Paspalum is one of the most common native grass genera of the New World grasslands, and it includes many wild natural forage species and rare domesticated ones. Polyploidy is widespread among the genus. Many species are multiploid, which basically involve two components: a sexual self-incompatible diploid cytotype and a conspecific apomictic tetraploid, pseudogamous, and self-compatible cytotype, though other apomictic polyploid levels may occur in the same species. Tetraploid individuals, reproducing exclusively sexually, have never been identified in a natural apomictic tetraploid Paspalum species. Doubling the chromosome number of a 2x cytotype is used to obtain a sexual autotetraploid to carry out sexual × apomictic crosses in breeding programs for plant improvement. After numerous attempts we generated only one autotetraploid plant of P. chaseanum (I4C) which reproduced sexually and was highly self-incompatible. An unexpected preferential chromosome pairing resulted in the cytological diploidization of I4C. Despite each chromosome having three copies in I4C, meiotic chromosome configurations showed just 9.9% chromosomes forming multivalents (trivalents and quadrivalents), 82.1% bivalents, plus 7.9% univalents. The possible causes of this preferential pairing were analyzed. Although highly self-incompatible, it was fertile in crosses following intra- and interspecific pollinations, but with variable seed set, from over 45% when crossed with an apomictic natural tetraploid strain of P. chaseanum, to 0.9% with a strain of P. wrightii. Thus, a novel autotetraploid P. chaseanum was synthesized with very interesting characteristics: sexual reproduction, high self-incompatibility, variable cross-compatibility, and high cytological diploidization. All valuable attributes for breeding programs in a forage grass.

中文翻译：

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从雀稗二倍体细胞型诱导的有性高度二倍体同源四倍体植物

雀稗是新大陆草原最常见的原生草属之一，包括许多野生天然牧草品种和稀有驯化品种。多倍体在该属中广泛存在。许多物种是多倍体，基本上涉及两个组成部分：有性自交不相容二倍体细胞型和同种无融合生殖四倍体、假配子和自交相容细胞型，尽管在同一物种中可能出现其他无融合生殖多倍体水平。四倍体个体，完全有性繁殖，从未在天然无融合生殖四倍体雀稗属物种中被发现。将 2 x的染色体数加倍细胞型用于获得有性同源四倍体，以在植物改良育种计划中进行有性×无融合生殖杂交。经过无数次尝试，我们只生成了一种P. chaseanum的同源四倍体植物(I4C) 有性繁殖并且高度自交不相容。意外的优先染色体配对导致 I4C 的细胞学二倍体化。尽管在 I4C 中每条染色体都有三个拷贝，但减数分裂染色体配置仅显示 9.9% 的染色体形成多价（三价和四价），82.1% 二价，加上 7.9% 单价。分析了这种优先配对的可能原因。虽然高度自交不亲和，但它在种内和种间授粉后的杂交中可育，但结实率可变，从与 P. chaseanum 的无融合生殖天然四倍体菌株杂交时的 45% 以上到与P. chaseanum菌株杂交时的 0.9% 。 wrightii。因此，一种新的同源四倍体P. chaseanum合成后具有非常有趣的特征：有性繁殖、高度自亲不亲和性、可变的交叉亲和性和高度细胞学二倍体化。饲草育种计划的所有有价值的属性。