Up to now, diploid and triploid cultivars were reported for the ornamental crop Hydrangea macrophylla. Especially, the origin of triploids and their crossing behaviors are unknown, but the underlying mechanisms are highly relevant for breeding polyploids. By screening a cultivar collection, we identified diploid, triploid, tetraploid and even aneuploid H. macrophylla varieties. The pollen viability of triploids and tetraploids was comparable to that of diploids. Systematic crosses with these cultivars resulted in viable diploid, triploid, tetraploid and aneuploid offspring. Interestingly, crosses between diploids produced diploid and 0 or 1–94% triploid offspring, depending on the cultivars used as pollen parent. This finding suggests that specific diploids form unreduced pollen, either at low or high frequencies. In contrast, crosses of triploids with diploids or tetraploids produced many viable aneuploids, whose 2C DNA contents ranged between the parental 2C values. As expected, crosses between diploid and tetraploid individuals generated triploid offspring. Putative tetraploid plants were obtained at low frequencies in crosses between diploids and in interploid crosses of triploids with either diploid or tetraploid plants. The analysis of offspring populations indicated the production of 1n = 2x gametes for tetraploid plants, whereas triploids produced obviously reduced, aneuploid gametes with chromosome numbers ranging between haploid and diploid level. While euploid offspring grew normally, aneuploid plants showed mostly an abnormal development and a huge phenotypic variation within offspring populations, most likely due to the variation in chromosome numbers. Subsequent crosses with putative diploid, triploid and aneuploid offspring plants from interploid crosses resulted in viable offspring and germination rates ranging from 21 to 100%. The existence of diploids that form unreduced pollen and of tetraploids allows the targeted breeding of polyploid H. macrophylla. Different ploidy levels can be addressed by combining the appropriate crossing partners. In contrast to artificial polyploidization, cross-based polyploidization is easy, cheap and results in genetically variable offspring that allows the direct selection of more robust and stress tolerant polyploid varieties. Furthermore, the generation of polyploid H. macrophylla plants will favor interspecific breeding programs within the genus Hydrangea.

中文翻译：

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通过杂交育种有针对性地在绣球中产生多倍体

到目前为止，已报道了观赏作物绣球花的二倍体和三倍体品种。特别是，三倍体的起源及其交叉行为尚不清楚，但其潜在机制与多倍体的繁殖高度相关。通过筛选一个品种集合，我们确定了二倍体，三倍体，四倍体，甚至非整倍体H. macrophylla品种。三倍体和四倍体的花粉生存力与二倍体相当。与这些品种的系统杂交产生了可行的二倍体，三倍体，四倍体和非整倍体后代。有趣的是，二倍体之间的杂交产生了二倍体和0或1-94％的三倍体后代，这取决于用作花粉亲本的品种。该发现表明特定的二倍体在低频或高频下均形成未还原的花粉。相反，三倍体与二倍体或四倍体的杂交产生了许多可行的非整倍体，其2C DNA含量介于亲本2C值之间。如预期的那样，二倍体和四倍体个体之间的杂交产生了三倍体后代。在二倍体之间的杂交以及三倍体与二倍体或四倍体的三倍体间的杂交中，低频获得推定的四倍体植物。对后代种群的分析表明，四倍体植物产生1n = 2x配子，而三倍体产生明显减少的非整倍体配子，其染色体数在单倍体和二倍体水平之间。虽然整倍体后代正常生长，但非整倍体植物在后代种群中大多表现出异常发育和巨大的表型变异，这很可能是由于染色体数目的变化。随后与二倍体杂交的假定的二倍体，三倍体和非整倍体后代杂交产生的后代和发芽率在21％至100％之间。形成未还原花粉的二倍体和四倍体的存在使多倍体H. macrophylla有针对性地繁殖。不同的倍性水平可以通过组合适当的杂交伙伴来解决。与人工多倍体化相反，基于交叉的多倍体化容易，便宜，并导致遗传变异的后代，从而可以直接选择更强壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。来自三倍体的三倍体和非整倍体后代植物的存活后代和发芽率范围为21％至100％。形成未还原花粉的二倍体和四倍体的存在使多倍体H. macrophylla有针对性地繁殖。不同的倍性水平可以通过组合适当的杂交伙伴来解决。与人工多倍体化相反，基于交叉的多倍体化容易，便宜，并导致遗传变异的后代，从而可以直接选择更强壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。来自三倍体的三倍体和非整倍体后代植物的存活后代和发芽率范围为21％至100％。形成未还原花粉的二倍体和四倍体的存在使多倍体H. macrophylla有针对性地繁殖。不同的倍性水平可以通过组合适当的杂交伙伴来解决。与人工多倍体化相反，基于交叉的多倍体化容易，便宜，并导致遗传变异的后代，从而可以直接选择更强壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。形成未还原花粉的二倍体和四倍体的存在使多倍体H. macrophylla有针对性地繁殖。不同的倍性水平可以通过组合适当的杂交伙伴来解决。与人工多倍体化相反，基于交叉的多倍体化是容易，廉价的，并且会导致遗传变异的后代，从而可以直接选择更健壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。形成未还原花粉的二倍体和四倍体的存在使多倍体H. macrophylla有针对性地繁殖。不同的倍性水平可以通过组合适当的杂交伙伴来解决。与人工多倍体化相反，基于交叉的多倍体化容易，便宜，并导致遗传变异的后代，从而可以直接选择更强壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。便宜，并产生了可遗传遗传的后代，从而可以直接选择更健壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。便宜，并产生了可遗传遗传的后代，从而可以直接选择更健壮和耐胁迫的多倍体品种。此外，多倍体H.phylphylla植物的产生将有利于绣球属内的种间育种程序。