Abstract:

The high genetic quality and ample yield are the key to seed orchard management, and also an urgent problem awaiting solution at present. This task is closly related with the investigation on the mating pattern of seed orchards. Therefore, during 1984—2000 in a seed orchard of Pinus tabulaeformis, located in Xingcheng County, Liaoning Province, open-pollination seeds were collected from the seed orchard in 5 years (1984, 1987, 1993, 1996 and 2000), Seeds were germinated, and both diploid embryos and haploid gametophytes were analyzed by starch-gel electrophoresis, while 10 loci were involved for both kinds of tissue and used as genetic markers for estimating mating index and contamination rates. Firstly, the variations of mating system with time and factors influencing gametogamy were revealed, the multilocus outcrossing rates before thinning(1984 and 1993) were 0.975 and 0.962 respectively, the multilocus outcrossing rates after turnning decreased to 0.795 and 0.801 respectively for 1996 and 2000, while the multilocus selfing rates increased to 0.205 and 0.199. Secondly, by studing the variation of enzyme bands of seed samples in different positions of crown, the spatial variations of mating system was proclaimed too, the outcrossing rate was higher for seeds from the upper position of the crown in comparison with those from the middle and lower position. At last, pollen contamination rates of the seed orchard for 4 years were analyzed. The estimation method relies on differences of electrophoretic allele frequencies at single loci between natural stands and the seed orchard, from which an average contamination at loci was estimated. Results showed that the pollen contamination rates of the seed orchard for 4 years ranged from 0.354 to 0.583. Factors influencing the pollen contamination of seed orchard have been discussed and some related management measures proposed.

Key words: Pinus tabulaeformis, Seed orchard, Mating system, Pollen contamination