Irradiation and organic grain protectants for enhancing strorability of rice seeds

Abstract

The present study entitled “Irradiation and organic grain protectants for enhancing storability of rice seeds” was carried out in the Department of Seed Science and Technology, College of Agriculture, Vellayani during 2023-2024, with an objective to standardization of the dose of gamma rays for irradiation and organic grain protectants to enhance the storage life of rice seeds. The study was divided into two experiments which were conducted in Completely Randomized Block Design (CRD) with three replications. In the first experiment, the seeds were irradiated with five different doses (100 Gy to 500 Gy) at Kerala Agricultural University, Thrissur. Another set of seeds were treated with five different organic grain protectants [Arka (Calotropis gigantea) leaf powder-12.5g, Neem (Azadirachta indica) leaf powder-12.5g, Pongamia (Pongamia pinnata) leaf powder-12.5g, sweet flag (Acorus calamus) rhizome powder- 5g, Arappu (Albizia amara) leaf powder-12.5g]. Treated seeds were then shade dried and packed in cloth bags and stored for ten months along with control. In the first experiment, the damage percentage recorded was 20.333 percent, 10.667 percent, 2.333 percent and 0.333 percent in treatment T1 (100 Gy), T2 (200 Gy), T3 (300 Gy) and T4 (400 Gy) respectively in the tenth month of storage. However, in control, the seed damage was observed varied from 0.333 % in initial month to 62.333 % in tenth month of storage with a seed weight loss of 16.253 percent. The treatment T5 (500 Gy) was not affected till the end of ten months of storage. The storage pest infested during ten months of storage period were lesser grain borer (Rhyzopertha dominica), rice weevil (Sitophilus oryzae) and Angoumois grain moth (Sitotroga cerealella). The rice seeds irradiated with 400 Gy and 500 Gy gamma rays were not affected by storage pest throughout the storage period. The infested mycoflora Aspergillus flavus, was recorded highest in control 69.333 % at the end of storage. Seeds irradiated with 400 Gy and 500 Gy were not infested by mycoflora till the end of storage period. Germination parameters were studied in the undamaged seeds to study the effect of irradiation in seed aging. Among the different doses of gamma irradiation, T1 (100 Gy) resulted highest seed germination percentage (82.33 %), germination energy (77.70%), root shoot ratio (0.896), germination index (502.62), vigour index (1023.00), seedling shoot length (12.33 cm) and seedling root length (12.23 cm). All the germination parameters showed increased value at lower doses of gamma rays (100 Gy, 200 Gy and 300 Gy) and declined at higher doses (400 Gy and 500 Gy) compared to control. Morphological evaluation of gamma irradiated seeds grown in pots showed that morphological parameters did not vary significantly from the control in treatments with gamma doses 100 Gy and 200 Gy. Gamma irradiation at 300 Gy also did not show variation in morphological parameters compared to control except for germination percentage. But progressive decrease in all morphological parameters was observed for the treatments with gamma doses 400 Gy and 500 Gy. Reduction in germination percentage, panicle length, panicle number and grain per panicle was observed when compared to control. In second experiment, among all organic grain protectants treatment T4 [Sweet flag (Acorus calamus) rhizome powder] resulted least seed damage percentage (5.667%). The damage percentage was observed from fourth month of storage in treatment T1 [Arka (Calotropis gigantea) leaf powder], T2 [Neem (Azadirachta indica) leaf powder], T3 [Pongamia (Pongamia pinnata) leaf powder], T5 [Arappu (Albizia amara) leaf powder] and recorded 12.333 per cent, 13.333 per cent, 8.667 per cent and 20.333 per cent, whereas control was recorded maximum damage percentage with 62.333% at tenth month of storage. The storage pest infestation was lowest in T4 [Sweet flag (Acorus calamus) rhizome powder]. The mycoflora infestation was maximum in control (69.33%) and least in sweet flag (Acorus calamus) rhizome powder (10.16%) in tenth month of storage. Among the different organic grain protectants sweet flag (Acorus calamus) rhizome powder recorded the highest seed germination percentage (82.00%), germination energy (81.00%), germination index (541.00), vigour index (1029.20), seedling shoot length (13.03 cm) and seedling root length (12.40 cm). In this study gamma irradiation proved to be an effective method for controlling storage pest and mycoflora infestation during storage in rice seeds. However, the treatment with higher doses 400 Gy and 500 Gy affected the germination parameters negatively and produced some abnormalities in the progeny. Hence, gamma irradiation at 100 Gy to 300 Gy can be recommended for safe storage of rice seeds. Among the organic grain protectants sweet flag (Acorus calamus) rhizome powder exhibited higher values of germination parameters and least infestation of storage pest and mycoflora till the protectants are eco-friendly methods in enhancing the storage life of rice seeds and were effective in controlling the storage pests. Since gamma irradiation requires special facilities for seed treatment, organic grain protectants will be better technology for small scale farmers.