Standardization of Suitable Concentration and duration of Seed Biopriming with Liquid Biofertilizers for Seedling Vigour Improvement in Rice

Rice (Oryza saiva L.)is the world’smost important staple food-grain grown in over 100 countries, consumed regularly by over two billion people and the primary source of protein for millions. India is the leading rice producing country in terms of area and is the second largest producer next to China. Rice plays an important role in food as well as livelihood security for almost every household, more so in India. To feed this estimated 1.6 billion population of India by 2050 calls for stepping up the current production of 106 mt of milled rice to 140 mt. Higher production and productivity of crop is possible only through use of good quality seeds and proper management practices (Punithavathi et al.,2020). Good quality seeds imply vigour, uniformity and structural soundness besides its genetic and physical purity. Seed priming with living bacterial inoculum is termed as biopriming that involves the application of plant growth promoting rhizobacteria. This type of priming increases germination rate, seedling vigour and also protects seeds against various soil and seed borne pathogens. Bio priming also enhances the ability of plants to withstand against extreme environmental conditions. The bacteria used in biopriming are able to colonize the rhizosphere and help plant through director indirect mechanism. Biopriming has emerged as an effective approach for increasing seed vigour. The biofertilizers were found to have not only the ability to fix nitrogen but also the ability to release phytohormones similar to gibberellic acid and indole acetic acid, which could stimulate plant growth, absorption of nutrients, and photosynthesis (Kokila and Baskaran,2016). There is no standard procedure in biopriming as the treatment duration, concentration depends on species, cultivars and seed types. The optimum such variability is a major limitation of the priming method since numerous trials are required to identify the most appropriate strategy for each situation. There is no general rule concerning modalities of seed priming and there is no clear trend of priming response according to the taxonomic position of the species. This undoubtedly limits the commercial implementation of priming treatments. At present, the carrier based biofertilizers are replaced by liquid formulations which are easy to use as it spreads well, mixed uniformly and does not require sticker agent (Nethery, 1991). Rice and Olsen, 1992 suggested that liquid formulations were an effective method for seed inoculation of biofertilizer than carrier based inoculants application. Many studies are available on the beneficial effects of inoculating biofertilizers on crop productivity. Research information on the use of liquid biofertilizers as seed treatment is very scanty and the concentrations or duration of soaking are to be indifferent crops. With this background, the present investigation was carried out to standardize the appropriate concentration and priming duration for rice var. PMK(R)