Cotton PHYA1 RNAi improves fiber quality, root elongation, flowering, maturity and yield potential in Gossypium hirsutum L

Improvement of fiber quality of Upland cultivars (Gossypium hirsutum), while maintaining early maturity and productivity, is a fundamental problem in conventional cotton breeding. Phytochromes play a fundamental role in plant development, flowering and cotton fiber length. Targeted RNAi of PHYA1 genes in cotton suppressed expression of PHYA1 and/or PHYB, resulting in over-expression of the remaining PHYA2/B/C/E genes. This altered expression induced a number of phytochrome-associated phenotypes, including increased root length and mass, increased anthocyanin-pigment, vigorous shoot development and vegetative growth, early flowering, early boll maturity, increased fiber length and increased seed cotton yield compared to control plants. These RNAi phenotypes were stably inherited and expressed through four generations (T0-3) and were transferable from RNAi Coker-312 plants to Upland cultivars via conventional hybridization.U