Influence of Fungicidal Seed Treatments against Pathogen Complex Found on Paddy Seed and Their Effects on Seedling Germination, Growth, and Plant Vigor

A paddy (Oryza sativa) seed treatment study was conducted by the Plant Pathology Department, GRDB, RRS, Burma to evaluate the effectiveness of eight fungicides [Amistar Xtra 28SC, Saaf 75 WP, Glory 75WG, Tridium 70WG, Antracol 70WP, Rodazim 50 SC, Carbendazim 50SC and Manzate Pro Stick TM], at varying rates, along with a healthy check and untreated control, on germination and seedling vigour of paddy, and identifying suitable fungicides to be used as pre-sowing seed treatment. Trials were carried out under laboratory, potted and field conditions. A completely randomized block (CRD) was used for the laboratory and pot trials and randomized complete block design (RCBD) was used for the field trials, with three replicates. These trials were conducted in both rice growing seasons (Spring and Autumn) in Guyana during 2020 and 2021. Dry seed examination and blotter test unearthed the presence of four dominant pathogenic genera (Curvularia lunata, Bipolaris oryzae, Pyricularia oryzae and Aspergillus spp). from the paddy seeds before being treated and in the untreated control. The results of the germination test during 2020 showed variability among treatments, percentage germination ranged from 61% in seeds treated with Amistar Xtra 28 SC 3.7ml/L to 91% in seeds treated with Saaf 75 WP 5.6g/L. While in 2021 the percentage germination ranged from 79% in seeds treated with Tridium 70 WG 4.3g/L to 95% in seed treated with Saaf 75 WP 5.6g/L. Results from the in vitro studies showed seeds treated with Saaf (3.1g/L and 5.6g/L), Manzate Pro Stick TM (3.7 g/L), Glory at 12.4g/L, Rodazim (at 3.7ml/L) and the healthy control produced seedlings with taller shoots, longer roots and ultimately the higher seedling vigour at 14 and 21 days after treatment as compared to other treatments and the untreated control. Similarly, under potted condition seed treated with Rodazim (1.2ml/L and 3.7ml/L), Saaf (5.6g/L) and Glory (7.4g/L and 12.4g/L) demonstrated SVI compared to the other treatments and the untreated control. Further, under field condition the three fungicides viz. Rodazim, Manzate and Glory found to be promising in previous trials were selected and evaluated against an untreated control. Data collected revealed no significant difference among any of the treatments for grain yield, number of tillers/m2, plant height, the weight per 1000 grain nor the number of unfilled grains per panicle. However, treatment with Manzate Pro Stick TM (3.7 g/L) produced the largest number of filled grains as compared to the other treatment and control. It is therefore recommended that farmers should employ seed treatment prior to sowing if do not have clean, certified disease free seeds and use the paddy seed treatment [Saaf (5.6g/L), Manzate Pro Stick TM (3.7 g/L), Glory at (12.4g/L), Rodazim (3.7ml/L)] as a method of controlling seed borne pathogens, enhancing germination, seedling vigour and ultimately improving productivity.