Variability for Morphological and Forage Quality Traits in Sericea Lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don] Cultivars
Type of Degreethesis
Agronomy and Soils
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Sericea lespedeza is a summer perennial forage legume adapted to the environmental conditions of the southeastern USA. Seasonal variations in temperature and genotype play an important role in early growth in this plant but their effect on late growth and regrowth needed to be ascertained. Morphological differences within the canopy have been observed among genotypes developed due to breeding efforts, but they have not been documented experimentally. A growth chamber study that included two experiments was undertaken to determine the effect of temperature and genotype influencing growth and regrowth in five cultivars of sericea lespedeza. Additionally, field experiments were conducted in 2008 and 2009 using five cultivars of sericea lespedeza namely Arlington, Okinawa, Serala, AU Lotan, and AU Grazer released in 1939, 1944, 1962, 1980, and 1997, respectively, to compare characteristics of plant parts such as leaves and stems in the canopy. The growth chamber study revealed that temperature had a significant (P < 0.01) effect-either linear or quadratic on all the traits measured for growth, regrowth as well as on the strata of the plant canopy. Cultivar-temperature interaction was significant for leaf dry weight, stem dry weight, total dry weight for first cut, height and stem thickness for second cut in the first experiment as well as for number of branches and leaf dry weight for upper portion in the second experiment. Results of the field study indicate that portion effects were significant (P < 0.001) in both years. Cultivar-portion interaction was significant mostly for the first year (2008) for stem dry weight, number of branches, branch stem weight and branch leaf weight for cut 1 and for stem dry weight, leaf dry weight, number of branches and total dry weight for cut 2. Shear force was the only trait for which interaction was significant in second year (2009). AU Grazer was the best or among the best cultivars for plant characteristics important from a production point of view. It ranked last (most pliable) or among the last cultivars in terms of characteristics that reduce pliability such as stem thickness and shear force. Okinawa was judged as the poor performer as it had more stem thickness and required more shear force, though it had a good proportion of leaves as compared to stems. Forage quality analysis conducted on the plants harvested from field in 2009 showed that there was little variation for all the traits measured such as Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), Acid Detergent Lignin (ADL), Tannin and nitrogen content across cultivars in leaves and stems of both plant portions. NDF, ADF, tannin and nitrogen values for upper and lower portion leaves were almost similar in both the cuts. ADL content for leaves was similar in both portions during growth while upper portion showed less ADL values during regrowth. NDF, ADF and ADL content was lower while tannin and nitrogen content was higher for the upper portion stems in both the cuts. New cultivars had lower NDF and ADF values than old cultivars while they had higher ADL values for upper portion stems and leaves during growth and regrowth. Tannin content was also higher in new cultivars. Nitrogen (protein) content was higher in old cultivars.