Development and Characterization of Synthetic Allotetraploids Between Diploid Species and for Cotton Genetic Improvement.

Expanding genetic variability of cultivated cotton () is essential for improving fiber quality and pest resistance. This study synthesized allotetraploids through interspecific hybridization between (A) and (G). Upon chromosome doubling using 0.2% colchicine, fertile FC allotetraploids (AAGG) were developed. Cytogenetic analysis confirmed chromosome stability of synthetic allotetraploids, and 74 polymorphic SSR markers verified hybridity and parental contributions. The FC hybrids exhibited enhanced resistance to cotton aphids () and whiteflies (Aleyrodidae), with respective infestation rates of 5.2-5.6% and 5.4-5.8%, lower than those of cv. Ravnak-1 (22.1% and 23.9%). Superior fiber length (25.0-26.0 mm) was observed in complex hybrids and backcross progeny, confirming the potential for trait introgression into elite cultivars. Phylogenetic analysis based on SSR data clearly differentiated from Australian wild species, demonstrating successful bridging of divergent genomes. The FC hybrids consistently expressed dominant -derived traits regardless of the hybridization direction and clustered phylogenetically closer to the wild parent. These synthetic allotetraploids could broaden the genetic base of , addressing cultivation constraints through improved biotic stress resilience and fiber quality traits. The study establishes a robust framework for utilizing wild species to overcome genetic bottlenecks in conventional cotton breeding programs.