Relationship between root activity and carbohydrate distribution between scion and rootstock in grafted mango trees under flooding

Abstract

Grafted mango trees tend to die when the graft union is submerged in water. In this study, we investigated the root vigor using triphenyl tetrazolium chloride (TTC) reduction tests in relation to carbohydrate distribution and defoliation, when the trees were submerged up to 5 cm above the graft union. Immediately after the commencement of flooding treatment, the root sugar content increased due to the decrease in the root vigor. Although the root vigor did not recover during flooding treatment, the root sugar content gradually decreased to a level not significantly different from that in the non-treated control. Defoliation in flooding trees varied greatly and was correlated with the sugar content of the roots and wood of the rootstock. As the root vigor during the flooding treatment was positively correlated with root sugar content, it was considered that the decrease in root vigor due to flooding was not only caused by oxygen deficiency but also by the decreased supply of photoassimilates from the scion.