Department of Soil and Crop Sciences, Texas A&M University, College Station, TX, 77843-2474, USA.
Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
Sci Rep. 2019 Nov 29;9(1):17901. doi: 10.1038/s41598-019-53193-3.
Tetraploid johnsongrass [Sorghum halepense (L.) Pers.] is a sexually-compatible weedy relative of diploid sorghum [Sorghum bicolor (L.) Moench]. To determine the extent of interspecific hybridization between male sterile grain sorghum and johnsongrass and the ploidy of their progeny, cytoplasmic (CMS), genetic (GMS) and chemically induced male sterile lines of Tx623 and Tx631 were pollinated with johnsongrass pollen. At maturity 1% and 0.07% of the developing seeds of Tx623 and Tx631 respectively were recovered. Ninety-one percent of recovered hybrids were tetraploid and two percent were triploid, the tetraploids resulting from 2n gametes present in the sorghum female parent. Their formation appears to be genotype dependent as more tetraploids were recovered from Tx623 than Tx631. Because a tetraploid sorghum x johnsongrass hybrid has a balanced genome, they are male and female fertile providing opportunities for gene flow between the two species. Given the differences in 2n gamete formation among Tx623 and Tx631, seed parent selection may be one way of reducing the likelihood of gene flow. These studies were conducted in controlled and optimum conditions; the actual outcrossing rate in natural conditions is expected to be much lower. More studies are needed to assess the rates of hybridization, fitness, and fertility of the progeny under field conditions.
四倍体约翰逊草（Sorghum halepense（L.）Pers.）是二倍体高粱（Sorghum bicolor（L.）Moench）的可交配杂草近缘种。为了确定雄性不育谷物高粱与约翰逊草之间的种间杂交程度及其后代的倍性，用约翰逊草花粉对 Tx623 和 Tx631 的细胞质雄性不育（CMS）、遗传雄性不育（GMS）和化学诱导雄性不育系进行授粉。成熟时，分别从 Tx623 和 Tx631 中回收 1%和 0.07%的发育种子。回收杂种的 91%为四倍体，2%为三倍体，四倍体是由于高粱母本存在 2n 配子形成的。它们的形成似乎是基因型依赖性的，因为从 Tx623 中回收的四倍体比 Tx631 多。由于四倍体高粱 x 约翰逊草杂种具有平衡的基因组，它们是雌雄可育的，为两个物种之间的基因流动提供了机会。鉴于 Tx623 和 Tx631 中 2n 配子形成的差异，种子母本的选择可能是减少基因流动可能性的一种方法。这些研究是在受控和最佳条件下进行的；预计在自然条件下的实际异交率要低得多。需要进行更多的研究来评估田间条件下杂种的杂交率、适应性和育性。
