Seed invigoration studies in okra [Abelmoschus esculentus (L.) Moench]

Abstract

The study entitled “Seed invigoration studies in okra [Abelmoschus esculentus (L.) Moench]”was conducted at the Department of Seed Science and Technology, College of Agriculture, Vellanikkara, during 2022-2024. This research investigated the effects of osmopriming with PEG 6000 (13.5% at -0.25 MPa for six hours) and biopriming with Pseudomonas fluorescens @10g/kg on growth, yield, seed quality and seed longevity of five okra varieties—Aruna (V1), Anjitha (V2), Pusa-5 (V3), Salkeerthi (V4), and Varsha Uphar (V5).

The study comprised two experiments. Experiment 1 focused on the effects of priming treatments on the varietal performance of okra in terms of growth, yield, and seed quality, while experiment 2 examined seed longevity under storage conditions. Experiment 1 followed a Randomized Complete Block Design (RCBD) with three replications, resulting in 15 treatment-variety combinations. Seeds of the five okra varieties were subjected to three priming treatments: T1 (osmopriming with PEG 6000 solution at -0.25 MPa for six hours), T2 (Pseudomonas fluorescens at 10 g/kg of seed), and a control (non-primed seeds). Experiment 2 followed a Completely Randomized Design (CRD) with the same priming treatments and varieties replicated three times.

Seed initial quality parameters were assessed immediately after priming treatment. Among the varieties Salkeerthi (V4) achieved the highest germination rate followed by Varsha Uphar and showed superior performance over other varieties due to high seed vigour indices and lowest EC. The combination Salkeerthi-PF (V4×T2: 93.66 %) followed by Varsha Uphar-PF (V5xT2: 90.66%) showed superiority in seedling vigour and growth attributes of okra

In the Experiment 1, the results indicated that both priming treatments significantly enhanced field performance across all varieties compared to the control. Varieties displayed significant variation in growth, yield, and seed quality traits. Varsha Uphar (V5) emerged as the top performer for field emergence, early flowering plant height and seed yield per plant under priming conditions. Pusa-5 (V3) showed superior fruit weight and yield per plant, with the combination Pusa-5 x Pseudomonas

fluorescens recording the highest number of fruits per plant and Pusa-5 x PEG producing the highest fruit weight and yield. Salkeerthi (V4) exhibited the highest seed count per pod.

Among the treatments, T2 (Pseudomonas fluorescens) consistently demonstrated a greater positive impact on growth, fruit yield, and seed quality compared to T1 (PEG 6000 (13.5% at -0.25 MPa for six hours).

In the Experiment 2, storage study was conducted with the same five okra varieties, using the same priming treatments along with control. Seed quality parameters were monitored for six months. All varieties and treatments maintained germination rates well above the Indian Minimum Seed Certification Standard (IMSCS) threshold of 65 percent. However a progressive decline in seed quality was observed over time. This decline was evident in reductions in key traits such as shoot length, root length, seedling dry weight, vigour indices, and enzymatic activities including dehydrogenase, α-amylase, and catalase. Concurrently, negative trends were noted, with increases in parameters such as electrical conductivity (indicating membrane deterioration), mean germination time, time to 50 percent germination, seed moisture content, and the percentage of microflora contamination, all of which are indicators of seed aging and reduced vigour.

Among the varieties evaluated, Salkeerthi (V4) consistently emerged as the top performer in maintaining superior seed quality during the storage period followed by Varsha Uphar. This was particularly notable when the seeds were treated with T2 (Pseudomonas fluorescens). Seeds treated with T2 retained higher enzymatic activity, including significantly enhanced levels of dehydrogenase, α-amylase and catalase, which are critical for metabolic processes during germination. These enzymes are known to play essential roles in energy production, starch breakdown, and oxidative stress management, contributing to better seed vigour and viability. This superior performance highlighted the potential of biological priming with Pseudomonas fluorescens not only improved seedling vigour during cultivation but also mitigate the negative effects of storage, ensuring sustained seed quality over time.

The findings of this study highlighted the significant role of priming treatments in improving the growth, yield, and seed quality of okra varieties. Among the varieties studied, Varsha Uphar (V5) and Pusa-5 (V3) demonstrated superior field performance, with Pseudomonas fluorescens (T2) emerging as the most effective priming treatment.

Although Salkeerthi (V4) demonstrated superior initial seed quality, its field performance was comparatively lower, highlighting the role of environmental factors and genotypic traits in bridging the gap between seed quality and productivity.

Biopriming has demonstrated significant efficacy in maintaining seed viability and quality during storage. Notably, the okra varieties Salkeerthi and Varsha Uphar have shown exceptional resilience, consistently preserving seed quality parameters. These results underscored the potential of incorporating Pseudomonas fluorescens as a seed priming agent to enhance both okra productivity and seed longevity. Furthermore, research exploring the molecular mechanisms behind the observed enhancements in seed vigor and resilience, particularly focusing on enzyme activities such as dehydrogenase, α-amylase, and catalase, could offer a deeper understanding of the biological processes involved.