Today's current varieties of tomatoes – ones grown in gardens and available in produce sections and farmers' markets – are a bit spoiled. Through thousands of years of cultivation, the root systems of cultivated crops have become "trusting" that people will provide them with the resources they need to grow. The May 22, 2022 Sustainable, Secure Food Blog explains how rootstocks help in breeding new varieties of tomatoes that can tolerate heat and drought.
According to blogger Steven Bristow, this trust that resources will be available allows plant to increase production of shoots and fruits – increasing yields. However, that tradeoff comes at the expense of root growth. That means that plants are less suited to care for themselves under challenging environmental conditions such as heat and drought.
Fortunately, tomato rootstocks often retain more of the wild traits from their undomesticated ancestors. This means they can be better suited at managing stressful environmental conditions. For those reasons, grafting a desirable cultivar onto a vigorous rootstock is an approach worthy of research and consideration.
Grafting is a common technique used to grow many different types of fruits and vegetables. For tomatoes, a desirable-fruit-bearing scion (the shoot) is placed atop a rootstock (the roots) that contains some other desirable characteristic. This characteristic could be stress tolerance or disease resistance. Humans do the splicing, biology does the healing, and the result is a new grafted plant with the desired characteristics of the grower.
Certain rootstocks may improve plant performance by enhancing the amount of root biomass used to support shoot function (often referred to as a root-to-shoot ratio). Having more roots per shoot means that under stressful conditions shoots can continue to operate efficiently during the hottest parts of the day and the hottest days of the year.
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