The race against time: breeding resilient apple rootstocks for a changing climate
The apple industry is facing a silent crisis. As the climate crisis accelerates, extreme weather events are becoming more frequent and intense, threatening the very foundation of apple orchards: their rootstocks. These time-tested rootstocks, developed over a century ago, may not withstand the challenges of a rapidly changing climate, endangering the US apple industry's economic stability and food security.
Terence Robinson, a Cornell University horticulture professor, witnessed the devastating impact of a sudden temperature drop on apple orchards in 2015. This event, known as the 'Valentine's Day Massacre', highlighted the vulnerability of rootstocks to extreme weather. The damage wasn't to the trunks or limbs but to the rootstocks themselves, the very foundation of the trees.
The M9 rootstock, widely planted and developed over a century ago, may not be up to the task of a future climate. As temperatures fluctuate and extreme weather events become more common, the industry must adapt. This is where the Geneva Apple Rootstock Breeding Program comes in, a collaborative effort between Cornell University and the USDA.
Since 1968, researchers like Robinson and Gennaro Fazio have been crossing and evaluating apple trees, seeking rootstocks with greater resilience. While initial focus was on disease resistance, the program has evolved to prioritize traits like dwarf stature, early production, drought resistance, and tolerance of high-salt-content soils and moderate winters.
The project demands patience, as crossing and evaluating trees can take 30 years or more. Lee Kalcsits, a professor of tree fruit physiology, emphasizes the importance of breeding without a specific climate in mind. Growers invest in orchards for long-term returns, but unexpected climate events can devastate their profits.
Research by Kalcsits and colleagues revealed warming fall and spring temperatures, making it harder for apples to meet their chilling requirements. This, coupled with a weakened polar jet stream, leads to more frequent and damaging cold snaps in prime apple-growing areas. Rootstocks play a crucial role in shaping trees' responses to climate, influencing their acclimation to cold and chilling requirements.
The Cornell/USDA breeding program is already showing promise, with newer varieties demonstrating less damage than the standard M9. By continuing to cross these new rootstocks, scientists aim to combine their strengths and produce superior options for a changing climate. They are also exploring wild apples from Central Asia for genetic diversity.
The journey of these new rootstocks is far from over. Once crosses are made, the most promising offspring are tested across the country as part of the NC-140 collaboration. One such experimental orchard is located at North Carolina State University's Mountain Horticultural Crops Research Station.
Mike Parker, a tree fruit extension specialist, oversees rootstock trials, carefully monitoring survival rate, trunk size, fruit size, and yield. This long-term data is invaluable for breeders and horticulturalists, helping them make informed decisions about new rootstocks.
However, concerns arise as the current generation of scientists ages out of orchard research. Robinson worries that funding agencies may prioritize short-term projects over long-term rootstock development. The industry's future depends on continued investment in this crucial area, despite the challenges of attracting young scientists.
In conclusion, the apple industry's battle against the climate crisis is far from over. The development of resilient rootstocks is a race against time, requiring patience, collaboration, and a commitment to long-term perspectives. As the climate continues to change, the industry must adapt, ensuring the survival of apple orchards and the economic stability they provide.
