Analysis of Seed Vigor Responses in Soybean to Invasive Silver Carp (Hypophthalmichthys molitrix) Protein Hydrolysate Treatments

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.