Anatomical study on the compatibility of distant hybridization in Camellia yuhsienensis
[Objective]In order to explore the biological mechanism of compatibility of distant hybridization in Camellia yuhsienensis.[Method]In this study,C.mairei var.lapidea(Y.C.Wu)Sealy(SG),C.hainanica'Haiyou 3'(HN-3)and C.oleifera'Deyou6'(DY-6)were used as male parent,self-and cross-pollination of C.yuhsienensis were studied by conventional pollination and mixed pollination methods.The parental ploidy was measured by the flow cytometry,and the pollen viability of the male parent was examined by in vitro germination.The pollen germination,pollen tube growth and early fruit and ovule development were observed by microscopy,and the fruit setting rate and dropping rate of each pollination combination were investigated in the field.[Result](1)YX was hexaploidy,SG was diploid,HN-3 was octaploid and DY-6 was hexaploidy.(2)The pollen of four samples had strong viability and fertility,and the highest pollen viability was DY-6(70.13%),the lowest pollen viability was YX(40.68%).(3)Pollen of all combinations of self-and cross-pollination could germinate normally on stigma,and their pollen tubes grew to the base of style at 12h after pollination,but pollen tubes of self-pollination and YX×SG were blocked after entering ovary and could not reach ovule.The pollen tubes of YX×HN-3 and YX×DY-6 reached the ovule 72 h after pollination.(4)Within 100 d after self-and cross-pollination,transverse and longitudinal diameter of fruit of YX×DY-6 were the largest,while transverse and longitudinal diameter of fruit of YX×SG were the smallest.The number of abortive ovule of YX×DY-6 was the lowest,with an average of 3.83 ovule/fruit,and the number of abortive ovule of YX×SG was the highest,with an average of 6.00 ovule/fruit.(5)Within 100d after self-and cross-pollination,the fruit setting rate of YX×DY-6 was the highest(68.0%).The fruit setting rate of YX×SG was the lowest(4.0%).The fruit setting rate of YX×HN-3 was 16.0%,and the peak of fruit dropping was mainly concentrated on 0-30 d and 40-70 d after pollination,respectively.The fruit setting rate of mixed pollination combination YX×SD was 22.0%.[Conclusion]The hybridization barriers of self-pollination and YX×SG were mainly pre-fertilization barriers,while the hybridization barriers of YX×HN-3 were pre-and post-fertilization barriers.The compatibility of distant hybridization in C.yuhsienensis was also related to parental ploidy,and the compatibility size was YX(hexaploid)×DY-6(hexaploid)>YX×HN-3(octaploid)>YX×YX>YX×SG(diploid).The mixed pollination method can improve the compatibility of distant hybridization in C.yuhsienensis.These results provided a cytological basis for the compatibility mechanism of distant hybridization of C.yuhsienensis,and also laid a theoretical reference for the work of distant hybridization breeding of oil tea.
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