Effects of Heat Stress on Cotton Production in the Low Deserts of Arizona

High temperature trends in the low desert of Arizona can have a severe negative impact on cotton production.  Heat stress indices have been developed for tracking heat stress effects on cotton fruiting patterns and ultimately yield.  This protocol evaluates the effects of level two (L2 - crop canopy temperature above 86^oF) heat stress on flower formation, pollen shed, fruit retention and distribution, and ultimately yield.  A set of 42 pre-commercial and commercial lines were planted at the Maricopa Agricultural Center in Maricopa, AZ.  Two varieties included in this trial are known to have significant tolerance to heat stress and serve as controls for comparison.  A series of plant measurements and flower viability measurements were collected over the course of the 2019 growing season to evaluate the effects of L2 heat stress on fruiting distribution patterns.  These measurements included in season fruit retention, height to node ratios, nodes above white flower, flower morphology, and pollen dehiscence.  End of season measurements included a complete plant map including incidence of misshapen bolls.  Boll samples were also collected to obtain seed index, boll size, and seeds per boll.  Final lint yield was obtained by harvesting the plot with a mechanical harvester equipped with load cells.  Samples were collected from each plot to determine gin turnout and fiber quality.