Cotton Yield Component Indices: 1. Seed-Score

Improving yield is the primary objective of most if not all cotton breeding programs.  Yields may be improved by volume of selection/testing, improved testing precision, statistical tools, and/or by utilizing yield components.  The simplest component model for lint yield in cotton is number of seed per area (SPA) times the weight of lint per seed (LI).   Since more plant energy is required to produce seed than fiber, lint yields produced with relative preference of LI over SPA are preferred.  We have used the relative contributions of SPA and LI to lint yield in strain tests for several years to subjectively characterize a yield component rating (YCr) for each strain.  Since large seed tend to have higher LI, seed size (SI) is considered to some extent in YCr.  YC1 was developed as an objective index to characterize yield components.  YC1 incorporates user-defined proportions of SI, LI and lint percentage (L%) into an index, which utilizes a similar approach used in Quality Score (QS).  Standard deviations for SI, LI, and L% were determined from 20+ years of variety and strain tests in Arkansas.  We found that YC1 based on 50% SI and 50% LI were highly correlated with YC1 based on 50% SI, 25% LI, and 25% L%.  Also, YC1 values were closely aligned with the subjective YCr – even though YC1 does not consider SPA.  YC1 may provide a method to identify lines which possess optimum SI and produce physiologically efficient lint yields.