Impact of cotton leaf and bract characteristics on cotton leaf grade

The remnants of leaf material in harvested cotton (Gossypium hirsutum L.) can signifi cantly increase leaf grade values, resulting in discounts to the producers and increased ginning cost. The impacts of leaf and bract pubescence and leaf and bract area of diff erent cotton cultivars were studied on cotton leaf grade during 2011 and 2012, and the accuracy of industry leaf hairiness rating was evaluated. Three replicated trials were conducted during 2011 in Texas in the Lower and Upper Coastal Bend and the Blackland Prairie, and Tifton, GA was added as a fourth location in 2012. Two separate commercial-scale (multi-acre) trials were conducted during 2011 and 2012 to compare leaf grade values of a smooth leaf cultivar Deltapine 0935 B2RF and a hairy leaf cultivar Deltapine 0949 B2RF. Results demonstrated that increased leaf and bract trichome density increased the propensity for greater leaf grades in small-plot and commercial fi eld trials. Leaf area and bract length were not diff erent among the cultivars at most of the locations, suggesting minimal relation with leaf grade. Pubescence quantifi cation indicated substantial variation in cultivars, and discrepancies between company-based rating systems; for example, semi-smooth cultivar Phytogen 499 WRF was found to have denser trichomes compared with all smooth, semi-smooth, and hairy cultivars. Overall, this study identifi ed a detrimental relationship between leaf pubescence and leaf grade while other plant characteristics studied contributed little to greater leaf grades. Standardizations of leaf pubescence ratings among cotton cultivars will allow producers interested in improving leaf grade to accurately select their cultivar.