Mwathi Margaret W, Schiessl Sarah V, Batley Jacqueline, Mason Annaliese S
School of Agriculture and Food Sciences, University of Queensland, Brisbane, QLD, 4072, Australia.
School of Biological Sciences, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
Chromosoma. 2019 Dec;128(4):521-532. doi: 10.1007/s00412-019-00720-w. Epub 2019 Aug 4.
Microspore culture stimulates immature pollen grains to develop into plants via tissue culture and is used routinely in many crop species to produce "doubled haploids": homozygous, true-breeding lines. However, microspore culture is also often used on material that does not have stable meiosis, such as interspecific hybrids. In this case, the resulting progeny may lose their "doubled haploid" homozygous status as a result of chromosome missegregation and homoeologous exchanges. However, little is known about the frequency of these effects. We assessed fertility, meiosis and genetic variability in self-pollinated progeny sets (the MDL2 population) resulting from first-generation plants (the MDL1 population) derived from microspores of a near-allohexaploid interspecific hybrid from the cross (Brassica napus × B. carinata) × B. juncea. Allelic inheritance and copy number variation were predicted using single nucleotide polymorphism marker data from the Illumina Infinium 60K Brassica array. Seed fertility and viability decreased substantially from the MDL1 to the MDL2 generation. In the MDL2 population, 87% of individuals differed genetically from their MDL1 parent. These genetic differences resulted from novel homoeologous exchanges between chromosomes, chromosome loss and gain, and segregation and instability of pre-existing karyotype abnormalities. Novel karyotype change was extremely common, with 2.2 new variants observed per MDL2 individual. Significant differences between progeny sets in the number of novel genetic variants were also observed. Meiotic instability clearly has the potential to dramatically change karyotypes (often without detectable effects on the presence or absence of alleles) in putatively homozygous, microspore-derived lines, resulting in loss of fertility and viability.
小孢子培养通过组织培养刺激未成熟花粉粒发育成植株，常用于许多作物品种以产生“双单倍体”：纯合的、真实遗传的品系。然而，小孢子培养也常用于减数分裂不稳定的材料，如种间杂种。在这种情况下，由于染色体错分离和部分同源染色体交换，后代可能会失去其“双单倍体”纯合状态。然而，对于这些效应的频率知之甚少。我们评估了由近异源六倍体种间杂种（甘蓝型油菜×非洲芥）×芥菜型油菜的小孢子产生的第一代植株（MDL1群体）自花授粉后代群体（MDL2群体）的育性、减数分裂和遗传变异性。利用Illumina Infinium 60K甘蓝型油菜芯片的单核苷酸多态性标记数据预测等位基因遗传和拷贝数变异。从MDL1代到MDL2代，种子育性和活力大幅下降。在MDL2群体中，87%的个体在遗传上与其MDL1亲本不同。这些遗传差异源于染色体间新的部分同源染色体交换、染色体的丢失和增加，以及先前存在的核型异常的分离和不稳定性。新的核型变化极为常见，每个MDL2个体观察到2.2个新变异。在后代群体中也观察到新遗传变异数量的显著差异。减数分裂不稳定性显然有可能在假定为纯合的、小孢子衍生的品系中显著改变核型（通常对基因座的有无没有可检测到的影响），导致育性和活力丧失。
