Less-seed and seedless traits are desirable characteristics in watermelon (Citrullus lanatus). Hybridization between watermelon chromosomal translocated lines and wild lines significantly reduced seed counts in the hybrid fruits, approaching even seedless. However, the allelic relationships and the chromosomal translocation breakpoints from different sources are unclear, which limits their utility in breeding practices. This study focused on three groups of chromosomal translocation materials from different sources and conducted inheritance and allelic relationship analysis of translocation points. The results from third-generation genome sequencing and fluorescence in situ hybridization (FISH) revealed that the specific translocations in naturally mutated material MT-a involved reciprocal translocations between Chr6 and Chr10. The Co60γ radiation-induced mutant material MT-b involved reciprocal translocations between Chr1 and Chr5, Chr4 and Chr8. And the Co60γ radiation-induced mutant material MT-c involved complex translocations among Chr1, Chr5, and Chr11. Cytological observation showed that heterozygous translocation hybrids showed chromosomal synapsis abnormalities during meiotic diakinesis. Further, the dominant and co-dominant molecular markers were developed on both sides of the translocation breakpoints, which could facilitate rapid and efficient identification of chromosome translocation lines. This study provides technical guidance for utilizing chromosomal translocation materials in the development of less-seed watermelon varieties.

中文翻译：

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少籽西瓜染色体易位系等位关系及易位区域的鉴定

少籽和无籽性状是西瓜 (Citrullus lanatus) 的理想特征。西瓜染色体易位品系与野生品系之间的杂交显着减少了杂交果实中的种子数量，甚至接近无籽。然而，不同来源的等位基因关系和染色体易位断点尚不清楚，这限制了它们在育种实践中的实用性。本研究针对三组不同来源的染色体易位材料，对易位点进行遗传和等位关系分析。第三代基因组测序和荧光原位杂交（FISH）结果表明，自然突变材料MT-a中的特异性易位涉及Chr6和Chr10之间的相互易位。 Co60γ辐射诱导的突变材料MT-b涉及Chr1和Chr5、Chr4和Chr8之间的相互易位。 Co60γ辐射诱导突变材料MT-c涉及Chr1、Chr5和Chr11之间复杂的易位。细胞学观察表明，杂合易位杂交体在减数分裂终变过程中表现出染色体突触异常。此外，在易位断点两侧开发了显性和共显性分子标记，有助于快速有效地鉴定染色体易位系。该研究为利用染色体易位材料开发少籽西瓜品种提供技术指导。