| Hybridization and polyploidy can lead to rich variation of plant phenotype,which is the main way of plant genetic improvement.Among them,the allopolyploidization pathway of 2n female gametes not only shows the ploidy advantage brought by gene dose effect,but also strengthens the heterosis produced by heterogametopy combination,which has made great achievements in genetic improvement of Populus.However,due to the lack of experimental forest constructed with the same hybrid combination of polyploid materials for a long time,the analysis of the genetic variation rule and genetic effect of the important traits of allopolyploid poplar was mainly based on the seedling experiment,which was not thorough and comprehensive enough.In this study,variations of short-branch leaf,reproductive development and wood properties between full-sib diploid and triploid hybrids of 10-year-old clone experimental forest of P.pseudo-simonii × P.nigra ‘Zheyin3#’ and P.× beijingensis by the way of unilateral sexual polyploidy of 2n female gametes were analyzed.The effects of ploidy effect,genotype effect and gender on the variation of important traits of Populus were further analyzed.The relevant research provided practical basis for the "large population,strong selection" polyploid breeding of Populus,and laid a foundation for the further development of new polyploid varieties breeding.The main results are as follows:(1)The short branch leaf and stomatal traits of section Tacamahaca and Sect.Aigeiros of Populus were mainly affected by ploidy effect and genotype effect,and the effect of gender was the least.The leaf length,leaf width,leaf area,stomatal length and stomatal width of triploid hybrids showed a certain greatness,while the serration number and stomatal density were significantly smaller than that of diploid.Influenced by genotypes,there were significant differences in leaf and stomatal traits among clones.(2)The variation of disk number per male catkin between section Tacamahaca and Sect.Aigeiros of Populus was mainly affected by environmental effect,and the variation of other catkin traits was most affected by genotype effect.The length of male and female catkins of triploid hybrids was significantly longer than that of diploid.The average number of disks per male catkin was significantly larger than that of diploid,while there was no significant difference in other catkin traits between different ploidy.Under the influence by genotypes,there were significant differences in catkin traits among clones.(3)The variation of abnormal chromosome behavior during meiosis of pollen mother cells in triploid hybrids was rich.There were some phenomena such as precocious chromosome migration,lagging chromosomes,chromosome bridge,micronucleus,spindle abnormality,abnormal cytokinesis,which had a serious impact on development and production of gametes.(4)The triploid hybrids between section Tacamahaca and Sect.Aigeiros of Populus had a high degree of gametophyte abortion,but it was not completely sterile and can participate in fertilization.The results showed that the full pollen diameter of the hybrid triploid was significantly larger than that of the diploid,the frequency of shrunken grains was higher,and the rate of pollen germination was only 3.01% ± 0.36,showing a high degree of sterility.After pollination and backcrossing of some triploids with the female parent,it was found that only 23 seeds were produced in each catkin,and the average rate of seed germination was 0.53%,which was significantly lower than that of the backcrossing of diploid.(5)The effects of ploidy and genotype on the wood properties between section Tacamahaca and Sect.Aigeiros of Populus were greater than that of gender.There were significant differences in wood basic density,fiber length and fiber length width ratio between different ploidy,but the differences in lignin content and fiber width between different ploidy were not significant.There were significant differences in wood properties among clones,and clones had higher repeatability,which was under strong genetic control. |
