Analysis of Seed Vigor Responses in Soybean to Invasive Silver Carp (Hypophthalmichthys molitrix) Protein Hydrolysate Treatments
S. P. Thomson
Department of Food Science, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907, USA
A. M. Liceaga *
Department of Food Science, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907, USA
B. M. Applegate
Department of Food Science, 745 Agriculture Mall Drive, Purdue University, West Lafayette, IN 47907, USA and Department of Biology, Purdue University, 225 South University Street, West Lafayette, IN 47907, USA
R. D. Martyn
Department of Botany and Plant Pathology, Purdue University, 915 W State Street, West Lafayette, IN 47907, USA.
*Author to whom correspondence should be addressed.
Abstract
Aim: To produce fish protein hydrolysates (FPH) from invasive silver carp (Hypophthalmichthys molitrix) under controlled hydrolysis conditions, and to examine the effects of FPH on seed vigor, using standard vigor tests.
Methodology: Soybeans were treated with FPH hydrolyzed for 1, 5.5 and 10 hrs with papain (FPH-Pa), pepsin (FPH-P) and trypsin (FPH-T), respectively. Overall vigor tests (accelerated aging and warm and cold germination dry weight, height, total phenolics and guaiacol peroxidase assessment-GuPx) were compared to a distilled-water control over a 12-day germination period.
Results: Seeds treated with FPH-P and FPH-Pa at 1 hr (23% degree of hydrolysis) elicited the greatest growth responses. FPH-Pa at 1 hr increased (P=0.05) weight (1.38 g) and height (53 mm) compared to water control (1.25 g and 46.8 mm, respectively). FPH-Pa at 1 hr also had the highest GuPx values, which are indicative of lignification. FPH-Pa appeared to stimulate lignification and thus enhance weight and height of the seedling. FPH-P elicited the greatest phenolic response, with the highest total phenolic content on day 4 (1.27 mg GAE/g FW) and day 12 (1.43 mg GAE/g FW) compared to water control (0.59 mg GAE/g FW on day 4, 1.10 mg GAE/ g FW on day 8). Higher phenolic content may have protected against oxidation during accelerated aging vigor test, resulting in higher germination rates (53.8% germination) for soybeans primed with FPH-P at 1 h compared to water controls (32.2% germination). Most FPH treatments increased germination under warm conditions, compared to water control. GuPx values overall were higher in FPH-treated soybeans.
Conclusion: Results suggest that the use of FPH produced with the enzymes papain and pepsin at 1 hour of hydrolysis are comprised of free amino acids and peptides that are beneficial to the stimulation of the proline-linked pentose phosphate pathway, which enhanced the vigor parameters measured.
Keywords: Silver carp, fish protein hydrolysates, seed vigor, seed treatment