| Torreya grandis is a coniferous species, which has high economic values for its edible nut seeds.With50female trees from a natural population and half-sib families of their open pollinated offspring, astudy on genetic background of this species was conducted in terms of seed traits, seedling growth traits,and SRAP (sequence-related amplified polymorphism) marker-based genotyping of both maternalparents and their half-sib offspring, with a view to providing a theoretical rationale for selection andbreeding of elite germplasm and novel cultivars, seedling cultivation and development of the nutindustry. Results showed as follows:1) For seeds with aril on the average, their weight was8.96g (ranging from5.24to12.23g),their transverse diameter was2.368cm (1.963-3.018cm), and their vertical diameter was2.931cm(2.255-3.685cm); and for seeds without aril on the average, their weight was3.95g (2.30-5.19g), theirtransverse diameter was1.762cm (1.438-2.270cm), and their vertical diameter was2.507cm(2.009-3.208cm). The shape index of seeds with aril was0.811(ranging from0.695to0.902), and thatof seeds without aril was0.707(0.555-0.823). The weight percentage of seeds with aril to those withoutaril was45.15%(34.80-66.49%). For young seedlings on the average, the height of1-year-old seedlingswas19.4cm (ranging from9.0to35.0cm), and that of2-year-old seedlings was29.1cm (13.0-50.0cm);the basal diameter of1-year-old seedlings was3.61mm (1.56-5.63mm), and that of2-year-oldseedlings was4.38mm (2.64-6.98mm); and the branch number of2-year-old seedlings was about7(1-17).2) Seed phenotypic traits differed among half-sib families at a most significant level (p <0.01).The largest seed size was found from No.18maternal tree, and the smallest one from No.15,36and49maternal trees. No.25maternal tree had the slenderest seeds, and the seeds from No.35,36,46,47and80maternal trees were more or less round. Seeds from mother21had a highest weight percentage ofseeds with aril to those without aril.3) Any two seed phenotypic traits were positively correlated with each other at a most significantlevel (p <0.01), but the relationship between the seed shape and weight of both seeds with or withoutaril was irregular. Each phenotypic trait of young seedlings at different ages was in most significantlypositive correlation with the other (p <0.01). The seedlings generated from heavy seeds grew fast in terms of height or basal diameter, and if the seeds with or without aril had a large transverse diameter,they grew fast in height. However, there was no obvious correlation between vertical diameter of seedswith aril and seedling growth, neither was that between phenotypic traits of seeds and the branchnumber of seedlings.4) The genetic diversity of the natural maternal population was low, the Nei s genetic diversity(H) and Shannon information index (I) of which were0.1666and0.2623, respectively. D value wasused to measure the degree of linkage disequilibrium (LD) between markers. Marker pairs S18-18andS18-26got a smallest D value (-0.073), while S18-18and S18-27had a highest D value of0.159. Theaverage D value was0.014for all the marker combinations, with a standard deviation of0.018. Totally300marker pairs had a significant LD (p <0.05), accounting for1.11%of all the marker pairs, and20pairs had a most significant LD (p <0.01). These results indicated that there was no significant structurein half-sib population.5) There were23,6,1, and15SRAP markers identified to be significantly associated with heightof1-and2-year-old seedlings, basal diameter of2-year-old seedlings, and branch number of2-year-oldseedlings, with a cumulative contribution ratio of-27.036%,-12.330%,1.351%and-20.855%,respectively. However, no SRAP marker was significantly related with basal diameter of1-year-oldseedlings. Furthermore,3SRAP markers were discovered highly associated with height of1-and2-year-old seedlings and branch number of2-year-old seedlings simultaneously (p <0.01), which wereS57-13, S92-19and S18-18. Two SRAP markers, viz. S28-12and S92-19, were significantly relatedwith the same traits above (p <0.05). Marker S97-22was found significantly related with height of1-and2-year-old seedlings, too (p <0.05). |
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