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根据木薯的种内杂交、木薯和木薯属其他种的种间杂交,以及和木薯回交的三代种间杂种等的结实记录,来鉴定花粉和胚珠的稔性的变异。结论是,由于各个木薯品种是由非块根的野生类型进化而来和无性繁殖的,其结实能力已经衰退。发现稔性的变异很大,并且一个品种的花粉促进结实的能力与其雌花的稔性无关。如果两性的稔性的衰退是由于控制雄配子体机能的基因失却平衡,或由于有关雌配子体机能的基因或胚的营养组织的不平衡,就可以预期有上述的情况。不稔性的另外一些原因,也许包括减数分裂的不规则,这似乎在种间杂交的第一代就起作用,但这些因子在第一回交世代之后也许不大重要。黑柄木薯(Manihot melanobasis)是一种野生类型,通常由种子繁殖。就它和木薯的关系来说,可以说是木薯的亚种,它可提高它与木薯的杂交种的稔性。在木薯育种中,它可用作种子稔性的供体,但现有的一些仍然具有较高结实力的品种也可用作供体。在进行困难的杂交时,宜选择它们作为亲本。
Varieties of pollen and ovules were identified based on intraspecific crosses of cassava, interspecific hybridization of other cassava and cassava species, and robust records of three generations of interspecific hybrids with backcrossing of cassava. The conclusion is that, as each cassava variety evolved and vegetatively propagated by a non-tuberous wild type, its seed ability has receded. Variability was found to be very high, and the ability of one variety of pollen to promote fruiting was not related to the female’s flower. This could be expected if the decline of maleship is due to an imbalance in the genes controlling male gametocyte function or due to the imbalance of the vegetative tissues of the female gametophyte-related genes or embryos. Other reasons for impotence, perhaps including meiosis, may seem to work in the first generation of interspecific crosses, but these factors may not be important after the first backcross. Manihot melanobasis is a wild type, usually bred from seeds. In terms of its relation to cassava, it can be said to be a subspecies of cassava which enhances the romance of hybrids with cassava. In cassava breeding, it can be used as a donor for seeds, but some varieties that are still high in strength can also be used as donors. They should be chosen as their parents in difficult crossbreeding.