Characterization of New Populations in Sunn Hemp and Relationship of Their Traits to Yield.

Sunn hemp (Crotalaria juncea L.) is a green manure crop, which can be used in rotation schemes and promises to replenish organic matter in depleted soils. The breeding program for its adaptation in the climatic conditions of the continental U.S. has altered its physiology to produce smaller plants with early, uniform flowering and maturity that produce viable seed. Our objectives were to record any significant changes that happened over several cycles of recurrent selection among different populations and to determine which plant traits can be used to predict mature plant performance. Eight populations were planted in Tallassee and Shorter, AL and 13 characteristics were measured throughout their life-cycle. The traits measured were plant height at two and four weeks, days to flowering, leaf width and length as well as number of branches and stem diameter at the base and below the first flower, height at flowering, inflorescence length, height at harvesting, biomass and seed yield. The LSD t-tests at significance level 0.05 showed that leaf width and height at harvest became significantly smaller over several selection cycles and can be used to distinguish the populations based on their year of selection. Also, days to flowering has the highest correlation (r = 0.4389) to dry biomass followed by leaf width at flowering (r = 0.3768). This shows that plant size is being successfully reduced. Furthermore, plants that flower late as well as plants with wide leaves can be safely eliminated before harvest. This will allow for easier and faster evaluation of the remaining population, which will hasten the selection process.