Seed Priming: Triumphs and Tribulations K. Sivasubramaniam*, R. Geetha, K. Sujatha, K. Raja, A. Sripunitha and R. Selvarani Department of Seed Science and Technology Agricultural College and Research Institute, Madurai - 625 104 Priming has a long and chequered history dating back to time of Greeks. Seed priming has shown promise in enabling seeds to overcome biotic and abiotic stresses. Simple priming techniques using salt solutions gave way to elaborate and sophisticated media that warrant close monitoring. Biopriming of late has been practiced for making priming eco-friendly. Elucidation of molecular basis has shown the cause for invigoration but confirmation of DNA's role is yet to be done. Activation of preformed enzymes in providing vigor seems putative. Development of tests to determine primed seed quality is urgently warranted. Addressed in the paper are the ways and means for assessing the quality of primed seeds. Methods to store them for long periods are necessary conserve the benefits and market primed seeds to promote their use over time and space. Key words: Seed primimg, bioprimimg, priming techniques, advantages, disadvantages. *Corresponding author email: sstmac@tnau.ac.in Madras Agric. J., 98 (7-9): 197-209, September 2011 Review Consequent to germination, good crop establishment is a major constraint to crop production in the semi-arid tropics (Matarira et al., 2004). Seeds and seedlings often experience adverse physical conditions in the seedbed viz., mechanical resistance, high temperatures, high solute concentration at seed-water interface leading to peak osmotic potential and rapid soil drying and crusting (Parera and Cantliffe, 1994). Often slow, asynchronous, unreliable germination, delayed emergence and insufficient stand establishment are major problems in low-precipitation areas. Seed priming is an age old practice, practiced eons ago by Greeks. The word was coined by Heydecker in 1973 for the soaking drying seed treatments. Theophrastus (372-287 BC) had recommended presoaking of cucumber seeds in milk or water to make them germinate earlier and vigorously (Michael Evanari, 1984). Later, Heydecker (1973) successfully used seed priming to improve germination and emergence under stressful conditions. This technique is a treatment applied prior to sowing in a specific environment wherein seeds are partially hydrated to a point of germination process initiation sans visible symptom of radicle emergence (Bradford, 1986; Dell Aquila and Tritto, 1991; Kaur, 2002; Giri and Schilinger, 2003). During seed priming the amount of water absorption is controlled so as to allow necessary metabolic activities for germination to take place but prevent radicle emergence by limiting the seed water content Different physiological activities occur within the seed at different moisture levels. Primed seeds usually exhibit an increased germination rate, greater germination uniformity, and, at times, greater total germination percent (Basra et al.,2005), improved germination under sub-optimal conditions (Lin and Sung, 2001). Increased germination rate and uniformity have been attributed to metabolic repair during imbibition (Bray et al., 1989), buildup of germination-enhancing metabolites (Basra et al., 2005), osmotic adjustment (Bradford, 1986), and, for seeds that are not re dried after treatment, a simple reduction in imbibition lag time (Bradford,1986). Harris (2006) a veteran in promoting priming concept in least developed countries, reported that large numbers of farmers have tested seed priming for themselves and found improved yield in 204 (farmers) (40% per cent) with upland rice in Cameroon, 257 (70%) in Ghana, 274 (33%) in Sierra Leone, 145 (25%) in Gambia, 40 (113%) in Nigeria and 180 (10%) in Thailand. In case of chickpea, more than 300 (40%) farmers' trials have been implemented in Bangladesh, Nepal and Pakistan. In wheat, 275 farmers in India, Pakistan and Nepal have tested seed priming (5-35%). Maize trials by 72 (29%) farmers in Pakistan and Zimbabwe were also very successful. The farmers reported that seed priming was found to be effective in semi-arid (chickpea, mungbean, sorghum, finger millet, maize), high-potential (wheat, maize) and forest agriculture interface (upland rice) production systems. The concept has been extended through participatory approaches to enable farmers to test seed priming in Bangladesh, Cameroon, Gambia, Ghana, India, Nepal, Nigeria, Pakistan, Sierra Leone, Thailand and Zimbabwe.