Fusion of transgene and interspecies hybridization enhances seed yield and root rot disease resistance in Jatropha curcas.

Perennial woody plants play an indispensable role in sustainable production. To shorten their juvenile phase and improve health, Jatropha curcas, a classic bioenergy crop, serves as a model for a breeding strategy integrating transgenes with interspecific hybridization. Specifically, overexpressing JcFT (JcFT-OE) J. curcas exhibiting early flowering were crossed with Jatropha integerrima exhibiting bright flowers and robust stems. The resulting hybrids were then backcrossed (BC) with JcFT-OE plants to refine the desired traits. The F1 generation displayed early flowering and an intermediary type of parents, with hard stems, more xylem, lower seed yields, and higher C18:2 content in the seed oil compared to those of wildtype and JcFT-OE transgenic plants. The BC1 generation showed early flowering, diverse shapes of fruit and seeds, and higher seed yield than the F1 generation. Among these lines, BC1-3 produced the highest yield, while the seed yields of J. integerrima, F1 and BC1-1 had notably low yields attributed to fruit dropping. Notably, F1 and BC1 plants demonstrated enhanced resistance to root rot caused by Lasiodiplodia theobromae and lignin contents of stems compared to JcFT-OE, a trait inherited from J. integerrima. Overall, the hybrid plants inherited desirable traits such as precocity and root rot resistance from their parents, resulting in higher seed yields in BC1 individuals. Blending transgenes with hybridization in Jatropha curcas enriches traits, boosting yields and disease resistance in woody plants. Furthermore, FT overexpression has substantial superiority in accelerating the breeding process in woody trees.