The International Rootstock Symposium (IRS) makes its debut at Macfrut 2024 as part of an area entirely dedicated to genetic innovations in the rootstock sector. An international symposium with four in-depth seminars on the latest results of worldwide public and private research. Together with the world's leading experts and breeders, the latest innovations in the sector will be presented: innovations in rootstocks for apple, pear, stone fruit and citrus trees will be discussed.
Professor Gregory Lang of Michigan State University, USA, spoke about the situation and prospects of the stone fruit sector.
"Rootstocks have long provided the ability to grow – says Lang - across diverse and variable regions and soil types, specific scion varieties of fruit that are highly desired by consumer markets. This ability to adapt desirable varieties to diverse growing conditions and locations has only increased in importance with the challenges of a changing climate and critical labor issues (higher costs and decreasing availability) that are impacting production regions worldwide. Rootstocks can alter tree architecture, leading to more labor-efficient and mechanization-adaptable orchards, and also can alter the balance between vegetative and reproductive growth, leading to higher yields and improved fruit quality. Both of these factors are critical to profitability and sustainable production".
"Rootstock breeding generally addresses baseline goals of improved productivity and soil adaptability, as well as imparting various levels of tree vigor, with an increasing emphasis on additional traits that confer resistance to important pests and/or diseases, as well as resilience to extreme climatic events such as drought, flooding, and extraordinary high or low temperatures. Cherry rootstocks now present a wide range of vigor choices for growers, but resiliency to climatic extremes, particularly high temperatures, has limited their broad adoption.
Peach, plum, and apricot rootstocks have yet to achieve similar levels of vigor control across a wide range of available genotypes, though advances have been made in critical areas of disease tolerance and soil adaptation, but production of those fruits has been stagnant due to vigor-related orchard system inefficiencies. Consequently, broadening the range of vigor control and graft-compatibility for these stone fruit rootstocks, while retaining or advancing their adaptation to critical soil-based conditions, are among the current goals".
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Thanks to rootstock-induced vigour control, high-density, high-yield plants can now also be established in peach trees (Photo Lang)
And Lang continues: "The most important stone fruit rootstock breeding projects around the world today will be represented at MacFrut 2024. Each stone tree fruit species has specific and variable critical priorities, as do specific growing regions. For example, the Peach Tree Short Life complex (disease- and nematode-influenced) is critical for the Southeast United States, while resistance to Armillaria is broadly critical across U.S. growing regions.
The cultivation of apricot and plum trees is still largely tied to the use of rustic and vigorous rootstocks
The Gisela vigor-controlling cherry rootstocks tend to perform well in mild temperate climates such as northern Europe and northern North America, but underperform in hot arid climates such as southern Europe, California, and central Chile. Breeding programs that utilize severe screening thresholds for the traits of most critical importance to their stakeholder constituencies are the most likely to make significant and sustainable advances".
The cultivation of apricot and plum trees is still largely tied to the use of rustic and vigorous rootstocks
"Most of the world's stone fruit rootstock breeding programs are continuously generating new rootstock genotypes that are entered into various phases of testing, ultimately resulting in the periodic release of new rootstocks for grower adoption into contemporary plantings. MacFrut 2024 will highlight many of these new proven rootstocks, as well as some of those that continue to be promising through advanced but incomplete stages of evaluation.
US researchers are joining forces to find solutions to combat Armillaria root rot (photo Clemson University)
A critical consideration for growers that adopt specific new rootstocks, particularly rootstocks that confer a level of vigor that differs from those of the past, is to utilize an appropriate training system, canopy architecture, and management techniques that are matched to the rootstock (and site) vigor as well as the rootstock's impact on precocity and productivity. These are critical decisions for successful adoption and utilization of key rootstock traits in the quest to optimize production efficiency and sustainability" he concludes.
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