Department of Plant Production, EERA, INTA, Balcarce, Argentina.
Theor Appl Genet. 1977 Mar;49(2):53-61. doi: 10.1007/BF00275164.
Phureja-haploid Tuberosum hybrids, which produce 2n gametes in addition to n gametes, were used to obtain diploid progenies in 2x - 2x matings, and tetraploid progeny in 4x - 2x matings. Seven of these diploid clones were intermated in a modified diallel design, and also crossed to seven cultivars, to obtain 21, 16-clone diploid; and 49 (35, 2x X 4x and 14, 4x X 2x) 24-clone tetraploid families, respectively. These progenies were included together with the 14 parental clones, in a tuber yield trial conducted in two locations in Wisconsin. Heterotic responses were striking in 4x X 2x progenies. Three of these entries had mean yields of 5.0, 5.0 and 5.2 lbs/hill, for 24 unselected clones, thus outyielding not only the mid-parent but also the best tetraploid cultivars in the experiment, which are highly selected; Wis 643 (4.8 lbs/hill), and Kennebec (4.8 lbs/hill). As a group, the 14, 4x X 2x families averaged 4.4 lbs/hill, while the mean of all seven cultivars was 4.0 lbs/hill, and the mid-parent was at 3.4 lbs/hill. This unusually high mean performance of 336 unselected clones represented in the 14, 4x X 2x progenies, is interpreted as a manifestation of the capacity of 2n pollen, formed by first meiotic division restitution (FDR), to pass onto the progeny the already heterotic diploid genotype in a largely intact array. Beneficial intra and inter-locus interactions are presumably compounded upon syngamy with an unrelated n egg from the tetraploid parent. -The performance of 2x X 4x progenies was at or below that of the midparent. The failure of these families to perform as well as 4x X 2x families may be a reflection of the incapacity of 2n megasporogenesis to avoid meiotic reassortment as efficiently as FDR does, which would result in inbred 2n gametes. However, the method of 2n megasporogenesis is not known.Hereditary variances were large, both within and among families, and indicated considerable nonadditivity in the action of genes affecting tuber yield at both levels of ploidy. Inbreeding was strongly depressing at both ploidy levels.
Phureja 单倍体块茎杂种除产生 n 配子外，还能产生 2n 配子，因此可以用于 2x-2x 交配中获得二倍体后代，4x-2x 交配中获得四倍体后代。这 7 个二倍体克隆在改良的完全双列杂交设计中相互交配，与 7 个品种杂交，分别获得 21 个、16 个克隆的二倍体和 49 个（35 个 2xX4x 和 14 个 4xX2x）24 个克隆的四倍体家系。这些后代与 14 个亲本克隆一起，在威斯康星州的两个地点进行了块茎产量试验。在 4xX2x 后代中观察到明显的杂种优势反应。其中 3 个品系的平均产量为 5.0、5.0 和 5.2 磅/丘，而 24 个未经选择的克隆的产量为 4.8 磅/丘，不仅超过了中亲值，而且超过了实验中高度选择的两个最佳四倍体品种，威斯康星 643（4.8 磅/丘）和肯纳贝克（4.8 磅/丘）。作为一个群体，14 个 4xX2x 家系的平均产量为 4.4 磅/丘，而 7 个品种的平均产量为 4.0 磅/丘，中亲值为 3.4 磅/丘。在 14 个 4xX2x 后代中代表的 336 个未经选择的克隆的异常高的平均表现，被解释为第一次减数分裂后恢复（FDR）形成的 2n 花粉能够将已经杂种优势的二倍体基因型以大量完整的方式传递给后代的能力的体现。在与来自四倍体亲本的无关 n 卵子受精时，可能会产生有利的内部和外部基因座相互作用。-2xX4x 后代的表现与中亲值相同或低于中亲值。这些家系的表现不如 4xX2x 家系可能反映了 2n 大孢子发生无法像 FDR 那样有效地避免减数重组，这将导致自交 2n 配子。然而，2n 大孢子发生的方法尚不清楚。遗传方差在内部和家系之间都很大，表明在两个倍性水平上影响块茎产量的基因的作用存在相当大的非加性。在两个倍性水平上，自交都有强烈的抑制作用。
