significant,but the difference among different populations in the same area was not significant;and the geographical provenance of Zhejiang was superior to that of Anhui,viz.Longquan > Taishun >Xiuning,but families were in order of LQ6,LQ2,AH6 and LQ3.4.The research on resources found that the phenotypic variation was abundant in C.tibetana.The SSR primers from other species which also belong to Castanopsis had a good transferability in C.tibetana and 92% of 50 pairs of primers from 6 species was suitable for C.tibetana.Analysis found that the tested materials could be clustered by the geographical provenance.Materialsof geographical provenances and familieshad a Shannon's diversity index(I)of 0.97 for all loci,a coefficient(FST)of0.39 in gene differentiation,an expected heterozygosity(He)of 0.49,and a gene flow(Nm)of 1.078;and families from Xiuning had an average I of 0.64 and a He of 0.39 but those from Longquan had an I of 0.58 and a He of 0.36,both of which had no significant difference.Materials of geographical provenances and populationshad an I of 1.08 for all loci,a FST of 0.184 in gene differentiation,a He of0.51,and a Nm of 1.646;and populations from Xiuning had an average I of 0.82 and a He of 0.42 but those from Longquan had an I of 0.76 and a He of 0.41.The seed of C.tibetanais large is size and its mobility is poor.Since C.tibetanais a monoecious species,there exits certain natural crossing.Analysis of molecular variance(AMOVA)found the main difference in variance was among individuals,which was 72%.Based on the research results,it could be seen that there was significant difference in the traits of seeds and seedling growth in C.tibetana among the geographical provenances,individuals or families.Therefore,selective breeding of this species should be done first among provenances,followed by that done among individuals or families,which was supported by the result from analysis of geneticdiversity.Zhejiang and Anhui Provinces are on the northern edge of the natural distribution area in C.tibetana.In the production,it is necessary to introduce the seeds from the areas to the south of Zhejiang where trees of C.tibetana grow well.But a comparison test among provenances introducedshould be done first before real extension could be performed in production.