Seed priming and foliar application of GA3 enhance disease control in tomato (Solanum lycopersicum L.)

Seed priming is an effective approach to control diseases in tomato. In this context, the current study was undertaken to confirm the effectiveness of seed priming. Treatments included (1) dry seeds; (2) seed priming with 1 mL of moringa leaf extract diluted with 30 mL of distilled water for 18 hr; (3) seed priming with 1% NaCl for 36 hr; (4) seed priming with 10% polyethylene glycol (PEG) for 12 hr; (5) 100 ppm GA₃; (6) 5% KNO₃ under dark conditions and (7) 1000 ppm thiourea for 24 hr; (8) distilled water for 12 hr and (9) 2% KH₂PO₄; and 0.5 mmol · L⁻¹ NAA at 4°C for 6 hr. The treated seeds were immediately broadcasted in separate nursery beds; after that 21-day old seedlings were transplanted in main plots. Foliar application of GA₃ at 100 ppm was sprayed 25 days after the seedlings were transplanted. Two-year results revealed that tomato seeds primed with 2% KH₂PO₄ in combination with GA₃, significantly reduced bacterial wilt, leaf spot, early blight, late blight and leaf curl diseases. Additionally, the combination of 10% PEG with GA₃ has emerged as the most effective for controlling collar rot disease. While PEG decreased the incidence of collar rot, KH₂PO₄ strongly reduced bacterial wilt. Target leaf spot, early blight and late blight were less severe when KH₂PO₄, KNO₃ and moringa leaf extracts were used, indicating that seed priming was more crucial for prevention of disease severity. Application of GA₃ also enhanced the effect of nearly all priming agents.