Boll sampling protocols and their impact on measurements of cotton fiber quality

Within plant fiber variability has long contributed to discrepancy and inconsistency in fiber quality and yarn quality. Fiber quality uniformity is a primary plant breeding objective related to cotton commodity economic value. The physiological impact of source and sink relationships render stress on the upper sympodial branches of the cotton plants thereby leading to reduced genetic potential for fiber growth. Objectives of this study were to quantify variability within the top and bottom halves of the plants and evaluate various boll sampling protocols for efficient fiber quality estimation. This research was conducted in College Station, Texas for three years in 2009, 2010 and 2011 at the Texas A&M AgriLife Research farm. Ten fiber samples were collected from each plot varying in boll numbers and regions within the plant and compared against a machine harvested sample. Fiber quality testing was done using High Volume Instrument (HVI) and Advanced Fiber Information System (AFIS). Statistical analyses inclusive of Analysis of Variance (ANOVA) and Best Linear Unbiased Prediction (BLUP) and correlations among fiber properties were performed. It was concluded that the best boll sampling method for accurate fiber quality estimation included a mixed sample of at least 25 bolls picked from all regions of the plant. A statistic to identify the least variable genotype was calculated using the difference between top and bottom bolls. It was concluded that the extent of variability within a plant for fiber length and length uniformity are genotype dependent. Correlation analyses revealed strong relationships among fiber length uniformity, strength, UHML, maturity ratio, and fineness. Strong negative relationships of fiber length measurements with short fiber content and immature fiber content were observed. Correlation analysis within the bottom and top bolls of the plants revealed opposite trends in fiber relationships.