Rootstock vigour determines the size and growth habit of an apple tree. Selecting the appropriate rootstock is crucial for orchard management and fruit production.
The question asks to identify the apple rootstock among the given options that exhibits less vigour. Based on common classifications used in horticulture contexts:
We analyze the vigour level of each option provided:
| Rootstock | Vigour Level (as per question context) |
| M-2 | Vigorous |
| M-13 | Vigorous |
| Merton-793 | Vigorous |
| MM-106 | Not Vigorous |
Comparing the options, MM-106 is identified as the rootstock that is not vigorous in nature within the context of this question, differentiating it from the others listed which are considered more vigorous.