Delayed Initiation of Fruiting as a Mechanism of Improved Drought Avoidance in Cotton

Abstract

Delayed fruiting in cotton (Gossypium hirsutum L.) may result in enhanced root growth, which could improve the crop's ability to avoid episodic drought events. This study, conducted under a rainout shelter at the University of Georgia Coastal Plain Experiment Station, Tifton, examined the effects of delayed fruiting on cotton root growth and yield under irrigated and water deficit stress conditions. Delayed fruiting was achieved through fruiting branch removal at 35 and 41 d after planting (DAP) in 2000 and 41 and 48 DAP in 2001 such that the first fruiting branch occurred approximately at main stem node 9 in all plants within a plot. Water deficit stress was developed by withholding irrigation and rainfall beginning at first flower for 17 d in 2000 and 16 d in 2001. Root counts were made for six consecutive weeks beginning at first flower using a minirhizotron camera system. At harvest, 3 m of row in each plot was hand picked and boll counts and seed cotton yields were recorded. Delayed fruiting, irrespective of irrigation treatment, resulted in higher root counts. Delayed fruiting also delayed maturity and altered fruit distribution on the plant. Upper main stem nodes contributed more to boll number and seed cotton yield with delayed fruiting. In 2000, delayed fruiting with water deficit stress reduced yield whereas no such differences were detected in 2001. Thus, delayed fruiting resulted in increased root growth but did not enhance drought avoidance as determined by boll number or seed cotton yield.