Elicitor-Active Oligosaccharides from Algal Laminaran Stimulate the Production of Antifungal Compounds in Alfalfa

Natural polysaccharides w ere exam ined for their activity as elicitors o f phytoalexins and flavonoids in alfalfa cotyledons. O nly tw o polysaccharides, lam inaran and pectic acid, had e lic­ itor activity. Laminaran, w hich was m ore active than pectic acid, was hydrolyzed by tunicase and the hydrolysate was subjected to charcoal and gel filtration colum ns. Introduction o f the pyridylam ino group into the elicitor-active o ligosaccharides w as attem p ted in order to facili­ tate isolation . T he pyridylam ino derivatives w ere found to exhibit higher activity than the original oligosaccharides. T heir liquid chrom atography m ass spectrom etry (L C -M S) analysis revealed that the elicitor-active principles form tw o ion clusters w ith the sam e m olecular weights, m/z 1070 and 1232. T heir high perform ance liquid chrom atography (H PL C ) analy­ sis show ed three main peaks. T he individual peaks (L N -1, 2, 3) w ere co llected and subjected to the alfalfa cotyledon assay. L N -3 show ed the highest activity (m inim um effective con cen ­ tration, 0.8 jig/ml).