Development of Gossypium anomalum-derived microsatellite markers and their use for genome-wide identification of recombination between the G. anomalum and G. hirsutum genomes

KEY MESSAGE
We reported the first development of Gossypium anomalum -derived microsatellite markers and identification of recombination between sexually incompatible species by a synthesized hexaploid on genome level. To continue to develop improved cotton varieties, it is essential to transfer desired characters from diploid wild cotton species such as Gossypium anomalum to cultivated allotetraploid cotton species. However, interspecific reproductive barriers limit gene transfer between species. In a previous study, we used colchicine treatment to produce a synthesized hexaploid derived from an interspecific hybrid between Gossypium hirsutum and G. anomalum and demonstrated its hybridity and doubled status using morphological, cytological and molecular marker methods. In the current study, to effectively monitor G. anomalum genome components in the G. hirsutum background, we developed 5974 non-redundant G. anomalum-derived SSR primer pairs using RNA-Seq technology, which were combined with a publicly available physical map. Based on this combined map and segregation data from the BC2F1 population, we identified a set of 230 informative G. anomalum-specific SSR markers distributed on the chromosomes, which cover 95.72 % of the cotton genome. After analyzing BC2F1 segregation data, 50 recombination types from 357 recombination events were identified, which cover 81.48 % of the corresponding G. anomalum genome. A total of 203 recombination events occurred on chromosome 11, accounting for 56.86 % of the recombination events on all chromosomes. Recombination hotspots were observed at marker intervals JAAS1148-NAU5100 on chromosome 1 and JAAS0426-NAU998 on chromosome 2. Therefore, all G. anomalum chromosomes are capable of recombining with At chromosomes in G. hirsutum. This study represents an important step towards introgressing desirable traits into cultivated cotton from the wild cotton species G. anomalum.