Update on Cotton Race-Stock Screening and Phenotypic Characterization

Future progress in cotton breeding can be achieved if sufficient genetic variability remains within breeding stocks.  Genetic diversity in cotton has been narrowing in recent years with many successful commercial varieties sharing common parents and grandparents. As well as limiting the potential to improve fiber quality and yield, this reduced genetic diversity in commercial cultivars has also in some cases made them more susceptible to diseases and insects. Obsolete varieties, Texas race stocks and other wild cottons contain a wealth of genetic material when compared to the inbred commercial cultivars in use today.  For several years, the Cotton Improvement Program at Texas AgriLife Research in Lubbock has maintained a project to develop and refine effective screening methods for some economically important characteristics and to identify and make available to breeding programs useful, heritable traits.  In some cases, existing screening methods were too cumbersome to screen large numbers of cottons quickly, or simply did not exist.  Seed stocks of the obsolete and wild cottons have been increased, providing seed for testing and acting as a backup for other collections around the world.

Ongoing screening is being conducted for seedling growth characteristics, including root measurements, which could contribute to drought tolerance; thrips resistance using thrips colonization and leaf surface area reduction as indicators; and Lygus bug resistance using caging and evaluation of oviposition behavior and fruit damage. In two areas, salt tolerance and thrips resistance, research has progressed to breeding stock development.  Seed stocks of 208 accessions were increased in 2007-2009, bringing the total number increased since project inception to 739.  Numbers of cottons screened for drought tolerance, salt tolerance, thrips resistance and Lygus resistance were 65, 21, 151, and 37, respectively.  The phenotype and lint quality of each accession increased are also characterized and documented.