Effects of Mepiquat Pentaborate on Cotton Cultivars with Different Maturities

Authors: Johnson, Joseph; Pettigrew, William

Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2006
Publication Date: 3/3/2006
Citation: Johnson, J.T., Pettigrew, W.T. 2006. Effects of Mepiquat Pentaborate on Cotton Cultivars with Different Maturities. Journal of Cotton Science. 10:128-135.

Interpretive Summary: The wide range of maturity available to cotton producers has made testing cultivars in an unbiased manner difficult for researchers, often prompting them to conduct more than one test based on maturity, as all crop management inputs have the potential to benefit some cotton cultivars while harming others. In conventional production systems, cultivars often have some type of chemical growth regulator applied to control excess growth. A study conducted in 2003 and 2004 showed that yield and fiber quality of most cultivars were relatively unaffected by application of the growth regulator mepiquat pentaborate. However, yield of one cultivar increased with application of the growth regulator, suggesting that it received an unfair advantage in the yield evaluation. The results of this study are important to cotton researchers because it demonstrates the unpredictable response of cotton to this growth regulator, and use of the growth regulator may introduce unwanted bias in evaluations when early and late maturing types are grown together.

Technical Abstract: Variation in the growth habit and maturity of cotton (Gossypium hirsutum L.) cultivars is a complicating factor in testing, necessitating separate tests for early and full season cultivars. In conventional production systems, commercial cultivars often have some type of chemical growth regulator applied, but the interaction of these regulators with cotton cultivars of varying maturity is not fully understood. This study evaluated the use of Pentia® (mepiquat pentaborate) on a group of commercially available cultivars which vary in growth and maturity. Pentia® treatments were 115 g a.i. ha-1, 230 g a.i. ha-1, and an untreated check applied in two sprayings during the season. Treatments were applied to all cultivars on the same calendar dates, regardless of developmental stage. Four early and four late maturing cultivars were evaluated in 2003 and 2004 for the effects of Pentia® on yield, yield components, and fiber properties. Analyzed across years, data showed significant interactions between Pentia® treatments and cultivars for lint yield and lint percent resulting in a positive lint yield response in one cultivar, accompanied by varying reductions in lint percent for all cultivars. Pentia® application caused reductions in plant height, height to node ratio, and nodes above white flower. Pentia® treatments made minor, but statistically significant improvements on fiber length, strength, micronaire, uniformity and short fiber content. Significant variation in the short fiber content of cultivars was also detected. The results of this study support the perception that yield interactions may occur when plant growth regulators are used in cultivar testing.