Phenotypic Characterization of 16 Accessions of Sunn Hemp in Florida

• Published in: Agronomy journal 2016-11, Vol.108 (6), p.2417-2424
• Main Authors: Cho, Alyssa H., Chase, Carlene A., Koenig, Rosalie L., Treadwell, Danielle D., Gaskins, Jeremy, Morris, J. Bradley, Morales‐Payan, J. Pablo
• Format: Article
• Language: English
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2015.0531

Adoption of sunn hemp (Crotalaria juncea L.) as a cover crop has been limited primarily due to the availability of seed sources, leading to high seed costs and unreliable supplies. Seed production in Florida with the commercially available sunn hemp cultivar Tropic Sun has been largely unsuccessful. An experiment was designed to evaluate 16 accessions of sunn hemp for potential commercial seed production in Florida at three planting dates (May, June, July). Vegetative and reproductive characteristics were evaluated to provide baseline information for future development of a cultivar of sunn hemp that could produce seed in Florida with desirable cover crop attributes. The results indicate that the sunn hemp accessions could be separated into two groups. Regardless of planting date, accessions in Group 1 (PI 234771, PI 248491, PI 295851, PI 337080, PI 468956, PI 561720, PI 652939) displayed desirable cover crop characteristics, such as high biomass production and leaf area. Accessions in Group 1 had a short‐day flowering response and produced few to no pods and seeds. Group 2 accessions (PI 207657, PI 250485, PI 250486, PI 250487, PI 314239, PI 322377, PI 346297, PI 391567, PI 426626) were less sensitive to photoperiod, were generally smaller plants because of earlier transition to reproductive growth, and produced more seedpods and seeds. Seed production was generally better when seeds were sown at the earliest date. It appears that in Florida, sunn hemp accessions that are capable of flowering in summer rather than fall have greater potential for seed production. Core Ideas Based on vegetative and reproductive characteristics sunn hemp accessions could be divided into two groups. Group 1 accessions produce more shoot biomass and have a short‐day flowering response. Flowering occurs in fall when effective pollinators are absent. Group 2 accessions are less sensitive to photoperiod. Group 2 accessions flower in summer when effective pollinators occur and successfully set seed.