2007 Annual Report 1a.Objectives (from AD-416) 1. Identify and/or develop novel cotton germplasm with tolerance/resistance to Fusarium Wilt (FOV), and to develop molecular markers associated with FOV resistance to assist in the breeding process for disease tolerance/resistance in cotton. 1b.Approach (from AD-416) Upland and Pima germplasm will be evaluated as parental material in inoculated greenhouse and infested field conditions. Crosses will be initiated to improve the breeding germplasm for agronomic and fiber quality traits. Replicated experiments in at least two locations will be conducted on advanced breeding progeny. Potentially useful germplasm will be jointly released to the public by USDA-ARS and Cotton Incorporated. DNA will be extracted from the genetic populations and screened with microsatellite markers to identify markers that may tag FOV resistance. These will be published and placed in public databases for use in marker assisted selection. Documents Reimbursable with Cotton Inc. Log 29833. 3.Progress Report This report serves to document research conducted under a reimbursable agreement between ARS and Cotton Incorporated, entitled Traditional and Molecular Breeding for Disease Resistance (Fusarium Wilt, Fusarium Oxysporum F. Sp. Vasinfectum (FOV)) in Cotton. Additional details of the research can be found in the report for the parent CRIS 5303-21220-003-00D, Western Integrated Cropping Systems Research. Development of disease resistance to a recently discovered and highly virulent strain of Fusarium wilt (FOV race. 4)in cotton in the San Joaquin Valley of California is critical to ensure the profitability of cotton production in the region. This project was initiated in 2006 to identify and/or develop resistant germplasm and molecular markers associated with Fusarium wilt (FOV) resistance. Upland/Acala and Pima cotton varieties and germplasm were screened and designated as susceptible, tolerant, or resistant. Crosses of selected varieties were used to create diverse populations. Eight sources of mapping populations, which include tolerant Acala Shafter by susceptible Upland, Pima PS 6 by Pima 89590, Acala ‘NemX’ by Pima ‘Phytogen 800’, Pima PS 6 by Acala NemX, and Pima DP744 by Pima Phytogen 800, have been developed to facilitate the study of resistance to races 1 and 4 of FOV, as well as to the root-knot nematode. Efforts continue to complete DNA isolation of the developed populations, representing approximately 2,000 single plants or family lines, for the identification and development of molecular markers associated with FOV resistance. Additional progeny from selected populations (susceptible and resistant to FOV race. 4)screened in a preliminary greenhouse study were identified for DNA-marker analysis with the assistance of collaborators at the University of California at Riverside. Seventy molecular markers of known chromosome location were evaluated in 48 progeny-combinations of plants, arising from six populations, and designated as susceptible or resistant to FOV races 1 and 4. Preliminary analyses (FOV and molecular marker data) identified markers having minor to moderate associations with resistance or susceptibility to FOV race 1. Greenhouse and field evaluations to identify and confirm associations between markers and resistance to FOV races 1 and 4 continue, with plans to test approximately 1000 markers on selected progeny from designated mapping populations. The identification and development of molecular markers linked to FOV resistance will facilitate efficient incorporation of resistance genes into elite cultivars. Once molecular markers linked to resistance genes are developed, wide selection for Fusarium wilt resistance in cotton breeding can be achieved through marker-assisted selection. Activities during this project were documented through presentations at national and international meetings, publication of a peer-reviewed journal article and numerous proceedings, and through frequent contacts with collaborators.