STEVIA SEED GERMINATION BEHAVIOR UNDER SALINITY STRESS CONDATION IN DIFFERENT S0IL TYPES

Two experiments were conducted at the Agricultural Research Center in Giza, Egypt, the first one was done in nursery during 2022, while, the second one was undertaken in the greenhouse in 2023 to compare the germination rate of stevia (Stevia rebaudiana, Bertoni) seeds under salinity stress conditions. The first   experiment was conducted to evaluate three varieties (Spanti, China1 and Egy1) of stevia under salinity levels of 0, 600 and 1200 ppm, NaCl which was realized from Cynor Laboratories in factorial experiment (3x3) using completely randomized design (C.R.D.) with three replicates. The second experiment was conducted under normal conditions of green house, including three different types of soil i.e., [peat moss, peat moss + compost (1:1) v/v) and peat moss + compost + sand (1:1:1 v/v/v)], three varieties (Spanti, China1 and Egy1) and three levels of salinity  0, 600 and 1200 ppm, NaCl. Randomized complete block design in split-split plot design arrangement with three replicates was used. Soil media occupied the main plots, while, varieties occupied the sub-plots and salinity occupied the sub-sub-plots.
Spanti variety recorded the highest germination rate index ( GRI) of stevia seeds at the lowest salinity level (0.0 ppm). On the other hand, Egy1 variety showed the lowest GRI under salinity level of 0.0 ppm salinity level.    
Generally, the highest value of number of seedlings was recorded for Spanti variety with mixture peat moss + compost sown in under salinity level of 600 ppm., while the lowest one was obtained for Egy1 variety peat moss with under salinity level of 1200 ppm.
The highest value of seedling length was recorded for Spanti variety sown in peat moss + compost under 600 ppm salinity level, but the highest value of seedling root fresh weight was recorded for Spanti variety sown in peat moss + compost under 0.0 ppm salinity level, While, the highest value of seedling stem fresh weight was recorded for Spanti variety sown in peat moss under 0.0 ppm salinity level.