The Effect of Different Pretreatments on Seed Dormancy Elimination and Seed Germination Improvement of Guava (Psidium guajava)

Extend abstract Introduction: Guava (Psidium guajava L.) is one of the most important fruit crops of tropical and subtropical regions. Guava (Psidium guajava L.) can be propagated by seed, layering, grafting, cutting or tissue culture. Propagation by seed is used for the production of seedlings usable in breeding programs or rootstock production for grafting. Guava seeds germinate poorly and unevenly and require more time for seedling emergence. The dormancy in seeds might be due to hard seed coat and different methods are used for breaking dormancy in seeds to improve germination. The aim of this study was to evaluate efficiency of the different pretreatment on seed dormancy breaking and germination characteristics of guava. Materials and Methods: The experiment was laid out in a completely randomized design with three replications on guava seeds in genetic and breeding laboratory of Date Palm and Tropical Fruit Research Center at the summer of 2018. Treatments consisted of distilled water (24 and 48 h), 0.5 and 1% potassium nitrate (KNO3) for 24 h, warm water (70 ° C) for 5 and 10 min, 25% and 50% sulphuric acid for 5 min, and control (non-treated). In this study, the traits of germination percentage, germination rate and mean of daily germination, seed vigour index and fresh weight and length of seedling were measured.  Data analysis was done using the SAS 9.2 software and the Duncan's test at 5% probability level was used for mean comparison. Results: Results showed that the effect of treatments on seed germination indices (germination percentage, germination rate and mean of daily germination, seed vigour index) of guava was significant at p<0.01. The greatest germination percentage (53.1%), germination rate (6.6 seed/day) and seed vigour (2636.7) were observed in treatment of 1% potassium nitrate (KNO3) for 24 h. The lowest Mean time to germination (14 days) was obtained in distilled water for 48h. Warm water treatments at 70 °C and 25% and 50% sulfuric acid were not effective in improving seed germination compared to control. The highest seed length and weight were observed in 1% potassium nitrate and 0.5% potassium nitrate pretreatments, respectively. Conclusions: the results of this study show that among the different treatments, pre-treatment of seeds with 1%potassium nitrate may be considered as an effective way to improve seed germination of guava. Also, pretreatment with distilled water for 48 hours is an easy, low cost and effective way to increase guava seed germination indices. Highlights: 1- The effect of different chemical treatments on germination characteristics of guava was investigated. 2- The suitable method for seed dormancy elimination and seed germination improvement of guava was introduced.