|Williams, Mary - Mimi|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2008
Publication Date: 8/20/2008
Citation: Williams, M.J., Sinclair, T.R., Mislevy, P., Quesenberry, K.H., Blount, A.S., Coleman, S.W. 2008. Photoperiod sensitivity of rhizoma peanut germplasm. Agronomy Journal. Interpretive Summary: Rhizoma perennial peanut is a tropical forage legume with nutritive value similar to alfalfa that has gained commercial acceptance, primarily as a hay crop, in the Gulf Coast region of the US. Due to lack of significant seed production, breeding efforts with rhizoma perennial peanut are limited to evaluation of new germplasm from other countries. Current breeding efforts are targeted for greater tolerance to high water table and cold temperatures, but observational evidence suggests that, similar to tropical grasses, forage production declines during the fall more than warranted by low temperatures. It is thought this decline is due to shorter daylength that occurs during the fall and winter. We wanted to see if rhizoma perennial peanut was sensitive to shorter daylength by first testing material in a greenhouse type of environment and then in the field by extending daylength during fall and winter with lights. In the controlled environment study, some lines tested increased forage production by almost five fold the daylength was extended from a minimum of about 12 hours to 18 hours. In the field study, field forage yield was increased (2-3 fold) by a 15 hour extended light treatment during the fall. These studies show that plant breeders can increase rhizoma perennial peanut yield in the fall and winter by selecting lines that are not sensitive to daylength.
Technical Abstract: Observation suggested that aboveground dry matter (DM) production of rhizoma perennial Peanut (RPP; Arachis glabrata) declines during the fall more than warranted by low temperatures. The objective of this study was to determine if RPP exhibited photoperiod sensitivity under controlled environmental conditions (natural vs 15- or 18-h extended daylength) and field conditions (natural vs 15-h extended daylength). Rhizomes from six lines of RPP germplasm (cultivars Florigraze and Arbrook, Florida lines Ecoturf and Arbrook Select, and PI 262826 and PI262839) were established in pots and maintained in controlled environmental conditions where natural and extended photoperiod regimes were imposed starting 21 Sep. 2000 until the following May. Aboveground dry matter (DM) was harvested 5 times during that interval. Plants (n=4 replicates) were transplanted into the field so that they received natural light or the photoperiod extended between 20 Sep. 2001 and 19 Apr. 2002 and again during the winter of 2002-2003. Cover and aboveground DM were determined on approximately 9-wk intervals. In the controlled environment study, five of the six selections responded similarly with a yield increase for the 15-h treatment (< 4 fold) and the 18-h treatment (< 5 fold) with the maximum effect occurring when natural photoperiod was shortest. In the field study cover was enhanced by extended light treatment during the first winter, but there was no difference by about 12 months after planting. Aboveground DM yield was increased (3-2 fold) by extended light treatment during the fall of both years. These studies suggest that selection for late and early season aboveground DM production in RPP will select for photoperiod insensitivity.