Enhancing Canola Seed Quality Under Rhizoctonia solani Stress Through Seed Pelleting

Canola (Brassica napus L.) seeds are small and exhibit significant variability in size, resulting in a decreased emergence percentage (EP) and reduced uniformity in the field. Additionally, canola seedlings are susceptible to Rhizoctonia solani in the early growth stages. This research aimed to investigate the effects of seed pelleting with different fillers, binders and biomaterials on canola's emergence quality, early growth and seedling health. The first experiment was conducted in the seed laboratory and greenhouses. The treatments included four types of fillers: calcium sulphate + zeolite (CS + Z), calcium sulphate + talc (CS + T), calcium sulphate + calcium carbonate (CS + CC) and calcium carbonate + bentonite (CC + B). Additionally, three types of binder materials were evaluated: gum arabic, selenium dioxide and carboxymethylcellulose. The results showed that the composition of carboxymethylcellulose as a binder, combined with a filler mixture of calcium sulphate and calcium carbonate, significantly increased the emergence rate and early growth compared to non-pelleted seeds. Furthermore, this seed pelleting treatment did not adversely affect seed emergence. The highest emergence rate (0.185), leaf area (3.94 cm2), shoot growth rate (0.019 cm day−1), leaf chlorophyll content (41.03), plant length vigour index (3543), root value (1.35) and plant weight vigour index (26.66) were observed in seeds pelleted with a composition of CS + CC (200 g calcium sulphate + 50 g calcium carbonate per 10 g seed−1), and carboxymethylcellulose (30 g carboxymethylcellulose per 10 g seed−1). Because the seeds pelleted with this combination had the highest sphericity, pelleting efficiency and the lowest fragmentation number and dissolution time. The second experiment evaluated the effects of four levels (0, 500, 1000, 1500 and 2000 mg g−1) of extracts from Thymus vulgaris, Lavandula officinalis, Cinnamomum verum and Salvia rosmarinus. The results showed that T. vulgaris extract at a concentration of 2000 ppm significantly controlled the growth of R. solani. The third experiment was conducted in the seed laboratory and greenhouses. The treatments included pelleted seeds with the same superior treatment as in the first experiment (CS + CC (200 g/10 g−1 + 50 g/10 g−1) + CMC2 (30 g/10 g−1)), to which four medicinal plant extracts (T. vulgaris, L. officinalis, C. verum and S. rosmarinus) and five concentrations (0, 500, 1000, 1500 and 2000 ppm) were added. The results showed that the highest percentages of emergence (67%), emergence rate (0.085 seeds per day), leaf number (9.6), shoot dry weight (0.42 g), root dry weight (0.35 g) and seedling vigour index (57.49) were observed in seeds pelleted with 2000 ppm T. vulgaris extract. In conclusion, the use of a combination of calcium sulphate, calcium carbonate and carboxymethylcellulose for seed pelleting, alongside T. vulgaris extract as an environmentally friendly antifungal agent, has been shown to enhance the quality of canola seeds and improve the disease resistance of canola seedlings in soils infested with R. solani.