Bahram Dehdar Masjedlou 1 Alireza Motallebi Azar 2 Effect of normal and re-dried GA3 on true potato seed (TPS) germination Summary True potato seed (TPS) is important for increasing seed tubers and table potatoes. TPS was sown in seed beds to produce minitubers or to raise seedling for transplanting in the field. Soaking TPS of potato cultivars and advanced clones in gibberrelin (GA) solution prior to sowing has been shown to enhance germination.Freshly harvested open pollinated true potato(S.tuberosun L.) seeds of four genotypes were tested for germination after treated with GA3.TPS germination showed that Re-drying and storage for 10 days had little effect on final germination percentage and effect on the GA efficacy for germination enhancement. Soaking in 2000 ppm GA3 for 24h with immediate sowing was better than re-drying and control treatments. Results This study demonstrated that soaking of TPS in GA3 as a seed presowing technique for optimizing germination was more effective than the other teratments. Results of experiment showed that seed germination stimulation tests, cultivars and interaction between them were different at 1% level significantly. Average percentage of seed geraminations in 2000 ppm GA3 for 24 h in contrast with re-drying and storage for 10 days and control was higher ( 98 % respectively). Among genotypes, kizer with 95% in 2000 ppm GA3 for 24 h treatment was the best in comparison with other genotypes. These finding also support the suggestion perviously made by (Pallais,1987) that claimed the use of GA for TPS dormancy break must receive closer attention.   Introduction Using true potato seed (TPS) for potato tuber production has proven to be a viable alternative to the use of seed tubers, especially in developing countries (Malagamba,1988). TPS technology has potential for increasing potato production in warm – climate areas where seed tuber programs are hindered by the presence or virus-transmitting aphids. Freshly harvested TPS are dormant and the nature and environmental control of TPS dormancy is apparently not well understood(Tuku,1994). Presowing treatments which improve seed performance under field conditions may prove to be valuable for increasing the rate of adoption of TPS technology by farmers. One such treatment, which has shown potential for enhancing field emergence under unfavorable conditions in many small-seeded crops, is soaking in water or treatment with GA3. However, sowing dry seeds is faster and easier. Also, if seeds could be re-dried without loss of the gibberellins germination-enhancing effect or otherwise lose germinability, potato genebanks could distributed. Pre-treated seed lots, ready to sow might be particularly useful for recipients who do not have GA on hand, and for seedlots particularly dependent on GA for germination (Bamberg,1999). Citing various non-potato reports, Bewley and Black (1982) conclude that re-drying seeds usually has no deleterious effects. The author,s personal communication with various potato breeders and researchers indicates that GA3 soaking and re-drying is sometimes done, being regarded as presenting little risk to adequate germination.The objective of the present study was to condoct a systematic assessment of the effect re-drying and GA-induced germination enhancement. Bahram Dehdar Masjedlou 1 Alireza Motallebi Azar 2 Panahandeh Jaber2 1Phd student of Olericulture, Dept of Horticulture, Faculty of Agricultue, University of Tabriz, 51666-14766, Tabriz, Iran 2 Assos,Assist Prof,Dept of Horticulture, Faculty of Agricultue, University of Tabriz, 51666-14766, Tabriz, Iran Figure 2 - Effect of pre-sowing treatments on percentage of germination in four open pollinated TPS Conclusions For farmers ,quality seed should produce a fast and uniform seedling and considerable improvement in TPS seedling vigor are possible.It is recognized that most seed germination tests do not reflect potential seed vigor performance under unfavorable field conditions(Ching,1982). As a conclusion it can be said that soaking of TPS in GA3 still be a useful technique for optimizing true potato seed germination vigor traits in potato Figure 1. Place the true potato seeds(TPS) on the petri plates and watering. Materials and Methods Experiment were conducted at the research station of Agriculture and Natural Resources in Ardebil, Iran, with open-pollinated seed of commercial cultivars (kizer,Picasso) and 397097-14,397082-10 advances clones from Solanum toberosum L. in 2014.The TPS were produced according to the recommended practice for high quality seed in a large plot of the genotypes for basic seed tuber production in Ardebil. After harvesting the mature berries,the TPS were washed,dried (4-6%moisture content) and stored at 22 C. Each 100 seeds with 4 replication of genotyps were used to three treatments: a)Soaking in 2000 ppm GA3(sigma,90%min)for 24 h with immediate sowing, b)Soaking in water for 24h then re-drying at room temperature for 10 days.c)Soaking in water for 24h with immediate sowing (control). Seeds were sown on moist filter paper in glass petri plates and germinated in the dark. Seeds were submerge when soaked(Fig 1).The germination environment was at a temperature of 30/25 C day/night condition. Garmination was recorded every day or two for four weeks after sowing.Daily emergence counts were made at the first appearance of a radicle or hypocotyl-hook signified germination,respectively and seeds were removed as they sprouted.Finally percentage of germination were evaluated after four week. Bibliography Bamberg,JB.1999.Dependence on exogenous gibberellin for seed germination in Solanum acaule Bitter and other Solanum (potato) species.Amer.J.Potato.Res.76:351-355 Bewley,JD and M,Black.1982.Physiology and Biotechnology of Seeds,volume 2.Springer Verlag,Berlin Pallais, N . 1987. True potato seed quality .Theoretical and Applied Genetics.73:784- 792 Ching,TM.1982.Adenosine triphosphate and seed vigor.In:The physiology and Biochemistry of seed development,Dormancy and Germination,(Ed.)Khan,AA.,Elsevier Biomedical Press.pp.487-506 Yuku,BT.1994.The utilization of true potato seed (TPS) as an alternative method of potato production.Wageningon,The Netherland.p131.