Increased yield and revenue with a seedling transplanting system for hybrid seed production in Bt cotton

Rapid adoption of Bacillus thuringiensis (Bt) transgenic hybrid cotton (Gossypium hirsutum L.) in China is greatly attributed to high-quality hybrid seed produced in northern Shandong cotton production area; however, seed yield has reached a plateau in this area in recent years. Shifting the growing season earlier in the year by planting earlier in a greenhouse-like hut and transplanting the raised seedlings to the open fields later may allow the crop to produce more seeds. Four-year consecutive experiments conducted in Huimin County (northern Shandong, China) showed that early-season chilling stress on seedlings was avoided in such a hut, and that the blooming period was extended by about I week longer and the peak blooming occurred 5 days earlier in the year in the transplanting system than in the normal planting system. The number of early-season blooms and the number of bolls retained per unit area in transplanting system were significantly higher than those in normal planting system, but there were no significant differences in boll size and lint percentage between the two planting systems. Seed yield and quality parameters were significantly improved in the transplanting system through the increased number of bolls per square metre and earlier blooming respectively. As a result of improvement in seed yield and quality, the net revenue for seed producers with the transplanting system was increased by 20.8 and 22.5 % in 2002 and 2003, respectively, compared with the corresponding net revenue in the normal planting system. Seedling transplanting is a potent way to enhance hybrid seed production in Bt transgenic cotton.