Seed Development and Maturation Studies and the Impact of Different Threshing Methods in Sirukeerai (Amaranthus polygonoides L.) var. PLR 1

In developing countries, vegetable amaranth serves as an affordable alternative source of nutrition, particularly for vegetarian populations, as it provides carotenoids, proteins, vitamins, dietary fibre and a wide range of minerals. Seed processing is a fundamental component of any planned seed production, as it aims to improve seed quality characteristics. The study aimed to explore the impact of different threshing methods in Sirukeerai (Amaranthus polygonoides L.) var. PLR 1. The study was conducted with Sirukeerai (Amaranthus polygonoides) seeds. The field experiment (Kharif season) was carried out at the Department of Seed Science and Technology, Agricultural College and Research Institute, Madurai, Tamil Nadu, India. Ten spikes were harvested at five-day intervals from the date of tagging and designated as days after anthesis (DAA). The maturation status of seeds during developmental stages was evaluated using various growth parameters. Plants were subjected to three threshing methods: hand rubbing, beating with a pliable stick and tractor treading. The present investigation (2017–2018) on seed development and maturation in Sirukeerai (Amaranthus polygonoides L.) revealed that seeds attained physiological maturity at 30 days after anthesis. This stage was indicated by the fresh weight of spike (0.063 mg), dry weight of spike (0.019 mg), spike moisture content (36.33%), seed fresh weight (0.051 mg), seed dry weight (0.013 mg) and seed moisture content (18.63%). At 30 days after anthesis, maximum seed quality parameters were recorded, including germination (93%), shoot length (6.1 cm), root length (4.3 cm), dry matter production (7.21 mg/10 seedlings) and vigour index (967). After harvest at physiological maturity, freshly harvested spikes were used to evaluate the impact of different threshing methods on seed quality in Sirukeerai. Following fertilisation, moisture content initially increases during the early days, but subsequently decreases as seed development progresses, until equilibrium is reached with the surrounding environmental conditions. Hand rubbing recorded the highest threshing efficiency (62.4%) and germination (91%), followed by stick beating (85%) and tractor treading (75%). The superior performance of hand rubbing was attributed to reduced mechanical damage compared to stick beating and tractor treading, which caused seed coat injury and higher proportions of abnormal seedlings.