Evaluation Of Major Filbert Germplasm Resources And Hybrid Progenies

The filbert tree is rich in germplasm resources and widely distributed in China. In order to fully protect and utilize these resources and provide a theoretical basis for classification and breeding of this Corylus plant, this thesis project focuses evaluation of major filbert germplasm and its selective breeding by hybrid progenies through lab experiments and field trials. Three aspects were involved in the study. Firstly, the probability grading, principal component analysis and cluster analysis were used for hazelnuts phenotypic traits, and botanical traits were described for C. heterophylla Fisch.. The hybrid offsprings of hazelnut were analyzed by correlation analysis and factor analysis. Secondly, the pollen morphological characteristics were identified by scanning electron microscopy, and 14 accessions were clustered by clustering analysis. Thirdly, based on EST sequences of hazelnut transcriptome, SSR markers were developed for analyzing the genetic diversity of C. heterophylla Fisch.. The main results are as follows:1. Grading standards of the major quantitative traits of C. heterophylla Fisch. were formulated on the baisi of the rich variety of the 24 phenotypic variation in the 99 C. heterophylla Fisch. accessions studied.Principal component analysis indictaed that among the 10 quantitative traits, yield factor, size factor, processing factor, shape factor,4 factors posed significant impact on the nut quality, which reflected the direction of genetic improvement and directive breeding.By cluster analysis the 99 C. heterophylla Fisch. accessions were divided into 5 groups:the first group included accessions that can be used as cultivars and breeding parents for hybridization for smooth nut surface; the second group included accessions that can be used as parental material for hybridization for big nut type varieties that are suitable for mechanical processing; the third group included accessions whose nuts are showing a good commodity character; the fourth group included accessions that can be used as parental material for hybridization for round type nuts without stripes on the shell surface; the fifth group included accessions that can be used as cultivars and parental material for hybridization for highly prolific varieties.2. The hazelnut traits of 161 hybrid accessions were significantly correlated. The distribution of nuts traits and factor analysis showed that cross combination 4 was the best in terms of comprehensive traits, and cross combinations 1,6,7, and 9 can be used as candidates for further screening in the process of directive breeding. The composite score by factor analysis of the top 10 accessions was in the descending order of 118,144, 120,35,22,32,67,137,140, and 69. It provided the basis for the selection of high quality hybrid hazelnut.3. The observation of pollen in 14 Corylus accessions by scanning electron microscopy showed that pollen grains were single grained with three apertures, and medium to small in size, oblate spheroidal in shape, triangular in polar view, elliptic in equatorial views, belonging to N3P4C4 type. The outer wall was rugulate and echinate. Different accessions showed different exine sculpture. According to the pollen morphology characteristics,14 accessions were classed into 3 groups. The first group included C. chinensis Franch., C. fargesii Schneid., C. kweichowensis Hu,’Da wei’, ’Liao zhen No.3’,’Casina’,’Ennis’, and their pollen size was medium except for C. kweichowensis Hu, with none of them obviously ragulated. The second group included C. heterophylla Fisch. (’JMS’,’HLP’, and’WC’), and C. mandshurica Maxim.et Rupr., and rugulate of pollen was not obvious, and echinate were small and dense. The third group included C.ferox Wall. var. thibetica (Batal.) Franch.,’Maria’,’Liao zhen No.7’, and their pollen exine showed clear rugulate and sparse echinate. The Corylus pollen were quite different in grain size, regulate ornamentation, and echinate size and density, which can provide palynology evidences in classification of Corylus plants.4. Based on EST sequences of hazelnut transcriptome data whose EST-SSR amplification efficiency was 70.18% and polymorphism amplification efficiency was 13.75%,4 pairs of SSR primers with the PIC>0.5, and 7 pairs of SSR primers with the 0.25<PIC<0.5 were developed. When we used the above 11 polymorphic SSR primers and C. avellana L. microstatellite (CAC-B005) to detect C. heterophylla Fisch. populations,62 alleles were presented at 12 SSR loci. The average value of allele (Na) was 5.1667; the observed total heterozygosity (Ho) mean was 0.4990; the expected total heterozygosity (He) was 0.5354; Shannon diversity index (I) was 1.0110; Nei’s gene diversity index (H) was 0.5320. These indexes indicated that C. heterophylla Fisch. populations had a high level of genetic diversity.5. The genetic differentiation coefficient (FST) of 9 C. heterophylla Fisch. populations was 0.1527, and main variation within population was 84.73%, gene flow (Nm) was 1.3870. UPGMA clustering by genetic distance showed that each population was distributed by different groups, indicating that a higher level of genetic differentiation and gene flow existed among populations, and a rich genetic variation was found within populations.