Submitted to: Peanut Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/6/2009
Publication Date: 7/2/2009
Citation: Rowland, D., Beasley, J., Faircloth, W.H. 2009. Genotypic patterns of peanut (Arachis hypogaea L.) phenology and the inability of current irrigation scheduling methods to modify them. Peanut Science. 36:133-137. Interpretive Summary: It is often assumed that currently grown peanut varieties do not differ very much in their growth and reproduction because they come from a similar genetic background. However, there is no known information about the amount of differences among varieties that may exist. This study measured several growth traits, reproductive output, and water-use efficiency among eight different peanut varieties and how irrigation treatment affected any differences that may have existed. It was found that irrigation had no effect on the traits that were measured, but that there was a great deal of variation in traits among varieties. Varieties differed in leaf and canopy characteristics, reproduction, and water-use efficiency. In addition, some of the growth characteristics related to the development of the plant canopy were good predictors of overall yield. This study documented important growth and reproductive differences among peanut varieties that could ultimately be used to improve yield in new varieties in the future.
Technical Abstract: By understanding differences among peanut (Arachis hypogaea L.) cultivars in growth and phenology it becomes possible to predict differences in yield potential or performance in variable environments. Despite the importance of this information, very little quantifiable 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 treatment affected the development in these traits through the season in 2004 and 2005. As expected, climate differences among years significantly affected growth habit across cultivars, while differences throughout the season within years illustrated changes in phenology as the crop developed. However, the irrigation environment, despite differences in total water applied during the season, had no effect on any of the measured traits. Although the expectation of trait differences among cultivars was low due to low genetic variability, significant differences existed in all of the measured traits. Further, the lack of significant interactions between year and cultivar for most of the plant growth and reproductive characteristics showed 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, with the Georgia-01R cultivar having the highest values overall. Reproductive characters showed variability among cultivars that was likely genetically based because patterns of variation were similar across years. Among cultivars, Georgia-01R had a significantly greater number of flowers per plant than Georgia-02C, Tifunner, and Carver, with the other four cultivars having intermediate values. Reproductive differences were also illustrated by differences in harvest index. The cultivar Georgia-03L had the highest harvest index value than any of the cultivars except Georgia Green; while at the opposite spectrum, Georgia-01R and Tifrunner had the lowest harvest indices except for AP3, C99R and Georgia-02C which had slightly higher numerical values. 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. These sources of variability in growth and phenology in peanut and their linkage to yield can ultimately be utilized to maximize production.