Temperature and seed weight affect the germination of peach rootstock seeds and the growth of rootstock seedlings

Seeds of five cultivars of peach rootstocks were assessed to determine the effect of seed quality and temperature on germination and seedling growth. The weight of each seed and its surrounding endocarp was determined. Based on weight, the seeds were divided into four quartiles, stratified, and grown at 23 °C with a 16 h photoperiod. The percentage of seeds germinating over an 8-week period was then recorded. Seed weight significantly affected germination characteristics of the rootstock seeds. The final percentage, time and duration of germination correlated with quartile. In addition, relative growth rate during the first 3 weeks of growth and final plant height also correlated with quartile. Therefore, the heaviest seeds produced the most vigorous seedlings. In a second trial, seeds were grown at constant temperatures (10, 15, 20 or 25 °C) or under ambient conditions. For seeds germinated at 15–25 °C and ambient temperatures, there was no difference in either their speed or duration of germination. However, those placed at 10 °C were both slower to germinate and had a greater duration of germination. At constant temperatures, there was a trend for percentage germination to increase with temperature. However, the highest germination was found in seeds germinated at ambient temperatures that varied diurnally. For each individual cultivar, there was a strong correlation between seed size and the size of the endocarp or stone. Therefore, the grading of either stones or seeds on the basis of size or weight and the removal of the smallest individuals will help improve germination, seedling quality and uniformity.