Induction of potato systemic resistance against the potato virus Y (PVYNTN), using crude filtrates of Streptomyces spp. under greenhouse conditions

The potato virus Y (PVY) is considered one of the most important viruses in terms of both economical and biological impact. Potential of using three different Streptomyces spp. crude filtrates (SCF) to induce of resistance against tuber necrotic strain of potato virus Y (PVYNTN) in four potato cultivars namely, Spunta, Nicola, Selatar, and Diamant, were evaluated. Foliar spraying of Streptomyces netropsis DSM 40093 (SCF7), S. ambofaciens (SCF11) and S. actuosus (SCF20), applied separately on potato cultivated in pots, showed various inhibitory activities against PVYNTN infection in all the potato cultivars. SCF20 was the most effective one, as expressed by (100%) reduction of apical necrosis symptoms on potato cv. Spunta, Nicola, and Diamant leaves under greenhouse conditions. Application was done 7 days before virus inoculation with PVYNTN (DBVI) and 7 days after inoculation (DAVI). The concentration of PVYNTN in treatments was significantly reduced than in the untreated PVYNTN infected plants as detected by DAS-ELISA (expressed by decreasing in OD value). Expression of PR-1b gene was detected 21 (DAVI) in all SCF11-treated cultivars but was not expressed in healthy and infected control plants. Gas chromatography-mass spectrometry (GC-MS) analysis of S. actuosus (SCF20) ethyl acetate extract revealed the majority of fatty acids (FAs) and their derivatives, Citroflex A, Hexanoic acid, anhydride, Hexadecanoic acid, Hexadecanoic acid, ethyl ester, and Diisooctyl phthalate which suggested to act as elicitor molecules for induction of systemic acquired resistance (SAR). Overall, the application of culture filtrates of Streptomyces has the potentiality to be used as inducer against PVYNTN infection.