Genotypic variation for root penetration of a soil pan

Cotton production has increased dramatically on the Coastal Plain of the so utheastern USA since eradication of the boil weevil (Anthonomus grandis [Bo h.]) in the late 1980s. Most of the cotton production in this area occurs o n soils possessing subsoil pans. Soil pans limit root growth, requiring mec hanical disruption to increase the root zone and facilitate cotton growth. Mechanical amelioration of a soil pan has several disadvantages including e xpenses for equipment and energy, equipment to break up the pan may not be available, and the effects of mechanical disruption are temporary and contr ibute to soil erosion. The need for soil pan disruption might be eliminated or reduced with cotton germplasm capable of rooting through high strength soil. Our objective was to identify germplasm with superior rooting ability and thereby initiate breeding efforts incorporating this trait into cultiv ars. Cultivars and Pee Dee germplasm lines were evaluated at Florence, SC f or 2-yr without irrigation for root penetration of a naturally occurring so il pan. Roots were excavated at maturity and rated on a 1-5 scale based on magnitude of the root penetration of the pan. Combined analysis of variance over years revealed significant genotypic variation and a genotype x yr in teraction for root penetration of the pan. Despite the genotype x yr intera ction, we identified germplasm that could partially root through the pan. A dditionally, we were able to eliminate those genotypes with poor rooting ch aracteristics from further consideration as parents in the breeding program . Cultivars with ability to penetrate a soil pan would make a valuable cont ribution to sustainable cotton production systems for the USA and developin g countries.