Abstract
A simple and reliable Frankia inoculation method was investigated to establish an effective rapid seedling cultivating method for pottedseedlings of Alnus hirsuta using the root-nodulating Frankia. Because the nodulation rate of Frankia in seedlings raised in commercial sterilized potting soil was low, at 30% or below, root nodules were collected from naturally growing seedlings of A. hirsuta and homogenized in tap water to produce a suspension. The nodulation rate was significantly increased by applying the suspension to newly germinated seeds. In addition, the plant height and the abundance of root nodules were positively correlated, and it was found that inoculation with a suspension having a concentration of 0.1 g/L was highly effective, and that the effects on seedling growth differed depending on the nodule sources used in inoculating Alnus hirsuta. This method is practical because it is simple and reliable. By providing suitable cultivating conditions that enhance the infection rate of Frankia and selecting root nodules infected with an effective strain with high nitrogen fixing ability, it is anticipated that it will be possible to raise such potted seedlings in less than a year for shipment.
