Assembly and field evaluation of a set of naturally occurring day-neutral cotton landraces under rainfed and irrigated conditions.

key messageThis study demonstrates that the US cotton landrace collection provides a rich resource of genetic resources for improved agronomic and fiber quality performance for future cotton improvement. The Gossypium hirsutum L. landrace collection (n ~ 2500), maintained by the US cotton germplasm collection in College Station, TX, USA, has been underutilized in cotton cultivar development programs. Underutilization is due to: (1) the common photoperiod sensitive growth habit of landraces that requires short day length to stimulate reproductive growth and (2) a lack of relevant phenotypic data for traits of interest in cotton production. In this study, the entire G. hirsutum landrace collection was first field evaluated in the Southeastern United States for photoperiod insensitivity. A total of 186 naturally occurring day-neutral accessions were identified and self-pollinated over 2-3 years to maintain heterogeneity and assemble a total of 216 accessions (including some component lines). Second, the 216 day-neutral accessions, along with eight elite, upland breeding lines and cultivars, were evaluated over 2 years for per se agronomic and fiber quality performance in replicated field trials under rainfed and irrigated conditions. On average, day-neutral landraces produced lint yield and lint percent lower than elite checks while they did not differ from elite checks for seed protein, seed oil, and fiber quality properties. Several day-neutral landraces were identified with desirable lint yield and fiber quality under rainfed and/or irrigated conditions. In total, this large evaluation of day-neutral landrace per se agronomic and fiber quality performance provides a much-needed resource to facilitate their efficient selection as breeding parents for cotton improvement.