Enhancing Seedling Vigour, Disease Suppression and Productivity of Organic Linseed (Linum usitatissimum L.) through Azospirillum and Trichoderma harzianum Seed Treatments

Under organic cultivation, linseed productivity may be constrained by inadequate crop establishment and disease. This study evaluated the effects of Azospirillum and Trichoderma harzianum seed treatments on seedling vigour, Fusarium wilt incidence and yield. A laboratory experiment involving five treatments was conducted in a completely randomised design with four replications, while a field experiment involving eight treatments was conducted in a randomised block design with three replications during the 2017–18 rabi season at Assam Agricultural University, Jorhat. Treatments included hydropriming, microbial seed priming and soil application of T. harzianum. Germination, seedling growth, field emergence, disease incidence, yield attributes and seed yield were assessed. Under laboratory conditions, the combined seed-priming treatment T₅ recorded the highest germination (94.0%), compared with 80.5% in the untreated control. In the field, T₈, combining Azospirillum and T. harzianum seed priming with soil application of T. harzianum, recorded the highest field emergence (77.08%) and seed yield (9.71 q ha⁻¹), together with the lowest Fusarium wilt incidence (9.53%). Corresponding control values were 33.19%, 4.97 q ha⁻¹ and 26.19%, respectively. Treatment T₄, involving T. harzianum seed priming alone, produced 9.42 q ha⁻¹ seed yield and the highest harvest index (39.62%). Seedling vigour and several growth and yield traits were positively associated with seed yield, whereas disease incidence was negatively associated with productivity indicators. The results indicate potential benefits of T. harzianum-based seed treatment under the experimental conditions.