Comparison of three stability measures in guayule

Guayule (Parthenium argentatum Gray), a desert shrub native to the Chihuahuan desert of North America, is being domesticated as a potential rubber source. Two Uniform Regional Guayule Variety Trials were conducted in eleven locations using a total of twelve entries. Data from each of these trials were used to compute stability coefficients using the methods of Finlay and Wilkinson (1963), Eberhart and Russell (1966) and Zhang and Geng (1986). Results and interpretations of these methods were compared. Zhang and Geng's method was the most useful because it allowed comparison of entries grown in the two different yield trials. Using this method, the following conclusions were reached: Arizona breeding line AZ101 was significantly less stable than average in biomass and resin yield, '11605' was less stable than average for percent rubber, and 'Cal-6' and 'Cal-7' were less stable than average for rubber yield. Six entries ('N565', 'N576', '11591', '11605', '11619' and '12229') were significantly more stable than average for biomass yield, resin yield and rubber yield. Germplasm line N396 was also more stable than average for resin yield and percent resin. AZ101 was more stable than average for rubber percentage and rubber yield. Over all entries, there was a negative correlation between stability and yields of resin and rubber.