Studies On Hybridization Of Tacamahaca And Populus Euphratica And Their Chromosome Doubling Technique

Populus ephratica.Oliver (section Turanga, family Salicaceae, genus Populus) is the only tree species naturally distributed in desert region and has many excellent characteristics, such as salt-tolerance, higher drought-tolerance attribution. However, it is difficult in clone reproduction to P. ephratica. Studies on hybridization of Populus euphratica with other poplar species can help to solve the rooting problem of P. ephratica. In this thesis, Pollen Mother Cell(PMC) meiosis of P. simonii×P.euphratica produced by Xu et al. (1959) and P.euphratica hybridization between P. pseudo-simonii and P. simonii, pollen choromosome doubling of P.euphratica, female gamete and zygote chromosome doubling of P. pseudo-simonii and P. simonii were studied. The results were as follows:1. It was proved that P.simonii Carr×P.euphratica which produced by Xu et al. (1959) was true hybrids by cytogenetic observation. During PMC meiosis of the hybrids, a great number of univalent were found in diakinesis, and these behaved as laggards in anaphase, indicating that the relative affinities between genomes in Populus simonii Carr.×P.euphratica were wide, and there was no chromosome elimination in Populus simonii Carr.×P.euphratica;2. P.simonii×P.euphratica, P.pseudo-simonii×P.euphratica hybrids were obtained through hybridization between Populus ephratica and Sect. Tacamahaca Spach using common pollination method.7304 seeds of P.pseudo-simonii×P.euphratica and 1627 of P.simonii×P.euphratica were obtained respectively. After sowed,1570 seedlings of P.pseudo-simonii×P.euphratica and 260 of P.simonii×P.euphratica were produced. Because the hybrid seedlings were very weak in growth, majority of them died after immigration to field. only 6 P.pseudo-simonii×P.euphratica seedlings are survived, Some of whose leaves present oval and serrated blade shape like their female parent, the others are lanceolate type like P.euphratica.3. Based on the PMC meiosis of P.euphratica, pollen chromosome doubling was preliminary studied by high temperature treatment on male gamete of P.euphratica. The results showed that 2n pollen were obtained by using high temperature ranges from 38℃to 42℃treatments on male buds, ratio of 2n pollen ranged between zero and thirty-four percent, and the pollen amount decreased as the treatment temperature raised.38℃is the most suitable temperature for the induction of chromosome doubling of P.euphratica, diakinesis is the best treatment period of the meiosis, in which pollen mother cells in diakinesis in the various treatment combinations to sustain high temperature 38℃for 4 h, the average induction rate 2n pollen, reaching 21.55%, up to 34.00% for individual treatment. The relatively low rates of 2n pollen induced by high temperatures may attribute to a high asynchronism of meiosis of degree of P.euphratica.4. After pollinated with pollen of Populus euphratica, blastocyst and zygote chromosome doubling between P.pseudo-simonii, P.simonii and P.ephratica was carried out by using high temperature treatment.127 and 7 hybrid seedlings of P.pseudo-simonii×P.ephratica and P.simonii×P.ephratica were obtained by blastocyst chromosome doubling respectively; and 51 and 9 hybrid seedlings of P.pseudo-simonii×P.ephratica and P.simonii×P.ephratica were respectively obtained by zygote chromosome doubling. These treatment combinations of hybrid seedlings shall be tested by chromosome identification method to demonstrate their ploidy.