Genotypic Differences in Current Peanut (Arachis hypogaea L.) Cultivars in Phenology and Stability of These Traits under Different Irrigation Scheduling Methods

Understanding differences among peanut (Arachis hypogaea L.) cultivars in growth and phenology and the interactions with environment (G X E interactions) for these traits allows predictions for yield potential or performance in variable environments. Despite the importance of this information, very little quantitative data exists on the differences in aboveground growth, canopy architecture, and reproductive phenology for currently grown peanut cultivars. This study quantified differences in these traits among eight peanut cultivars and explored whether irrigation scheduling method (a factor of environment) affected the development in these traits through the season in 2004 and 2005. As expected, year to year variability in environmental conditions (most likely timing of rainfall events during the growing season) significantly affected growth habit across cultivars. However, the irrigation scheduling method, despite differences in total water applied among methods during the season, had no effect on any of the measured traits. This result is likely due to the fact that all methods were adequately supplying crop water demand. Genetic variability in all of the measured growth and phonological traits was strong despite the expectation that cultivars were genetically similar. Further, the lack of significant interactions between year and cultivar for most of the plant growth and reproductive characteristics also indicated a strong genetic component to these traits. One overall trend noted was that late-maturing cultivars had, on average, higher maximum values of LAI, stem mass, and leaf mass measured in the late growth period. Differences in isotopic composition were also strong among cultivars; the cultivars Georgia-02C and Tifrunner had significantly higher isotopic levels (and thus water-use efficiency) than Georgia-01R, Georgia Green, and AP3 across years. Aside from the obvious relationships between pod number and weight, the strongest predictors of reproductive output were late-season traits including leaf weight and LAI. This study successfully documented variability among peanut cultivars in many important traits linked to overall production.