Comparative Efficacy of Chemical and Biological Seed Treatments in Preserving Viability and Vigour of Discoloured Paddy (Oryza sativa L.) cv. Jyothi under Ambient Storage

Abstract

Grain discolouration in rice (Oryza sativa L.), driven by climate-induced temperature and humidity shifts, severely degrades seed viability and seedling vigour during storage. This study evaluated the physiological deterioration of discoloured seeds of paddy cv. Jyothi under ambient storage and compared the efficacy of synthetic fungicides and eco-friendly biological dressings. In a completely randomised design, seven treatments were evaluated: T1 (Carbendazim @ 2 g/kg), T2 (Mancozeb @ 2 g/kg), T3 (Trichoderma viride @ 10 g/kg), T4 (Bacillus subtilis @ 10 g/kg), T5 (Pseudomonas fluorescens @ 10 g/kg), untreated discoloured control (T6), and untreated healthy control (T7). The treatments had four replications and were monitored monthly for six months (0 to 6 months after storage [MAS]). Discoloured seeds initially (0 MAS) showed immediate physiological deficits, experiencing a 24.7% reduction in Seedling Vigour Index I (SVI-I: 974 vs. 1294) and a 7.1% reduction in SVI-II (1364 vs. 1468) compared to the healthy baseline. Over six months of ambient storage, the untreated discoloured control (T6) deteriorated rapidly, falling to 78.00% germination at 6 MAS, thereby failing the 80% Indian Minimum Seed Certification Standard (IMSCS). Conversely, Carbendazim (T1) was highly effective in arresting physiological decay, maintaining a superior 90.00% germination rate, 8.19 cm shoot, 20.84 cm root, and 0.186 g dry weight at 6 MAS (SVI-I: 2600, SVI-II: 1673; +43.3% SVI-I and +20.5% SVI-II over T6). Treatments with Trichoderma viride (T3) and Mancozeb (T2) also successfully preserved viability at 86.00% germination, with T3 achieving the highest seedling dry matter accumulation (0.188 g, +5.6% over T6) and SVI-II (1618, +16.5% over T6). These findings demonstrate that proactive seed dressings with systemic fungicides (Carbendazim) or biological agents (Trichoderma viride or Bacillus subtilis) are effective strategies for preserving physiological quality above the 80% certification threshold under ambient storage.