Effect of Thai mango rootstock varieties on the flood tolerance of grafted trees under graft-union submergence

Recently, flooding has affected numerous agricultural fields in Thailand. Mango fields are no exception. Grafted mango trees are particularly susceptible to death due to flooding. The effects of different rootstock varieties on mango tolerance to flooding remain unclear. Therefore, in the present study, we investigated the effects of different rootstock varieties on flood tolerance of grafted mango trees. Two types of grafted trees with two different rootstock varieties, 'Kaew' and 'Tarapnak', and the same scion variety 'Namdokmai', were submerged in water to above the graft union of the trunk. Trees with 'Tarapnak' as a rootstock survived longer than those with 'Kaew'. However, even with 'Tarapnak' as the rootstock, all trees eventually died. However, in one of the trees with 'Tarapnak' rootstock, only the scion died while the rootstock survived, suggesting that in grafted mango trees, when the trunk is submerged to above the graft union, the scion dies first. Therefore, even if flood- tolerant rootstocks are used, their effect on survival is limited.