Effects of AMINOSA on PR2 and PR3 Enzyme Activities in Marigold (Tagetes erecta) Seedlings

Abstract

This preliminary biochemical screening study assessed whether AMINOSA, a combined formulation of amino acids (27% w/v; AAs) and salicylic acid (SA), alters PR2 (β-1,3-glucanase) and PR3 (chitinase) activity trends in marigold seedlings. Twenty-one-day-old Tagetes erecta L. cv. ‘Cana Yellow’ seedlings were foliar-sprayed with water, AAs, SA (0.5 or 1 mM), or AMINOSA at the  corresponding SA concentrations under either a single-spray program (sampling at 3, 7, 14, 21, and 28 days) or a repeated-spray program (sprays at 0, 3, 7, 14, and 21 days; sampling at 7, 14, 21, and 28 days), giving 46 treatment combinations. Leaves from 10 plants per treatment were pooled into one composite sample at each time point. The total protein content was quantified by BCA assay, and PR2 and PR3 activities were measured colorimetrically and expressed as U/mg protein. AMINOSA, especially with 0.5 mM SA, tended to produce higher PR2 and PR3 activity trends than AAs alone and water. Repeated spraying produced stronger mid-term PR2 peaks but greater late-stage variability. As each treatment-timepoint was represented by a single pooled composite sample without independent replicated means, the data were interpreted descriptively as trend-level biochemical profiling and were not subjected to inferential statistical analysis. AMINOSA with 0.5 mM SA under single spraying emerged as a promising option for sustaining later-stage PR2/PR3 trends, whereas repeated spraying may be further evaluated for a stronger mid-term PR2 response. These findings suggested that time-course PR2/PR3 profiling may help select candidate formulations and spray programs. The next step is replicated pathogen-challenge validation, followed by greenhouse or field confirmation.